All-104 (1).pdf

Question Bank in DC Circuits A. DC CIRCUITS: BASIC PRINCIPLES 1. REE Board Exam March 1998 The substation bus bar is made up of 2 inches round copper bars 20 ft long. What is the resistance -6 of each bar if resistivity is 1.724 x 10 ohm-cm. -5 -5 A. 7.21 x 10 Ω C. 5.185 x 10 Ω -6 -5 B. 13.8 x 10 Ω D. 2.96 x 10 Ω 2.

3.

4.

REE October 1997 Determine the resistance of a busbar made of copper if the length is 10 meters long and the cross 2 section is a 4 x 4 cm . Use 1.7241 micro ohm-cm as the resistivity. -4 -5 A. 2.121 x 10 Ω C. 3.431 x 10 Ω -4 -4 B. 4.312 x 10 Ω D. 1.078 x 10 Ω EE Board Exam October 1991 One turn of a copper bar is produced by cutting copper washer along a radius and spreading the ends. The washer is cut from soft drawn copper -6 having a resistivity at 20°C of 1.732 x 10 ohm-cm. The washer is 0.125 inch thick and has inside diameter and outside diameter of 1 inch and 9 inches respectively. Calculate the exact resistance between the two ends of the turn to direct current, taking into account the non-uniform current distribution. Assume the contact along the ends of the turn to be perfect over the entire cross section. -6 -6 A. 12.74 x 10 Ω C. 17.22 x 10 Ω -6 -6 B. 15.53 x 10 Ω D. 14.83 x 10 Ω EE Board Exam October 1990 Determine the resistance of a conductor 0.10 m long, with a uniform diameter of 1.0 cm and having a resistivity which varies as a function of length L measured from the one end of the conductor -4 2 according to ρ = 0.003 + 10 L ohm-cm. A. 0.0852 ohm C. 0.0806 ohm B. 0.0915 ohm D. 0.0902 ohm

5.

EE Board Exam April 1992 A coil has 6,000 turns of wire and a resistance of 380 ohms. The coil is rewound with the same quantity (weight) of wire, but has 13,400 turns. How many ohms will the new coil have? A. 1895 ohms C. 1792 ohms B. 1825 ohms D. 1905 ohms

6.

EE Board Exam April 1992 A copper wire of unknown length has a resistance of 0.80 ohm. By successive passes through drawing dies, the length of the wire is increased by 2 ½ times its original value. Assuming that resistivity remains unchanged during the drawing process, determine the new value of its resistance. A. 4 ohms C. 5 ohms B. 3 ohms D. 6 ohms

7.

REE Board Exam October 1998 A one-meter rod of 2-cm diameter is drawn until its resistance is 100 times the initial resistance. Its length afterwards is? A. 10 m C. 12.5 m B. 100 m D. 5 m

8.

EE Board Exam April 1993 A kilometer of wire having a diameter of 11.7 mm and a resistance of 0.031 ohm is drawn down so that its diameter is 5.0 mm. What does its resistance become? A. 0.85 ohm C. 0.93 ohm B. 0.78 ohm D. 0.81 ohm

9.

EE Board Exam April 1995 A certain wire has a resistance R. The resistance of another wire identical with the first except for having twice its diameter is A. 4R C. 2R B. R/2 D. R/4

10. REE Board Exam October 1996 2 What is the size in square millimeter (mm ) is the cable of 250 MCM size? 2 2 A. 118.656 mm C. 112.565 mm 2 2 B. 126.675 mm D. 132.348 mm 11. REE Board Exam October 1998, September 2001 The resistance of a copper wire at 30°C is 50 ohms. If the temperature coefficient of copper at 0°C is 0.00427, what is the resistance at 100°C? A. 72.26 ohms C. 63.24 ohms B. 54.25 ohms D. 58.15 ohms 12. REE Board Exam March 1998 The resistance of a wire is 126.48 Ω at 100°C and 100 Ω at 30°C. Determine the temperature coefficient of copper at 0°C. A. 0.00427/°C C. 0.0256/°C B. 0.00615/°C D. 0.365/°C 13. EE Board Exam October 1991 Two heating elements which is 500 ohms and 250 ohms are connected in series with temperature coefficients of 0.001 and 0.003 ohms per °C, respectively at 20°C. Calculate the effective temperature coefficient of the combination. A. 0.00215 C. 0.00712 B. 0.00626 D. 0.00167 14. EE Board Exam October 1992 The insulation resistance of a kilometer of the cable having a diameter of 2 cm and an insulation thickness of 2 cm is 600 ohms. If the thickness of the insulation is increased to 3 cm, find the insulation resistance of the cable. A, 725 ohms C. 757 ohms B. 850 ohms D. 828 ohms 15. EE Board Exam April 1989 It is required that a loading of 3 kW be maintained in a heating element at an initial temperature of 20°C,

a voltage of 220 V is necessary for the purpose. After the element has settled down to steady state, it is found that a voltage of 240 volts is necessary to maintain the 3 kW loading. The element resistance temperature coefficient is 0.0006 per degree centigrade at 20°C. Calculate the final temperature of the heating element. A. 345.43°C C. 336.84°C B. 326.42°C D. 318.48°C 16. REE Board Exam October 1999 How long must a current of 5 A pass through a 10 ohm resistor until a charge of 12000 coulomb passes through? A. 1 min C. 3 min B. 2 min D. 4 min

B.

8.14 μΩ

D.

0.814 μΩ

24. REE Board Exam April 2001 The resistance of the field winding of a DC machine is 0.25 Ω at 25°C. When operating at full-load, the temperature of the winding is 75°C. The temperature coefficient of resistance of copper is 0.00427 per °C at 0°C. Find the resistance of the field winding at full-load. A. 0.298 Ω C. 0.512 Ω B. 0.315 Ω D. 0.271 Ω 25. REE Board Exam October 2000 A coil of copper has resistance of 5.46 Ω at 75°C. What will be its resistance at 25°C? A. 4.58 Ω C. 5.02 Ω B. 4.84 Ω D. 4.35 Ω

17. REE Board Exam October 1999 What is the power required to transfer 97,000 coulombs of charge through a potential rise of 50 volts in one hour? A. 0.5 kW C. 1.3 kW B. 0.9 kW D. 2.8 kW

26. REE Board Exam April 2001 A certain generator generates 1,500,000 joules per minute. What is the output in kW? A. 50 C. 25 B. 500 D. 125

18. REE Board Exam April 2001 A round wire has 250 MCM. Find its diameter in inches. A. ½ C. 0.16 B. ¼ D. 0.08

27. ECE BOARD NOV 2001 _____ is anything that has weight had occupies space. It may be solid, liquid or gas. A. Amalgam C. Matter B. Alloy D. Compound

19. REE Board Exam September 2003 In the American wire gauge, as the number of gauge increases, the diameter of wire ____ A. increases B. decreases C. does not change D. become twice

28. ECE Board Exam April 2000 It is defined as anything that occupies space and has weight. A. atom C. molecule B. compound D. matter

20. REE Board Exam September 2003 In cgs system, what is the unit of emf where I is in abampere and P is in erg per second? A. millivolt C. abvolt B. kilovolt D. volt 21. REE Board Exam September 2002 One (1) kW is equal to ____ hp. A. 0.746 C. 550 B. 1.34 D. 1.5 22. REE Board Exam October 1998 Two copper conductors have equal length. The cross-sectional area of one conductor is three times that of the other. If the resistance of the conductor having smaller cross-sectional area is 20 Ω, what is the resistance of the other? A. 20/3 Ω C. 180 Ω B. 60 Ω D. 20/9 Ω 23. REE Board Exam October 2000 A copper bar has a length of 20 ft., width of 4 inches and thickness of 0.5 inch. If the resistivity of copper is 10.37 Ω-CM/ft, what is the resistance of the bar? A. 81.4 μΩ C. 814 μΩ

29. ECE Board Exam November 1999 The lightest kind of atom or element A. hydrogen C. titanium B. helium D. oxygen 30. ECE Board Exam November 1998 In order to have a good conductor material, such material shall have _____ valence electrons. A. one C. more than ten B. five D. twenty one 31. ECE Board Exam November 1997 Electric power refers to _____ A. volt ampere C. volt coulomb B. watt second D. joule 32. ECE Board Exam November 1995 What composes all matter whether a liquid, solid or gas? A. electrons C. protons B. atoms D. neutrons 33. ECE Board Exam November 2001 What is a physical combination of compounds or elements NOT chemically combined that can be separated by physical means? A. substance C. mixture

B.

atom

D.

molecule

34. ECE Board Exam April 1998 Determine the equivalent work of 166 watt-second. A. 10 joules C. 16.6 joules B. 100 joules D. 166 joules 35. ECE Board Exam November 2001 One of the following is the best conductor of electricity. A. Air C. Carbon B. Copper D. Silicon 36. ECE Board Exam November 1999 What is the basic unit for measuring current flow? A. coulomb C. volt B. ampere D. atomic weight 37. ECE Board Exam November 1995 ______ has a unit of electron volt A. Energy C. Current B. Potential difference D. Charge 38. ECE Board Exam November 2001 The motion of charged particles especially colloidal particles through a relative stationary liquid under the influence of an applied electric provided. A. hysteresis C. electrophoresis B. electrolysis D. electro analysis 39. ECE Board Exam April 2001 What is a symbol that represents a quantity or a single object? A. unit C. item B. number D. base 40. ECE Board Exam April 2000 Determine which of the following has the least number of electrons found at the outer shell. A. semi-insulator C. semiconductor B. insulator D. conductor 41. ECE Board Exam April 2001 The term describes a material whose resistance remains relatively constant with changes in temperature A. positive temperature coefficient B. negative temperature coefficient C. neutral temperature coefficient D. zero temperature coefficient 42. ECE Board Exam November 1998 Resulting effect when electron is made to move A. dynamic electricity C. lines of force B. static electricity D. magnetic lines 43. ECE Board Exam November 1997 One of the following characteristics of a resistive material which do not change its resistive value with respect to time is its _____ A. fidelity C. stability B. sensitivity D. selectivity

44. ECE Board Exam November 2001 What do you call the element that conducts electricity very readily? A. semi-conductors C. insulators B. conductors D. dielectric 45. ECE Board Exam April 2001 Which of the following material is referred to as a medium whereby electrons can move easily from atom to atom? A. insulator C. mica B. dielectric D. conductor 46. ECE Board Exam November 2001 A chemical combination of elements can be separated by chemical means but not by physical means. It is created by chemically combining two or more elements. A. molecules C. matter B. compound D. mixture 47. ECE Board Exam April 2000 A substance which cannot be reduced to a simpler substance by chemical means A. atom C. matter B. molecule D. element 48. ECE Board Exam November 2001 Calculate the equivalent power in watt of 100 joules per second. A. 1.66 watts C. 16.66 watts B. 100 watts D. 1,000 watts 49. ECE Board Exam April 2001 It is a neutral particle that has no electrical charge. A. atom C. electron B. proton D. neutron 50. ECE Board Exam November 1999 Which material has more free electrons? A. mica C. conductor B. insulator D. dielectric 51. ECE Board Exam November 2001 The new and preferred term for conductance or mho A. Siemens C. Seaman B. She-man D. ROM 52. ECE Board Exam April 2001 Represents the current flow produced by one volt working across one ohm of resistance. A. resistance B. ampere C. voltage D. electromotive force 53. ECE Board Exam November 1995 When an atom gains an additional _____, it results to a negative ion. A. atom C. proton B. neutron D. electron

54. ECE Board Exam November 1999 The definite discrete amount of energy required to move an electron from a lower shell to higher shell. A. quantum B. positive energy C. negative energy D. quanta 55. ECE Board Exam November 1999 What will happen to an atom if an electron is either taken out or taken into the same atom? A. becomes a negative ion B. becomes an ion C. becomes a positive ion D. nothing will happen 56. ECE Board Exam April 1999 The energy in an electron that is called the energy of motion A. electromotive force B. kinematics C. kinetic energy D. potential energy 57. ECE Board Exam November 1996 Electric charge of neutron is the same as ______. A. atom C. current B. electron D. proton 58. ECE Board Exam April 1998 Ion is _____. A. free electron B. nucleus without protons C. proton D. an atom with unbalanced charges 59. ECE Board Exam November 1997 An insulating element or material has capability of _____. A. storing voltage B. preventing short circuit between two conducting wires C. conducting large current D. storing high current 60. ECE Board Exam April 1998 What is the value of a resistor with colors from left: Orange, Blue, Gold and Silver? A. 34 ohms + /-10% B. 36 ohms +/-10% C. 3.4 ohms +/-10% D. 3.6 0hms +/-10% 61. ECE Board Exam April 2001 A three-terminal resistor with one or more sliding contacts which functions as an adjustable voltage divider A. Rheostat C. Potentiometer B. Bleeder resistor D. Voltage divider 62. ECE Board Exam November 2000 A resistor which is used to draw a fixed amount of current

A. B.

potentiometer bleeder resistor

C. D.

fixed resistor rheostat

63. ECE Board Exam November 2001 Find the value of a resistor with the following color codes: Orange, Yellow, Red, Red A. 34 k ohms +/-5% B. 3.4 ohms +/-2% C. 3.4 k ohms +/-10% D. 34 k ohms +/-20% 64. ECE Board Exam November 1996 Electric energy refers to ______. A. Joules divided by time C. Watt B. Volt-ampere D. Volt-coulomb 65. ECE Board Exam April 2001 What is the resistance of an open fuse circuit? A. at least 1000 ohms B. infinity C. zero D. 100 ohms at standard temperature 66. ECE Board Exam April 1998 When should a fuse be replaced with a higher rated unit? A. when the fuse of the original value is small in size B. when the original is not available C. never D. if it blows 67. ECE Board Exam November 2000 The ability to do work A. energy C. potential B. kinetic D. voltage 68. ECE Board Exam November 2001 Which type of variable resistor should you use for controlling large amount of current? A. Potentiometer C. Variac B. Adjustable wirewound D. Rheostat 69. ECE Board Exam April 2000 What does the fourth loop of an electronic resistor color code represent? A. Multiplier B. Temperature C. First digit of the equivalent value D. Tolerance 70. ECE Board Exam November 2000 Ten micro-microfarads is equivalent to _____ A. 100 picofarads B. 100 nanofarad C. 1000 milli microfarad D. 10.0 picofarads 71. ECE Board Exam November 1995 How much is the resistance of a germanium slag 10 cm long and cross sectional area of 1 square cm? A. 55 k ohms C. 550 k ohms B. 5.5 k ohms D. 550 ohms

72. ECE Board Exam November 2001 A variable resistor normally used as a voltage divider A. Carbon film resistor B. Potentiometer C. Adjustable resistor D. Metal film resistor 73. ECE Board Exam April 2001 Determine the equivalent horse power of 2.611 kilowatts. A. 3.50 hp C. 2.25 hp B. 2.50 hp D. 1.50 hp

81. ECE Board Exam November 1998 What is the value of a resistor having the following colored bands: Yellow-Gray-Red-Silver? A. 4800 ohms ±10% B. 480 ohms ±10% C. 3800 ohms ±1% D. 4.8 ohms ±1% 82. ECE Board Exam November 1997 Find the value of resistor with the following color codes; Brown, White, Orange, Red A. 190 ohms 10% B. 19 k ohms 2% C. 1.9 k ohms 10% D. 19 k ohms 20%

74. ECE Board Exam November 2000 Find the lowest resistance value of the following resistors. A. White, black, black B. Violet, gray, yellow, silver C. Red, black, gold D. Gray, gray, black

83. ECE Board Exam November 1998 Resistor with colored bands in the body A. Adjustable resistor B. Wire-wound resistor C. Variable resistor D. Carbon composition resistor

75. ECE Board Exam November 1998 If the bands on a resistor are yellow, violet, red and gold, what is the resistance value? A. 470 ohms 5% B. 470 ohms 10% C. 47000 ohms 5% D. 4700 ohms 5%

84. ECE Board Exam November 1998 If the bands on a resistor are red, red, orange and silver, what is the resistance value? A. 220 ohms 5% B. 223 0hms 10% C. 22,000 ohms 10% D. 2200 ohms 20%

76. ECE Board Exam November 1997 Rust in electrical (wire) connections will result to _____ A. Conductance C. Voltage B. Resistance D. Inductance

85. ECE Board Exam November 1997 What does the second strip of an electronic resistor color code represent? A. Tolerance B. Second digit of the value C. Temperature D. Multiplier

77. ECE Board Exam November 1996 The area of a conductor whose diameter is 0.001 inch is equal to A. One micron C. One circular mil B. One angstrom D. One steradian 78. ECE Board Exam November 1995 _____ is the term used to express the amount of electrical energy in an electrostatic field. A. Joule C. Volt B. Coulomb D. Watt 79. ECE Board Exam November 1995 Which of the following statement is correct? A. Potentiometer has two terminals B. Transistor has two terminals C. Typical power rating of a carbon-composition resistor ranged from 0.125 W to 2 W D. Open resistor has small resistance 80. ECE Board Exam November 1996 _____ is one factor that does not affect resistance. A. Resistivity C. Length B. Cross sectional area D. Mass

86. ECE Board Exam November 2000 The energy in an electron that is called the energy of position A. Kinetic energy B. Kinematics C. Electromotive force D. Potential energy 87. ECE Board Exam April 1999 If an electronic resistor does not have the fourth color strip it means it has a tolerance of _____. A. 5% C. 10% B. 20% D. 1% 88. ECE Board Exam April 1998 What happens to the resistance of a conductor wire when its temperature is lowered? A. Decreased C. Zero B. Steady D. Increased 89. ECE Board Exam April 1998 Which of the following does not refer to electric energy? A. Joule C. Volt coulomb

B.

Watt second

D.

Volt ampere

90. ECE Board Exam March 1996 Which of the following statement is incorrect? A. open transistor has three (3) terminals B. transistors have three (3) terminals C. typical power rating of carbon-composition resistor ranged 0.001 W to 0.1 W D. potentiometer has three (3) terminals 91. ECE Board Exam November 1997 Term used in electronic measuring device when a metal increases resistance due to heat produced by current flowing through them. A. positive resistance coefficient B. positive temperature coefficient C. negative temperature coefficient D. negative resistance coefficient 92. A 1 km cable consists of 12 identical strands of aluminum each 3 mm in diameter. What is the resistance of the cable? A. 0.34 ohm C. 0.44 ohm B. 0.54 ohm D. 0.24 ohm 93. A piece of wire has a resistance of 0.5 ohm. The length is doubled and the area is increased four times. What is its resistance? A. 0.75 ohm C. 0.25 ohm B. 0.50 ohm D. 1 ohm 94. Copper wire of certain length and resistance is drawn out to four times its length without change in volume. What is the resistance of the bar? A. unchanged C. 16R B. R/16 D. 4R 95. Current is simply _____. A. Flow of electrons B. Flow of protons

C. D.

Radiation Emission

96. The resistance of a coil of wire is 1 kΩ at 20°C. If the coil is immersed into oil, the resistance falls to 880 Ω. If the wire has a temperature coefficient of 0.006 at 20°C, how much is the temperature of the liquid? A. 0°C C. 17.6°C B. -20°C D. none of these 97. The copper field coils of a motor was measured at 21°C and found to have a resistance of 68 Ω. After the motor has run for a given time, the resistance is found to be 96 Ω. What is the hot temperature of the winding? A. 106.36°C C. 103.66°C B. 166.30°C D. none of these 98. A wire has a resistance of 30 Ω at 20°C. What will its resistance be at 60°C? Assume the temperature coefficient of resistance to be 0.000385 at 20°C. A. 34.26 Ω C. 32.46 Ω B. 36.42 Ω D. none of these

99. Determine the length of a copper wire (ρ = 10.37 ΩCM/ft) where diameter is 0.30 inch and resistance of 0.5 Ω at 20°C. A. 4,339 ft C. 6,125 ft B. 5.225 ft D. none of these 100. An electric water heater has a rating of 1 kW, 230 V. The coil used as the heating element is 10 m -6 long and has a resistivity of 1.724 x 10 ohm-cm. Determine the required diameter of the wire in mils. A. 2.43 mils C. 3.21 mils B. 2.52 mils D. 1.35 mils 101. A certain wire 20 ft long and 100 circular mil area has a resistance of 1.6 . What is its resistivity? A. 10.3 ohm-CM/ft B. 2.2 ohm-CM/ft C. 8 ohm-CM/ft D. 15.2 ohm-CM/ft 102. How many circular mils does a round copper rod of 0.25 inch diameter have? A. 196,000 C. 1,963,500 B. 62,500 D. 49,000 103. A substance whose molecules consist of the same kind of atoms is called ____. A. mixture B. element C. compound D. none of the above 104. The diameter of the atom is about ____. -10 -2 A. 10 m C. 10 m -8 -15 B. 10 m D. 10 m 105. The number of compounds available in nature is ____. A. 105 C. 1000 B. 300 D. unlimited 106. The mass of a proton is ____ the mass of an electron. A. equal to B. less than C. about 1837 times D. 200 times 107. The maximum number of electrons that can be accommodated in the last orbit is ____. A. 4 C. 18 B. 8 D. 2 108. The electrons in the last orbit of an atom are called ____ electrons. A. free C. valence B. bound D. thermionic 109. If the number of valence electrons of an atom is less than 4, the substance is usually ____. A. a conductor B. an insulator C. a semiconductor

D.

none of the above

110. If the number of valence electrons of an atom is more than 4, the substance is usually ____. A. a semiconductor B. a conductor C. an insulator D. none of the above 111. If the number of valence electrons of an atom is exactly 4, the substance is usually ____. A. a semiconductor B. an insulator C. a conductor D. a semiconductor 112. The number of valence electrons of an atom is less than 4. The substance will be probably ____. A. a metal B. a non-metal C. an insulator D. a semiconductor 113. One coulomb of charge is equal to the charge on ____ electrons. 16 16 A. 628 x 10 C. 62.8 x 10 16 16 B. 6.28 x 10 D. 0.628 x 10 114. One cc of copper has about ____ free electrons at room temperature. 22 A. 200 C. 8.5 x 10 10 5 B. 20 x 10 D. 3 x 10 115. Electric current in a wire is the flow of ____. A. free electrons B. bound electrons C. valence electrons D. atoms 116. EMF in a circuit is ____. A. cause current to flow B. maintains potential difference C. increases the circuit resistance D. none of these 117. EMF has the unit of _____. A. power B. energy

C. D.

charge none of these

120. If the length and area of cross-section of a wire are doubled up, then its resistance ____. A. becomes four times B. remains unchanged C. becomes sixteen times D. none of the above 121. A length of wire has a resistance of 6 ohms. The resistance of a wire of the same material three times as long and twice the cross-sectional area will be ____. A. 36 ohms C. 9 ohms B. 12 ohms D. 1 ohm 122. The SI unit of specific resistance is ____. 2 A. mho C. ohm-m B. ohm-m D. ohm-cm 123. The specific resistance of a conductor ____ with rise in temperature. A. increases B. decreases C. remains unchanged D. none of the above 124. The SI unit of conductivity is ____. A. ohm-m C. mho-m B. ohm/m D. mho/m 125. The SI unit of conductance is ____. A. mho C. ohm-m B. ohm D. ohm-cm 2

126. The resistance of a material 2 m long and 2 m in -8 cross-sectional area is 1.6 x 10 Ω. Its specific resistance will be ____. -8 A. 3.2 x 10 ohm-m -8 B. 6.4 x 10 ohm-m -8 C. 1.6 x 10 ohm-m -8 D. 0.16 x 10 ohm-m 127. Conductors have ____ temperature coefficient of resistance. A. positive B. negative C. zero D. none of the above

118. Potential difference has the unit of ____ . A. charge B. power C. energy D. none of the above

128. Semiconductors have ____ temperature coefficient of resistance. A. negative B. positive C. zero D. none of the above

119. The resistance of a material is ____ its area of cross-section. A. directly proportional to B. inversely proportional to C. independent of D. none of the above

129. The value of α (i.e. temperature coefficient of resistance) depends upon A. length of the material B. cross-sectional area of the material C. volume of the material D. nature of the material and temperature

Resistance (Ω)

130. The temperature coefficient of resistance of a conductor ____ with rise in temperature. A. increases B. decreases C. remains unchanged D. none of the above

45°

20 Ω

132. Eureka has ____ temperature resistance. A. positive B. negative C. almost zero D. none of the above

coefficient

of

A. B.

t 40°C Temperature Fig. 1.2 C. 35 ohms D. 50 ohms

70 ohms 40 ohms

137. Referring to Fig. 1.2, the value of α40 will be ____. Resistance (Ω)

131. Insulators have ____ temperature coefficient of resistance. A. zero B. positive C. negative D. none of the above

45°

20 Ω t 40°C Temperature Fig. 1.2

Resistance (Ω)

133. Fig. 1.1 shows the temperature/resistance graph of a conductor. The value of α0 is ____.

40 Ω

A. B.

0.005/°C 0.004/°C

A. B.

50 Ω t 50°C Temperature Fig. 1.1 C. 0.1/°C D. 0.4/°C

Resistance (Ω)

134. Referring to Fig. 1.1, the value of the α50 will be ____.

40 Ω

A. B.

0.005/°C 0.004/°C

50 Ω t 50°C Temperature Fig. 1.1 C. 0.1/°C D. 0.4/°C

135. Referring to Fig. 1.2, the value of α0 is ____. A. 1/30 per °C B. 1/40 per °C C. 1/1200 per °C D. none of the above 136. Referring to Fig. 1.2, the value of R40 will be ____.

1/30 per °C 1/70 per °C

C. D.

1/50 per °C 1/1200 per °C

138. The value of α0 of a conductor is 1/236 per °C. The value of α18 will be ____. A. 1/218 per °C B. 1/272 per °C C. 1/254 per °C D. none of the above 139. The value of α50 of a conductor is 1/230 per °C. The value of α0 will be ____. A. 1/180 per °C B. 1/280 per °C C. 1/250 per °C D. none of the above 140. A good electric conductor is one that A. has low conductance B. is always made of copper wire C. produces a minimum voltage drop D. has few free electrons 141. Two wires A and B have the same cross-section and are made of the same material, RA = 600 Ω and RB = 100 Ω. The number of times A is longer than B is A. 6 C. 4 B. 2 D. 5 142. A coil has a resistance of 100 Ω at 90°C. At 100°C, its resistance is 101 Ω. The temperature coefficient of wire at 90°C is A. 0.01 C. 0.0001 B. 0.1 D. 0.001 143. Which of the following material has nearly zero temperature-coefficient of resistance? A. carbon C. copper

B.

porcelain

D.

manganin

144. Which of the following material has a negative temperature coefficient of resistance? A. brass C. aluminum B. copper D. carbon

153. REE Board Exam March 1998 Three resistors of 10, 15 and 20 connected in parallel. What is resistance? A. 45 ohms C. B. 17.2 ohms D.

145. A cylindrical wire 1 m in length, has a resistance of 100 . What would be the resistance of a wire made from the same material both the length and the cross-sectional area are doubled? A. 200 C. 100 B. 400 D. 50

154. REE Board Exam March 1998 Three resistors of 10, 15 and 20 connected in parallel. What conductance? A. 0.217 siemens C. B. 3.41 siemens D.

146. Carbon composition resistors are most popular because they A. cost the least B. are smaller C. can withstand overload D. do not produce electric noise

155. REE Board Exam October 1997 A 5-ohm resistance is connected in parallel with a 10-ohm resistance. Another set, a 6-ohm and an 8ohm resistances are also connected in parallel. The two sets are connected in series. What is the equivalent resistance? A. 6.76 ohm C. 14.4 ohms B. 9.25 ohm D. 21.2 ohms

147. A unique feature of a wire-wound resistor is its A. lower power rating C. high stability B. low cost D. small size °

148. A coil has a resistance of 100 ohms at 90 C. At 100°C, its resistance is 101 ohms. What is the ° temperature coefficient of the wire at 90 C? A. 0.01 C. 0.0001 B. 0.1 D. 0.001 149. What is the unit for charge (Q)? A. Farad C. B. Joule D.

Siemens Coulomb

150. The charge delivered by a constant voltage source is shown. Determine the current supplied by the source at (a) t = 1 s (b) t = 3 s.

A. B.

5 ma, -3.33 ma 5 ma, 3.33 ma

C. D.

–3.33 ma, 5 ma 3.33 ma, 5 ma

B. OHM’S LAW AND ELECTRIC CIRCUITS 151. REE Board Exam October 1998 The resistance of 120 meters of wire is 12 ohms. What is its conductance? A. 0.0521 siemens C. 6 siemens B. 0.0833 siemens D. 12 siemens 152. EE April 1981, October 1984 Two (2) 115-V incandescent lamps A and B are connected in series across a 230-V source. If lamp A is rated 75 watts and lamp B is rated 50 watts, determine the current drawn by the series connection. A. 0.52 A C. 0.48 A B. 0.64 A D. 0.57 A

ohms each are the equivalent 0.22 ohm 4.62 ohms ohms each are is the total 4.52 siemens 0.562 siemens

156. REE Board Exam March 1998 Two resistances of 10 and 15 ohms each respectively are connected in parallel. The two are then connected in series with a 5-ohm resistance. What is the equivalent resistance? A. 11 ohms C. 10 ohms B. 12 ohms D. 9 ohms 157. REE Board Exam October 1997 A 10-ohm and a 20-ohm resistance are connected in parallel. Another resistance of 5-ohm is connected in series with the two. If the supply voltage is 48 volts, what is the current through the 10-ohm resistor? A. 3.21 A C. 4.02 A B. 2.74 A D. 5.72 A 158. REE Board Exam March 1998 Two resistances of 10 and 15 ohms, each respectively are connected in parallel. The two are then connected in series with a 5-ohm resistance. It is then connected across a 12-V battery, what are the current and power? A. 1.2 A, 17.28 W C. 1.09 A, 13.1 W B. 0.96 A, 11.52 W D. 1.5 A, 20.25 W 159. REE Board Exam September 2001 Three resistors 10-Ω, 15-Ω and 20-Ω are connected in series across a 48-V source. What is the voltage across the 15-Ω resistor? A. 20 V C. 24 V B. 16 V D. 12 V 160. REE Board Exam September 2001 Three resistors 10-Ω, 15-Ω and 20-Ω are connected in parallel. What is the total resistance? A. 3.56 Ω C. 0.217 Ω B. 4.62 Ω D. 45 Ω

161. REE Board Exam September 2000 Two 10-Ω resistances are connected in parallel. The two are then connected in series with a 5-Ω resistance. It is then connected across a 24-volt battery; find the voltage across the 5-Ω resistor. A. 12 volts C. 9 volts B. 24 volts D. 15 volts 162. REE Board Exam April 1997 A circuit consists of three resistors rated 3-Ω, 4-Ω and 5-Ω connected in parallel. If the circuit is connected to a battery which has an internal resistance of 0.2-Ω, what would be the current through the 4-Ω resistor? A. 2.04 A C. 2.4 A B. 4.8 A D. 3.0 A 163. REE Board Exam September 2000 How many abvolts in 1 volt? 8 A. 10 abvolts C. 1 abvolt -8 B. 10 abvolts D. 10 abvolt 164. REE Board Exam September 2003 A total current of 60 A is divided among 3 parallel branches having resistances of 10 Ω, 6 Ω and 12 Ω, respectively. What is the current that flows through the branch with 10 Ω resistance? A. 17.1 A C. 14.3 A B. 28.6 A D. 42.9 A 165. REE Board Exam October 2000 Two 10-ohm parallel resistors are connected in series with a 5-ohm resistor. The combination is then connected across a 24 volts battery. Find the voltage drop across the 5-ohm resistor. A. 6 V C. 12 V B. 18 V D. 20 V 166. ECE Board Exam November 1998 The theory of Ohm’s law is applied in a _____ circuit. A. linear C. trivalent B. exponential D. unilateral 167. ECE Board Exam April 2000 Refers to the most important components in controlling flow of electrons A. voltage, electromotive force and current B. reactance, current and resistance C. conductance, resistance and reactance D. voltage, resistance and current 168. ECE Board Exam November 1999 Which of the following is not a valid expression of ohm’s law? A. E = IR C. R = E/I B. R = PI D. I = E/R 169. ECE Board Exam November 2000 A simple electronic equipment which takes a 2 amperes current from a power source has a total load resistance of 100 ohms. How much power does it use?

A. B.

200 watts 100 watts

C. D.

400 watts 50 watts

170. ECE Board Exam November 1996 What do you expect when you use the two 20 kohms, 1 watt resistor in parallel instead of one 10 kohms, 1 watt? A. Provide lighter current B. Provide wider tolerance C. Provide more power D. Provide less power 171. ECE Board Exam November 1999 The total resistance of a two similar wire conductors connected in parallel is ______ A. same resistance of one wire B. double the resistance of one wire C. one half the resistance of one wire D. resistance of one wire multiplied by 4 172. ECE Board Exam March 1996 When you increase the resistance in a circuit, the flow of electrons will ______. A. be constant C. be stopped B. flow faster D. be decreased 173. ECE Board Exam April 2001 Which of the following allows more current if applied to the same voltage? A. 0.002 siemen C. 0.004 siemen B. 25 ohms D. 2.5 ohms 174. ECE Board Exam April 1998 Ohm’s law refers to _____. A. power is directly proportional to both voltage squared and the resistance B. power is directly proportional to the resistance and inversely as the current squared C. current varies directly as the voltage and inversely as the resistance D. current is directly proportional to both voltage and resistance 175. ECE Board Exam November 2000 A circuit which a break exists in the complete conduction pathway A. Open circuit C. Close circuit B. Short circuit D. Circuit 176. ECE Board Exam November 1997 How much is the equivalent power in watts can a 3 horse power provide? A. 3000 watts C. 1492 watts B. 248.66 watts D. 2238 watts 177. ECE Board Exam March 1996 The current needed to operate a soldering iron which has a rating of 600 watts at 110 volts is A. 18,200 A C. 66,000 A B. 0.182 A D. 5.455 A

178. ECE Board Exam November 1997 Find the power across the resistor of 5 ohms delivered from a battery of an internal resistance of 3 ohms and a constant emf of 4 volts. A. 120 watts C. 60 watts B. 100 watts D. 1.25 watts 179. ECE Board Exam April 2000 A series circuit in which desired portions of the source voltage may be tapped off for use equipment. A. Voltage trap B. Voltage selector C. Voltage divider D. Dividing network 180. ECE Board Exam April 1998 An electronic device draws 300 watts from its 24 volt power source. Find effective resistance. A. 1.25 Ω C. 19.20 Ω B. 1.92 Ω D. 12.50 Ω 181. ECE Board Exam November 1997 How much power does an electronic equipment consume, assuming a 5.50 amperes current flowing and a 120 volts power source? A. 125.5 watts C. 660 watts B. 66 watts D. 60 watts 182. ECE Board Exam March 1996 What type of circuit whose parameters are constant which do not change with voltage or current? A. Tuned circuit C. Reactive circuit B. Linear circuit D. Lumped circuit 183. ECE Board Exam April 2000 If three circuits, each with a value of 560 ohms are connected in parallel, what is the total resistance of the combination? A. 1680 ohms C. 18567 ohms B. 560 ohms D. 187 0hms 184. ECE Board Exam November 1997 Other factors remaining constant, what would be the effect on the current flow in a given circuit if the applied potential were doubled? A. It would double B. It would increase 4 times C. It would remain the same D. It would be decrease by ½ 185. ECE Board Exam April 1999 Find used power of a circuit whose power source supplies 20 volts and a load resistance of 200 ohms. A. 1 watt C. 10 watts B. 4 kilowatts D. 2 watts 186. ECE Board Exam April 1998 When resistors are connected in series, what happens? A. Nothing

B. C. D.

The tolerance is decreased The effective resistance is decreased The effective resistance is increased

187. ECE Board Exam November 1999 A condition in which the heat in of around the circuit increases beyond or to a higher than normal level. A. Excessive heat condition B. Open condition C. Direct short D. Grounded 188. ECE Board Exam November 1999 A 33 kilo ohms resistor is connected in a series parallel combination made up of a 56 kilo ohm resistor and a 7.8 kilo ohm resistor. What is the total combined resistance of these three resistors? A. 39067 ohms C. 63769 ohms B. 49069 ohms D. 95800 ohms 189. ECE Board Exam April 2001 If 3,300 ohms resistor and a are connected in series, resistance? A. 18,700 ohms B. 25,300 ohms

22,000 ohms resistor what is the total C. D.

5,500 ohms 2,870 ohms

190. ECE Board Exam November 2000 A device that draws current A. Source C. Load B. No load D. Shunt 191. ECE Board Exam April 1998 With the same voltage applied which of the following allows more current? A. 25 ohms C. 2.5 ohms B. 250 ohms D. 0.25 ohms 192. ECE Board Exam April 1998 If 12 V are applied to a circuit that consumes 78 W, what is the current flow through the circuits? A. 6.5 A C. 0.15 A B. 936 A D. 9.36 A 193. ECE Board Exam April 1998 Find the current that flows through the filament of a 400 watt flat iron connected to a 220 volt power line. A. 50 mA C. 5 mA B. 500 mA D. 5 A 194. Four equal resistances are connected in parallel across a certain supply producing P power. How much power will be produced if the resistances are now connected in series across the same supply? A. 16P C. 4P B. P/16 D. P/4 195. A resistor R is connected across a 120 V supply. A voltmeter of 10,000 ohms resistance is connected between the center of the resistor and one side of the supply and reads 40 V. What is the value of the resistance R? A. 10,000  C. 30,000 

B.

20,000 

D.

196. A 240 V motor requiring 2,000 W is located 1 km from a power source. What diameter of copper wire is to be used if the power loss is to be kept 5%? A. 0.49 cm C. 0.39 cm B. 0.54 cm D. 0.35 cm 197. Three resistors of 10, 12 and “x” ohms, respectively are connected in parallel across a constant current source of 8 A. Determine “x” if this resistor draws 2.5 A. A. 10 Ω C. 13 Ω B. 12 Ω D. 11 Ω 198. An arc lamp takes 10 A at 50 volts. A resistance R is to be place in series so that the lamp my burn correctly from a 110 V supply. Find the power wasted in this resistor. A. 800 watts C. 700 watts B. 600 watts D. 900 watts 199. A 20  and 10  resistors are connected in parallel and a 5  resistor is connected in series with the parallel combination. The circuit is connected across a 48 V source with an internal resistance of 0.2 . Calculate the current through the 5  resistor. A. 5.57 amperes C. 3.58 amperes B. 4.04 amperes D. 7.63 amperes

205. The hot resistance of an incandescent lamp is about ____ its cold resistance. A. 10 times C. 100 times B. 2 times D. 50 times 206. A d.c. circuit usually has ____ as the load. A. resistance B. inductance C. capacitance D. both inductance and capacitance 207. The purpose of load in an electric circuit is to ____. A. increase the circuit current B. utilize electrical energy C. decrease the circuit current D. none of the above 208. Electrical appliances are not connected in series because ____ A. series circuit is complicated B. appliances have different current rating C. power loss is more D. none of the above 209. Electrical appliances are connected in parallel because it ____ A. is a simple circuit B. draws less current C. results in reduce in power loss D. makes the operation of appliances independent of each other

200. A variable resistor R is connected in parallel with a fixed resistor of 1.25 ohms. The combination is then connected across a 12 V battery with internal resistance of 0.25 Ω. Solve for the maximum power that can delivered to R. A. 130.20 W C. 120.21 W B. 115.52 W D. 142.42 W

210. Inductance and capacitance are not relevant in a d.c. circuit because ____ A. frequency of d.c. is zero B. it is a simple circuit C. they do not exist in a d.c. circuit D. none of the above

201. The hot resistance of an incandescent lamp is 10 ohms and the rated voltage is 50 V. Find the series resistance required to operate the lamp from an 80 V supply. A. 8  C. 6  B. 4  D. 10 

211. The hot resistance of a 100 watt, 250 V incandescent lamp would be A. 2.5 ohms B. 625 ohms C. 25 ohms D. none of the above

202. Ohm’s law is not applicable to A. copper B. silver C. silicon carbide D. aluminum 203. The practical unit of electrical energy is A. watt B. kilowatt C. kilowatt-hour D. megawatt 204. A 100 watt lamp working for 20 hours will consume ____ units. A. 200 C. 2 B. 20 D. 5

212. The voltage drop across 14.5 ohm resistor in Fig. 2.1 is ____. 14.5 Ω

25.5 Ω +

200 V

60 Ω -

Fig. 2.1

A. B.

29 V 14 V

C. D.

30.5 V 18 V

213. The circuit shown in Fig. 2.1 is called a series circuit because ____

14.5 Ω

25.5 Ω +

60 Ω

4 ohms 6 ohms

C. D.

3 ohms 9 ohms

219. The current in 2.5 ohm resistor in Fig. 2.4 will be ____

-

200 V

A. B.

2.5 Ω

Fig. 2.1

7A

A. B.

it contains a few resistances it carries the same current throughout the circuit C. it is a simple circuit D. none of the above Referring to Fig. 2.2, the total circuit resistance will be ____ 214. 100 W, 200 V 40 W, 200 V

4.5 Ω Fig. 2.4

A. B.

3A 4.5 A

C. D.

2.5 A 2A

220. The current in 4.5 ohms resistor in Fig. 1.4 will be ____. 2.5 Ω 7A

Lamp A +

Lamp B 200 V

Fig. 2.4

Fig. 2.2

A. B.

1000 ohms 400 ohms

C. D.

215. In Fig. 2.2 ____ 100 W, 200 V

+

1400 ohms 135 ohms

40 W, 200 V

Lamp A

Lamp B 200 V

-

Fig. 2.2

A. B. C. D.

4.5 Ω

-

the lamp A will be brighter than lamp B the lamp B will be brighter than lamp A the two lamps will be equally bright none of the above

A. B.

3.5 A 3A

218. The value of R that will give a total resistance of 1.5 ohms in Fig. 2.3 is ____ 3Ω

222. Two incandescent lamps of 100 W, 200 V are in parallel across 200 V supply. The total resistance will be ____. A. 800 ohms C. 400 ohms B. 200 ohms D. 600 ohms 223. The resistance across the terminals AB of the circuit shown in Fig. 2.5 is ____ A 18 Ω

12 Ω 6Ω

B

C

Fig. 2.5

A. B.

36 ohms 18 ohms

C. D.

9 ohms 15 ohms

224. If a d.c. supply of 180 V is connected across terminals AB in Fig. 2.5, then current in 6 ohm resistor will be ____. A 18 Ω

R

12 Ω 6Ω

B

Fig. 2.3

2A 2.5 A

221. If 18 resistances, each of value 36 ohms, are connected in parallel, then the total resistance is ____ A. 2 ohms B. 54 ohms C. 36 ohms D. none of the above

216. When a number of resistances are connected in parallel, the total resistance is ____ A. less than the smaller resistance B. greater than the smaller resistance C. between the smaller and greatest resistance D. none of the above 217. Two resistances of 6 ohms and 3 ohms are connected in parallel. The total resistance is ____ A. 9 ohms C. 0.5 ohm B. 18 ohms D. 2 ohms

C. D.

Fig. 2.5

C

A. B.

10 A 5A

C. D.

12 A 6A

A 12 Ω 6Ω B

C

36 ohms 9 ohms

C. D.

6Ω

4Ω

Fig. 2.6

6 mhos 2.5 mhos

10 Ω

Fig. 2.7

A. B.

3 mhos 6 mhos

C. D.

2 mhos 1.5 mhos

2.5 Ω

4Ω

15 A

10 Ω

34 ohms 8 ohms

227. If a battery of 24 V is applied across terminals AB of the circuit shown in Fig. 2.6, then current in 2 ohm resistor will be ____ 5Ω 2Ω A 6Ω

2Ω

1Ω

2Ω

C. D.

8Ω

C. D.

231. The voltage across the parallel circuit shown in Fig. 2.8 is ____

B

4 ohms 18 ohms

13 mhos 1.6 mhos

18 ohms 8 ohms

226. The resistance across terminals AB of the circuit shown in Fig. 2.6 is ____ 5Ω 2Ω A 8Ω

A. B.

230. If 10 ohms resistance is removed in Fig. 2.7, then total conductance of the circuit will be ____

Fig. 2.5

A. B.

10 Ω

Fig. 2.7

18 Ω

A. B.

2Ω

1Ω

225. The resistance across terminals AC in Fig. 2.5 is ____

Fig. 2.8

A. B.

15 V 10 V

C. D.

30 V 12. 5 V

232. The current in 10 ohms resistor in Fig. 2.8 is ____

B

2.5 A 1.5 A

228. If a battery of 24 V is applied across terminals AB in Fig. 2.6, then power loss in 5 ohms resistor will be ____ 5Ω 2Ω A 8Ω

6Ω

4Ω

Fig. 2.8

A. B.

3A 2.5 A

C. D.

2Ω

2Ω

Fig. 2.6

180 W 45 W

C. D.

1

90 W 24 W

229. The total conductance of the circuit shown in Fig. 2.7 is ____

1.5 A 3.5 A

233. The total resistance between terminals 1 and 2 of the circuit shown in Fig. 2.9 is ____

B

A. B.

2.5 Ω

15 A

C. D.

2Ω

3A 6A

10 Ω

Fig. 2.6

A. B.

4Ω

2

Fig. 2.9

A. B.

12 ohms 2.67 ohms

C. D.

2 ohms 64 ohms

234. If a battery of 12 V is applied across terminals 1 and 2 of Fig. 1.9, then current through 4 ohms resistor will be ____

2Ω

2Ω 4Ω

1

2

Fig. 1.9

A. B.

1.5 A 3A

C. D.

2A 2.5 A

239. Two equal resistances are connected in series across a certain supply. If the resistances are now connected in parallel across the same supply, the power produced will be ____ that of series connection. A. two times C. one-half B. four times D. one-fourth 240. Referring to Fig. 1.13, the resistance across terminals BE is ____

235. The resistance between terminals 1 and 2 of Fig. 1.10 is ____ 2Ω

13 Ω

A

72

12 ohms 8 ohms

F

C. D.

16 ohms 3 ohms

236. The resistance between terminals 1 and 2 in Fig. 1.11 is ____ 1Ω

A. B. C. D.

241. Referring to Fig. 1.13, the resistance across terminals AF is ____ 13 Ω

Ω

72

1Ω

11 Ω

B

18 Ω

Ω

2

44 V

6Ω

14

2Ω

C

Ω

2

1

D

9Ω

9 ohms 18 ohms 10 ohms none of the above

A

1Ω

E Fig. 1.13

Fig. 1.10

A. B.

Ω

2Ω 2

6Ω

6Ω

14

2Ω 1

C

18 Ω

Ω

44 V

11 Ω

B

Fig. 1.11

A. B.

2 ohms 1.5 ohms

C. D.

1 ohm 4 ohms

237. If a battery of 6 V is applied across terminals 1 and 2 in Fig. 1.11, then current in the horizontal 2 ohm resistor will be ____ 1Ω 2

1

Ω

1Ω

F

E

A. B. C. D.

20.5 ohms 18 ohms 11 ohms none of the above

242. Referring to Fig. 1.13, the current in 18 ohms resistor will be ___ 1Ω

A

13 Ω

2Ω

72

14

3A 0.5 A

238. The resistance across terminals 1 and 2 in Fig. 1.12 is ____ 2

A. B.

6 ohms 12 ohms

Ω

1Ω

6Ω

Ω

44 V

C. D.

1

C

18 Ω

Ω

1A 2A

11 Ω

B

2

Fig. 1.11

A. B.

D

9Ω

Fig. 1.13

1Ω 2

2Ω

C. D.

18 ohms 24 ohms

F

E

9Ω

D

Fig. 1.13

A. B. C. D.

2A 1.5 A 1A none of the above

243. Referring to Fig. 1.13, the power loss in 11 ohms will be ____

A

13 Ω

11 Ω

B

72

S1

40 W, 200 V L1

18 Ω

Ω

100 W, 200 V L2

S2

6Ω

L3

14

Ω

44 V

C

F

E

9Ω

100 W, 200 V + 200 V -

D

Fig. 1.14

Fig. 1.13

A. B. C. D.

A. B. C. D.

11 W 24 W 16 W none of the above

244. If in Fig. 1.14, switches S1 and S2 are closed, then total circuit resistance is ____ 40 W, 200 V L1

S1

248. If in Fig. 1.14 switches S1 and S2 are closed and the supply voltage is increased to 400 V, then ____

100 W, 200 V L2

S2

less than 40 W more than 40 W equal to 40 W none of the above

S1

40 W, 200 V L1

S2

L3

Fig. 1.14

Fig. 1.14

400 ohms 1200 ohms

C. D.

1000 ohms 2400 ohms

245. If switch S1 is open and switch S2 is closed in Fig. 1.14, then circuit resistance will be ____ 40 W, 200 V L1

S1

L3

100 W, 200 V + 200 V -

100 W, 200 V + 200 V -

A. B.

100 W, 200 V L2

100 W, 200 V L2

A. B. C. D.

lamp L1 will burn out lamp L2 will burn out both lamps L2 and L3 will burn out all the lamps will be safe

249. If in Fig. 1.1, resistor R2 becomes open-circuited, the reading of the voltmeter will become V

S2

L3

100 W, 200 V + 200 V -

R1

R2

R3

R4

20 Ω

20 Ω

20 Ω

20 Ω

Fig. 1.14

A. B.

1200 ohms 1000 ohms

C. D.

1400 ohms 2400 ohms

246. If in Fig. 1.14, both switches S1 and S2 are closed, then ____ 40 W, 200 V L1

S1

100 W, 200 V L2

S2

L3

200 V

Figure 1.1 A. B.

zero 150 V

C. D.

250. Whatever the battery voltage in Fig. 1.2, it is certain that smallest current will flow in the resistance of ____ ohm. 300 Ω

100 W, 200 V + 200 V -

500 Ω

Fig. 1.14

A. B. C. D.

50 V 200 V

L1 will be brighter than L2 or L3 L1 will be dimmer than L2 or L3 L1 will be as bright as L2 or L3 none of the above

100 Ω 200 Ω

247. If in Fig. 1.14 switches S1 and S2 are open, then lamp L1 will give output ____

Figure 1.2 A. B.

300 500

C. D.

200 100

4Ω

251. Which of the following statement is TRUE both for a series and parallel d.c circuit? A. powers are additive B. voltages are additive C. current additive D. elements have individual currents 252. A 100-W, 110-V and a 50-W lamp are connected in series across a 220-V dc source. If the resistances of the two lamps are assumed to remain constant, the voltage across the 100-W lamp is ____ volt. A. 110 C. 146.7 B. 73.3 D. 220

24 V 3 Ω

A. B. C. D.

6Ω

Figure 1.6 the 3  resistor is short circuited the 6  resistor is short circuited nothing is wrong with the circuit the 3  resistor is open-circuited

257. With reference to Fig 1.7, which of the following statement is true? R3

R1

253. In the parallel circuit of Fig.1.3, the value of V0 is ____ volt. 2Ω VO

E

R2

2Ω 12 V

12 V

A. B. C. D.

Figure 1.3 A. B.

12 24

C. D.

0 -12

254. In the series circuit of Fig 1.4, the value of V0 is ____ volt. 2Ω

Figure 1.7 E and R1 form a series circuit R1 is in series with R3 R1 is in series with R2 there is no series circuit

258. Which of the following statements is correct concerning the Fig. 1.8? R2

VO

R1 12 V

2Ω

Figure 1.4 A. B.

12 -12

C. D.

0 6

255. In Fig 1.5, there is a drop of 20 V on each resistor. The potential of point A would be ____ volt. A

B

80 V

A. B. C. D.

Figure 1.8 R2 and R3 form a series of path E is in series with R1 R1 is in parallel in R3 R1, R2 and R3 form a series of circuit

259. What is the equivalent resistance in ohms between points A and B of Fig. 1.9? All resistances are in ohms A 12 Ω

G

D

6Ω

4Ω B

C

Figure 1.5 A. B.

+80 -40

R3

E

C. D.

+40 -80

256. From the voltmeter reading of Fig. 1.6, is it obvious that

Figure 1.9 A. B.

12 14.4

C. D.

22 2

260. What do you call a resistor that does not obey Ohm’s Law? A. Potentiometer B. Carbon-Film Resistor C. Wire-Wound Type

D.

Non-linear Resistor

B.

261. A 100 W, 110 V and 50 W, 110 V lamps are connected in series across a 220 V DC source. If the resistances of the two lamps are assumed to remain constant, the voltage across the 100 W lamp is _____ volt? A. 110 V C. 146.7 V B. 73.3 V D. 220 V 262. A potential divider of resistance of 50 ohms is connected across a 100 V DC source. A load resistance of 10 ohms is connected across a tap in the potential divider and the negative terminal of the source. If a current of 4 A flows towards the load, what is the current supplied by the source? A. 5.32 A C. 5.21 A B. 5.05 A D. 5.48 A 263. Two resistors A and B made of different materials have temperature coefficients of resistance at 20C of 0.004 and 0.006 respectively. When connected across a voltage source at 20C, they draw current equally. What percentage of the total current at 100C does resistor A carry? A. 47.14% C. 61.34% B. 52.86% D. 38.66% 264. A conductor has a resistance 20C, the resistance has Calculate the temperature conductor at 20C. A. 1/300 /°C B. 1/400 /°C

of 7 ohms at 0C. At become 7.5 ohms. coefficient of the C. D.

1/500 /°C 1/600 /°C

265. Which of the following is a non-linear element? A. diode B. heater coil C. transistor D. electric arc with unlike electrode C. ELECTRICAL AND HEAT ENERGY 266. EE Board Exam April 1992 An electric kettle was marked 500 W, 230 V found to take 15 minutes to bring 1 kilogram of water at 15°C to boiling point. Determine the heat efficiency of the kettle. A. 79.1% C. 72.4% B. 75.3% D. 74.8% 267. REE Board Exam October 1997 A process equipment contains 100 gallons of water at 25°C. It is required to bring it to boiling in 10 minutes. The heat loss is estimated to be 5%. What is the kW rating of the heater? A. 125 kW C. 50.5 kW B. 252 kW D. 207 kW 268. EE October 1989 A total of 0.8 kg of water at 20°C is placed in a 1-kW electric kettle. How long a time in minute is needed to raise the temperature of the water to 100°C? A. 4.46 min C. 5.34 min

5.32 min

D.

4,.56 min

269. REE October 1998 How many calories does an electric heater of 100 watts generate per second? A. 10 C. 23.88 B. 1000 D. 42.25 270. REE Board Exam October 1997 The electric energy required to raise the temperature of water in a pool is 1000 kWh. If the heat losses are 25%, the heating energy required will be ____. A. 1111 kWh C. 1750 kWh B. 1266 kWh D. 1333 kWh 271. EE Board Exam April 1992 An electric heater carries 12 A at 110 V, is submerged in 22.5 lbs of water for 30 minutes. What will be the final temperature of the water if its initial temperature is 35°F? A. 135.43°F C. 133.56°F B. 125.42°F D. 128.33°F 272. EE Board Exam October 1990 In an electric heater the inlet temperature is 15°C. Water is flowing at the rate of 300 grams per minute. The voltmeter measuring voltage across the heating element reads 120 volts and an ammeter measuring current taken reads 10 amperes. When steady state is finally reached, what is the final reading of the outlet thermometer? A. 57.6°C C. 72.6°C B. 68.4°C D. 42.6°C 273. EE Board Exam October 1991 Four cubic meters of water is to be heated by means of four 1.5 kW, 230-V immersion heating elements. Assuming the efficiency of the heater as 90%, determine the time required in boiling the water if the initial temperature is 20°C and if all four elements are connected in parallel. A. 71 hrs C. 69 hrs B. 63 hrs D. 66 hrs 274. EE Board Exam October 1991 Four cubic meters of water is to be heated by means of four 1.5 kW, 230-V immersion heating elements. Assuming the efficiency of the heater as 90%, determine the time required in boiling the water if the initial temperature is 20°C and if the elements are connected two in series in parallel with two in series. A. 275.6 hrs C. 252.2 hrs B. 295.3 hrs D. 264.4 hrs 275. REE Board Exam September 2001 How many joules per second are then in 10 watts? A. 10 C. 20 B. 5 D. 24.5 276. REE Board Exam September 2001 13 10 ergs/sec is equal to how many kilowatts?

A. B.

1,000 250

C. D.

100 10

277. REE Board Exam September 2000 What is 1 kW-hr in BTU? A. 4,186 C. 746 B. 3,413 D. 1,000 278. REE Board Exam October 1998 What is the work in ergs needed to raise a 10 g weight 100 m up? 5 7 A. 4.9 x 10 C. 98 x 10 7 7 B. 9.8 x 10 D. 1.96 x 10 279. REE Board Exam October 1999 The quantity of heat required to raise the temperature of water by 1°C. A. energy C. calorie B. specific heat D. BTU 280. REE Board Exam October 1999 When heat is transferred into any other form of energy or when other forms of energy are converted into heat, the total amount of energy is constant. This is known as A. First law of thermodynamics B. Boyle’s law C. Specific heat D. Isothermal expansion 281. REE Board Exam September 2002 12 What is 10 ergs/sec in kW? A. 100 kW C. 10 kW B. 1,000 kW D. 10,000 kW 282. REE Board Exam October 2000 An electric heater is used to heat up 600 grams of water. It takes 14 minutes to raise the temperature of water by 40°C. If the supply voltage is 220 volts, what is the power rating of the heater neglecting heat losses? A. 180 W C. 200 W B. 120 W D. 60 W 283. REE Board Exam April 2001 A 100 liter of water is heated How many kWHR of electricity no heat loss? A. 4.2 B. 2.3

from 20°C to 40°C. is needed assuming C. D.

5.6 3.7

284. REE Board Exam April 2002 Ten (10) kW is equal to ____ gram-cal/sec. A. 156 C. 2,388 B. 436 D. 425 285. ECE Board Exam November 1995 Two heaters A and B are in parallel across supply voltage V. Heater A produces 500 kcal in 20 minutes and B produces 1000 kcal in 10 minutes. The resistance of A is 10 ohms. What is the resistance of B, if the same heaters are connected in series voltage V?

A. B.

4.5 ohms 2.5 ohms

C. D.

4.5 ohms 0.14 ohm

286. In the SI system of units, the unit of force is A. kg-wt C. Joule B. Newton D. N-m 287. The basic unit of electric charge is A. ampere-hour C. coulomb B. watt-hour D. farad 288. The SI unit of energy is A. Joule B. kWh

C. D.

kcal m-kg

289. The SI unit of energy is A. Joule B. kWh

C. D.

kcal m-kg

290. Two heating elements, each of 230-V, 3.5 kW rating are first joined in parallel and then in series to heat same amount of water through the same range of temperature. The ratio of the time taken in the two cases would be A. 1:2 C. 1:4 B. 2:1 D. 4:1 291. If a 220 V heater is used on 110 V supply, heat produced by it will be ____ as much A. one-half C. one-fourth B. twice D. four times 292. For a given line voltage, four heating coils will produce maximum heat when connected A. all in parallel B. all in series C. with two parallel pairs in series D. one pair in parallel with the other two in series 293. The electric energy required to raise the temperature of a given amount of water is 1000 kWh. If heat losses are 25%, the total heating energy required is ____ kWh. A. 1500 C. 1333 B. 1250 D. 1000 294. One kWh of energy equals nearly A. 1000 W C. B. 860 kcal D.

4186 J 735.5 W

295. A force of 10,000 N accelerates a body to velocity 0.1 km/s. The power developed is ____ kW. A. 1,000,000 C. 3600 B. 36,000 D. 1000 296. A 100 W light bulb burns on an average of 10 hours a day for one week. The weekly consumption of energy will be ____ unit/s. A. 7 C. 0.7 B. 70 D. 0.07 297. Two heaters, rated at 1000 W, 250 volts each, are connected in series across a 250 volt, 50 Hz A.C.

mains. The total power drawn from the supply would be ____ watt. A. 1000 C. 250 B. 500 D. 2000 298. One watt is equal to ____. A. 4.19 cal/sec B. 778 BTU/sec

C. D.

7

10 ergs/sec -7 10 ergs/sec

299. The current in an electric lamp is 5 amperes. What quantity of electricity flows toward the filament in 6 minutes? A. 30 C C. 72 C B. 3600 C D. 1800 C 300. An electric heater is rated at 120 volts, 1000 watts and is used to boil water. Calculate the time in minutes to raise the temperature of 1 liter of water from 15°C to boiling. The heater has an over-all efficiency of 92%. A. 6.4 minutes C. 4.4 minutes B. 5.4 minutes D. 3.4 minutes 301. For a given line voltage, four heating coils will produce maximum heat when connected A. all in parallel B. all in series C. with two parallel pairs in series D. one pair in parallel with the other two in series 302. Four heaters having the same voltage rating will produce maximum heat if connected in A. Series C. Series-Parallel B. Parallel D. Parallel-Series 303. 1000 kW is equal to how many is ergs/sec. 13 13 A. 2 x 10 C. 1 x 10 16 10 B. 1 x 10 D. 2 x 10 304. When current flows through heater coil, it glows but supply wiring does not glow because A. supply wiring is covered with insulation wiring B. current through supply line flows at slower speed C. supply wires are made of superior material D. resistance of heater coil is more than that of supply wire

A. B.

174.5 ohms 145.7 ohms

C. D.

147.5 ohms 157.4 ohms

307. REE Board Exam April 1997 If a resistor rated at 5 watts and 6 volts are connected across a battery with an open circuit voltage of 6 volts. What is the internal resistance of the battery if the resulting current is 0.8 A? A. 0.30 ohm C. 0.23 ohm B. 0.26 ohm D. 0.03 ohm 308. REE Board Exam October 1998 A 12 V battery of 0.05-ohm resistance and another battery of 12 V and 0.075 ohm resistance supply power to a 2-ohm resistor. What is the current through the load? A. 5.85 A C. 5.72 A B. 5.63 A D. 5.91 A 309. REE Board Exam October 1996 The lead batteries “A” and “B” are connected in parallel. “A” has an open circuit voltage of 12 V and an internal resistance of 0.2 ohm. Battery “B” has an open circuit voltage of 12.2 V and an internal resistance of 0.3 ohm. The two batteries together deliver power to a 0.5 ohm power resistor. Neglecting effects of temperature, how much current is contributed by battery “A”? A. 29.62 A C. 12.85 A B. 16.00 A D. 25.24 A 310. EE Board Exam October 1981 A charger, a battery and a load are connected in parallel. The voltage across the charger is 12.5 volts and the battery has an emf of 12 volts and internal resistance of 0.1 ohm. The load consists of a 2 ohms resistor. Find the current through the charger. A. 6.61 A C. 6.42 A B. 6.25 A D. 6.50 A 311. REE Board Exam October 1996 A lead storage battery is rated at 12 volts. If the internal resistance is 0.01 ohm, what is the maximum power that can be delivered to the load? A. 1,200 W C. 7,200 W B. 3,600 W D. 1,800 W

D. ELECTRIC CELLS 305. REE Board Exam October 1997 A load of 10 ohms was connected to a 12-volt battery. The current drawn was 1.18 amperes. What is the internal resistance of the battery? A. 0.35 ohm C. 0.25 ohm B. 0.20 ohm D. 0.30 ohm

312. EE Board Exam April 1995 A 120-V battery having an internal resistance of 0.5 ohm is connected through a line resistance of 0.5 ohms to a variable load resistor. What maximum power will the battery deliver to the load resistor? A. 36 watts C. 630 watts B. 63 watts D. 360 watts

306. REE Board Exam April 1997 The electromotive force of a standard cell is measured with a potentiometer that gives a reading of 1.3562 V. When a 1.0 megaohm resistor is connected across the standard cell terminals, the potentiometer reading drops to 1.3560 V, what is the internal resistance of the standard cell?

313. REE Board Exam April 2002 A 12 volts battery has a 50 ampere-hour capacity. The internal resistance is 0.1 ohm. A 5 ohm load is connected for 5 hours. How many ampere-hours are still left? A. 28.51 C. 38.23 B. 41.24 D. 35.92

D. 314. REE Board Exam April 2002 Two-24 volt battery supply power to a 20 ohm load. One battery has 0.2 ohm internal resistance while the other has 0.4 ohm. What power does the load draws? A. 28.4 W C. 30.8 W B. 22.2 W D. 18.6 W 315. ECE Board Exam March 1996 Which statement is not true? A. Secondary cell can be recharged B. The internal resistance of a cell limits the amount of output current C. The negative terminal of a chemical cell has a charge of excess electrons D. Two electrodes of the same metal provide the highest voltage output 316. ECE Board Exam November 2001 In the operation of dry cell we normally refer to the supply of current load resistance where its current neutralizes the separated charges at the electrodes. A. Aligning the cells B. Charging the cells C. Discharging the cells D. Polarizing the cells 317. ECE Board Exam November 2000 Refers to a power source or cell which can be rechargeable A. Battery C. Primary B. Secondary D. Storage 318. ECE Board Exam November 2001 In the operation of dry cell we normally refer to the supply of current load resistance where its current neutralizes the separated charge s at the electrodes. A. Aligning the cells B. Charging the cells C. Discharging the cells D. Polarizing the cells 319. ECE Board Exam November 2000 The part of the cell of the solution that acts upon the electrodes providing a path for electron flow A. Container C. Sealing way B. Electrolyte D. Electrolysis 320. ECE Board Exam April 1999 Type of cell used mostly for emergency equipment. It is light, small, and has a large capacity of power for its size. A. Ni-Cd cell C. Silver-zinc cell B. Silver-cadmium cell D. Mercury cell 321. ECE Board Exam March 1996 The purpose of cells connected in parallel is to_____. A. increase internal resistance B. increase in voltage output C. decrease current capacity

increase in current capacity

322. ECE Board Exam November 1995 Find the output of a four (4) lead acid cells. A. 3.2 V C. 5.8 V B. 8.4 V D. 1.6 V 323. ECE Board Exam November 1997 How many silver zinc cells in series are needed for a 9V battery? A. 9 C. 3 B. 6 D. 7 324. ECE Board Exam November 1995 _____ is the specific gravity reading for a good lead acid cell. A. 1170 C. 1070 B. 1270 D. 1370 325. ECE Board Exam November 1998 Refers to a power source or cell that is not rechargeable? A. Secondary C. Storage B. Primary D. Battery 326. ECE Board Exam April 1998 Which of the following is not a primary type cell? A. Zinc-chloride C. Silver oxide B. Silver-zinc D. Carbon zinc 327. ECE Board Exam November 1997 A battery should not be charged or discharged at a high current in order to avoid this defect. A. Corrosion C. Buckling B. Sedimentation D. Sulphation 328. ECE Board Exam April 2001 It is a cell in which the chemical action finally destroys one of the electrons electrodes, usually the negative and cannot be recharged. A. Dry cell C. Wet cell B. Secondary cell D. Primary cell 329. ECE Board Exam November 2001 Which of the following statements is not true? A. Output of solar cell is normally 0.5 V B. Edison cell is storage type C. The Ni-Cd cell is primary type D. Primary cells can be charged 330. ECE Board Exam April 2001 Which of the following statements is not true? A. A primary cell has irreversible chemical reaction B. A carbon zinc cell has unlimited shelf life C. A storage cell has irreversible chemical reaction D. A lead acid cell can be recharged 331. ECE Board Exam November 1999 A device that transforms chemical energy into electrical energy A. Battery

B. C. D.

Cell Primary battery Secondary battery

332. ECE Board Exam April 1999 What is the effect of connecting battery cells in parallel? A. Current decreases B. Voltage increases C. Voltage decreases D. Current increases 333. ECE Board Exam November 1997 Determine how long a battery will last whose rating is 100 Ah, 24 volts and will run a 300 watts electronic equipment and a 50 watts light. A. 6.85 hours C. 26.65 hours B. 50.05 hours D. 12.00 hours 334. ECE Board Exam April 2001 The process of reversing the current flow through the battery to store the battery to its original condition A. Electrolysis C. Reverse flow B. Ionization D. Battery charge 335. ECE Board Exam November 2000 The type of cell commonly referred to as “flashlight battery” A. Nickel-cadmium battery C. Dry cell B. Mercury cell D. Lead acid cell 336. ECE Board Exam November 1998 How does a battery behave whose cells are connected in series? A. Increase current supply B. Reduces total voltage C. Increases voltage supply D. Reduces internal resistance 337. ECE Board Exam April 1998 Another very useful cell to solar cells however the junction is bombarded by beta particles from radioactive materials A. Alkaline cells C. Selenium cells B. Nucleus cells D. Lithium cells 338. ECE Board Exam November 2001 The continuation of current flow within the cell there is no external load A. Local action C. Self-discharge B. Polarization D. Electrolysis 339. ECE Board Exam November 1998 Type of power source in electronics that cannot be recharged after it has delivered its rated capacity A. Cells B. Primary cells C. Battery D. Secondary cells

340. ECE Board Exam November 1995 Which has the largest diameter of the following dry cells? A. Type C C. Type AAA B. Type AA D. Type D 341. ECE Board Exam April 1998 How many nickel-cadmium cells are needed in series for a 10 V battery? A. 8 C. 5 B. 12 D. 10 342. ECE Board Exam March 1996 Current in a chemical cell refers to the movement of _____. A. Negative ions only B. Negative and positive ions C. Positive ions only D. Negative hole charge 343. ECE Board Exam November 1998 Find the output of a two (2) lead acid cells. A. 0.952 V C. 3.2 V B. 2.1 V D. 4.2 V 344. ECE Board Exam November 2000 The liquid solution that forms ion charges in a lead acid battery A. Electrolyte C. Sulfuric acid B. Hydrochloric acid D. Nitric acid 345. ECE Board Exam April 1998 Single device that converts chemical energy into electrical energy is called A. Battery C. Solar B. Generator D. Cell 346. ECE Board Exam November 1995 There are _____ identical cells in parallel needed to double the current reading of each cells. A. 3 C. 2 B. 4 D. 1 347. ECE Board Exam April 2001 What is the effect of connecting battery cells in series? A. Voltage increases B. Current increases C. Voltage decreases D. Current decreases 348. ECE Board Exam November 2000 How long can a battery last with capacity of 50 ampere-hour running equipment of 5 amperes? A. 250 hours C. 100 hours B. 25 hours D. 10 hours 349. ECE Board Exam April 1998 How long will a battery need to operate a 240-watt equipment, whose capacity is 100 Ah and 24 volts rating? A. 10 hours C. 1 hour B. 5 hours D. 0.10 hour

D. 350. ECE Board Exam November 2001 What is affected when a lead battery overcharged? A. Carbon C. Plates B. Grid D. Electrolytes

is

351. ECE Board Exam November 1995 When the cells are in series voltages add, while current capacity is _____. A. The same as one cell B. Zero C. Infinite D. The sum of each cell 352. ECE Board Exam April 1999 Refers to an action in the operation of secondary cells reforming the electrodes in a chemical reaction where dc voltage is supplied externally. A. Polarizing cells B. Charging cells C. Aligning cells D. Discharging cells 353. ECE Board Exam November 1999 What type of cell that cannot be recharged which cannot restore chemical reaction? A. Primary cell B. Secondary cell C. Lead-acid wet cell D. Nickel-cadmium cell 354. ECE Board Exam November 2000 An ordinary flashlight battery is which of the following? A. A load C. A storage cell B. A dry cell D. A wet cell 355. ECE Board Exam April 1998 Refers to dry storage cell carbon zinc. A. cell B. Edison cell C. Mercury cell D. Nickel cadmium cell 356. ECE Board Exam April 1998 What is the other term of the secondary cells considering its capability to accept recharging? A. Reaction cell C. Storage cell B. Primary cell D. Dry cell 357. ECE Board Exam November 1996 Find the required battery capacity needed to operate an equipment of 30 amperes at 5 hours. A. 6 C. 3 B. 30 D. 150 358. ECE Board Exam March 1996 When batteries have cells connected in series the effect is A. Reduced output voltage B. Increased current supply C. Increased voltage supply

Reduced internal resistance

359. ECE Board Exam November 2000 Find the required battery capacity needed to operate on electronic equipment with power rating of 200 watts and 10 volts at 6 hours. A. 60 C. 20 B. 1200 D. 120 360. ECE Board Exam November 2000 A cell(s) that can be operated or used in a horizontal, vertical or any position where its electrolyte cannot be spilled in any position A. Primary cells C. Dry cells B. Secondary cells D. Battery 361. ECE Board Exam April 1999 It is an indication of the current supplying capability of the battery for a specific period of time, e.g. 400 ampere-hour. A. Rating C. Capability B. Capacity D. Current load 362. ECE Board Exam March 1996 Which of the following is not a secondary type cell? A. Lithium C. Silver cadmium B. Lead-acid D. Silver-zinc 363. ECE Board Exam March 1996 How many lithium cells in series are needed for a 12 V battery? A. 12 cells C. 8 cells B. 4 cells D. 10 cells 364. ECE Board Exam November 1996 Component of solar battery which uses light energy to produce electromagnetic force A. Alkaline cell C. Lithium cell B. Polymer cell D. Selenium cell 365. ECE Board Exam March 1996 If a dry cell has an internal resistance of 0.50 ohm and emf of 2 volts, find power delivered in a one ohm resistor. A. 1.33 watts C. 3.66 watts B. 1.66 watts D. 1.77 watts 366. ECE Board Exam March 1996 Parallel cells have the same voltage as one cell but have _____. A. Unstable resistance B. Less current capability C. Fluctuating power output D. More current capacity 367. ECE Board Exam April 1999 A battery with capacity of 100 Ah and 12 volts rating will run an electronic equipment at exactly 20 hours, how much power is needed? A. 60 watts C. 10 watts B. 20 watts D. 30 watts 368. ECE Board Exam March 1996

It is the output voltage of a carbon-zinc cell. A. 3.5 V C. 1.5 V B. 2.5 V D. 0.5 V 369. ECE Board Exam March 1996 What is the reason why more cells can be stored in a given area with dynamic cells? A. They consume less power B. They are smaller C. They are larger D. They travel faster 370. ECE Board Exam November 1997 A radio equipment will be used at 70% at 50 amperes rating for 5 hours. How much capacity of dry battery is needed? A. 35 C. 250 B. 17.5 D. 175 371. The potential at the terminals of the battery falls from 9 V on open circuit to 6 volts when a resistor of 10 ohms is connected across its terminals. What is the internal resistance of the battery? A. 5 Ω C. 3 Ω B. 4 Ω D. 2 Ω 372. A battery is formed of five cells joined in series. When the external resistance is 4 ohms, the current is 1.5 A and when the external resistance is 9 ohms, the current falls to 0.75 A. Find the internal resistance of each cell. A. 0.5 ohm C. 0.2 ohm B. 1.0 ohm D. 0.3 ohm 373. A 12 V source with 0.05  resistance is connected in series with another 12 volt with 0.075 Ω resistance with a load of 2 . Calculate the power dissipated in the load. A. 365 watts C. 105 watts B. 127 watts D. 255 watts 374. A 24 V source with 0.05  resistance is connected in parallel with another 24 V with 0.075  resistance to a load of 2 . Calculate the current delivered by the source with a 0.05  resistor. A. 7 amperes C. 5 amperes B. 10 amperes D. 12 amperes 375. A battery can deliver 10 joules of energy to move 5 coulombs of charge. What is the potential difference between the terminals of the battery? A. 2 V C. 0.5 V B. 50 V D. 5 V 376. An ordinary dry cell can deliver about ____ continuously. A. 3 A B. 2 A C. 1/8 A D. none of the above 377. Cells are connected in series when ____ is required.

A. B. C. D.

high voltage high current high voltage as well as high current none of the above

378. Cells are connected in series–parallel when ____ is required. A. high current B. high voltage C. high current as well a high voltage D. none of the above 379. Four cells, each of internal resistance 1 ohm, are connected in parallel. The battery resistance will be ____ A. 4 ohms C. 2 ohms B. 0.25 ohm D. 1 ohm 380. The e.m.f. of a cell depends upon ____ A. nature of electrodes and electrolyte B. size of electrodes C. spacing between electrodes D. none of the above 381. In order to get maximum current in series – parallel grouping, the external resistance should be ____ the total internal resistance of the battery. A. less than B. more than C. equal to D. none of the above 382. The positive terminal of a 6-V battery is connected to the negative terminal of a 12-V battery whose positive terminal is grounded. The potential at the negative terminal of the 6V battery is ____ volt. A. +18 C. -6 B. –12 D. -18 383. The positive terminal of a 6-V battery is connected to the negative terminal of a 12-V battery whose positive terminal is grounded. The potential at the positive terminal of the 6-V battery is ____ volt. A. +6 C. -12 B. -6 D. +12 384. Active materials of a lead-acid cell are A. lead peroxide B. sponge lead C. dilute sulfuric acid D. all of the above 385. During the charging of lead-acid cell A. its cathode becomes dark chocolate brown in colour B. its voltage increases C. it gives out energy D. specific gravity of H2SO4 is decreased 386. The ratio of Ah efficiency to Wh efficiency of a leadacid cell is A. always less than one B. just one

C. D.

always greater than one either A or B

387. The capacity of a cell is measured in A. watt-hours C. amperes B. watts D. ampere-hours 388. The capacity of a lead-acid cell does NOT depend on its A. rate of charge B. rate of discharge C. temperature D. quantity of active materials 389. As compared to constant-current system, the constant-voltage system of charging a lead-acid cell has the advantage of A. avoiding excessive gassing B. reducing time of charging C. increasing cell capacity D. both B and C 390. Sulphation in a lead-acid battery occurs due to A. trickle charging B. incomplete charging C. heavy discharging D. fast charging 391. The active materials of a nickel-iron battery are A. nickel hydroxide B. powdered iron and its oxides C. 21% solution of caustic potash D. all of the above 392. During charging and discharging of a nickel-iron cell A. its e.m.f. remains constant B. water is neither formed nor absorbed C. corrosive fumes are produced D. nickel hydroxide remains unsplit 393. As compared to a lead-acid cell, the efficiency of a nickel-iron cell is less due to its A. lower e.m.f. B. smaller quantity of electrolyte used C. higher internal resistance D. compactness 394. Trickle charging of a storage battery helps to A. prevent sulphation B. keep it fresh and fully charged C. maintain proper electrolyte level D. increase its reserve capacity 395. A dead storage battery can be revived by A. a dose of H2SO4 B. adding so-called battery restorer C. adding distilled water D. none of the above 396. The sediment which accumulates at the bottom of a lead-acid battery consist largely of A. lead-peroxide B. lead-sulphate

C. D.

antimony-lead alloy graphite

397. The reduction of battery capacity at high rates of discharge is primarily due to A. increase in its internal resistance B. decrease in its terminal voltage C. rapid formation of PbSO4 on the plates D. non-diffusion of acid to the inside active materials 398. Floating battery system are widely used for A. power stations B. emergency lighting C. telephone exchange installation D. all of the above 399. Any charge given to the battery when taken off the vehicle is called A. bench charge C. float charge B. step charge D. trickle charge 400. Storage battery electrolyte is formed by the dissolving of ____ acid in water. A. hydrochloric C. acetic B. sulfuric D. atric 401. The central terminal of a dry cell is said to be A. positive C. neutral B. negative D. charged 402. A 24 V battery of internal resistance r = 4 Ω is connected to a variable resistance R, the rate of heat dissipation in the resistor is maximum when the current drawn from the battery is I. Current drawn from the battery will be I/2 when R is equal to A. 8 Ω C. 16 Ω B. 12 Ω D. 20 Ω 403. What is the other term used for rechargeable battery? A. primary B. lead-acid C. storage D. nickel-cadmium E. NETWORK THEOREMS 404. REE Board Exam April 1997 A circuit consisting of three resistors rated: 10 ohms, 15 ohms and 20 ohms are connected in delta. What would be the resistance of the equivalent wye connected load? A. 0.30, 0.23 & 0.15 ohm B. 3.0, 4.0 & 5.0 ohms C. 3.33, 4.44 & 6.66 ohms D. 5.77, 8.66 & 11.55 ohms 405. EE Board Exam October 1994 The equivalent wye element of a 3 equal resistors each equal to R and connected in delta is A. R C. R/3 B. 3R/2 D. 3R

406. EE Board Exam April 1988 A Barangay power station supplies 60 kW to a load 2 over 2,500 ft, 100 mm , two-conductor copper feeder, the resistance of which is 0.078 ohm per 1000 ft. The bus bar voltage is maintained constant at 600 V. Determine the load current. A. 105 A C. 110 A B. 108 A D. 102 A 407. EE Board Exam October 1986 An LRT car, 5 km distance from the Tayuman station, takes 100 A over a 100 mm hard drawn copper trolley wire having a resistance of 0.270 ohm per km. The rail and ground return has a resistance of 0.06 ohm per km. If the station voltage is 750 V, what is the voltage of the car? A. 585 V C. 595 V B. 590 V D. 580 V 408. EE Board Exam April 1989 The LRT trolley system 10 miles long is fed by two substations that generate 600 volts and 560 volts, respectively. The resistance of the trolley wire and rail return is 0.3 ohm per mile. If the car is located 4 miles from the 600 volt station draws 200 A from the line. How much is the current supplied by each station? A. 133.33 A, 66.67 A B. 123.67 A, 76.33 A C. 117.44 A, 82.56 A D. 125.54 A, 63.05 A 409. EE Board Exam April 1992 In Manila, the LRT runs between Gil Puyat Station and Tayuman Station, which is 4 km apart and maintains voltages of 420 volts and 410 volts respectively. The resistance of go and return is 0.05 ohm per km. The train draws a constant current of 300 A while in motion. What are the currents supplied by the two stations if the train is at the distance of minimum potential? A. 175 A, 125 A C. 164 A, 136 A B. 183 A, 117 A D. 172 A, 123 A 410. EE Board Exam October 1986 An LRT car, 5 km distance from the Tayuman station, takes 100 A over a 100 mm hard drawn copper trolley wire having a resistance of 0.270 ohm per km. The rail and ground return has a resistance of 0.06 ohm per km. If the station voltage is 750 V, what is the efficiency of transmission? A. 78% C. 74% B. 81% D. 79% 411. EE Board Exam April 1988 A barangay power station supplies 60 kW to a load over 2,500 ft of 0002-conductor copper feeder the resistance of which is 0.078 ohm per 1,000 ft. The bus bar voltage is maintained constant at 600 volts. Determine the maximum power which can be transmitted. A. 220.35 kW C. 242.73 kW B. 230.77 kW D. 223.94 kW

412. EE Board Exam April 1991 Twelve similar wires each of resistance 2 ohms are connected so as to form a cube. Find the resistance between the two diagonally opposite corners. A. 1.45 ohms C. 2.01 ohms B. 1.66 ohms D. 1.28 ohms 413. EE Board Exam April 1991 Twelve similar wires each of resistance 2 ohms are connected so as to form a cube. Find the resistance between the two corners of the same edge. A. 1.133 ohms C. 1.125 ohms B. 1.102 ohms D. 1.167 ohms 414. EE Board Exam October 1991 Twelve identical wires each of resistance 6 ohms are arranged to form the edge of a cube. A current of 40 mA is led into the cube at one corner and out at the other diagonally opposite corners. Calculate the potential difference developed between these corners. A. 0.20 V C. 0.22 V B. 0.28 V D. 0.24 V 415. EE Board Exam August 1976 Find the value of the voltage V. 1Ω

0.1 Ω

+ 24 V

Lamp 60 W 12 V

4Ω

V 12 V

G

-

A. B.

12.34 V 11.24 V

C. D.

12.19 V 11.66 V

416. EE Board Exam April 1982 Referring to the circuit diagram below, if the charger voltage is 130 volts and the battery voltage is 120 volts, solve for the current Ib. 3Ω +

Battery Charger

A. B.

Ib

2Ω

40 Ω Battery

-

-0.215 A 0.215 A

C. D.

-0.306 A 0.306 A

417. EE Board Exam August 1977 In the figure below R1 = 1 ohm, R2 = 1 ohm, R3 = 3 ohms, I2 = 2 A and VB = 120 V. Find Eg. R1

R2

I2 R3

+ Eg

G

-

VB

A. B.

182.41 V 153.32 V

C. D.

164.67 V 157.22 V

418. EE Board Exam October 1980, April 1984 In the dc circuit as shown, the high resistance voltmeter gives a reading of 0.435 volt. What is the value of the resistance R?

12 V

10 Ω

R

+

+

20 Ω

A. B.

V

-

50 Ω

4 ohms 5 ohms

C. D.

3 ohms 2 ohms

419. EE Board Exam April 1980 Determine I in the figure. 20 Ω

10 Ω 50 Ω

12 V 40 Ω

A. B.

I

0.028 A 0.010 A

30 Ω

C. D.

0.025 A 0.014 A

420. ECE Board Exam April 1999 In Kirchhoff’s current law, which terminal of a resistance element is assumed to be at a higher potential (more positive) than the other? A. The terminal where the current exits the resistance elements B. The terminal where the current enters the resistance elements C. Either A or B can be arbitrarily selected D. The terminal closest to the node being analyzed 421. ECE Board Exam April 2000 According to Kichhoff’s current law, what is the algebraic sum of all currents entering and exiting a node. A. zero B. a negative value C. the algebraic sum of all currents D. a positive value 422. ECE Board Exam November 1997 Find the Thevenin’s impedance equivalent across R2 of a linear close circuit having 10 volts supply in series with the resistors (R1 = 100 ohms and R2 = 200 ohms). A. 6.66 ohms C. 66.6 ohms B. 6.666 kohms D. 666 ohms 423. ECE Board Exam April 1999 What is a node?

A. B. C. D.

A terminal point for a loop current A connection point between two or more conductors A formula A mathematical fiction

424. ECE Board Exam November 1998 If a resistance element is part of two loops, how many voltage drops must be calculated for that component? A. Two C. One B. Three D. None 425. ECE Board Exam April 1998 How many nodes are needed to completely analyze a circuit according to Kirchhoff’s current law? A. One B. Two C. One less than the total number of nodes in the circuit D. All nodes in the circuit 426. ECE Board Exam November 1996 Find the Thevenin’s impedance equivalent across R2 of a linear close circuit having 10 volt supply in series with two resistors (R1=50 ohms and R2 = 200 ohms). A. 400 ohms C. 4 ohms B. 40 ohms D. 4 kohms 427. ECE Board Exam November 1995 In order to match the load to the generator means making load resistance ______. A. lower than generator’s internal resistance B. increased to more generator’s internal resistance C. decreased D. equal to generator’s internal resistance 428. A circuit contains a 5 A current source in parallel with an 8 ohm resistor. What is the Thevenin’s voltage and Thevenin’s resistance of the circuit? A. 40 V, 8  C. 5 V, 8  B. 5/8 V, 40  D. 5/8 V, 8  429. In the Norton’s equivalent circuit, the source is a A. constant voltage source B. constant current source C. constant voltage, constant current D. none of these 430. The superposition theorem requires as many circuits to be solved as there are A. meshes B. source C. nodes D. all of the above 431. Three resistors of 6-ohm resistance are connected in delta. Inside the delta another 6-ohm resistors are connected in wye. Find its resistance between any two corners. A. 2 ohms C. 4 ohms

B.

3 ohms

D.

1 ohm

432. A 2-wire dc distribution line has sending end voltage of 240 V and total line resistance of 0.4 ohm. The maximum kW that can be transmitted by the line is ____. A. 108 C. 36 B. 72 D. 144 433. An active element in a circuit is one which ____. A. receives energy B. supplies energy C. both receives and supplies energy D. none of the above

437. In the circuit shown in Fig. 3.1, the number of nodes is ____

E1

C E2

R2 D Fig. 3.1

A. B.

one two

C. D.

two four three none of the above

440. The circuit shown in Fig. 3.1 has ____ loops.

R1

R3

E1

R2 D

R3

E1

C E2

R2 D

two four three none of the above

441. In the circuit shown in Fig. 3.1, there are ___ meshes.

three four two none of the above

439. The circuit shown in Fig. 3.1 has ____ branches.

C E2

R2 D Fig. 3.1

A. B. C. D.

two three four none of the above

442. To solve the circuit shown in Fig. 3.2 by Kirchhoff’s laws, we require ____ 3Ω 4Ω

I1 I3

2Ω

I2

40 V

Fig. 3.2 A. B.

E2

R3

E1

35 V

C

R1

A

three four

Fig. 3.1 A. B. C. D.

R1

A

438. In the circuit shown in Fig. 3.1, there are ____ junctions.

A

E2

R2 D Fig. 3.1

A. B. C. D.

A. B. C. D.

436. A linear circuit is one whose parameters (e.g. resistances etc.) ____. A. change with change in current B. change with change in voltage C. do not change with change in voltage and current D. none of the above

R3

C

Fig. 3.1

435. An electric circuit contains ____. A. active elements only B. passive element only C. both active and passive elements D. none of the above

R1

R3

E1

434. An passive element in a circuit is one which ____. A. supplies energy B. receives energy C. both receives and supplies energy D. none of the above

A

R1

A

one equation two equations

C. D.

three equations four equations

443. To solve the circuit shown in Fig. 3.2 by nodal analysis, we require ____ 3Ω 4Ω

35 V

I1 I3

2Ω Fig. 3.2

I2

40 V

A. B. C. D.

one equation two equation three equations none of the above

448. In order to solve the circuit shown in Fig. 3.3 by nodal analysis, we require 3Ω B 2Ω

35 V

A. B. C. D.

I1 I3

2Ω

I2

40 V

Fig. 3.2 one circuit two circuits three circuits none of the above

445. To solve the circuit shown in Fig. 3.2 by Maxwell’s mesh current equation, we require 3Ω 4Ω

35 V

I1 I3

2Ω

I2

A. B. C. D.

450. Fig. 3.4(b) shows the Thevenin’s equivalent circuit of Fig. 3.4(a). The value of Thevenin’s voltage V th is ____. 4Ω

5Ω

Rth

A RL

6Ω

RL B

(a)

(b) Fig. 3.4

A. B.

2Ω D

I2

20 V 24 V

C. D.

12 V 36 V

451. The value of Rth in Fig. 3.4(b) is ____. 4Ω

5Ω

40 V

Rth

A RL

6Ω

RL B

(a)

(b) Fig. 3.4

A. B.

15 Ω 3.5 Ω

C. D.

6.4 Ω 7.4 Ω

452. The open-circuited voltage at terminals AB in Fig. 3.4(a) is 4Ω

447. The current in 2 Ω horizontal resistor in Fig. 3.3 is ____. 3Ω B 2Ω

5Ω

40 V

Rth

A RL

6Ω

2Ω D

I2

20 V

RL B

10 A 5A

(a)

(b) Fig. 3.4

Fig. 3.3

A. B.

A

Vth

B

I1 I3

A

Vth

B

20 V

2A 5A 2.5 A none of the above

30 V

A

Vth

B

Fig. 3.3

A. B. C. D.

20 V

one equation two equation three equations none of the above

40 V

446. In the circuit shown in Fig. 3.3, the voltage at node B wrt D is calculated to be 15 V. The current in the 3 Ω resistor will be 3Ω B 2Ω 30 V

I2

449. The superposition theorem is used when the circuit contains A. a single voltage source B. a number of passive source C. passive elements only D. none of the above

40 V

one equation three equations two equations none of the above

I1 I3

2Ω D Fig. 3.3

Fig. 3.2 A. B. C. D.

I1 I3

30 V

444. To solve the circuit shown in Fig. 3.2 by superposition theorem, we require ____ 3Ω 4Ω

C. D.

2A 2.5 A

A. B.

12 V 20 V

C. D.

24 V 40 V

453. For transfer of maximum power in the circuit shown in Fig. 3.4(a), the value of RL should be ____.

40 V

Rth

A RL

6Ω

C. D.

A

Vth

RL B

B (a)

(b) Fig. 3.4

A. B.

3.5 Ω 6.4 Ω

C. D.

7.4 Ω 15 Ω

2Ω

3Ω

12 V

RL

IN

RN

Rth

RL

(a)

A. B.

5Ω 4.5 Ω 10.5 Ω none of the above

Vth B

1.5 V 0.866 V

C. D.

IN = 2 A

Rth

A

A

RN

(a)

RL

B (b)

Fig. 3.5

3A 1A 2A none of the above

456. Thevenin’s theorem is ____ form on an equivalent circuit. A. voltage B. current C. both voltage and current D. none of the above 457. Norton’s theorem is ____ Thevenin’s theorem. A the same as. B. converse of C. equal to D. none of the above 458. In the analysis of a vacuum tube circuit, we generally use ____. A. superposition C. Thevenin’s B. Norton’s D. reciprocity 459. Norton’s theorem is ____ form of an equivalent circuit A. voltage B. current

A

Vth B

B (b)

Fig. 3.6

A. B.

3Ω 2Ω

C. D.

1.5 Ω 6Ω

463. If in Fig. 3.6(a), the value of IN is 3 A, then value of Vth in Fig. 3.6(b) will be ____. Rth RN = 3 Ω

IN

IN = 2 A

RL

6Ω B

A. B. C. D.

3V 6V

A

(a)

12 V

B (b)

462. The value of Rth in Fig. 3.6(b) is ____.

455. The value of IN in Fig. 3.5(b) is ____. 3Ω

A

Fig. 3.6

(b) Fig. 3.5

2Ω

A

(a)

B

B

A. B. C. D.

461. Fig. 3.6(a) shows Norton’s equivalent circuit of a network whereas Fig. 3.6(b) shows its Thevenin’s equivalent circuit. The value of Vth is ____.

A

A

6Ω

460. In the analysis of a transistor circuit, we generally use ____. A. Norton’s C. reciprocity B. Thevenin’s D. superposition

IN = 2 A

454. Fig. 3.5(b) shows Norton’s equivalent circuit of Fig. 3.5(a). The value of RN is ____.

both voltage and current none of the above

RN = 3 Ω

5Ω

RN = 3 Ω

4Ω

A

A

Vth B

(a)

B (b)

Fig. 3.6

A. B. C. D.

1V 9V 5V none of the above

464. For maximum power transfer, the relation between load resistance RL and internal resistance Ri of the voltage source is ____. A. RL = 2Ri C. RL = 1.5Ri B. RL = 0.5Ri D. RL = Ri 465. Under the conditions of maximum power transfer, the efficiency is ____. A. 75% C. 50% B. 100% D. 25%

466. The open-circuited voltage at terminals of load RL is 30 V Under the conditions of maximum power transfer, the load voltage would be ____. A. 30 V C. 5 V B. 10 V D. 15 V 467. The maximum power transfer theorem is used in ____. A. electronic circuits B. power system C. home lighting circuits D. none of the above 468. Under the conditions of maximum power transfer, a voltage source is delivering a power of 30 W to the load. The power generated by the source is ____. A. 45 W C. 60 W B. 30 W D. 90 W 469. For the circuit shown in Fig. 3.7, the power transferred will be maximum when RL is equal to ____. 3Ω 4Ω A

18 V

RL

6Ω B Fig. 3.7

A. B. C. D.

470. The open-circuited voltage at terminals AB in Fig. 3.7 is ____. 3Ω 4Ω A

RL

6Ω B Fig. 3.7

A. B.

12 V 6V

C. D.

15 V 9.5 V

471. If in Fig. 3.7, the value of RL = 6 Ω, then current through RL is ____. 3Ω 4Ω A

18 V

RL

6Ω B Fig. 3.7

A. B.

2A 1.5 A

18 V

4Ω

A RL

6Ω B Fig. 3.7

A. B.

6V 4V

C. D.

9V 12 V

473. The output resistance of a voltage source is 4 Ω. Its internal resistance will be ____. A. 4 Ω C. 1 Ω B. 2 Ω D. infinite 474. Delta/star of star/delta transformation technique is applied to ___. A. one terminal B. two terminal C. three terminal D. none of the above 475. Kirchhoff’s current law is applicable to only A. closed loops in a network B. electronic circuits C. conjunctions in a network D. electric circuits 476. Kirchhoff’s voltage law is concerned with A. IR drops B. battery e.m.f.s. C. junction voltages D. both A and B

4.5 Ω 6Ω 3Ω none of the above

18 V

3Ω

C. D.

1.75 A 1A

472. Under the conditions of maximum power transfer, the voltage across RL in Fig. 3.7 is ____.

477. According to KVL, the algebraic sum of all IR drops and e.m.f.s in any closed loop of a network is always A. zero B. positive C. negative D. determined by the battery e.m.f.s 478. The algebraic sign of an IR drop is primarily dependent upon the A. amount of current flowing through it B. value of R C. direction of current flow D. battery connection 479. Maxwell’s loop current method of solving electrical networks A. uses branch currents B. utilizes Kirchhoff’s voltage law C. is confined to single-loop circuits D. is a network reduction method 480. Point out the WRONG statement. In the nodevoltage technique of solving networks, choice of a reference node does not A. affect the operation of the circuit B. change the voltage across any element C. alter the p.d. between any pair of nodes

D.

affect the voltages of various nodes

481. The nodal analysis is primarily based on the application of A. KVL C. Ohm’s Law B. KCL D. both B and C

B.

9

D.

489. The Norton equivalent circuit for the network of Fig. 2.2 between A and B is ____ current source with parallel resistance of ____. A

482. Superposition theorem is can be applied only to circuits having ____ elements. A. non-linear C. linear bilateral B. passive D. resistive 483. The Superposition theorem is essentially based on the concept of A. duality C. reciprocity B. linearity D. non-linearity

18

6Ω 3Ω 18 V

B

Fig. 2.2 A. B.

2 A, 6 Ω 3 A, 2 Ω

C. D.

2 A, 3 Ω 3 A, 9 Ω

484. While Thevenizing a circuit between two terminals, Vth equals A. short-circuit terminal voltage B. open circuit terminal voltage C. EMF of the battery nearest to the terminal D. net voltage available in the circuit

490. The Norton equivalent of a circuit consists of a 2 A current source in parallel with a 4  resistor. Thevenin equivalent of this circuit is a ____ volt source in series with a 4  resistor. A. 2 C. 6 B. 0.5 D. 8

485. Thevenin resistance Rth is found A. between any two “open” terminals B. by short-circuiting the given two terminals C. by removing voltage sources along with their internal resistance D. between same open terminals as for Vth

491. If two identical 3 A, 4  Norton equivalent circuits are connected in parallel with like polarity to like, the combined Norton equivalent circuit is A. 6 A, 4  C. 3 A, 2 Ω B. 6 A, 2  D. 6 A, 8 Ω

486. While calculating Rth, constant-current sources in the circuit are A. replaced by “opens” B. replaced by “shorts” C. treated in parallel with other voltage sources D. converted into equivalent voltage sources

492. Two 6 V, 2  batteries are connected in series aiding. This combination can be replaced by a single equivalent current generator of ____ with a parallel resistance of ____ ohm. A. 3 A, 4  C. 3 A, 1 Ω B. 3 A, 2  D. 5 A, 2 Ω

487. Thevenin resistance of the circuit of Fig. 2.1 across its terminals A and B is ____ ohm. 3Ω A 12 V

3Ω

B

Fig. 2.1 A. B.

6 3

C. D.

9 2

493. Two identical 3 A, 1  batteries are connected in parallel with like polarity with like polarity to like. The Norton equivalent circuit of the combination is A. 3 A, 0.5  C. 3 A, 1 Ω B. 6 A, 1  D. 6 A, 0.5 Ω 494. Thevenin equivalent circuit of the network shown in Fig. 2.3 is required. The value of the open-circuit voltage across terminals a and b of this circuit is ____ volt. 5Ω a

488. The load resistance needed to extract maximum power from the circuit of Fig. 2.2 is ____ ohm.

+ -

A

10 Ω

2i

b

6Ω 3Ω

Fig. 2.3 A. B.

18 V

B

Fig. 2.2 A.

2

C.

6

zero 2i/10

C. D.

2i/5

495. For a linear network containing generators and impedance, the ratio of the voltage to the current produced in other loop is the same as the ratio of

voltage and current obtained when the positions of the voltage source and the ammeter measuring the current are interchanged. This network theorem is known as ____ theorem. A. Millman’s C. Tellegen’s B. Norton’s D. Reciprocity 496. A 12 volt source with an internal resistance of 1.2 ohms is connected across a wire-wound resistor. Maximum power will be dissipated in the resistor when its resistance is equal to A. zero C. 12 ohms B. 1.2 ohm D. infinity 497. Three 3.33  resistors are connected in wye. What is the value of the equivalent resistors connected in delta? A. 3.33  C. 6.67  B. 10  D. 20 

A. B.

14 V 12 V

C. D.

0V 1V

502. What should be the value of R so the resistor will receive the maximum power? All resistances are in ohms.

498. Find the equivalent resistance between terminals a & b of the circuit shown. Each resistance has a value of 1 ohm. A. B.

10.0 ohms 3.875 ohms

C. D.

0.968 ohms 1.60 ohms

503. Determine the value VO in the ideal op-amp circuit below. A. B.

5/6 ohms 5/11 ohms

C. D.

5/14 ohms 5/21 ohms

499. What do you call the head to tail connection of two or more op-amp circuits wherein the output of one op-amp is the input of another op-amp? A. Parallel Op-Amps B. Follow-Thru Connection C. Cascade Connection D. Series Op-Amps

A. B.

-8 V -6 V

C. D.

-4 V -3 V

504. Determine the value VO in the op-amp circuit below.

500. Find the power dissipation in the 6 ohms resistor in the next figure.

A. B.

54 W 216 W

C. D.

121.5 W 150 W

501. Determine the value of node voltage V2. All resistances are in ohms.

A. B.

-4 V -8 V

C. D.

-2 V -3 V

505. If the voltage source (dependent or independent) is connected between two non-reference nodes, the two non-reference nodes form a ______ A. Common Node B. Supernode C. Complex Node D. Reference node 506. The theorem that states that “the voltage across or current through an element in a linear circuit is the

algebraic sum of the voltages across or current through that element due to each independent source acting alone”. A. Superposition Theorem B. Thevenin’s Theorem C. Norton’s Theorem D. Reciprocity Theorem 507. Kirchhoff’s Current Law states that A. the algebraic sum of the currents flowing into any point in a circuit must equal zero B. the algebraic sum of the currents entering and leaving any point in a circuit must equal zero C. the algebraic sum of the currents flowing away from any point in a circuit must equal zero D. the algebraic sum of the currents around any closed path must equal zero 508. When applying Kirchhoff’s Current Law, A. consider all the currents flowing into a branch point positive and all currents directed away from that point negative B. consider all the currents flowing into a branch point negative and all currents directed away from that point positive C. remember that the total of all the currents entering a branch point must always be greater than the sum of the currents leaving that point D. the algebraic sum of the currents entering and leaving a branch point does not necessarily have to be zero 509. When applying Kirchhoff’s Voltage Law, a closed path is commonly referred to as a A. node C. loop B. principal node D. branch point 510. Kirchhoff’s Voltage Law states that A. the algebraic sum of the voltage sources and IR voltage drops in any closed path must total zero B. the algebraic sum of the voltage sources and IR voltage drops around any closed path can never equal zero C. the algebraic sum of all the currents flowing around any closed path must equal zero D. none of the above 511. When applying Kirchhoff’s Voltage Law A. consider any voltage whose positive terminal is reached first as negative and any voltage whose negative terminal is reached first as positive B. always consider all voltage sources as positive and all resistor voltage drops as negative C. consider any voltage whose negative terminal is reached first as negative and any voltage whose positive terminal is reached first as positive D. always consider all resistor voltage drops as positive and all voltage sources as negative 512. The algebraic sum of +40 V and -30 V is

A. B.

-10 V +10 V

C. D.

+70 V -70 V

513. A principal node is A. a closed path or loop where the algebraic sum of the voltages must equal zero B. the simplest possible closed path around a circuit C. a junction where branch current can combine or divide D. none of the above 514. How many equations are necessary to solve a circuit with two principal nodes? A. 3 C. 4 B. 2 D. 1 515. The difference between a mesh current and a branch current is A. a mesh current is an assumed current and a branch current is an actual current B. the direction of the current themselves C. a mesh current does not divide at a branch point D. both A and B above 516. Using the method of mesh currents, any resistance common to two meshes has A. two opposing mesh currents B. one common mesh current C. zero current D. none of the above 517. The fact that the sum of the resistor voltage drops equals the applied voltage in a series circuit is the basis for A. Kirchhoff’s Current Law B. node voltage analysis C. Kirchhoff’s Voltage Law D. the method of mesh currents 518. The fact that the sum of the individual branch currents equals the total current in a parallel circuit is the basis for A. Kirchhoff’s Current Law B. node voltage analysis C. Kirchhoff’s Voltage Law D. the method of mesh currents 519. If you do not go completely around the loop when applying Kirchhoff’s Voltage Law, then A. the algebraic sum of the voltages will always be positive B. the algebraic sum is the voltage between the start and finish points C. the algebraic sum of the voltages will always be negative D. the algebraic sum of the voltages cannot be determined 520. A resistor is an example of a(n) A. bilateral component B. active component

C. D.

passive component both A and C

B. C.

521. To apply Superposition theorem, all components must be A. the active type B. both linear and bilateral C. grounded D. both nonlinear and unidirectional 522. When converting from a Norton-equivalent circuit to a Thevenin equivalent circuit or vice versa A. RN and RTH have the same value B. RN will always be larger than RTH C. IN is shorted-circuit to find VTH D. VTH is short-circuited to find IN 523. When solving for the Thevenin equivalent resistance, RTH, A. all voltage sources must be opened B. all voltage sources must be short-circuited C. all voltage sources must be converted to current sources D. none of the above 524. Thevenin’s Theorem states that an entire network connected to a pair of terminals can be replaced with A. a single current source in parallel with a single resistance B. a single voltage source in parallel with a single resistance C. a single voltage source in series with a single resistance D. a single current source in series with a single resistance 525. Norton’s Theorem states that an entire network connected to a pair of terminals can be replaced with A. a single current source in parallel with a single resistance B. a single voltage source in parallel with a single resistance C. a single voltage source in series with a single resistance D. a single current source in series with a single resistance 526. With respect to terminals A and B in a complex network, the Thevenin voltage, VTH, is A. the voltage across terminals A and B when they are short-circuited B. the open-circuit voltage across terminals A and B C. the same as the voltage applied to the complex network D. none of the above 527. With respect to terminals A and B in a complex network, the Norton current, IN, is A. the current flowing between terminals A and B when they are open

D.

the total current supplied by the applied voltage to the network zero when terminals A and B are shortcircuited the current flowing terminals A and B when they are short-circuited

528. Which theorem provides a shortcut for finding the common voltage across any number of parallel branches with different sources? A. The Superposition Theorem B. Thevenin’s Theorem C. Norton’s Theorem D. Millman’s Theorem 529. A d.c. circuit usually has ____ as the load A. Resistance B. Capacitance C. Inductance D. both inductance and capacitance 530. Electrical appliances are connected in parallel because it ____ A. is a simple circuit B. draws less current C. results in reduce in power loss D. makes the operation of appliances independent of each other 531. The purpose of load in an electric circuit is to ____ A. increase the circuit current B. utilize electrical energy C. decrease the circuit current D. none of the above 532. A passive network has A. no emf source B. no current source C. neither emf nor current source D. none of these 533. The relationship between voltage and current is the same for two opposite directions of current in case of A. bilateral network B. active network C. unilateral network D. passive network 534. Which of the following statement is not correct? A. voltage source is an active element B. current source is a passive element C. resistance is a passive element D. conductance is a passive element 535. A resistance R is connected across two batteries, A and B connected in parallel. The open circuit emfs and internal resistances of the batteries are 12 V, 2 ohms and 8 V, 1 ohm respectively. Determine the ohmic value of R if the power absorbed by R is 7.656 watts. A. 10  C. 9  B. 12  D. 8 

536. A network has 7 nodes and 5 independent loops. The number of branches in the network is A. 13 C. 11 B. 12 D. 10

A. B.

3 4

C. D.

6 7

546. Equivalent impedance seen across terminals a, b is

537. The nodal method of circuit analysis is based on A. Kirchhoff’s Voltage Law & Ohm’s law B. Kirchhoff’s Current Law & Ohm‘s law C. Kirchhoff’s Current Law & Kirchhoff’s Voltage Law D. Kirchhoff’s Current Law & Kirchhoff’s Voltage Law & Ohm‘s law 538. For a network of seven branches and four nodes, the number of independent loops will be A. 11 C. 7 B. 8 D. 4

A. B.

16/3 Ω 8/3 Ω

C. D.

8/3 + j12 none of these

547. What is the Rab in the circuit when all resistors values are R?

539. A network has b branches and nodes. For this mesh analysis will be simpler then node analysis if n is greater then A. b C. (b/2) + 1 B. b + 1 D. b/2 540. The number of independent loops for a network with n nodes and b branches is A. n - 1 B. b - n C. b - n + 1 D. independent no. of nodes

A. B.

2R R

C. D.

R/2 3R

548. Find Rab. All values are in ohms.

541. The following constitutes a bilateral element A. Resistor C. Vacuum Tube B. FET D. metal rectifier 542. Kirchhoff’s Laws fail in the case of A. linear networks B. non-linear networks C. dual networks D. distributed parameter networks 543. Ohm’s law, Kirchhoff’s Current Law & Kirchhoff’s Voltage will fail at A. Low frequency C. high power B. high frequency D. none of these

A. B.

22.5 40

C. D.

30 none of these

549. Find the equivalent resistance of the circuit in the figure.

544. Total no, of mesh equations required is equal to A. number of links B. number of tree branches C. number of nodes D. none of these 545. The minimum number of equations required to analyze the circuit

A. B.

3 ohms 4 ohms

C. D.

5 ohms 6 ohms

550. Find the equivalent resistance of the circuit in this figure.

A. B.

R 2R

C. D.

3R 4R

A. B.

2V 3V

C. D.

1V none of these

C. D.

2V none of these

C. D.

2V none of these

C. D.

97.3 V 103 V

557. Find V in the circuit shown.

551. Find the total resistance Rin is in the circuit shown .

A. B.

√ √

C. D.

√ none of these

552. What is the value of i1?

A. B.

–3V +3 V

558. Find V in the circuit shown.

A. B.

0 –6

C. D.

6 none of these

553. Find Ix in the circuit shown.

A. B.

+3V –3V

559. Determine VX of this circuit

A. B.

3A –3 A

C. D.

0 none of these

554. Find value of R in the given circuit. A. B. A. B.

8.2 Ω 6Ω

C. D.

10 Ω none of these

42.2 V 83.3 V

560. Find voltage eo in the fig shown.

555. The voltage V in the figure always equal to A. B.

2V 4/3 V

C. D.

4V 8V

C. D.

0V 10 V

561. Find VX in the circuit shown A. B.

9V 5V

556. Find V in the circuit shown.

C. D.

1V none of these A. B.

2.5 V -2.5 V

562. Find voltage eo in the fig shown

B.

30 V

D.

10 V

568. In the circuit of the given figure. The value of the voltage source E is

A. B.

48 V 24 V

C. D.

36 V 28 V

C. D.

ae – be at bt ae + be

563. The voltage v(t) is

A. B.

at

-bt

e –e at bt e +e

at

bt

564. Find current through 5 Ω resistor

A. B.

–16 V 4V

C. D.

–6 V 16 V

C. D.

-2/3 A none of these

569. Find i2 in the figure shown.

A. B.

0 2A

C. D.

3A 7A

565. Find Vxy

A. B.

10 V 46 V

A. B.

C. D.

13 V 58 V

566. What is VAB?

A. B.

3V 54V

20 V

570. When a resistor R is connected to a current source, it consumes a power of 18 W. When the same R is connected to a voltage source having same magnitude as the current source, the power absorbed by R is 4.5 W. The magnitude of the current source & value of R are A. √ A & 1 ohm C. 1 A & 18 ohms B. 3 A & 2 ohms D. 6 A & 0.5 ohms 571. In the circuit shown in the figure. If I = 2, then the value of the battery voltage V will be

C. D.

24 V none of these

567. What is Vxy?

A.

4A 2/3 A

A. B.

5V 3V

C. D.

572. Find E and I in the figure shown.

C.

–10 V

A.

I = 13 A and E = 31 V

2V 1V

B. C. D.

I = 31 A and E = 13V E = 31 V and I = 31A none of these

A. B.

573. Find the voltage across the terminals a and b.

A. B.

0.5 V 3.0 V

C. D.

3.5 V 4.0 V

574. What is the current supplied by 1 V source when each resistance is 1 ohm?

8/15 A 15/4 A

C. D.

4/15 A none of these

C. D.

5V none of these

C. D.

4A 8A

578. In the circuit shown in the given figure, the potential difference V2 – V1 is

A. B.

–4.5 V 0

C. D.

4.5 V 6V

C. D.

40 V none of these

C. D.

-4 V 4V

579. Find V in the figure shown.

A. B. A. B.

1A 2A

56.25 V 85 V

580. What is VA?

575. The voltage V is equal to

A. B.

3V –3 V

576. The voltage across 15 ohms resistor is

A. B.

-105 V +105 V

C. D.

–15 V + 15 V

577. In the circuit of the given figure. The current I will be

A. B.

-2 V 2V

581. What is the value of I4 in the fig shown?

A. B. C. D.

–4 A –2 A known only if V1, V2 and R are known known only if V1, V2 are known

582. If the voltage of each source in the given network is doubled, then which of the following statement would be true?

1. 2. 3. 4. A. B.

Current flowing in the network will be doubled Voltages across each resistor will be doubled Power absorbed by each resistor will be doubled Power delivered by each source will be doubled 1, 2, 3, 4 C. 2, 3 1, 2 D. 1, 3, 4

583. For a given network, the number of independent mesh equation (Nm) and the number of independent node equation (Nn) obey the following: A. Nm = Nn B. Nm > Nn C. Nm < Nn D. any one of the above, depending on the network

A. B.

2A 1.5 A

C. D.

0.5 A 0A

588. In the circuit shown in the given figure, current I is

A. B.

–2/5 24/5

C. D.

18/5 2/5

589. A 35 V source is connected to a series circuit of 600Ω and R as shown. If a voltmeter of internal resistance1.2 kΩ is connected across 600 Ω resistor it reads 5 V, find the value of R.

584. In the circuit of the given figure. What is the current I?

A. B. A. B.

1A 4/3 A

C. D.

2A 3A

1.2 kΩ 2.4 kΩ

C. D.

3.6 kΩ 7.2 kΩ

590. Find the current in RL in the circuit below.

585. Find the value of R for which the power supplied by the voltage source is zero.

A. B.

0 1.5 ohms

C. D.

6 ohms 0.667 ohms

586. What value of R which ensures that the current through the 60 ohm resistor of this circuit is 1 A?

A. B.

5 ohms 10 ohms

C. D.

15 ohms 20 ohms

587. The current I in the circuit of the figure is

A. B.

0 2/3

C. D.

1/3 none

591. The current flowing through the voltage source in the given circuit is

A. B.

1.0 A 0.75 A

C. D.

0.5 A 0.25 A

592. In the circuit shown, the voltage across 2Ω resistor is 20 V. The 5 Ω resistor connected between the terminals A and B can be replaced by an ideal

B.

–2 A

D.

none of these

597. A particular resistor R dissipates a power of 4W when V alone is active. The same resistor R dissipates a power of 9 watts when I alone is active. The power dissipated by R when both sources are active will be A. B. C. D.

Voltage source of 25 V with +ve terminal upward Voltage source of 25 V with +ve terminal downward Current source of 2 A upward Current source of 2A downward

593. In the circuit shown in the figure. The effective resistance faced by the voltage source is

A. B.

1Ω 2Ω

C. D.

1A 0.5 A

C. D.

1W 5W

C. D.

13 W 25 W

598. The linear network contains only resistors if is1 = 8A, is2 = 12A, Vx is found to be 80v. If is1 = -8A, is2 = 4A, Vx = 0 . Find Vx when is1 = is2 = 20A.

3Ω 3.3 Ω

594. If a resistance ‘R’ of 1Ω is connected across the terminals AB as shown in the given fig. Then the current flowing through R will be

A. B.

A. B.

0.25 A 0.125 A

A. B.

–150 150

C. D.

100 50

599. When R = 10 ohms, VR = 20 V, when R = 20 ohms VR = 30 V. Find VR when R = 80 ohms.

A. B.

40 160

C. D.

48 none

C. D.

6 V, 6 V 12 V, 12 V

600. Find V1 & V2.

595. Find VL across the ¼ ohm resistor of this circuit.

A. B. A. B.

1/52 V 2/52 V

C. D.

3/52 V 5/52 V

4 V, 8 V 8 V, 4 V

601. The network shown in the figure draws current I when ab is open. If the ends ab were shorted, the current drawn would be

596. Find Ix in the fig shown

A. B. A.

1A

C.

2A

∞ 4I

C. D.

2I I

602. In the figure below, the voltage across the 18 ohm resistor is 90 volts. What is the total voltage across the combined circuit?

A. B.

1A 2A

C. D.

2.5 A 3A

C. D.

24 ohms 12 ohms

607. In the figure, the value of R is A. B.

125 V 16 V

C. D.

24 V 40 V

603. Find the current transfer ratio I2/I1 for the network shown in the figure. All resistors are given as 2 ohms.

A. B.

0.25 0.40

C. D.

0.50 0.75

604. In the network shown in the given figure, the effective resistance faced by the voltage source is

A. B.

4 ohms 3 ohms

C. D.

2 ohms 1 mega ohms

605. The V-I relation for the network shown in the given box is V = 4I - 9. If now a resistor R = 2 ohms is connected across it, then the value of I will be

A. B.

10 ohms 18 ohms

608. An ideal constant voltage source is connected in series with an ideal constant current source. Considered together, the combination will be a A. constant voltage source B. constant current source C. constant voltage source and constant current D. source or a constant power source 609. A network contains only independent current sources and resistors. If the values of all the resistors are doubled, the values of the node voltage A. will become half B. will remain unchanged C. will become double D. cannot be determined unless the circuit configuration and the values of the resistors are known 610. A network N is a dual of network N if A. both of them have same mesh equations B. both of them have same node equations C. mesh equations of one are the node equations of the other D. KCL and KVL equations are the same

A. B.

–4.5 A –1.5 A

C. D.

1.5 A 4.5 A

606. In the circuit shown in the figure, for R = 20 ohms the current I is 2 A. When R is 10 ohms the current I would be

611. A certain network consists of two ideal voltage sources and a large number of ideal resistors. The power consumed in one of the resistor is 4 W when either of the two sources is active and the other is replaced by a short circuit. The power consumed by the same resistor when both the sources are simultaneously active would be A. zero or 16 W C. zero or 8 W B. 4W or 8 W D. 8 W or 16 W

612. All the resistances in the circuit are R ohms each. The switch is initially open. What happens to the lamp intensity when the switch is closed?

A. B.

1 A, 2.73 Ω 2.73 A, 1 Ω

C. D.

5A, 30/11 Ω none of these

617. The value of equivalent voltage and resistance across a and b. A. B. C. D.

increases decreases remain constant depends on the value of R

613. If R1 = R2 = R4 = R and R3 = 1.1R in the bridge circuit shown in figure, then the reading in the ideal voltmeter connected across a and b is

A. B.

0.238 V 0.138 V

C. D.

614. A network has b branches and n mesh analysis will be simpler than n is greater than A. b C. B. b + 1 D.

–0.238 V 1V nodes. For this node analysis if b/2 +1 b/2

I1/I2 P1/P2 P1 in Watts P2 in Watts

A. B.

ABCD 3541 2341

– 100 V, 30 Ω - 2 V, 30 Ω

C. D.

10/3 V, 30 Ω none of these

618. Identify correct statement with respect to fig. (a) and (b).

A. B. C. D.

power supplied by both the sources is same current flowing through 5 Ω resistors are same current flowing through 1 Ω resistors are same all are correct

619. Practical current source internal resistance should be A. Less than RL C. equal to RL B. greater than RL D. none of these 620. The equivalent circuit of the following circuit is

615. Match the following

A. B. C. D.

A. B.

1. 2. 3. 4. 5. C. D.

600 0.3 2 500 1.2 ABCD 3514 1314

616. Find single current source equivalent.

A. B. C. D.

V in series with 3R 3V in series with 3R V in series with R/3 3V in series with R/3

621. Obtain potential of node B with respect to G in the network shown in figure.

626. Find the total power absorbed by all resistors in the circuit shown.

A. B.

15 W 20 W

C. D.

25 W 30 W

627. What will be the power consumed by the voltage source, current source and resistance respectively A. B.

64/63 V 1V

C. D.

63/64 V 32/63 V

622. Find power dissipated in resistor 1 Ω.

A. B.

1 W, 1 W, 2 W 0 W, -1 W, 1 W

C. D.

1 W, 0 W, 1 W 0 W, 0 W, 0 W

628. Power absorbed by 6 Ω resistor is 24 W. Determine Io A. B.

0 6W

C. D.

9W none of these

623. Find power delivered at t = 0.8 s.

A. B.

51 W 34.68 W

C. D.

A. B. – 34.68 W none of these

4A -4 A

C. D.

2A none of these

629. The dependent current source shown

624. The total power consumed in the circuit shown in the figure is A. B.

Delivers 80 W absorbs 80 W

C. D.

delivers 40 W absorbs 40 W

630. Find power absorbed by dependent source.

A. B.

10 W 12 W

C. D.

16 W 20 W

625. In the circuit shown in the given figure, power dissipation in the 5 Ω resistor is

A. B.

–3 W 3W

C. D.

0W none of these

631. What is the power supplied by 2 A current source.

A. B.

zero 80 W

C. D.

125 W 405 W

A. B.

R R-1

C. D.

R/2 (6/11) R

637. What is the equivalent resistance between AB when each branch resistance is 2 ohms?

A. B. A. B.

–70 W 70 W

C. D.

50 W none of these

632. Each branch resistance is 1 ohm. Find equivalent resistance in each path out of 3 paths.

3.23 ohm 2 ohm

C. D.

difficult to find none of these

638. Superposition theorem is not applicable in the network when it is A. Linear C. Time varying B. non-linear D. Time invarying 639. The superposition theorem is valid for A. all linear networks B. linear and symmetrical networks only C. only linear networks having no dependent sources D. linear as well as nonlinear networks

A. B.

15/6 ohms 5/6 ohms

C. D.

6/5 ohms none of these

633. If each branch of a delta circuit has impedance √ Z, then each branch of the equivalent Wye circuit has impedance A. Z/√ C. 3√ Z B. 3Z D. Z/3 634. A delta–connected network with its WYE-equivalent is shown. The resistances R1 R2 & R3 are

A. B.

1.5 Ω, 3 Ω, 9 Ω 3 Ω, 6 Ω, 1.5 Ω

C. D.

9 Ω, 3 Ω, 1.5 Ω 3 Ω, 1.5 Ω, 9 Ω

635. When all resistances in delta connection are having equal value of R. What is the equivalent resistance in star connection? A. RY = RΔ C. RY = RΔ/3 B. RΔ = RY/3 D. none of these 636. The effective resistance between the terminals A and B in the circuit shown in the figure is (all resistors are equal to R)

640. Substitution theorem is not used in the analysis of networks in which they contain elements as A. Linear C. Time varying B. non-linear D. none of these 641. Thevenin’s theorem is not applicable when 1. Load is coupled with the network 2. Linear 3. Time invariant 4. none of these 5. Non linear 6. Time varying A. 1, 5, 6 C. 1, 5 B. 5, 6 D. 1, 3, 5, 6 642. Tellegen’s theorem is applicable when A. Nature of elements is irrelevant B. Elements are linear time varying C. KVL and KCL is not satisfied D. none of these 643. Reciprocity theorem is applicable when network is 1. Linear 2. Time invariant 3. Passive 4. Independent source 5. Dependent source 6. Mutual inductors Identify the correct combination A. 1, 2, 6 C. 1, 2, 4 B. 1, 2, 3, 6 D. 1, 2, 3 644. Consider the following statements: 1. Tellegen’s theorem is applicable to any lumped networks 2. The reciprocity theorem is applicable to linear bilateral networks

3.

Thevenin’s theorem is applicable to two terminal linear active networks 4. Norton’s theorem is applicable to two terminal linear active networks Which of these statements are correct? A. 1, 2 and 3 C. 1, 2 and 4 B. 1, 2, 3 and 4 D. 3 and 4 645. Match List–I with List-II and select the correct answer using the codes given below the lists: List I List II Network Theorems Most distinguished property of network A. Reciprocity 1. Impedance Matching B. Tellegen’s 2. Bilateral C. Superposition 3.∑ D. Maximum power 4. Linear Transfer 5. Non linear CODES: CODES: ABCD ABCD A. 1 2 3 4 C. 2 3 4 1 B. 1 2 3 5 D. 2 3 5 1 646. In a linear circuit the super position principle can be applied to calculate the A. Voltage and power B. voltage and current C. current and power D. voltage, current and power 647. In applying Thevenin’s theorem, to find the Thevenin impedance, some sources (call them set S1) have to be replaced by their internal impedances, while others (call them set S2) should be left undisturbed. A. S1 consists of independent sources while S2 includes all independent sources B. S1 consists of dependent sources while S2 includes all independent sources C. S2 is a null set D. S1 is a null set 648. In the network shown, which one of the following theorems can be conveniently used to calculate the power consumed by the 10 ohm resistor.

A. B.

0.2 Ω 0.4 Ω

C. D.

2Ω none of these

650. A dc current source is connected as shown in below figure. The Thevenin’s equivalent of the network at terminals a – b will be

A. B. C. D.

4 V voltage source parallel with 2 ohms resistor 4 V voltage source 2 V voltage source parallel with 2 ohms resistor none of these

651. In the network shown in the given figure current i= 0 when E = 4 V, I = 2 A and I = 1 A when E = 8 V, I = 2A. The Thevenin voltage and the resistance looking into the terminals AB are

A. B.

4 V, 2 Ω 4 V, 4 Ω

C. D.

8 V, 2 Ω 8 V, 4 Ω

652. A battery charger can drive a current of 5A into a 1 ohm resistance connected at its output terminals. If it is able to charge an ideal 2V battery at 7A rate, then its Thevenin’s equivalent circuit will be A. 7.5V in series with 0.5 ohm B. 12.5 V in series with 1.5 ohms C. 7.5V in parallel with 0.5 ohm D. 12.5V in parallel with 0.5 ohm 653. Find Va for which maximum power is transferred to the load.

A. B. C. D.

Thevenin’s theorem Maximum power transfer theorem Millman’s theorem Superposition theorem

649. Find the Thevenin equivalent resistance of the circuit to the left of the terminals marked a and b in the figure.

A. B.

7.5 V 20 V

C. D.

10 V none of these

654. If the networks shown in fig. I and II are equivalent at terminals A-B, then the values of V (in volts) and Z (in ohms), will be

A. B.

V 100 60

Z 12 12

C. D.

V 100 60

Z 30 30

655. In the circuit shown, the power dissipated in 30 ohm resistor will be maximum if the value of R is

A. B.

30 ohms 16 ohms

C. D.

9 ohms zero

656. In the circuit shown, the power consumed in the resistance R is measured when one source is acting at a time. These values are 18 W, 50 W and 98 W. When all the sources are acting simultaneously, the possible maximum and minimum values of power in R will be

A. B.

98W and 18 W 166 W and 18 W

C. D.

A. B.

2.75 Ω 7.5 Ω

C. D.

25 Ω 27 Ω

659. For the circuit shown, identify the correct statement.

A. B. C. D.

Efficiency of power transmission is maximum when RS = RL efficiency of power transmission is maximum when RS < RL efficiency of power transmission is maximum when RS > RL none of these

660. The V-I characteristics as seen from the terminalpair (A, B) of the network of figure (a) is shown in figure (b). If a variable resistance RL is connected across the terminal – pair (A, B) the maximum power that can be supplied to RL would be

450 W and 2 W 166 W and 2 W

657. The value of Rx so that power dissipated in it is maximum

A. B. C. D.

80 W 40 W 20 W Indeterminate unless the actual network is given

661. In the lattice network, find the value of R for the maximum power transfer to the load.

A. B.

33.4 kohms 17.6 kohms

C. D.

10 kohms 5 kohms

658. In the circuit shown in the given figure RL will absorb maximum power when its value is

A. B.

5Ω 6.5 Ω

C. D.

8Ω 9Ω

662. In the network of the given figure, the maximum power is delivered to RL if its value is

667. Find the value of R and r. Thevenin’s equivalent circuit is given by circuit as shown

A. B.

16 ohms 40/3 ohms

C. D.

60 ohms 20 ohms

663. Find the current I in the given figure.

A. B. C. D.

R = r = 20 ohms R = r = 5 ohms R = 10 ohms; r = 5 ohms R = r = 10 ohms

668. Thevenin’s equivalent of the circuit shown in the figure: Vth, Zth values are

A. B.

1.5 A 2.0 A

C. D.

1.2 A –4/5 A

664. In the circuit of the given figure, the maximum power will be delivered to RL and RL equals

A. B.

6Ω 2Ω

C. D.

4/3 Ω 1Ω

665. The maximum power that can be transferred to the load resister RL from the voltage source in the figure is

A. B.

1W 10 W

C. D.

0.25 W 0.5 W

666. For the circuit shown, Thevenin’s voltage and Thevenin’s equivalent resistance at terminals a and b is

A. B. C. D.

5 V and 2 ohms 7.5 V and 2.5 ohms 4 V and 2 ohms 3 V and 2.5 ohms

A. B.

20 V, 9 ohms 40 V, 19/3 ohms

C. D.

40 V, 9 ohms 40 V, 8 ohms

F. ELECTRICAL TRANSIENTS 669. EE Board Exam April 1979, October 1982 In an RL circuit, Kirchhoff’s law gives the following relation: E = Ldi/dt + Ri where: E = supply voltage (200 volts) R = resistance (20 ohms) L = inductance (1 Henry) t = time in seconds i = current in amperes If i = 0 when t = 0, find i when t = 0.02 second. A. 3.3 A C. 3.2 A B. 3.1 A D. 3.0 A 670. EE Board Exam October 1980 In an RL circuit, Kirchhoff’s law gives the following relation: E = Ldi/dt + Ri where: E = supply voltage (200 volts) R = resistance (20 ohms) L = inductance (1 Henry) t = time in seconds i = current in amperes If i = 0 when t = 0, find i after a long time. A. 10 A C. 0 B. 11.2 A D. infinite 671. EE Board Exam October 1990 A 6 H coil whose resistance is 12 ohms is connected in series with a 24 ohms resistor and to a 144 V battery and a switch. The switch is closed at t = 0. Determine the time constant and the steady state current of the circuit. A. 0.36 sec, 12 A C. 0.66 sec, 3 A B. 0.45 sec, 4 A D. 0.50 sec, 6 A 672. EE Board Exam April 1990

A time of 10 milliseconds is required for the current on a series RL dc circuit to reach 90% of its final steady state value. Assume at t = 0, i(0) = 0. What is the time constant in seconds for the circuit? A. 4.25 ms C. 3.39 ms B. 3.86 ms D. 4.34 ms 673. EE Board Exam April 1995 The shunt winding of a machine has a resistance of 80 ohms and an inductance of 4 H is suddenly switched on to a 220 V supply. Find the time taken for the current to rise to half its steady state value. A. 0.0512 sec C. 0.0251 sec B. 0.0346 sec D. 0.0172 sec 674. EE Board Exam October 1990 A 6 H coil whose resistance is 12 ohms is connected in series with a 24 ohms resistor and to a 144 V battery and a switch. The switch is closed at t = 0. Determine the current at t = 0.1 second. A. 1.538 A C. 1.805 A B. 1.750 A D. 1.624 A 675. EE Board Exam October 1992 An uncharged capacitor in series with a 120 volt voltmeter of 10,000 ohms resistance is suddenly connected to a 100 V battery. One second later, the voltmeter reads 60 volt. Determine the capacitance of the capacitor. A. 187.54 μF C. 195.76 μF B. 190.62 μF D. 192.23 μF 676. REE Board Exam April 1999 A 20 ohm resistance R and a 0.001 farad capacitance C are in series. A direct current voltage E of 100 volts is applied across the series circuit at t = 0 and the initial current i(0) = 5 A. Determine the resulting current i(t) at t = 0.01 second. A. 3.34 A C. 2.78 A B. 3.67 A D. 3.03 A 677. EE Board Exam October 1991 A series RC circuit consist of R = 2 MΩ and an uncharged capacitor C = 5 μF. The circuit is connected across a 100 V DC source at t = 0. Determine the voltage across the resistor 5 seconds later. A. 63.31 V C. 66.24 V B. 60.65 V D. 69.22 A 678. EE Board Exam October 1991 An uncharged capacitor in series with a 120 volt voltmeter of 10,000 ohms resistance is suddenly connected to a 100 V battery. One second later, the voltmeter reads 60 volt. Determine the rate at which the voltage across the capacitor is charging. -0.55t -0.55t A. 51 e C. 55 e -0.51t -0.51t B. 51 e D. 55 e 679. EE Board Exam October 1981 In a circuit consisting of a series resistance and capacitance and connected to a DC source, R = 20

ohms, C = 250 microfarad and E = 100 volts, find i after a long time. A. 1 A C. infinity B. 0 A D. 5 A 680. EE Board Exam April 1993 A 100 μF capacitor initially charged to 24 V is discharge across a series combination of a 1 kΩ resistor and a 200 μF capacitor. Find the current after 1 sec. A. 7.34 nA C. 8.43 nA B. 7.24 nA D. 8.84 nA 681. EE Board Exam October 1991 A series RC circuit consist of R = 2 MΩ and an uncharged capacitor C = 5 μF. The circuit is connected across a 100 V DC source at t = 0. What is the initial rate of change of voltage across the resistor? A. -10 V/s C. -12.4 V/s B. 10 V/s D. none of these 682. REE Board Exam March 1998 A 10 ohm resistance R and a 1 Henry inductance L are connected in series. An AC voltage e(t) = 100 sin 377t is applied across the connection. Solve for the particular solution (without the complementary solution) and determine the amplitude of the resulting sinusoidal current i(t). A. 0.321 A C. 0.241 A B. 0.292 A D. 0.265 A 683. EE Board Exam April 1991 A certain electric welder has a basic circuit equivalent to a series RL with R = 0.1 Ω and L = 1 mH. It is connected to an AC source “e” through a switch “s” operated by an automatic timer, which closes the circuit at any desired point on the 60 cycle, sinusoidal wave ”e”. Calculate the magnitude of the transient current resulting when “s” closes as “e” is passing through its peak value of 100 volts. A. 256.41 A C. 80.54 A B. 65.74 A D. 76.32 A 684. REE Board Exam October 1999 A series RL circuit is connected to an AC source of 100 sin 377t. Where L = 0.1 Henry, R = 10 ohms and i(0) = 0. Determine the current at t = 0.01 second. A. 2.784 A C. 2.531 A B. 2.301 A D. 3.062 A 685. REE Board Exam April 1999 A series circuit has R = 10 ohms. L = 0.1 Henry and C = 0.0001 Farad. An AC voltage e = 100 sin 377t is applied across the series circuit. Solve for the particular solution (without the complementary solution) and determine the amplitude of the resulting sinusoidal current i(t). A. 5.51 A C. 6.67 A B. 6.06 A D. 7.34 A 686. REE Board Exam October 1999

A 10 ohm resistance R and a 0.001 Farad capacitance C are in series. An AC voltage e(t) = 100 sin 377t is applied across the series circuit. Solve for the particular solution (without the complementary solution) and determine the amplitude of the resulting sinusoidal current i(t). A. 9.67 A C. 8.79 A B. 10.63 A D. 11.70 A 687. REE Board Exam October 1999 If R = 50 ohms, C = 0.0001 Farad, E = 100 volts and i(0) = 2 amperes, determine the Laplace transform expression for I(s). A. I(s) = 2/(s + 200) C. I(s) = 2/(s + 50) B. I(s) = 2/[s(s + 2)] D. I(s) = 2/(s + 2) 688. REE March 1998 A generator has a field winding with an inductance L = 10 Henry and a resistance Rf = 0.1 ohm. To break the initial field current of 1000 amperes, the field breaker inserts a field discharge resistance Rd across the field terminals before the main contacts open. As a result, the field current decays to zero according to the differential equation. Where: R = Rf + Rd preventing a sudden decrease of i to zero, and a resulting high inductive voltage due to L. Solve the differential equation and determine the value of Rd that would limit the initial voltage across it to 1,000 volts A. 0.90 ohm C. 0.85 ohm B. 0.80 ohm D. 0.95 ohm 689. EE Board Exam April 1995 The growth of current in an inductive circuit follows A. Linear law C. Ohm’s law B. Exponential law D. Hyperbolic law 690. EE Board Exam April 1994 The time constant of an RL series circuit is A. R + L C. L/R B. R/L D. RL 691. EE Board Exam April 1998, April 1995 If a dc voltage is applied to an initially uncharged series RC circuit, the initial value of the current is A. zero C. infinite B. V/R D. CV 692. ECE Board Exam April 1999 What is the voltage drop across the resistor in an RC charging circuit when the charge on the capacitor is equal to the battery voltage? A. 0.10 volt C. zero B. 1.0 volt D. 10 volts 693. ECE Board Exam April 2000 What is the RC time constant of a series RC circuit that contains a 12 MΩ resistor and a 12 F capacitor? A. 144 seconds C. 14.4 seconds B. 1.44 seconds D. 1440 seconds

694. ECE Board Exam April 2000 What is the time constant of a 500 mH coil and a 3,300 ohm resistor in series? A. 0.0015 sec C. 1650 secs B. 6.6 secs D. 0.00015 sec 695. ECE Board Exam November 2000 In RL circuit, the time constant is the time required for the induced current to reach what percentage of its full value? A. 100% C. 37% B. 63% D. 0% 696. EE Board Exam April 1990, October 1990 A 6 H coil whose resistance is 12 ohms is connected in series with a 24 ohms resistor and to a 144 V battery and a switch. The switch is closed at t = 0. Determine the time constant of the circuit and the steady-state current. A. 0.5 sec; 6 A C. 0.1667 sec; 4 A B. 0.25 sec; 12 A D. 0.131 sec; 6 A 697. EE Board Exam October 1991 A series RC circuit consist of R = 2 MΩ and an uncharged capacitor C = 5 μF. The circuit is connected across a 100 V DC source at t = 0. Determine the voltage across the resistor at the instant the switch is closed and 5 seconds after the switched has been closed. A. 100 V, 60.65 V C. 100 V, 0 V B. 0 V, 60.65 V D. 0 V, 100 V 698. The rate of rise of current through an inductive coil is maximum A. after 1 time constant B. at the start of current flow C. near the final maximum value of current D. at 63.2% of its maximum steady state value 699. Energy stored by a coil is doubled when its current is increased by ____. A. 100% C. 50% B. 41.4% D. 25% 700. The initial current in an RL series circuit when a dc source is suddenly applied A. unity C. infinite B. V/R D. zero 701. At steady state in an RL circuit, the inductance will act as A. open circuit C. transient circuit B. short circuit D. coupled circuit 702. The rise of the current in an RL series circuit is what? A. linear C. exponential B. sinusoidal D. symmetrical 703. The transient current is undamped if A. R = 0 2 B. [R/2L] > [1/(LC)]

C. D.

2

[R/2L] = [1/(LC)] 2 [R/2L] < [1/(LC)]

704. The transient current is oscillatory if A. R = 0 2 B. [R/2L] > [1/(LC)] 2 C. [R/2L] = [1/(LC)] 2 D. [R/2L] < [1/(LC)] 705. The capacitor in a series RC circuit at steady state is A. open circuit C. transient circuit B. short circuit D. coupled circuit 706. What is the time constant in an RC series circuit? A. C/R C. RC B. R/C D. C 707. A circuit of resistance and inductance in series has an applied voltage of 200 volts across it. What is the voltage drop across the inductance at the instance of switching? A. 200 V C. 20 V B. 0 V D. 2,000 V 708. The current in series RC circuit at steady state is A. zero C. constant B. infinite D. V/R 709. Transient disturbance is produced in a circuit whenever A. it is suddenly connected or disconnected from the supply B. it is shorted C. its applied voltage is changed suddenly D. all of the above 710. There are no transients in pure resistive circuits because they A. offer high resistance B. obey Ohm’s law C. have no stored energy D. are linear circuits 711. Transient currents in electrical circuit are associated with A. inductors C. resistors B. capacitors D. both A and B 712. The transients which are produced due to sudden but energetic changes from one steady state of a circuit to another are called ____ transients. A. initiation C. relaxation B. transition D. subsidence 713. In a R-L circuit connected to an alternating sinusoidal voltage, size of transient current primarily depends on A. the instant in the voltage cycle at which circuit is closed B. the peak value of steady-state current C. the circuit impedance D. the voltage frequency

714. Double-energy transients are produced in circuits consisting of A. two or more resistors B. resistance and inductance C. resistance and capacitance D. resistance, inductance and capacitance 715. The transient current in a loss-free L-C circuit when excited from an ac source is a/an ____ sine wave. A. over damped B. undamped C. under damped D. critically damped 716. Transient currents in an R-L-C circuit is oscillatory when A. C. √ B. D. √ √ 717. A coil has a time constant of 1 second and an inductance of 8 H. If the coil is connected to a 100 V dc source, determine the rate of rise of current at the instant of switching. A. 8 amp/sec C. 0.25 amp/sec B. 12.5 amp/sec D. 0.04 amp/sec 718. A 20 ohm resistor, a 0.01 H inductor and a 100 uF capacitor are connected in series to a 200 V DC supply. The capacitor is initially uncharged. Find the maximum instantaneous current. A. 8.44 A C. 6.44 A B. 7.44 A D. 5.44 A . 719. A 10,000 ohms voltmeter connected in series with 80 F capacitor is suddenly connected to a 100 V dc source at t = 0. At what time does the voltmeter read 40 volts? A. 0.654 sec C. 0.733 sec B. 0.51 sec D. 0.1 sec 720. A series RLC circuit with inductance of 100 Henry has a transient resonant frequency of 5 cps. Solve the capacitance of the circuit if the effect of R on the frequency is negligible. A. 10.1 F C. 400 F B. 0.104 F D. 4 F 721. A 60 μF capacitor is connected in series with a 400 ohm resistor. If the capacitor is initially uncharged, determine the resistor and capacitor voltages when t = 1.5 times the time constant for a suddenly applied source emf of 120 volts. A. 26.78 V, 93.22 V B. 120 V, 0 V C. 93.22 V, 26.78 V D. 0 V, 120 V 722. A series RL network, with R = 2 ohms and L = 0.5 H, has an applied voltage v(t). Find the time constant for the circuit current. A. 4 sec C. 2 sec

B.

0.5 sec

D.

0.25 sec

723. A coil having a resistance of 10 ohms and an inductance of 4 H is switched across a 20-V dc source. Calculate the time taken by the current to reach 50% of its final steady state value. A. 151.8 V C. 88.2 V B. 189.4 V D. 101.2 V 724. A constant voltage is applied to a series RL circuit at t = 0 by closing the switch. The voltage across L is 25 volts at t = 0 and drops to 5 volts at t = 0.025 second. If L = 2 H, what must be the value of R in ohms? A. 188.30 C. 128.80 B. 1288 D. 182.80 725. A circuit whose resistance is 20 ohms and inductance of 10 H has a steady state voltage of 100 volts suddenly applied to it. For the instant of 0.50 second after the voltage is applied, determine the total power input to the circuit. A. 200 watts C. 316 watts B. 116 watts D. 500 watts 726. A circuit of resistance R ohms and inductance L Henry has a direct voltage of 230 volts applied to it. 0.30 second after switching on, the current was found to be 5 ampere. After the current had reached its final value, the circuit was suddenly shortcircuited. The current was again found to be 5 ampere at 0.30 second after short-circuiting the coil. Find the value of R and L. A. 230 Ω, 10 H C. 10 ohms. 23 H B. 23 Ω, 10 H D. 10 Ω, 32 H

closing the switch. The value of current 2 seconds after the switch is closed is A. 1.74 A C. 1.17 A B. 1.47 A D. 1.71 A 731. A DC voltage of 80 volts is applied to a circuit containing a resistance of 80 ohms in series with an inductance of 20 Henry. Calculate the growth of current at the instant of completing the circuit. A. 4 A/s C. ½ A/s B. 2 A/s D. ¼ A/s 732. A 200 volt DC supply is suddenly switched to a relay coil which has a time constant of 3 ms. If the current in the coil reaches 0.20 ampere after 3 ms determine the steady state value of the current. A. 0.361 A C. 0.316 A B. 0.163 A D. 0.631 A 733. A relay has a resistance of 300 ohms and is switched to a 100 V DC supply. If the current reaches 63.2% of its final value at 0.02 sec, determine the inductance of the circuit. A. 5 H C. 4 H B. 6 H D. 13 H 734. Energy stored by a coil is doubled when its current is increased by ____ percent. A. 100 C. 50 B. 141.4 D. 25 735. A 60 volt potential difference is suddenly applied to a coil of inductive 60 mH and resistance 180 ohms. At what rate is it rising after 0.005 sec? A. 322 A/sec C. 22.3 A/sec B. 223 A/sec D. 32.2 A/sec

727. The field winding of a separately-excited DC generator has an inductance of 60 H and a resistance of 30 ohms. The discharge resistance of 50 ohms is permanently connected in parallel with winding which is excited from a 200 volt supply. Find the value of the decay current 0.60 sec after the supply has been switched off. A. 4.94 A C. 1.12 A B. 3.67 A D. 3 A

736. A voltage rise linearly form zero to 100 volts in 1 second, falls instantaneously to zero at t = 1 second and remains zero thereafter. This voltage is applied to an RL series circuit in which R = 5 ohms and L = 100 mH. What is the current when t = 0.50 second? A. 6.90 A C. 9.60 A B. 96 A D. 69 A

728. A 5 microfarad capacitor is discharged suddenly through a coil having an inductance of 2 H and a resistance of 200 ohms. The capacitor is initially charge to a voltage of 10 volts. Find the additional resistance required just to be prevent oscillation. A. 1625 ohms C. 1265 ohms B. 1065 ohms D. 1025 ohms

737. A capacitance of 10 microfarad is connected in series with a resistance of 8,000 ohms. If the combination is suddenly connected to a 100 V DC supply. Find the initial rate of rise in potential across the capacitor. A. 12500 V/s C. 1250 V/s B. 125 V/s D. 12.50 V/s

729. The rate of rise of current through an inductive coil is maximum A. after 1 time constant B. at the start of current flow C. near the final maximum value of current D. at 63.2% of its maximum steady state value

738. A 25 microfarad capacitor is connected in series with a 0.50 M-ohm resistor and a 120 volt storage battery. What is the potential difference in the capacitor 6 sec after the circuit is closed? A. 64 volts C. 4.60 volts B. 46 volts D. 6.40 volts

730. A coil of 15 H inductance and 10 ohms resistance is suddenly connected to a 20 volts DC source by

739. A capacitor of 2 microfarad with an initial charge q0 is connected across the terminals of a 10 ohm

resistor and the switch is closed at t = 0. Find q0 (micro-coulomb) if the transient power in the resistor is known to be A. 1200 C. 102 B. 120 D. 2100 740. The transient current in a loss-free L-C circuit when excited from an ac source is ____ a/an sine wave . A. overdamped B. undamped C. underdamped D. critically damped 741. A series RLC circuit with R = 5 ohms, L = 0.10 H, C = 500 microfarad has a constant voltage V = 10 volts applied at t = 0. Find the resulting transient current. -50t A. 0.707e sin 139t -25t B. 0.272e sin 278t -25t C. 0.720e sin 139t D. none of these 742. A circuit consisting of 20 ohms resistor, 20 mH inductor and a 100 microfarad capacitor in series is connected to a 200 V DC supply. The capacitor is initially uncharged. Find the maximum instantaneous current. A. 6.45 A C. 8.45 A B. 7.45 A D. 9.45 A 743. A time of 10 ms is required for the current in an RL circuit to reach 90% of its final value. If R is 10 ohms, find the value of C to be inserted in series with the RL circuit so that the frequency of oscillation of the resulting current is 1000 cycles per second. -8 A. 5.38 x 10 Farad -7 B. 5.83 x 10 Farad -6 C. 5.83 x 10 Farad -5 D. 5.83 x 10 Farad 744. A series RLC circuit with R = 1 kΩ, L = 1 H and C = 6.25 μF is suddenly connected across a 24 V dc source. At t = 0, i= 0 and q = 0. Determine the current after 0.01 sec. A. 3.45 mA C. 5.40 mA B. 4.61 mA D. 5.05 mA 745. A series RLC circuit has R = 200 Ω, L = 0.1 H and a capacitor C = 10 μF. If a 100 V dc source is connected across the terminals of the series circuit at t = 0, determine the current after 1 millisecond. Assume zero initial conditions. A. 0.353 A C. 0.253 A B. 0.229 A D. 0.368 A 746. Double energy transient are produced in circuits consisting of A. two or more resistors B. resistance and inductance C. resistance and capacitance D. resistance, inductance and capacitance

747. A DC voltage source is connected across a series RLC circuit, under steady state conditions, the applied DC voltage drops entirely across the A. R only B. L only C. C only D. R & L combinations 748. Consider a DC voltage source connected to a series RC circuit. When the steady state reaches, the ratio of energy stored in the capacitor to the total energy supplied by the voltage source is equal to A. 0.362 C. 0.632 B. 0.500 D. 1.00 749. An inductor at t = 0 with initial current I0 acts as A. short C. current source B. open D. voltage source 750. An inductor L carries steady state current I0, suddenly at time t = 0 the inductor is removed from circuit and connected to a resistor R. The current through the inductor at time t is equal -Rt/L +Rt/L A. I0e C. I0e -Rt/L +Rt/L B. I0 (1-e ) D. I0 (1-e ) 751. Transient current in a circuit results from A. voltage applied to the circuit B. impedance of the circuit C. changes in the stored energy in inductors and capacitors D. resistance of the circuit 752. A two terminal black box contains a single element which can be R, L, C or M. As soon as the box is connected to a dc voltage source, a finite non-zero current is observed to flow through the element. The element is a/an A. resistance B. inductance C. capacitance D. Mutual inductance 753. In a circuit the voltage across an element is v(t) = -100t 10 (t - 0.01)e V. The circuit is A. un-damped B. under damped C. critically damped D. Over damped 754. A unit step voltage is applied at t = 0 to a series RL circuit with zero initial conditions A. It is possible for the current to be oscillatory B. The voltage across the resistor at t = 0+ is zero C. The energy stored in the inductor in the steady state is zero D. The resistor current eventually falls to zero 755. A 1 µF capacitor charged through a 2 kΩ resistor by a 10 V dc source. The initial growth of capacitor voltage will be at the rate A. 316 V/ms. C. 6.32 V/ms

B.

5.0 V/ms

D.

10.0 V/ ms

756. A series R-C circuit has a capacitor with an initial voltage of 11 V. A 15 V dc source is now connected across the R-C circuit. The initial rate of change of capacitor voltage can be A. 15 Χ 0.368 / RC C. 11/RC B. 15Χ 0.632 / RC D. 4/RC

0 V

C. D.

can’t find none of these

758. The switch K opened at t = 0 after the network has attained a steady state with the switch closed. Find vs (0+) across the switch.

A. B.

VR1/R2 V

C. D.

V + VR1/R2 0

759. The switch SPST is closed at t = 0, find d/dt i1 (0+).

A. B.

0 40

C. D.

20/3 V none of these

C. D.

50 none of these

50 µC 100 µC

C. D.

250 µC none of these

763. Switch K is opened at t = 0, find IL (0+).

A. B.

5A 0

C. D.

2A none of these

764. Given L1 = 1 H, R = 10 Ω , L2 = 2 H , iL1 (0-) = 2A. Find iL2 (∞).

A. B. A. B.

7.5 V 0

762. Given initial charge in C0 = 500 µC. In the steady state find charge in 1 µf capacitor?

757. What is vc (o+)?

A. B.

A. B.

2/3 A 0

C. D.

4/3 A 1A

765. What is VL (0 +), when switch K is closed at t = 0.

760. SPST is closed at t = 0.What is the time constant of the circuit?

A. B.

A. B.

26/7 7/26

C. D.

7/13 none of these

761. Given VC1 (0-) = 10 V, VC2 (0-) = 5 V find VC2 (∞) = ?

2V -2 V

C. D.

0 none of these

766. An impulse current 2 δ(t) A, with t in second, is made to flow through an initially relaxed 3 F capacitor. The capacitor voltage at T = 0+ is A. 6V C. 2/3 V B. 2V D. zero 767. The circuit of the given figure is initially relaxed. At t = 0+, ____.

A. B.

v =0 V i=0A

C. D.

v = 100 V i=∞

768. The time constant of the circuit shown in figure is

A. B.

0.5 ohm 2.0 ohm

C. D.

4.0 ohm 12 ohm

772. In the circuit shown below, the switch is closed at t = 0. The current through the capacitor will decrease exponentially with a time constant A. B.

C(R1 +R2 ) CR1R2/(R1+R2 )

C. D.

CR1 CR2

769. If i1(t) is 5 A at t = 0, find i1(t) for all t when is(t) = 10 -2t e .

A. B.

0.5 s 1s

C. D.

2s 10s

773. In the network shown, the switch is opened at t = 0. Prior to that, network was in the steady- state, Vs (t) at t =0 is A. B.

-2t

e -2t 20e

C. D.

-2t

30e -2t 6.67e - 1.67

770. The switch in the circuit of the figure has been closed for a long time. It is opened at t = 0. A. B.

A. B. C. D.

v(0+) = 1 V, i (0+) = 0 A v(0+) = 0 V, i(0+) = 0 A v(0+) = 0 V, i (0+) =1 A v (0+) = 1 V, i(0+) = 1 A

0 5V

C. D.

10V 15V

774. For the circuit shown different time constants are given. What are the charging and discharging times respectively? -3 1. 0.5 x 10 S -3 2. 2 x 10 S -3 3. 0.25 x 10 S -3 4. 10 S

771. In the circuit shown, the switch is moved from position A to B at time t = 0. The current i through the inductor satisfies the following conditions 1. i(0) = -8A 2. di/dt (t = 0) = 3 A/s 3. i(∞) = -4A The value of R is A. B.

1, 2 2, 3

C. D.

775. A. B.

C. D.

1, 3 2, 4

776. A. B.

C. D.

A. B.

C. D.

A. B.

C. D.

A. B.

C. D.

777.

778.

779.

780. If Vs = 40t V for t > 0 and iL (0) = 5A, what is the value of i(t) at t = 2sec? A. B.

24A 34A

C. D.

29A 39A

781. A. B.

C. D.

A. B.

C. D.

A. B.

C. D.

782.

783.

784. Consider the following units: -1 1. sec 2 -2 2. rad -sec 3. second 4. Ohm The units of R/L, 1/LC, CR and √ are respectively ____. A. 1, 2, 4 and 3 C. 2, 4, 1 and 3 B. 3, 2, 1 and 4 D. 1, 2, 3 and 4

Started on State Completed on Time taken Grade

Saturday, 14 March 2015, 6:34 PM Finished Saturday, 14 March 2015, 8:19 PM 1 hour 44 mins 40.00 out of a maximum of 50.00 (80%)

Question 1 Correct Mark 1.00 out of 1.00

Flag question

Question text A solenoid 30-cm long is wound with 300 turns, what is the value of its field strength inside the solenoid, when the coil is carrying a current of 2 amperes? Select one: a. 1500 AT/m b. none of these

c. 2000 AT/m d. 1800 AT/m Feedback The correct answer is: 2000 AT/m Question 2 Correct Mark 1.00 out of 1.00

Flag question

Question text What does the second strip of an electronic resistor color code represent? Select one: a. Tolerance b. Multiplier c. Temperature

d. Second digit of the value Feedback The correct answer is: Second digit of the value Question 3 Correct Mark 1.00 out of 1.00

Flag question

Question text Two impedances Z1 = 3 + j4 and Z2 = 5 - j8.66 ohms respectively are connected in parallel. If the combination is connected across a 240 V AC source, how much is the total current? Select one: a. 42.1 A b. 39.9 A

c. 44.4 A

d. 40.6 A Feedback The correct answer is: 44.4 A Question 4 Correct Mark 1.00 out of 1.00

Flag question

Question text A single-phase, 60 Hz, 5 hp squirrel cage induction motor draws a current of 53 A at 117 V. If it has a 78.5% electrical to mechanical conversion efficiency, what capacitance should be connected at the terminals of the motor in order to increase the power factor of the load combination to 92%? Select one:

a. 380 uF b. 480 uF c. 420 uF d. 320 uF Feedback The correct answer is: 380 uF Question 5 Correct Mark 1.00 out of 1.00

Flag question

Question text

Power loss in an electrical circuit can take place in Select one:

a. resistance only b. inductance only c. inductance and resistance d. capacitance only Feedback The correct answer is: resistance only Question 6 Correct Mark 1.00 out of 1.00

Flag question

Question text Electric lines of force leave and enter the charge surface at what angle? Select one: a. 45 deg b. 30 deg c. 15 deg

d. 90 deg Feedback The correct answer is: 90 deg Question 7 Correct

Mark 1.00 out of 1.00

Flag question

Question text If the admittance of a parallel ac circuit is increased, the circuit current Select one: a. is decreased b. none of these c. remains constant

d. is increased Feedback The correct answer is: is increased Question 8 Incorrect Mark 0.00 out of 1.00

Flag question

Question text A magnetic circuit consists of silicon steel of 2000 permeability of 10 cm length and cross sectional area of 22 sq cm and an air gap of the same cross section area and of 1 cm length. A one ampere current flows through 500 turns of coil. Calculate the field intensity across the gap. Select one: a. 622 Oersted

b. 590 Oersted

c. 350 Oersted d. 755 Oersted Feedback The correct answer is: 622 Oersted Question 9 Incorrect Mark 0.00 out of 1.00

Flag question

Question text To double the current range of a 50-micro-amp, 2 kilo-ohm moving coil meter movement, the shunt resistance should be Select one: a. 18 kilo-ohms b. 2 kilo-ohms c. 50 kilo-ohms

d. 1 kilo-ohm Feedback The correct answer is: 2 kilo-ohms Question 10 Incorrect Mark 0.00 out of 1.00

Flag question

Question text The permeability of free space Select one: a. 8.854 x 10^-7 H/m

b. 8.854 x 10^-12 F/m c. 12.56 x 10^-7 F/m d. 4pi x 10^-7 H/m Feedback The correct answer is: 4pi x 10^-7 H/m Question 11 Correct Mark 1.00 out of 1.00

Flag question

Question text What is the energy stored in a 50 uF capacitor if the impressed voltage is 220 volts? Select one: a. 5.51 joules b. 3.63 joules c. 2.42 joules

d. 1.21 joules Feedback The correct answer is: 1.21 joules Question 12 Correct

Mark 1.00 out of 1.00

Flag question

Question text A 1 km cable consists of 12 identical strands of aluminum each 3 mm in diameter. What is the resistance of the cable? Select one: a. 0.24 ohm

b. 0.34 ohm c. 0.44 ohm d. 0.54 ohm Feedback The correct answer is: 0.34 ohm Question 13 Correct Mark 1.00 out of 1.00

Flag question

Question text A 12 volts battery has a 50 ampere-hour capacity. The internal resistance is 0.1 ohm. A 5 ohm load is connected for 5 hours. How many ampere-hours are still left? Select one: a. 41.24 b. 28.51

c. 38.23 d. 35.92 Feedback The correct answer is: 38.23 Question 14 Correct Mark 1.00 out of 1.00

Flag question

Question text Storage battery electrolyte is formed by the dissolving of ____ acid in water. Select one: a. acetic b. atric c. hydrochloric

d. sulfuric Feedback The correct answer is: sulfuric Question 15 Correct Mark 1.00 out of 1.00

Flag question

Question text

A voltmeter using a 20 micro-amp meter movement has an ohm/V rating of Select one: a. 20 kilo-ohms/V b. 10 mega-ohms/V

c. 50 kilo-ohms/V d. 1 kilo-ohm/V Feedback The correct answer is: 50 kilo-ohms/V Question 16 Incorrect Mark 0.00 out of 1.00

Flag question

Question text A core of annealed steel sheet is wound with 1500 turns to wire through which a current of 40 mA is flowing. If the length of the coil is 20 cm, calculate the magnetic strength is Amp-turns per meter. Select one:

a. 300 b. 350 c. 450 d. 400 Feedback The correct answer is: 400 Question 17 Correct

Mark 1.00 out of 1.00

Flag question

Question text The rms value of a half-wave rectified current is 100 A. Its value for full-wave rectification would be ____ amperes. Select one: a. 400/pi A

b. 141.4 A c. 200/pi A d. 200 A Feedback The correct answer is: 141.4 A Question 18 Correct Mark 1.00 out of 1.00

Flag question

Question text To increase the capacity of an ammeter, what should be added to the circuit? Select one:

a. A shunt resistance in parallel with the meter b. A shunt capacitance in parallel with the meter

c. A series resistance d. A series inductance Feedback The correct answer is: A shunt resistance in parallel with the meter Question 19 Correct Mark 1.00 out of 1.00

Flag question

Question text The straight line passing through the two poles of a magnet is called Select one: a. real axis b. imaginary axis

c. magnetic axis d. Cartesian axis Feedback The correct answer is: magnetic axis Question 20 Correct Mark 1.00 out of 1.00

Flag question

Question text

A 30 ohm resistor is connected in parallel with an inductor of inductive reactance XL. The combination is then connected in series with a capacitor of reactance XC. What is the value of XL and XC if the total impedance is 1.92 ohms? Select one: a. 44.8 and 84.21 b. 47.4 and 47.3 c. 84.7 and 34.7

d. 7.84 and 7.34 Feedback The correct answer is: 7.84 and 7.34 Question 21 Correct Mark 1.00 out of 1.00

Flag question

Question text The positive and negative halves of a complex wave are symmetrical when Select one: a. it contains even harmonics b. phase difference between even harmonics and fundamental is 0 or pi

c. it contains odd harmonics d. phase difference between even harmonies and fundamental is either pi/2 or 3pi/2 Feedback The correct answer is: it contains odd harmonics

Question 22 Incorrect Mark 0.00 out of 1.00

Flag question

Question text A milliameter with full-scale deflection of 1 mA and a resistance of 25 ohms was used to measure an unknown current by shunting the meter with a 1-ohm resistor. The meter then reads half-scale. What is the unknown value? Select one: a. 130 mA b. 13 mA c. 12.5 mA

d. 125 mA Feedback The correct answer is: 13 mA Question 23 Correct Mark 1.00 out of 1.00

Flag question

Question text The damping force acts on the moving systems of an indicating instrument only when it is Select one: a. just starting to move

b. stationary c. near its full deflection

d. moving Feedback The correct answer is: moving Question 24 Incorrect Mark 0.00 out of 1.00

Flag question

Question text A condenser of 1 microfarad capacitance is charged to 100 volts and then disconnected from the power supply. A second but uncharged capacitor of 3 microfarad is connected across the first capacitor. The voltage across the parallel combination is Select one: a. 110 volts b. 25 volts

c. 66 2/3 volts d. 45 volts Feedback The correct answer is: 25 volts Question 25 Correct Mark 1.00 out of 1.00

Flag question

Question text What is the effect in terms of bandwidth when the Q of a single-tuned stage is doubled? Select one:

a. halved b. doubled c. four times d. the same Feedback The correct answer is: halved Question 26 Correct Mark 1.00 out of 1.00

Flag question

Question text What is the unit of magnetic flux density? Select one: a. ampere-turns

b. tesla c. maxwell d. gauss

Feedback The correct answer is: tesla Question 27 Correct Mark 1.00 out of 1.00

Flag question

Question text Energy stored by a coil is doubled when its current is increased by ____ per cent. Select one: a. 25 b. 100

c. 41.4 d. 50 Feedback The correct answer is: 41.4 Question 28 Correct Mark 1.00 out of 1.00

Flag question

Question text An analog ohmmeter reads 18 on R X 10 k range. What is the value of the measured resistance? Select one:

a. 180 kilo-ohms b. 18 kilo-ohms c. 18 ohms d. 180 ohms Feedback The correct answer is: 180 kilo-ohms Question 29 Correct Mark 1.00 out of 1.00

Flag question

Question text An electronic/electrical component/device used to store electrical energy. Select one: a. Inductor b. lightning arrester

c. Capacitor d. Resistor Feedback The correct answer is: Capacitor Question 30 Correct Mark 1.00 out of 1.00

Flag question

Question text In a series R-L-C circuit below resonance, the current Select one: a. leads or lags behind the applied voltage depending upon the actual values of L and C b. lags behind the applied voltage c. is in phase with the voltage

d. leads the applied voltage Feedback The correct answer is: leads the applied voltage Question 31 Correct Mark 1.00 out of 1.00

Flag question

Question text Which of the given below can produce the most induced voltage? Select one: a. 50 A, DC b. 1 A, 400 Hz

c. 1 A, 800 Hz d. 1 A, 60 Hz

Feedback The correct answer is: 1 A, 800 Hz Question 32 Correct Mark 1.00 out of 1.00

Flag question

Question text Refers to an action in the operation of secondary cells reforming the electrodes in a chemical reaction where dc voltage is supplied externally. Select one: a. Discharging cells

b. Charging cells c. Polarizing cells d. Aligning cells Feedback The correct answer is: Charging cells Question 33 Correct Mark 1.00 out of 1.00

Flag question

Question text In an experiment, a sinusoidal wave form is observed to complete 8 cycles in 25 msec. Determine the frequency of the wave form.

Select one: a. 200 Hz b. 40 Hz c. 64 Hz

d. 320 Hz Feedback The correct answer is: 320 Hz Question 34 Correct Mark 1.00 out of 1.00

Flag question

Question text What is the force between a point charge 2 x 10^-5 coulomb and another 3 x 10^-6 coulomb when they are 10 cm apart in vacuum? Select one: a. 5.5 kg b. 5.395 x 10^-3 kg

c. 53.95 kg d. 45.5 kg Feedback The correct answer is: 53.95 kg Question 35 Incorrect Mark 0.00 out of 1.00

Flag question

Question text Which is not a part of cathode-ray tube oscilloscope? Select one:

a. Aquadag coating b. Electron gun c. Deflection plates d. Digital panel meter Feedback The correct answer is: Digital panel meter Question 36 Correct Mark 1.00 out of 1.00

Flag question

Question text If a body is considered as a conducting sphere of 0.5 m radius, its capacitance to infinity is Select one: a. 55 uF b. 55 F

c. 55 pF d. 55 nF

Feedback The correct answer is: 55 pF Question 37 Correct Mark 1.00 out of 1.00

Flag question

Question text It is the reciprocal of reluctance and implies the readiness of a material to develop magnetic flux Select one: a. susceptance

b. permeance c. elastance d. conductance Feedback The correct answer is: permeance Question 38 Incorrect Mark 0.00 out of 1.00

Flag question

Question text What is an electronic instrument capable of showing on screen and maybe on print, relative spacing of transmitter carriers, their sidebands and harmonics? Select one:

a. Trigger oscilloscope b. counter c. Spectrum analyzer d. Multimeter Feedback The correct answer is: Spectrum analyzer Question 39 Correct Mark 1.00 out of 1.00

Flag question

Question text A 1% d Arsonval meter movement has coil and swamping resistance adding to 200 ohms. The full -scale voltage is 50 mV. Determine the shunt resistance required producing 1 A full scale current meter. Select one: a. 48.74 milli-ohms b. 49.22 milli-ohms c. 52.02 milli-ohms

d. 50.01 milli-ohms Feedback The correct answer is: 50.01 milli-ohms Question 40 Correct Mark 1.00 out of 1.00

Flag question

Question text A solenoid has an inductance of 1.58 mH. How many turns of wire does it have if the solenoid is 25 cm long and its radius is 2.5 cm? Select one:

a. 400 turns b. 600 turns c. 160,000 turns d. 350 turns Feedback The correct answer is: 400 turns Question 41 Incorrect Mark 0.00 out of 1.00

Flag question

Question text Electric flux remaining from an electric charge of +Q coulomb is Select one: a. Q/(permittivity of free space*relative permittivity) b. Q/(relative permittivity)

c. Q/(permittivity of free space)

d. Q Feedback The correct answer is: Q Question 42 Correct Mark 1.00 out of 1.00

Flag question

Question text What is the other term used for rechargeable battery? Select one: a. primary b. nickel-cadmium c. lead-acid

d. storage Feedback The correct answer is: storage Question 43 Correct Mark 1.00 out of 1.00

Flag question

Question text Two 10-ohm parallel resistors are connected in series with a 5-ohm resistor. The combination is then connected across a 24 volts battery. Find the voltage drop across the 5-ohm resistor.

Select one:

a. 12 V b. 6 V c. 18 V d. 20 V Feedback The correct answer is: 12 V Question 44 Correct Mark 1.00 out of 1.00

Flag question

Question text Two resistances of 10 and 15 ohms, each respectively are connected in parallel. The two are then connected in series with a 5-ohm resistance. It is then connected across a 12-V battery, what are the current and power? Select one: a. 1.2 A, 17.28 W b. 1.5 A, 20.25 W

c. 1.09 A, 13.1 W d. 0.96 A, 11.52 W Feedback The correct answer is: 1.09 A, 13.1 W Question 45 Correct

Mark 1.00 out of 1.00

Flag question

Question text A 100-W, 110-V and a 50-W lamp are connected in series across a 220-V dc source. If the resistances of the two lamps are assumed to remain constant, the voltage across the 100-W lamp is ____ volt. Select one: a. 146.7 b. 73.3

c. 110 d. 220 Feedback The correct answer is: 110 Question 46 Correct Mark 1.00 out of 1.00

Flag question

Question text Two heaters, rated at 1000 W, 250 volts each, are connected in series across a 250 volt, 50 Hz A.C. mains. The total power drawn from the supply would be ____ watt. Select one: a. 2000 b. 250

c. 500 d. 1000 Feedback The correct answer is: 500 Question 47 Correct Mark 1.00 out of 1.00

Flag question

Question text Series resistors are used with voltmeters to Select one: a. decrease the voltage range of the instrument b. decrease the speed of the meter movement c. increase the speed of the meter movement

d. increase the voltage range of the instrument Feedback The correct answer is: increase the voltage range of the instrument Question 48 Incorrect Mark 0.00 out of 1.00

Flag question

Question text

The magnetic field of a bar magnet most closely resembles that of Select one: a. a current-carrying wire loop b. a stream of electrons moving parallel to one another c. a straight current-carrying wire

d. a horseshoe magnet Feedback The correct answer is: a current-carrying wire loop Question 49 Correct Mark 1.00 out of 1.00

Flag question

Question text _____ is used to store electrical energy in an electrostatic field. Select one: a. A transformer

b. A capacitor c. A battery d. An inductor Feedback The correct answer is: A capacitor Question 50 Correct

Mark 1.00 out of 1.00

Flag question

Question text A coaxial cable has a 10 mm diameter inside conductor and a metallic sheath with an inside diameter of 20 mm. If the insulating medium has a dielectric constant, k = 2, and a permittivity of 1.113 x 10^-10, what is the capacitance between the conductor and the sheath per km? Select one: a. 0.0803 uF/km

b. 0.1605 uF/km c. 0.0403 uF/km d. 0.8036 uF/km Feedback The correct answer is: 0.1605 uF/km

An isolated sphere 10 cm in radius is charged in air to 500 Volts. How much charge is required? Select one: a. 8.227 nC b. 5.563 nC c. 2.782 nC d. 6.553 nC Feedback The correct answer is: 5.563 nC Question 2 Correct Mark 1.00 out of 1.00

Flag question

Question text How much is the equivalent power in watts can a 3 horse power provide? Select one: a. 3000 watts b. 248.66 watts c. 2238 watts d. 1492 watts Feedback The correct answer is: 2238 watts Question 3 Incorrect Mark 0.00 out of 1.00

Flag question

Question text

If a current of 5A flowing in a coil of inductance 0.1 H is reversed in 10 ms, e.m.f. induced in it is ____ volt. Select one: a. 1 b. 50 c. 100 d. 10,000 Feedback The correct answer is: 100 Question 4 Incorrect Mark 0.00 out of 1.00

Flag question

Question text For a moving-coil meter movement, the full scale current deflection is Select one: a. the amount of current required in the moving coil to produce half-scale deflection of a pointer of the meter b. the amount of current needed in the moving-coil to produce full-scale deflection of a pointer of the meter c. the value of current flowing in the moving coil for any amount of pointer deflection d. none of the above Feedback The correct answer is: the amount of current needed in the moving-coil to produce full-scale deflection of a pointer of the meter Question 5 Correct Mark 1.00 out of 1.00

Flag question

Question text For the greatest accuracy, what should the input impedance of a VOM be? Select one: a. As small as possible b. As large as possible c. 1,000 ohms/V d. 50,000 ohms/V Feedback The correct answer is: As large as possible Question 6 Correct Mark 1.00 out of 1.00

Flag question

Question text _____ is used to store electrical energy in an electrostatic field. Select one: a. A transformer b. A capacitor c. An inductor d. A battery Feedback The correct answer is: A capacitor Question 7 Incorrect Mark 0.00 out of 1.00

Flag question

Question text As compared to a lead-acid cell, the efficiency of a nickel-iron cell is less due to its Select one: a. compactness b. higher internal resistance c. lower e.m.f. d. smaller quantity of electrolyte used Feedback The correct answer is: higher internal resistance Question 8 Incorrect Mark 0.00 out of 1.00

Flag question

Question text The rms value of the voltage waveform v(t) = sin 10t + sin 20t is ____. Select one: a. 1 b. 2^1/2 c. 1/(2^1/2) d. 1/2 Feedback The correct answer is: 1 Question 9 Incorrect Mark 0.00 out of 1.00

Flag question

Question text A 100-volt carbon filament lamp takes 1 amp when glowing with a filament temperature of 1615 deg C. Calculate the momentary current when the lamp is first switched on in air temperature of 15 deg C. The temperature coefficient of resistance for carbon may be taken as -0.000265 per deg C at 15 deg C Select one: a. 1.94 amperes b. 0.58 amperes c. 0.65 amperes d. 1.72 amperes Feedback The correct answer is: 1.94 amperes Question 10 Incorrect Mark 0.00 out of 1.00

Flag question

Question text Two resistors A and B made of different materials have temperature coefficients of resistance at 20 degrees C of 0.004 and 0.006 respectively. When connected across a voltage source at 20 degrees C, they draw current equally. What percentage of the total current at 100 degrees C does resistor A carry? Select one: a. 61.34% b. 38.66% c. 47.14% d. 52.86% Feedback The correct answer is: 52.86%

Question 11 Correct Mark 1.00 out of 1.00

Flag question

Question text The main purpose of using instrument transformer in a.c. measurements is to Select one: a. extend the range of ac instruments b. provide high transformation ratio c. eliminate instruments corrections d. reduce the possibility of shock Feedback The correct answer is: extend the range of ac instruments Question 12 Correct Mark 1.00 out of 1.00

Flag question

Question text A certain capacitor is charged at 48 volts after which its stored energy is 5.76 x 10^-2 joules. What is the capacitance of the capacitor? Select one: a. 30 uF b. 60 uF c. 2 F d. 50 uF Feedback The correct answer is: 50 uF

Question 13 Incorrect Mark 0.00 out of 1.00

Flag question

Question text A theory in magnetism which assumes that all magnetic material is composed of many tiny magnets Select one: a. Electromagnetics b. Magnetic theory c. Weber theory d. Hysteresis Feedback The correct answer is: Weber theory Question 14 Incorrect Mark 0.00 out of 1.00

Flag question

Question text In an RL circuit, Kirchhoff law gives the following relation: E = Ldi/dt + Ri where: E = supply voltage (200 volts), R = resistance (20 ohms), L = inductance (1 Henry), t = time in seconds, i = current in amperes. If i = 0 when t = 0, find i when t = 0.02 second. Select one: a. 3.1 A b. 3.0 A c. 3.2 A d. 3.3 A Feedback The correct answer is: 3.3 A

Question 15 Correct Mark 1.00 out of 1.00

Flag question

Question text The parallel RL circuit is having quality factor of Q1, when it is connected in series with R, the new quality factor Q2 will be Select one: a. Q2 > Q1 b. none of the above c. Q2 = Q1 d. Q2 < Q1 Feedback The correct answer is: Q2 < Q1 Question 16 Correct Mark 1.00 out of 1.00

Flag question

Question text If relative permittivity of mica is 5, its absolute permittivity is Select one: a. 5*(permittivity of free space) b. 5/(permittivity of free space) c. (permittivity of free space)/5 d. 8.854 x 10^-12 Feedback The correct answer is: 5*(permittivity of free space)

Question 17 Correct Mark 1.00 out of 1.00

Flag question

Question text A plate capacitor is made up of 501 sheet of aluminum 25 cm x 30 cm with a dielectric of paraffin paper 0.0015 cm thick. What is the capacitance in microfarads of the condenser (K for paraffin paper is 2.3)? Select one: a. 35 b. 75 c. 50 d. 25 Feedback The correct answer is: 25 Question 18 Correct Mark 1.00 out of 1.00

Flag question

Question text Which of the following is not a valid expression of Ohm law? Select one: a. I = E/R b. R = E/I c. R = PI d. E = IR Feedback The correct answer is: R = PI

Question 19 Correct Mark 1.00 out of 1.00

Flag question

Question text In a series RLC circuit Select one: a. the current leads VL by 90 degrees b. Z = jXL at resonance c. the current lags VL by 90 degrees d. XL leads Xc by 90 degrees Feedback The correct answer is: the current lags VL by 90 degrees Question 20 Correct Mark 1.00 out of 1.00

Flag question

Question text The phase of even symmetric signal is Select one: a. 0 degrees or + or - 180 degrees b. +90 degrees c. 0 degrees d. -90 degrees Feedback The correct answer is: 0 degrees or + or - 180 degrees Question 21

Correct Mark 1.00 out of 1.00

Flag question

Question text Solenoid 25 cm long is wound with 200 turns, what is the value of the field strength inside the solenoid, when carrying a current of 2 amperes. Select one: a. 1400 AT/m b. 1000 AT/m c. 1200 AT/m d. 1600 AT/m Feedback The correct answer is: 1600 AT/m Question 22 Correct Mark 1.00 out of 1.00

Flag question

Question text The kWh meter can be classified as a/an instrument Select one: a. indicating b. digital c. recording d. deflecting Feedback The correct answer is: recording Question 23

Incorrect Mark 0.00 out of 1.00

Flag question

Question text Pole strength 160 and 192 are separated by a distance has a force of 19600 dynes. What is the distance in cm? Select one: a. 2 b. 4 c. 1 d. 3 Feedback The correct answer is: 3 Question 24 Correct Mark 1.00 out of 1.00

Flag question

Question text A wattmeter measures ____ power. Select one: a. apparent b. reactive c. average d. instantaneous Feedback The correct answer is: average Question 25

Correct Mark 1.00 out of 1.00

Flag question

Question text In practice, earth is chosen as a place of zero electric potential because it Select one: a. it is non-conducting b. keeps losing and gaining electric charge every day c. has almost constant potential d. is easily available Feedback The correct answer is: has almost constant potential Question 26 Incorrect Mark 0.00 out of 1.00

Flag question

Question text An instrument used to measure high resistance as in the measurement of insulation resistance. Select one: a. ohmmeter b. megger c. Wheatstone bridge d. multi-tester Feedback The correct answer is: megger Question 27 Incorrect

Mark 0.00 out of 1.00

Flag question

Question text A power plant customer draws power at 220 volts from transformers on a pole. Current transformers with a ratio of 200/5 are used to meter the electrical usage. What is the multiplier of the kW -hr and demand meters? Select one: a. 100 b. 40 c. 200 d. 80 Feedback The correct answer is: 40 Question 28 Correct Mark 1.00 out of 1.00

Flag question

Question text It is defined as anything that occupies space and has weight. Select one: a. compound b. matter c. molecule d. atom Feedback The correct answer is: matter Question 29

Correct Mark 1.00 out of 1.00

Flag question

Question text Find the voltage drop developed across D Arsonval meter movement having an internal resistance of 1 kilo-ohms and full current of 150 micro amperes. Select one: a. 150 kV b. 150 micro V c. 150 mV d. 150 V Feedback The correct answer is: 150 V Question 30 Incorrect Mark 0.00 out of 1.00

Flag question

Question text The reluctance of a magnetic circuit is ____ relative permeability of the material comprising the circuit. Select one: a. directly proportional to b. independent of c. none of the above d. inversely proportional to Feedback The correct answer is: inversely proportional to Question 31

Incorrect Mark 0.00 out of 1.00

Flag question

Question text A coil of resistor of 5 ohms and inductance 0.4 H is connected to a 50 V d.c. supply. The energy stored in the field is Select one: a. 40 joules b. 10 joules c. 20 joules d. 80 joules Feedback The correct answer is: 20 joules Question 32 Correct Mark 1.00 out of 1.00

Flag question

Question text What is the symbol for magnetic flux density? Select one: a. H b. Q c. B d. E Feedback The correct answer is: B Question 33

Correct Mark 1.00 out of 1.00

Flag question

Question text Three impedances Z1 = 1 - j4 ohms, Z2 = -j6 ohms and Z3 = 4 + j3 ohms are connected in series -parallel. Z1 is connected in series with the parallel combination of Z2 and Z3. Determine the equivalent impedance of the combination. Select one: a. 6.76 - j5.68 ohms b. 5.42 - j7.21 ohms c. 2.23 - j3.32 ohms d. 4.32 - j1.21 ohms Feedback The correct answer is: 6.76 - j5.68 ohms Question 34 Correct Mark 1.00 out of 1.00

Flag question

Question text The three unbalanced currents are: Ia = 10 cis (-30 degrees), Ib = 0, Ic = 10 cis (150 degrees). Find the zero sequence current. Select one: a. 3.33 b. 3.33 cis 30 degrees c. 0 d. 5.77 Feedback

The correct answer is: 0 Question 35 Correct Mark 1.00 out of 1.00

Flag question

Question text An alternating voltage or current is a ____. Select one: a. none of the above b. phasor c. vector quantity d. scalar quantity Feedback The correct answer is: phasor Question 36 Correct Mark 1.00 out of 1.00

Flag question

Question text A current transformer has a single turn primary and a 200 turn secondary and is used to measure a.c. current with the help of a standard 5-A a.c. ammeter. These arrangements can measure a line current of up to ____ ampere, Select one: a. 40 b. 5000 c. 1000 d. 200

Feedback The correct answer is: 1000 Question 37 Correct Mark 1.00 out of 1.00

Flag question

Question text A certain 50 micro-A meter movement has a resistance of 90 ohms. What value of series multiplier is needed to make an instrument that will read 5 volts (maximum)? Select one: a. 102 kilo-ohms b. 99.91 kilo-ohms c. 98 kilo-ohms d. 110 kilo-ohms Feedback The correct answer is: 99.91 kilo-ohms Question 38 Correct Mark 1.00 out of 1.00

Flag question

Question text A 35 unit south pole is placed 1 inch to a 20 unit south pole. Determine the force between the poles. Select one: a. 108.5, repulsion b. 129.5, repulsion c. 108.5, attraction d. 129.5, attraction

Feedback The correct answer is: 108.5, repulsion Question 39 Incorrect Mark 0.00 out of 1.00

Flag question

Question text If a multiple capacitor has 10 plates, each of area 10 square cm, then Select one: a. 10 capacitors will be in parallel b. 9 capacitors will be in parallel c. 10 capacitors will be in series d. 9 capacitors will be in series Feedback The correct answer is: 9 capacitors will be in parallel Question 40 Correct Mark 1.00 out of 1.00

Flag question

Question text Susceptibility of a magnetic material depends on Select one: a. intensity of magnetization b. magnetizing force c. mass of the material d. both A and B Feedback

The correct answer is: both A and B Question 41 Incorrect Mark 0.00 out of 1.00

Flag question

Question text When an R-C circuit is currently connected across a d.c. voltage source, the initial rate of change of capacitor current is Select one: a. -Io/(damping factor) b. Io/(damping factor) c. V/R d. -V/(damping factor) Feedback The correct answer is: -Io/(damping factor) Question 42 Incorrect Mark 0.00 out of 1.00

Flag question

Question text A telephone circuit makes power available at a pair of terminals. The open circuit voltage across the terminals is 1 volt and the impedance looking into the terminals is 500 - j500 ohms. What is the maximum power that can be drawn from the circuit? Select one: a. 0.001 W b. 0.0005 W c. 0.002 W

d. 0.0014 W Feedback The correct answer is: 0.0005 W Question 43 Incorrect Mark 0.00 out of 1.00

Flag question

Question text A 3-phase feeder carries two lagging balanced loads. The power observed by each is measured by two wattmeter method, giving the following readings: First Load: W1 = 160 kW, W2 = 96 kW; Second Load: W1 = 90 kW, W2 = 48 kW. What is the combined kVA load on the feeder? Select one: a. 434.68 b. 462.35 c. 504.35 d. 420.12 Feedback The correct answer is: 434.68 Question 44 Correct Mark 1.00 out of 1.00

Flag question

Question text An analog ohmmeter reads 18 on R X 10 k range. What is the value of the measured resistance? Select one: a. 18 ohms b. 180 ohms

c. 180 kilo-ohms d. 18 kilo-ohms Feedback The correct answer is: 180 kilo-ohms Question 45 Correct Mark 1.00 out of 1.00

Flag question

Question text A 1 uF capacitor charged through a 2 k-ohm resistor by a 10 V dc source. The initial growth of capacitor voltage will be at the rate Select one: a. 3.16 V/ms b. 6.32 V/ms c. 10.0 V/ ms d. 5.0 V/ms Feedback The correct answer is: 5.0 V/ms Question 46 Incorrect Mark 0.00 out of 1.00

Flag question

Question text The time constant of an R-C circuit is defined as the time during which capacitor charging current becomes ____ percent of its ____ value. Select one: a. 63, final

b. 63, initial c. 37, initial d. 37, final Feedback The correct answer is: 37, initial Question 47 Incorrect Mark 0.00 out of 1.00

Flag question

Question text The concept whereby a small voltage is generated by a conductor with current in an external magnetic field refers to ______. Select one: a. magnetic effect b. skin effect c. hall effect d. flywheel effect Feedback The correct answer is: hall effect Question 48 Correct Mark 1.00 out of 1.00

Flag question

Question text The number of independent loops for a network with n nodes and b branches is Select one: a. b - n

b. b - n + 1 c. independent number of nodes d. n - 1 Feedback The correct answer is: b - n + 1 Question 49 Correct Mark 1.00 out of 1.00

Flag question

Question text The active materials of a nickel-iron battery are Select one: a. all of the above b. powdered iron and its oxides c. nickel hydroxide d. 21% solution of caustic potash Feedback The correct answer is: all of the above Question 50 Incorrect Mark 0.00 out of 1.00

Flag question

Question text A solenoid has a magnetic reluctance of 2.2 x 10^-3. It has 300 turns and a core area of 5 cm^2. What is the flux density when the current flowing is one ampere? Select one: a. 26,300 gauss

b. 21,200 gauss c. 34,200 gauss d. 12,200 gauss Feedback The correct answer is: 34,200 gauss

Started on State Completed on Time taken Grade

Saturday, 14 March 2015, 6:23 PM Finished Saturday, 14 March 2015, 8:36 PM 2 hours 12 mins 35.00 out of a maximum of 50.00 (70%)

Question 1 Incorrect Mark 0.00 out of 1.00

Flag question

Question text A series LCR circuit consisting of R = 10 ohms, |XL| = 20 ohms & |XC| = 20 ohms is connected across an a.c. supply of 200 Vrms. The rms voltage across the capacitor is Select one: a. 400 cis (-90 degrees) b. 200 cis (90 degrees) c. 200 cis (-90 degrees) d. 400 cis (90 degrees) Feedback The correct answer is: 400 cis (-90 degrees) Question 2 Correct Mark 1.00 out of 1.00

Flag question

Question text What factors determine the capacitance of a capacitor? Select one: a. Area of the plates, amount of charge on the plates and the dielectric constant of the material between the plates

b. Area of plates, distance between the plates and the dielectric constant of the material between the plates c. Area of the plates, voltage on the plates and distance between the plates d. Area of the plates, voltage on the plates and dielectric constant of the material between the plates Feedback The correct answer is: Area of plates, distance between the plates and the dielectric constant of the material between the plates Question 3 Correct Mark 1.00 out of 1.00

Flag question

Question text An alternating voltage e = 200 sin 314t is applied to a device which offers an ohmic resistance of 20 ohms to the flow of current in one direction while entirely preventing the flow in the opposite direction. The average value of current will be Select one: a. 5 A b. 1.57 A c. 3.18 A d. 1.10 A Feedback The correct answer is: 3.18 A Question 4 Correct Mark 1.00 out of 1.00

Flag question

Question text

In applying the right hand rule by holding a conductor with your right hand so that the thumb represents the current, the encircling fingers around the conductor represent _____. Select one: a. magnetic line of force b. electromagnetic field intensity c. electronic field of force d. electric line of force Feedback The correct answer is: magnetic line of force Question 5 Correct Mark 1.00 out of 1.00

Flag question

Question text The electric energy required to raise the temperature of water in a pool is 1000 kWh. If the heat losses are 25%, the heating energy required will be ____. Select one: a. 1750 kWh b. 1266 kWh c. 1333 kWh d. 1111 kWh Feedback The correct answer is: 1333 kWh Question 6 Incorrect Mark 0.00 out of 1.00

Flag question

Question text Three unequal single-phase loads so connected across the lines of a balanced, 3-phase, 230 volts circuit. The first takes 106 A at 0.78 pf lagging and is connected across lines 1 & 2. The second takes 142 A at 0.82 pf lagging and is connected across 2 & 3. And the third takes 28.4 kW at 0.77 pf lagging. Determine total apparent power. Select one: a. 101 kVA b. 83 kVA c. 78 kVA d. 94 kVA Feedback The correct answer is: 94 kVA Question 7 Correct Mark 1.00 out of 1.00

Flag question

Question text How long must a current of 5 A pass through a 10 ohm resistor until a charge of 12000 coulomb passes through? Select one: a. 1 min b. 4 min c. 2 min d. 3 min Feedback The correct answer is: 4 min Question 8 Correct Mark 1.00 out of 1.00

Flag question

Question text Which meter used dual triode tube and requires external power for operation? Select one: a. FETVM b. VTVM c. TVM d. VOM Feedback The correct answer is: VTVM Question 9 Correct Mark 1.00 out of 1.00

Flag question

Question text For an ac waveform, the period refers to Select one: a. the number of complete cycles per second b. the time it takes for the waveform to reach its peak value c. the length of time required to complete one cycle d. none of the above Feedback The correct answer is: the length of time required to complete one cycle Question 10 Incorrect Mark 0.00 out of 1.00

Flag question

Question text What is VOM? Select one: a. A measurement of the movement of the pointer of a meter b. A combinational ohmmeter, milliammeter, and voltmeter c. A combination of voltmeter and ohmmeter d. A voltage only meter Feedback The correct answer is: A combinational ohmmeter, milliammeter, and voltmeter Question 11 Correct Mark 1.00 out of 1.00

Flag question

Question text A plate capacitor is made up of 501 sheet of aluminum 25 cm x 30 cm with a dielectric of paraffin paper 0.0015 cm thick. What is the capacitance in microfarads of the condenser (K for paraffin paper is 2.3)? Select one: a. 75 b. 50 c. 25 d. 35 Feedback The correct answer is: 25 Question 12 Correct Mark 1.00 out of 1.00

Flag question

Question text A milliameter with full-scale deflection of 1 mA and a resistance of 25 ohms was used to measure an unknown current by shunting the meter with a 1-ohm resistor. The meter then reads half-scale. What is the unknown value? Select one: a. 125 mA b. 130 mA c. 12.5 mA d. 13 mA Feedback The correct answer is: 13 mA Question 13 Correct Mark 1.00 out of 1.00

Flag question

Question text _____ is called the magnetic field. Select one: a. A force set up when current flow through a conductor b. A current flow through space around a permanent magnet c. The force between the plates of a charged capacitor d. The force that drives current through a resistor Feedback The correct answer is: A force set up when current flow through a conductor Question 14 Correct

Mark 1.00 out of 1.00

Flag question

Question text The force acting on a pole of 3 Wb is 12 N. The magnetic intensity of the magnetic field is Select one: a. none of these b. 12 N/Wb c. 36 N/Wb d. 4 N/Wb Feedback The correct answer is: 4 N/Wb Question 15 Correct Mark 1.00 out of 1.00

Flag question

Question text Find the equivalent of 10 Oersted (Oe). Select one: a. 100 Gb/cm b. 1 Gb/m c. 10 Gb/cm d. 1 Gb/cm Feedback The correct answer is: 10 Gb/cm Question 16 Correct Mark 1.00 out of 1.00

Flag question

Question text A coil is wound with 500 turns. When a current of 4 amperes flows, the total flux threading the coil is found to be 0.06 milliweber. What is the inductance of the coil in henries? Select one: a. 7.5 b. 0.0075 c. 0.75 d. 0.075 Feedback The correct answer is: 0.0075 Question 17 Correct Mark 1.00 out of 1.00

Flag question

Question text A variable resistor normally used as a voltage divider Select one: a. Metal film resistor b. Carbon film resistor c. Potentiometer d. Adjustable resistor Feedback The correct answer is: Potentiometer Question 18 Correct Mark 1.00 out of 1.00

Flag question

Question text When both the inductance and resistance of a coil are doubled, the value of Select one: a. time constant remains unchanged b. final steady current is doubled c. initial rate of rise of current is doubled d. time constant is halved Feedback The correct answer is: time constant remains unchanged Question 19 Incorrect Mark 0.00 out of 1.00

Flag question

Question text Point charges in air are located accordingly: Q1 = 3 x 10^-8 C at (0, 0) meters, Q2 = 5 x 10^-8 C at (3, 0) meters and Q3 = -5 x 10^-8 C at (0, 4) meters. Calculate the field intensity at (3, 4) meters. Select one: a. 50.55 V/m b. 16.34 V/m c. 76.88 V/m d. 59.97 V/m Feedback The correct answer is: 59.97 V/m Question 20 Correct Mark 1.00 out of 1.00

Flag question

Question text What is the voltage drop across the resistor in an RC charging circuit when the charge on the capacitor is equal to the battery voltage? Select one: a. 1.0 volt b. zero c. 10 volts d. 0.10 volt Feedback The correct answer is: zero Question 21 Incorrect Mark 0.00 out of 1.00

Flag question

Question text Four 3 pCoul spheres are in corners of square q 1 cm on sides. Find the force in Newton? Select one: a. 4.05 x 10^(-10) b. 15.5 x 10^(-10) c. 20.25 x 10^(-10) d. 8.11 x 10^(-10) Feedback The correct answer is: 15.5 x 10^(-10) Question 22 Correct Mark 1.00 out of 1.00

Flag question

Question text A certain electric welder has a basic circuit equivalent to a series RL with R = 0.1 ohm and L = 1 mH. It is connected to an AC source e through a switch s operated by an automatic timer, which closes the circuit at any desired point on the 60 cycle, sinusoidal wave e. Calculate the magnitude of the transient current resulting when s closes as e is passing through its peak value of 100 volts. Select one: a. 256.41 A b. 76.32 A c. 80.54 A d. 65.74 A Feedback The correct answer is: 65.74 A Question 23 Incorrect Mark 0.00 out of 1.00

Flag question

Question text In order to have a good conductor material, such material shall have _____ valence electrons. Select one: a. one b. twenty one c. five d. more than ten Feedback The correct answer is: one Question 24

Incorrect Mark 0.00 out of 1.00

Flag question

Question text An electric milli-ammeter having an internal resistance of 500 ohms, reads full scale when 1 mA full scale. What size of resistor must be used so that the coil will not be damaged? Select one: a. 5.7 ohms b. 7.5 ohms c. 5.05 ohms d. 6.55 ohms Feedback The correct answer is: 5.05 ohms Question 25 Incorrect Mark 0.00 out of 1.00

Flag question

Question text The capacitance of a cable capacitor depends on Select one: a. core diameter b. ratio of cylinder radii c. insulation thickness d. potential difference Feedback The correct answer is: ratio of cylinder radii Question 26

Correct Mark 1.00 out of 1.00

Flag question

Question text Other measurement an ohmmeter can make beside resistance Select one: a. Circuit continuity b. Shunt c. Current d. Voltage Feedback The correct answer is: Circuit continuity Question 27 Correct Mark 1.00 out of 1.00

Flag question

Question text In a cable capacitor, voltage gradient is maximum at the surface of the Select one: a. sheath b. insulator c. conductor d. earth Feedback The correct answer is: conductor Question 28 Incorrect

Mark 0.00 out of 1.00

Flag question

Question text Given three unbalanced three-phase voltages: Va = 150 + j0 V, Vb = -90 - j120 V, Vc = -120 + j90 V. Determine Va1 Select one: a. 140.23 - j9.32 b. 145.62 + j13.66 c. 135.32 - j1.34 d. 142.43 + j12.35 Feedback The correct answer is: 145.62 + j13.66 Question 29 Incorrect Mark 0.00 out of 1.00

Flag question

Question text Four identical capacitors of 2 uF each are charged to 50 V, 100 V, 200 V and 250 V, respectively. They are then connected in parallel across an uncharged 4 uF capacitor. What is the voltage across the 4 uF capacitor? Select one: a. 120 V b. 100 V c. 50 V d. 300 V Feedback The correct answer is: 300 V

Question 30 Correct Mark 1.00 out of 1.00

Flag question

Question text The purpose of load in an electric circuit is to ____. Select one: a. none of the above b. utilize electrical energy c. increase the circuit current d. decrease the circuit current Feedback The correct answer is: utilize electrical energy Question 31 Incorrect Mark 0.00 out of 1.00

Flag question

Question text The a.c. system is preferred to d.c. system because ____ Select one: a. d.c. voltage cannot be used for domestic appliances b. high-voltage a.c. transmissions is less efficient c. a.c. voltages can easily be changed in magnitude d. d.c. motors do not have fine speed control Feedback The correct answer is: a.c. voltages can easily be changed in magnitude Question 32

Correct Mark 1.00 out of 1.00

Flag question

Question text Which of the following statement is incorrect? Select one: a. open transistor has three (3) terminals b. typical power rating of carbon-composition resistor ranged 0.001 W to 0.1 W c. transistors have three (3) terminals d. potentiometer has three (3) terminals Feedback The correct answer is: typical power rating of carbon-composition resistor ranged 0.001 W to 0.1 W Question 33 Correct Mark 1.00 out of 1.00

Flag question

Question text An analog ohmmeter reads 18 on R X 10 k range. What is the value of the measured resistance? Select one: a. 180 ohms b. 18 ohms c. 18 kilo-ohms d. 180 kilo-ohms Feedback The correct answer is: 180 kilo-ohms Question 34 Correct

Mark 1.00 out of 1.00

Flag question

Question text A 20 ohm resistor, a 0.01 H inductor and a 100 uF capacitor are connected in series to a 200 V DC supply. The capacitor is initially uncharged. Find the maximum instantaneous current. Select one: a. 7.44 A b. 6.44 A c. 8.44 A d. 5.44 A Feedback The correct answer is: 6.44 A Question 35 Correct Mark 1.00 out of 1.00

Flag question

Question text At a 115 kV substation, the PT ratio is 100 and the CT ratio is 1200/5. The potential going into the wattmeter is 115 volts. What is the MW indicated when the wattmeter reads 800 watts? Select one: a. 192 MW b. 15.0 MW c. 19.2 MW d. 150 MW Feedback The correct answer is: 192 MW Question 36

Incorrect Mark 0.00 out of 1.00

Flag question

Question text Measuring instrument that can be used only to measure voltages Select one: a. thermocouple b. permanent-magnet moving-coil c. electrostatic d. dynamometer Feedback The correct answer is: electrostatic Question 37 Correct Mark 1.00 out of 1.00

Flag question

Question text Kirchhoff Current Law states that Select one: a. the algebraic sum of the currents flowing away from any point in a circuit must equal zero b. the algebraic sum of the currents entering and leaving any point in a circuit must equal zero c. the algebraic sum of the currents around any closed path must equal zero d. the algebraic sum of the currents flowing into any point in a circuit must equal zero Feedback The correct answer is: the algebraic sum of the currents entering and leaving any point in a circuit must equal zero Question 38

Correct Mark 1.00 out of 1.00

Flag question

Question text If the combination of an ac voltage and a dc voltage has an instantaneous voltage that varies through a range from -2 V to +10 V, what is the peak ac voltage of the combination? Select one: a. 10 V b. 12 V c. 6 V d. 16 V Feedback The correct answer is: 12 V Question 39 Correct Mark 1.00 out of 1.00

Flag question

Question text Four capacitors A, B, C and D are connected across a 15-V DC source. The charges accumulated in A, B and C are equal to 2000, 750 and 1500 uC, respectively. If the total capacitance of the combination is known to be 35 uF, how much charge is accumulated in capacitor D? Select one: a. 1500 uC b. 1000 uC c. 1400 uC d. 1200 uC Feedback

The correct answer is: 1000 uC Question 40 Incorrect Mark 0.00 out of 1.00

Flag question

Question text The insulation resistance of a capacitor depends on Select one: a. core diameter b. applied voltage c. insulation thickness d. ratio of inner and outer radii Feedback The correct answer is: ratio of inner and outer radii Question 41 Correct Mark 1.00 out of 1.00

Flag question

Question text The type of a.c. distribution system commonly used to supply both light and power is the Select one: a. three phase star system with neutral wire b. three phase delta system c. three phase star system without neutral wire d. open delta system Feedback The correct answer is: three phase star system with neutral wire

Question 42 Correct Mark 1.00 out of 1.00

Flag question

Question text What is the unit of capacitance? Select one: a. Gauss b. Farad c. Weber d. Coulomb Feedback The correct answer is: Farad Question 43 Correct Mark 1.00 out of 1.00

Flag question

Question text The magnetic flux of 2000 lines is how many in maxwells? Select one: a. 8000 b. 1000 c. 4000 d. 2000 Feedback The correct answer is: 2000 Question 44

Correct Mark 1.00 out of 1.00

Flag question

Question text Most materials relative permittivity lies between Select one: a. 50 and 100 b. 0.01 and 1 c. 10 and 50 d. 1 and 10 Feedback The correct answer is: 1 and 10 Question 45 Correct Mark 1.00 out of 1.00

Flag question

Question text Permeability in a magnetic circuit corresponds to ____ in an electric circuit. Select one: a. conductance b. conductivity c. reluctivity d. resistivity Feedback The correct answer is: conductivity Question 46 Incorrect

Mark 0.00 out of 1.00

Flag question

Question text Meters with moving coil are normally used for measuring _____ Select one: a. Both ac and dc b. Only dc c. % of value of dc d. Only ac Feedback The correct answer is: Only dc Question 47 Correct Mark 1.00 out of 1.00

Flag question

Question text The inductive reactance of a circuit is ____ frequency. Select one: a. independent of b. none of the above c. directly proportional to d. inversely proportional Feedback The correct answer is: directly proportional to Question 48 Correct Mark 1.00 out of 1.00

Flag question

Question text A current transformer has a single turn primary and a 200 turn secondary and is used to measure a.c. current with the help of a standard 5-A a.c. ammeter. These arrangements can measure a line current of up to ____ ampere, Select one: a. 1000 b. 200 c. 40 d. 5000 Feedback The correct answer is: 1000 Question 49 Incorrect Mark 0.00 out of 1.00

Flag question

Question text A series circuit has R of 500 ohms, a 10 micro-henry inductance L and a 4 micro-farad capacitance C across a 60 Hz, 120-volt power source. Compute the load current. Select one: a. 0.150 A b. 0.100 A c. 0.120 A d. 0.144 A Feedback The correct answer is: 0.144 A Question 50

Correct Mark 1.00 out of 1.00

Flag question

Question text A magnetic circuit consists of silicon steel of 3000 permeability and an air gap. The length of the steel core is 10 cm and the air gap is 2 cm. Both have same cross section of 1.5 sq cm. A current of 1/2 ampere flows through the windings to produce 2351 maxwells flux. How many turns are there in the coil? Select one: a. 5,000 turns b. 4,120 turns c. 1,250 turns d. 2,500 turns Feedback The correct answer is: 5,000 turns

What is the energy stored in a 50 uF capacitor if the impressed voltage is 220 volts? Select one: a. 5.51 joules b. 1.21 joules c. 3.63 joules d. 2.42 joules Feedback The correct answer is: 1.21 joules Question 2 Correct Mark 1.00 out of 1.00 Flag question

Question text If R = 50 ohms, C = 0.0001 Farad, E = 100 volts and i(0) = 2 amperes, determine the Laplace transform expression for I(s). Select one: a. I(s) = 2/(s + 50) b. I(s) = 2/[s(s + 2)] c. I(s) = 2/(s + 200) d. I(s) = 2/(s + 2) Feedback The correct answer is: I(s) = 2/(s + 200) Question 3 Correct Mark 1.00 out of 1.00 Flag question

Question text Kirchhoff Laws fail in the case of Select one: a. distributed parameter networks b. linear networks c. dual networks d. non-linear networks

Feedback The correct answer is: distributed parameter networks Question 4 Correct Mark 1.00 out of 1.00 Flag question

Question text Refers to a force of field that exists between ions where they either repel or attract each other Select one: a. dielectric b. potential field c. electromotive d. resisting field Feedback The correct answer is: potential field Question 5 Correct Mark 1.00 out of 1.00 Flag question

Question text Find the reading of an AC voltmeter connected across the series source of 100 sin (wt - pi/2) and 100 sin wt. Select one: a. 170.71 b. 130.65 c. 100 d. 184.78 Feedback The correct answer is: 100 Question 6 Correct Mark 1.00 out of 1.00 Flag question

Question text

A series RC circuit consist of R = 2 M-ohms and an uncharged capacitor C = 5 uF. The circuit is connected across a 100 V DC source at t = 0. Determine the voltage across the resistor at the instant the switch is closed and 5 seconds after the switched has been closed. Select one: a. 100 V, 60.65 V b. 0 V, 60.65 V c. 100 V, 0 V d. 0 V, 100 V Feedback The correct answer is: 100 V, 60.65 V Question 7 Correct Mark 1.00 out of 1.00 Flag question

Question text What is the average value of a half wave rectified sinusoidal wave with 70.7 ampere amplitude? Select one: a. 22. 5 A b. 31.6 A c. 50 A d. 135.35 A Feedback The correct answer is: 22. 5 A Question 8 Correct Mark 1.00 out of 1.00 Flag question

Question text _____ is used to store electrical energy in an electrostatic field. Select one: a. An inductor b. A battery c. A transformer

d. A capacitor Feedback The correct answer is: A capacitor Question 9 Correct Mark 1.00 out of 1.00 Flag question

Question text Voltage in electrical circuits is analogous to _____ in magnetic circuits. Select one: a. Magnetizing force b. Flux c. Ampere-turn d. Magnetomotive force Feedback The correct answer is: Magnetomotive force Question 10 Correct Mark 1.00 out of 1.00 Flag question

Question text At a 115 kV substation, the PT ratio is 100 and the CT ratio is 1200/5. The potential going into the wattmeter is 115 volts. What is the MW indicated when the wattmeter reads 800 watts? Select one: a. 150 MW b. 192 MW c. 19.2 MW d. 15.0 MW Feedback The correct answer is: 192 MW Question 11 Correct Mark 1.00 out of 1.00

Flag question

Question text The theory of Ohm law is applied in a _____ circuit. Select one: a. exponential b. unilateral c. trivalent d. linear Feedback The correct answer is: linear Question 12 Incorrect Mark 0.00 out of 1.00 Flag question

Question text Which part of the oscilloscope emits electrons? Select one: a. Heater cathode b. Grid c. Accelerating anode d. Cathode ray tube Feedback The correct answer is: Heater cathode Question 13 Incorrect Mark 0.00 out of 1.00 Flag question

Question text The impedances of two parallel branches of a circuit are (10 + j10) and (10 - j10) respectively. The impedance of the parallel combination is Select one: a. 5 - j5

b. 10 + j0 c. 0 - j20 d. 20 + j0 Feedback The correct answer is: 5 - j5 Question 14 Incorrect Mark 0.00 out of 1.00 Flag question

Question text A metal transport plane has a wing spread of 88 ft. What difference of potential exists between the extremities of the wings, when the plane moves horizontally with the speed of 150 miles per hour? The value of the vertical-component of the magnetic field of the earth is 0.65 Gauss at the plane. Select one: a. 12 Volt b. 0.24 Volt c. 0.12 volt d. 1.2 Volt Feedback The correct answer is: 12 Volt Question 15 Correct Mark 1.00 out of 1.00 Flag question

Question text Find the dielectric constant to air Select one: a. Approximately 4 b. Approximately 0 c. Approximately 1 d. Approximately 2 Feedback The correct answer is: Approximately 1

Question 16 Correct Mark 1.00 out of 1.00 Flag question

Question text How much power does an electronic equipment consume, assuming a 5.50 amperes current flowing and a 120 volts power source? Select one: a. 60 watts b. 66 watts c. 660 watts d. 125.5 watts Feedback The correct answer is: 660 watts Question 17 Incorrect Mark 0.00 out of 1.00 Flag question

Question text In an R-C circuit across a d. c voltage source, which of the following is zero at the beginning of the transient? Select one: a. charging current b. drop across R c. capacitor voltage d. none of the above Feedback The correct answer is: capacitor voltage Question 18 Incorrect Mark 0.00 out of 1.00 Flag question

Question text An ac device used to measure the angle between the voltage and its current.

Select one: a. phase angle meter b. power factor meter c. demand meter d. reactive meter Feedback The correct answer is: power factor meter Question 19 Correct Mark 1.00 out of 1.00 Flag question

Question text A 24 volts battery delivers 15 amp to a motor load in 30 minutes per day. What is the energy delivered per month in kWh? Select one: a. 6.2 b. 7.31 c. 5.4 d. 0.18 Feedback The correct answer is: 5.4 Question 20 Correct Mark 1.00 out of 1.00 Flag question

Question text If a current of 5A flowing in a coil of inductance 0.1 H is reversed in 10 ms, e.m.f. induced in it is ____ volt. Select one: a. 10,000 b. 100 c. 50 d. 1

Feedback The correct answer is: 100 Question 21 Incorrect Mark 0.00 out of 1.00 Flag question

Question text The phase b voltage and the phase b current of a balanced 3-phase system are: v = 220 sin (wt + 210 deg) and i = 10 sin (wt - 180 degrees). What is the power of the system? Select one: a. 3300 W b. 3810 W c. 1905 W d. 5716 W Feedback The correct answer is: 1905 W Question 22 Incorrect Mark 0.00 out of 1.00 Flag question

Question text A parallel plate capacitor with air between its plates is charged until the potential difference V appears across it. Another capacitor having hard rubber (dielectric constant = 3) between its plates but otherwise identical, is also charged to the same potential difference. If the energy of the first capacitor is W, that of the second is Select one: a. W/3 b. 9W c. W d. 3W Feedback The correct answer is: 3W Question 23 Correct Mark 1.00 out of 1.00

Flag question

Question text An RLC series circuit has f1 and f2 as the half power frequencies and f0 as the resonant frequency. The Q-factor of the circuit is given by: Select one: a. (f1 - f0)/(f2 - f0) b. f0/(f1 - f2) c. (f1 + f2)/(2f0) d. (f1 - f2)/f0 Feedback The correct answer is: f0/(f1 - f2) Question 24 Correct Mark 1.00 out of 1.00 Flag question

Question text Electric power is almost exclusively generated, transmitted and distributed, by three phase system because it Select one: a. all of the above b. costs less than single-phase apparatus c. it is more efficient d. uses less material for a given capacity Feedback The correct answer is: all of the above Question 25 Correct Mark 1.00 out of 1.00 Flag question

Question text What is the relationship between frequency and the value of XC? Select one: a. frequency has no effect

b. XC varies directly with frequency c. XC varies indirectly with frequency d. XC varies inversely with frequency Feedback The correct answer is: XC varies inversely with frequency Question 26 Incorrect Mark 0.00 out of 1.00 Flag question

Question text The Meralco test of a 10 A wattmeter having a constant of 0.4, the disk makes 40 revolutions in 53.6 seconds. The average volts and amperes during the period of test are 116 volts and 9.4 A. What is the percent accuracy of the meter at this load? Select one: a. 98.58% b. 97.45% c. 98.07% d. 96.44% Feedback The correct answer is: 98.58% Question 27 Incorrect Mark 0.00 out of 1.00 Flag question

Question text A 0 - 10 mA galvanometer with a coil resistance of 20 ohms is converted to a 0 - 50 V galvanometer using Select one: a. 50 ohms shunt resistor b. 4980 ohms series resistor c. 5020 ohms series resistor d. 5000 ohms series resistor Feedback The correct answer is: 4980 ohms series resistor

Question 28 Correct Mark 1.00 out of 1.00 Flag question

Question text What type of tube is used to display signals on an oscilloscope? Select one: a. Filament tube b. Pentode c. Tetrode d. Cathode-ray tube Feedback The correct answer is: Cathode-ray tube Question 29 Correct Mark 1.00 out of 1.00 Flag question

Question text In a parallel RC circuit, Select one: a. VC and IR are 90 degrees out of phase b. VC and IR are in phase c. IC and IR are in phase d. VC and IC are in phase Feedback The correct answer is: VC and IR are in phase Question 30 Correct Mark 1.00 out of 1.00 Flag question

Question text Three equal impedances, each having a resistance of 8 ohms and an inductive reactance of 7 ohms are connected in delta to lines a, b and c of a 240 V, 3-phase, 3-wire line, phase sequence a-b-c. What is the

reading of a single-phase wattmeter connected with its current coil in line a and the potential coil across lines b and c? Select one: a. 6,324 W b. 6,561 W c. 6,180 W d. 6,004 W Feedback The correct answer is: 6,180 W Question 31 Incorrect Mark 0.00 out of 1.00 Flag question

Question text According to Gauss theorem, the surface integral of the normal component of the electric flux density D over a closed surface containing charge Q is Select one: a. Q*(permittivity of free space) b. Q^2/(permittivity of free space) c. Q/(permittivity of free space) d. Q Feedback The correct answer is: Q Question 32 Correct Mark 1.00 out of 1.00 Flag question

Question text The fact that the sum of the individual branch currents equals the total current in a parallel circuit is the basis for Select one: a. Kirchhoff Current Law b. node voltage analysis

c. the method of mesh currents d. Kirchhoff Voltage Law Feedback The correct answer is: Kirchhoff Current Law Question 33 Incorrect Mark 0.00 out of 1.00 Flag question

Question text Two electrons in a vacuum experience a force of 2 x 10^-15 N. How far apart are the electrons? Select one: a. 2.84 x 10^-12 m b. 5.05 x 10^-12 m c. 3.39 x 10^-7 m d. 0.48 x 10^-7 m Feedback The correct answer is: 3.39 x 10^-7 m Question 34 Correct Mark 1.00 out of 1.00 Flag question

Question text How is an ammeter connected to the circuit under test? Select one: a. In parallel b. In series c. Shunted d. Series-parallel Feedback The correct answer is: In series Question 35 Correct Mark 1.00 out of 1.00

Flag question

Question text To double the current range of a 50-micro-amp, 2 kilo-ohm moving coil meter movement, the shunt resistance should be Select one: a. 18 kilo-ohms b. 2 kilo-ohms c. 50 kilo-ohms d. 1 kilo-ohm Feedback The correct answer is: 2 kilo-ohms Question 36 Correct Mark 1.00 out of 1.00 Flag question

Question text An electronic/electrical component/device used to store electrical energy. Select one: a. Inductor b. Resistor c. lightning arrester d. Capacitor Feedback The correct answer is: Capacitor Question 37 Correct Mark 1.00 out of 1.00 Flag question

Question text If three shielded 100 mH coils are connected in series, what is the total effective inductance? Select one: a. 67.777 mH b. 33.333 mH

c. 300 mH d. 100 mH Feedback The correct answer is: 300 mH Question 38 Incorrect Mark 0.00 out of 1.00 Flag question

Question text Four capacitors A, B, C and D are connected across a 15-V DC source. The charges accumulated in A, B and C are equal to 2000, 750 and 1500 uC, respectively. If the total capacitance of the combination is known to be 35 uF, how much charge is accumulated in capacitor D? Select one: a. 1500 uC b. 1200 uC c. 1400 uC d. 1000 uC Feedback The correct answer is: 1000 uC Question 39 Correct Mark 1.00 out of 1.00 Flag question

Question text A solenoid has an inductance of 1.58 mH. How many turns of wire does it have if the solenoid is 25 cm long and its radius is 2.5 cm? Select one: a. 400 turns b. 160,000 turns c. 350 turns d. 600 turns Feedback The correct answer is: 400 turns

Question 40 Correct Mark 1.00 out of 1.00 Flag question

Question text The type of cell commonly referred to as flashlight battery Select one: a. Dry cell b. Mercury cell c. Nickel-cadmium battery d. Lead acid cell Feedback The correct answer is: Dry cell Question 41 Incorrect Mark 0.00 out of 1.00 Flag question

Question text In addition to supporting the moving coil, the aluminum bobbin in a permanent moving coil meter performs the function of one of the following. Which one is this? Select one: a. reduce the reluctance b. conducts magnetic flux lines c. dampens the needle movement d. balance the pointer Feedback The correct answer is: dampens the needle movement Question 42 Incorrect Mark 0.00 out of 1.00 Flag question

Question text

To test the accuracy of a kilowatt-hour meter an electrician used a wattmeter. He found out that the meter makes 5 revolutions in 18 seconds. The meter constant is 3.2. What is the percentage error if the wattmeter reading is 3368? Select one: a. 5% faster b. 8% faster c. 8% slower d. 5% slower Feedback The correct answer is: 5% slower Question 43 Incorrect Mark 0.00 out of 1.00 Flag question

Question text If a force of 4.8 x 10^(-2) N is required to move a 40 uC charge in an electric field between two points 20 cm apart. What is the potential difference between two points? Select one: a. 240 Volts b. 360 Volts c. 160 Volts d. 120 Volts Feedback The correct answer is: 240 Volts Question 44 Correct Mark 1.00 out of 1.00 Flag question

Question text A lead circuit has a phase angle that is Select one: a. Greater than 90 degrees b. The same as the input voltage

c. Between 0 and +90 degrees d. Between 0 and -90 degrees Feedback The correct answer is: Between 0 and +90 degrees Question 45 Correct Mark 1.00 out of 1.00 Flag question

Question text If a current of 5 A flows through a long wire of radius 0.004 meter, what is the magnetic intensity produced 0.02 meter away from the surface of the wire? Select one: a. 66.34 AT/m b. 19.70 AT/m c. 33.17 AT/m d. 39.80 AT/m Feedback The correct answer is: 39.80 AT/m Question 46 Correct Mark 1.00 out of 1.00 Flag question

Question text What is the effect of connecting battery cells in parallel? Select one: a. Voltage decreases b. Voltage increases c. Current decreases d. Current increases Feedback The correct answer is: Current increases Question 47 Incorrect

Mark 0.00 out of 1.00 Flag question

Question text The value of temperature coefficient of resistance at 0 degrees C of a conductor is 1/236 per degree C. Its value at 18 degrees will be ____. Select one: a. 1/218 per degree C b. 1/254 per degree C c. 1/272 per degree C d. none of the above Feedback The correct answer is: 1/254 per degree C Question 48 Correct Mark 1.00 out of 1.00 Flag question

Question text Which of the given below can produce the most induced voltage? Select one: a. 1 A, 60 Hz b. 1 A, 400 Hz c. 50 A, DC d. 1 A, 800 Hz Feedback The correct answer is: 1 A, 800 Hz Question 49 Correct Mark 1.00 out of 1.00 Flag question

Question text It exists in the space surrounding a magnet Select one: a. potential space

b. magnetic pole c. magnetic space d. magnetic field Feedback The correct answer is: magnetic field Question 50 Correct Mark 1.00 out of 1.00 Flag question

Question text It is that property of a material which enables it to attract pieces of iron. Select one: a. permitivity b. valence c. ionization d. magnetism Feedback The correct answer is: magnetism

The period during which current and voltage changes take place in a circuit is called ____. Select one: a. varying b. steady c. transient d. permanent Feedback The correct answer is: transient Question 2 Correct Mark 1.00 out of 1.00

Flag question

Question text Determine the rms value of a semi-circular current wave which has a maximum value of A. Select one: a. 0.816A b. 0.23 A c. 0.707A d. 0.866A Feedback The correct answer is: 0.816A Question 3 Correct Mark 1.00 out of 1.00

Flag question

Question text A given capacitor has a capacitance of 100 uF. Calculate the elastance. Select one: a. 100,000 b. 10,000

c. 100 d. 10 Feedback The correct answer is: 10,000 Question 4 Correct Mark 1.00 out of 1.00

Flag question

Question text In a delta connected system the line current is Select one: a. 1.414 times the phase current b. phasor sum of the two phase currents c. equal to the phase current d. 1.732 times the phase current Feedback The correct answer is: 1.732 times the phase current Question 5 Correct Mark 1.00 out of 1.00

Flag question

Question text The flux density emanating from a pole of generator is 20,000 gauss. A conductor one meter long cuts the flux perpendicularly at a speed of 40 meters per second. What voltage is developed? Select one: a. 80 volts b. 230 volts c. 800 volts d. 8 volts Feedback

The correct answer is: 80 volts Question 6 Correct Mark 1.00 out of 1.00

Flag question

Question text A combination of two charges with equal charge magnitude but opposite signs Select one: a. dynamic dipole b. static dipole c. electric dipole d. magnetic dipole Feedback The correct answer is: electric dipole Question 7 Correct Mark 1.00 out of 1.00

Flag question

Question text It is the reciprocal of reluctance and implies the readiness of a material to develop magnetic flux Select one: a. susceptance b. conductance c. permeance d. elastance Feedback The correct answer is: permeance Question 8 Correct Mark 1.00 out of 1.00

Flag question

Question text A conductor, 50 mm long, moves at a velocity of 2.5 meters per second across a magnetic field of 0.90 Wb/m^2. What is the voltage generated? Select one: a. 0.072 V b. 0.1125 V c. 0.0648 V d. 0.125 V Feedback The correct answer is: 0.1125 V Question 9 Incorrect Mark 0.00 out of 1.00

Flag question

Question text A two port network is reciprocal, if and only if Select one: a. BC - AD = -1 b. h12 = h21 c. Y12 = -Y21 d. Z11 = Z22 Feedback The correct answer is: BC - AD = -1 Question 10 Correct Mark 1.00 out of 1.00

Flag question

Question text A 1% d Arsonval meter movement has coil and swamping resistance adding to 200 ohms. The full scale voltage is 50 mV. Determine the shunt resistance required producing 1 A full scale current meter. Select one: a. 48.74 milli-ohms b. 50.01 milli-ohms c. 49.22 milli-ohms d. 52.02 milli-ohms Feedback The correct answer is: 50.01 milli-ohms Question 11 Correct Mark 1.00 out of 1.00

Flag question

Question text For a sine wave, the number of complete cycles per second is called the Select one: a. wavelength b. phase angle c. period d. frequency Feedback The correct answer is: frequency Question 12 Correct Mark 1.00 out of 1.00

Flag question

Question text A steel 1 m long and 30 cm wide is to be plated with 0.02 mm copper. The density of copper is 8.9 g/cm^3 and its electrochemical equivalent weight is 0.3292 x 10^-3 g/Coul. How long should the steel sheet remain in the electroplating bath that contains Copper (Cu^+2) ions in which the current is 100 A? Select one: a. 27 minutes b. 54 minutes c. 541 minutes d. 145 minutes Feedback The correct answer is: 54 minutes Question 13 Correct Mark 1.00 out of 1.00

Flag question

Question text If a 220 V heater is used on 110 V supply, heat produced by it will be ____ as much Select one: a. four times b. one-half c. twice d. one-fourth Feedback The correct answer is: one-fourth Question 14 Correct Mark 1.00 out of 1.00

Flag question

Question text What is the degree of exactness of measurement when compared to the expected value of the variable being measured? Select one: a. Precision b. Deviation c. Error d. Accuracy Feedback The correct answer is: Accuracy Question 15 Incorrect Mark 0.00 out of 1.00

Flag question

Question text Find the value of resistor with the following color codes: Brown, White, Orange, Red Select one: a. 19 k ohms + or - 2% b. 1.9 k ohms + or - 10% c. 190 ohms + or - 10% d. 19 k ohms + or - 20% Feedback The correct answer is: 19 k ohms + or - 20% Question 16 Correct Mark 1.00 out of 1.00

Flag question

Question text An ac source of 200 Vrms supplies active power of 600 W and reactive power of 800 VAR. The rms current drawn from the source is Select one: a. 10 A b. 2.5 A c. 3.75 A d. 5 A Feedback The correct answer is: 5 A Question 17 Correct Mark 1.00 out of 1.00

Flag question

Question text A current transformer has a single turn primary and a 200 turn secondary and is used to measure a.c. current with the help of a standard 5-A a.c. ammeter. These arrangements can measure a line current of up to ____ ampere, Select one: a. 5000 b. 1000 c. 200 d. 40 Feedback The correct answer is: 1000 Question 18 Correct Mark 1.00 out of 1.00

Flag question

Question text A one-meter rod of 2-cm diameter is drawn until its resistance is 100 times the initial resistance. Its length afterwards is? Select one: a. 100 m b. 10 m c. 12.5 m d. 5 m Feedback The correct answer is: 10 m Question 19 Correct Mark 1.00 out of 1.00

Flag question

Question text Knowing that the absolute permittivity of air is 8.854 x 10^-12 F/m, determine the absolute permeability of air. Select one: a. 4pi x 10^-7 H/m b. 3pi x 10^-7 H/m c. 12pi x 10^-7 H/m d. 2pi x 10^-7 H/m Feedback The correct answer is: 4pi x 10^-7 H/m Question 20 Correct Mark 1.00 out of 1.00

Flag question

Question text The field winding of a DC generator is wound with 900 turns and has a resistance of 50 ohms. If the winding is excited from a 240 V dc source, the magnetic flux linking the coil is 4 mWb. Determine the self-inductance of the coil. Select one: a. 0.83 H b. 0.75 H c. 0.92 H d. 0.56 H Feedback The correct answer is: 0.75 H Question 21 Correct Mark 1.00 out of 1.00

Flag question

Question text A galvanometer with a 20-ohm coil resistance has a full-scale deflection current of 10 mA. If a 0.02 ohm is placed across the meter to increase its capacity, what is the approximate new full scale current of the meter? Select one: a. 10.10 A b. 10.11 A c. 11.01 A d. 10.01 A Feedback The correct answer is: 10.01 A Question 22 Correct Mark 1.00 out of 1.00

Flag question

Question text If the electrical current carried by each of the two long parallel wire is doubled, and their separation is also doubled, the force between them Select one: a. also doubles b. decreases by a factor of four c. increases by a factor of four d. decreases by a factor of two Feedback The correct answer is: also doubles Question 23 Correct Mark 1.00 out of 1.00

Flag question

Question text A parallel plate capacitor with air between its plates is charged until the potential difference V appears across it. Another capacitor having hard rubber (dielectric constant = 3) between its plates but otherwise identical, is also charged to the same potential difference. If the energy of the first capacitor is W, that of the second is Select one: a. 3W b. W/3 c. 9W d. W Feedback The correct answer is: 3W Question 24 Correct Mark 1.00 out of 1.00

Flag question

Question text A milliameter with full-scale deflection of 1 mA and a resistance of 25 ohms was used to measure an unknown current by shunting the meter with a 1-ohm resistor. The meter then reads half-scale. What is the unknown value? Select one: a. 130 mA b. 125 mA c. 13 mA d. 12.5 mA Feedback The correct answer is: 13 mA Question 25 Correct Mark 1.00 out of 1.00

Flag question

Question text The SI unit of specific resistance is ____. Select one: a. ohm-m b. ohm-m^2 c. mho d. ohm-cm Feedback The correct answer is: ohm-m Question 26 Correct Mark 1.00 out of 1.00

Flag question

Question text Electric current in a wire is the flow of ____. Select one: a. atoms b. valence electrons c. free electrons d. bound electrons Feedback The correct answer is: free electrons Question 27 Correct Mark 1.00 out of 1.00

Flag question

Question text While a capacitor is still connected to a power source, the spacing between its plates is halved. Which of the following quantity would remain constant? Select one: a. potential difference b. plate charge c. electric flux density d. field strength Feedback The correct answer is: potential difference Question 28 Incorrect Mark 0.00 out of 1.00

Flag question

Question text Which of the following ammeter will be used to measure alternating currents only? Select one: a. induction-type b. electrodynamic type c. moving-iron d. permanent-magnet type Feedback The correct answer is: induction-type Question 29 Correct Mark 1.00 out of 1.00

Flag question

Question text Which is not a part of cathode-ray tube oscilloscope? Select one: a. Deflection plates b. Aquadag coating c. Electron gun d. Digital panel meter Feedback The correct answer is: Digital panel meter Question 30 Correct Mark 1.00 out of 1.00

Flag question

Question text What is the symbol for magnetic flux density? Select one: a. E b. Q c. B d. H Feedback The correct answer is: B Question 31 Correct Mark 1.00 out of 1.00

Flag question

Question text A 50 mH inductance is connected in series with a 20 ohms resistor. If the voltage is 220 volts, what power is drawn? Select one: a. 1280 watts b. 802 watts c. 560 watts d. 680 watts Feedback The correct answer is: 1280 watts Question 32 Correct Mark 1.00 out of 1.00

Flag question

Question text Ten impedances connected in parallel draw the following individual current: 5 cis(0 deg), 5 cis (5 deg), 5 cis (10 deg), 5 cis (15 deg), 5 cis (20 deg), 5 cis (25 deg), 5 cis (30 deg), 5 cis (35 deg), 5 cis (40 deg), 5 cis (45 deg). What is the effective value of the total current?

Select one: a. 25.345 A b. 48.444 A c. 84.389 A d. 34.255 A Feedback The correct answer is: 48.444 A Question 33 Incorrect Mark 0.00 out of 1.00

Flag question

Question text Which of the following is zero inside charge-conducting spheres? Select one: a. both A and B b. both B and C c. potential d. electric intensity Feedback The correct answer is: both A and B Question 34 Incorrect Mark 0.00 out of 1.00

Flag question

Question text A condenser of 1 microfarad capacitance is charged to 100 volts and then disconnected from the power supply. A second but uncharged capacitor of 3 microfarad is connected across the first capacitor. The voltage across the parallel combination is Select one: a. 110 volts b. 45 volts

c. 66 2/3 volts d. 25 volts Feedback The correct answer is: 25 volts Question 35 Correct Mark 1.00 out of 1.00

Flag question

Question text _____ is the property of magnetic materials which retain magnetism after magnetizing force withdrawn. Select one: a. Resistivity b. Conductivity c. Retentivity d. Reluctivity Feedback The correct answer is: Retentivity Question 36 Correct Mark 1.00 out of 1.00

Flag question

Question text The force acting on a pole of 3 Wb is 12 N. The magnetic intensity of the magnetic field is Select one: a. 36 N/Wb b. none of these c. 4 N/Wb d. 12 N/Wb Feedback

The correct answer is: 4 N/Wb Question 37 Correct Mark 1.00 out of 1.00

Flag question

Question text Calculate the capacitance between two parallel plates each of which is 100 cm^2 and 2 mm apart in air. Select one: a. 0.502 uF b. 0.452 uF c. 0.515 uF d. 0.443 uuF Feedback The correct answer is: 0.443 uuF Question 38 Correct Mark 1.00 out of 1.00

Flag question

Question text In an ac wave, 30 degrees of phase is _____ of a cycle. Select one: a. 1/12 b. 1/30 c. 1/2 d. 1/3 Feedback The correct answer is: 1/12 Question 39 Correct Mark 1.00 out of 1.00

Flag question

Question text The magnetizing force (H) and magnetic flux density (B) are connected by the relation. Select one: a. B = (relative permeability)*H/(permeability of free space) b. B = permeability*H c. B = (permeability of free space)*H/(relative permeability) d. B = H/(permeability of free space * relative permeability) Feedback The correct answer is: B = permeability*H Question 40 Correct Mark 1.00 out of 1.00

Flag question

Question text A certain capacitor is charged at 48 volts after which its stored energy is 5.76 x 10^-2 joules. What is the capacitance of the capacitor? Select one: a. 2 F b. 50 uF c. 60 uF d. 30 uF Feedback The correct answer is: 50 uF Question 41 Incorrect Mark 0.00 out of 1.00

Flag question

Question text A coil having an inductance of 50 mH and a resistance 10 ohms is connected in series with a 25 uF capacitor across a 200 V ac supply. Find the value of Q factor? Select one: a. 4.47 b. 3.54 c. 4.53 d. 7.4 Feedback The correct answer is: 4.47 Question 42 Correct Mark 1.00 out of 1.00

Flag question

Question text A circuit contains a 5 A current source in parallel with an 8 ohm resistor. What is the Thevenin voltage and Thevenin resistance of the circuit? Select one: a. 5 V, 8 ohms b. 5/8 V, 8 ohms c. 40 V, 8 ohms d. 5/8 V, 40 ohms Feedback The correct answer is: 40 V, 8 ohms Question 43 Correct Mark 1.00 out of 1.00

Flag question

Question text How does an ohmmeter behave if its positive lead is connected to the cathode of a diode while negative to anode? Select one: a. Has infinite high resistance b. Has decreasing resistance c. Has very low resistance d. Has unstable resistance Feedback The correct answer is: Has infinite high resistance Question 44 Correct Mark 1.00 out of 1.00

Flag question

Question text At half-power points of a resonance curve, the current is ____ times the maximum current. Select one: a. 1/2 b. 1/(2^1/2) c. 2^1/2 d. 2 Feedback The correct answer is: 2^1/2 Question 45 Correct Mark 1.00 out of 1.00

Flag question

Question text What is the value of a resistor with colors from left: Orange, Blue, Gold and Silver? Select one: a. 3.4 ohms + or - 10% b. 34 ohms + or - 10% c. 3.6 ohms + or - 10% d. 36 ohms + or - 10% Feedback The correct answer is: 3.6 ohms + or - 10% Question 46 Correct Mark 1.00 out of 1.00

Flag question

Question text A 20 ohm resistance R and a 0.001 farad capacitance C are in series. A direct current voltage E of 100 volts is applied across the series circuit at t = 0 and the initial current i(0) = 5 A. Determine the resulting current i(t) at t = 0.01 second. Select one: a. 2.78 A b. 3.03 A c. 3.67 A d. 3.34 A Feedback The correct answer is: 3.03 A Question 47 Correct Mark 1.00 out of 1.00

Flag question

Question text The capacitance of a cable capacitor depends on Select one: a. ratio of cylinder radii b. potential difference c. insulation thickness d. core diameter Feedback The correct answer is: ratio of cylinder radii Question 48 Correct Mark 1.00 out of 1.00

Flag question

Question text Which dynamometer instrument has a uniform scale? Select one: a. voltmeter b. ammeter c. ohmmeter d. wattmeter Feedback The correct answer is: wattmeter Question 49 Incorrect Mark 0.00 out of 1.00

Flag question

Question text The Meralco test of a 10 A wattmeter having a constant of 0.4, the disk makes 40 revolutions in 53.6 seconds. The average volts and amperes during the period of test are 116 volts and 9.4 A. What is the percent accuracy of the meter at this load? Select one: a. 97.45% b. 96.44% c. 98.07% d. 98.58% Feedback The correct answer is: 98.58% Question 50 Correct Mark 1.00 out of 1.00

Flag question

Question text An ordinary flashlight battery is which of the following? Select one: a. A load b. A dry cell c. A storage cell d. A wet cell Feedback The correct answer is: A dry cell

Skip to main content

You are logged in as GERONIMO ELIAS GUTIERREZ (Logout)

Page path Home / 
 ▶ My courses / 
 ▶ Schools / 
 ▶ EECE / 
 ▶ EE / 
 ▶ EE Exit Exam / 
 ▶ General / 
 ▶ EE104x Exit Exam END OF HEADER Started on

Friday, 5 December 2014, 6:28 PM

State

Finished

Completed on

Friday, 5 December 2014, 8:26 PM

Time taken

1 hour 58 mins

Grade

32.00 out of a maximum of 50.00 (64%)

Question

1

Incorrect Mark 0.00 out of 1.00 Flag question

Question text What is the self-inductance of a circuit in which there is induced emf of 100 volts when the current in the circuit changes uniformly from 1 to 5 amperes in 0.3 second? Select one: a. 5.2 H b. 0.5 H c. 0.25 H

d. 7.5 H Feedback The correct answer is: 7.5 H Question

2

Correct Mark 1.00 out of 1.00 Flag question

Question text A circular copper disc 10 cm in diameter rotates 1800 times per minute about a central axis at right angles to the plane of the disc. A uniform magnetic field of 1 Tesla is applied perpendicular to the plane of the disc. The voltage induced between the centre and the edge of the disc is Select one: a. 0.47 V b. 4.7 V c. 0.235 V d. 2.35 V Feedback The correct answer is: 0.235 V Question

3

Correct Mark 1.00 out of 1.00 Flag question

Question text Two voltage generators are in series. The voltage being generated are Vab = 50 sin(wt - 30 degrees) and Vbc = 100 sin(wt + 60 degrees). What is the output voltage Vac? Select one:

a. 111.83 cis 33.5 degrees b. 145.5 cis 50.1 degrees c. 50 cis 30 degrees d. 150 cis 30 degrees Feedback The correct answer is: 111.83 cis 33.5 degrees Question

4

Incorrect Mark 0.00 out of 1.00 Flag question

Question text An iron core 0.4 m long and 5 square cm in cross-section is wound with 300 turns. When a current of 0.5 A flows in the coil, how much is the inductance of the coil. Assume the core has a permeability of 2500. Select one: a. 0.35 H b. 0.42 H c. 0.26 H d. 0.31 H Feedback The correct answer is: 0.35 H Question

5

Incorrect Mark 0.00 out of 1.00 Flag question

Question text A moving coil instrument having meter resistance of 5 ohms is to be used as a voltmeter 0 - 100 volts. If the full-scale deflection current is 10 mA, the required series resistance is

Select one: a. 1000 ohms b. 20 ohms c. none of these d. 9995 ohms Feedback The correct answer is: 9995 ohms Question

6

Incorrect Mark 0.00 out of 1.00 Flag question

Question text A 12 micro-farad capacitor charged at 500 Volts and a 6 micro-farad capacitor charged at 250 Volts are connected in parallel. What is the potential difference in the combination? Select one: a. 417 Volts b. 450 Volts c. 500 Volts d. 750 Volts Feedback The correct answer is: 500 Volts Question

7

Correct Mark 1.00 out of 1.00 Flag question

Question text Assuming an ideal capacitor, with no leakage, what is the capacitive reactance of 10 microfarad capacitance of DC (0 Hz)?

Select one: a. 0 ohms b. infinite capacitive reactance c. 16000 ohms d. 1,000,000 ohms Feedback The correct answer is: infinite capacitive reactance Question

8

Correct Mark 1.00 out of 1.00 Flag question

Question text A coil of resistor of 5 ohms and inductance 0.4 H is connected to a 50 V d.c. supply. The energy stored in the field is Select one: a. 10 joules b. 80 joules c. 20 joules d. 40 joules Feedback The correct answer is: 20 joules Question

9

Correct Mark 1.00 out of 1.00 Flag question

Question text Two series connected 7 H inductors are adjacent to each other. Their coefficient of coupling is 0.64. What is the value of M? Select one:

a. 44.8 H b. 448 H c. 4.48 H d. 0.448 H Feedback The correct answer is: 4.48 H Question

10

Incorrect Mark 0.00 out of 1.00 Flag question

Question text A certain 50 micro-A meter movement has a resistance of 90 ohms. What value of series multiplier is needed to make an instrument that will read 5 volts (maximum)? Select one: a. 102 kilo-ohms b. 99.91 kilo-ohms c. 98 kilo-ohms d. 110 kilo-ohms Feedback The correct answer is: 99.91 kilo-ohms Question

11

Correct Mark 1.00 out of 1.00 Flag question

Question text A non-magnetic ring having a mean diameter of 30 cm the crosssection area is 4 sq. cm and uniformly wound with two conductors A and B over one another. A has 90 turns and B has 240 turns. Calculate

the first principle of mutual inductance between the cores. Select one: a. 11.52 b. 11.00 c. 10.62 d. 10.55 Feedback The correct answer is: 10.62 Question

12

Correct Mark 1.00 out of 1.00 Flag question

Question text A galvanometer with a 20-ohm coil resistance has a full-scale deflection current of 10 mA. If a 0.02 ohm is placed across the meter to increase its capacity, what is the approximate new full scale current of the meter? Select one: a. 10.11 A b. 11.01 A c. 10.01 A d. 10.10 A Feedback The correct answer is: 10.01 A Question

13

Incorrect Mark 0.00 out of 1.00 Flag question

Question text

A barangay power station supplies 60 kW to a load over 2,500 ft of 0002-conductor copper feeder the resistance of which is 0.078 ohm per 1,000 ft. The bus bar voltage is maintained constant at 600 volts. Determine the maximum power which can be transmitted. Select one: a. 220.35 kW b. 223.94 kW c. 230.77 kW d. 242.73 kW Feedback The correct answer is: 230.77 kW Question

14

Correct Mark 1.00 out of 1.00 Flag question

Question text Find L & C of a parallel RLC circuit to resonate at 1 rad/sec with a Q of 5 and resistance of 1 ohm. Select one: a. 5 H, 1/5 F b. 1 H, 1 F c. 1/5 H, 5 F d. 5 H, 5 F Feedback The correct answer is: 1/5 H, 5 F Question

15

Correct Mark 1.00 out of 1.00 Flag question

Question text If a force of 4.8 x 10^(-2) N is required to move a 40 uC charge in an electric field between two points 20 cm apart. What is the potential difference between two points? Select one: a. 160 Volts b. 240 Volts c. 360 Volts d. 120 Volts Feedback The correct answer is: 240 Volts Question

16

Incorrect Mark 0.00 out of 1.00 Flag question

Question text A lead-sheath cable for underground service has a copper conductor (diameter = 0.350 inch) surrounded by 0.20 inch wall of rubber insulation. Assuming the dielectric constant of 4.3 for rubber, calculate the capacitance of the cable per mile length. Select one: a. 0.76 uF/mile b. 1.01 uF/mile c. 0.252 uF/mile d. 0.504 uF/mile Feedback The correct answer is: 0.504 uF/mile Question Incorrect

17

Mark 0.00 out of 1.00 Flag question

Question text A series RC circuit consist of R = 2 M-ohms and an uncharged capacitor C = 5 uF. The circuit is connected across a 100 V DC source at t = 0. What is the initial rate of change of voltage across the resistor? Select one: a. none of these b. -12.4 V/s c. 10 V/s d. -10 V/s Feedback The correct answer is: -10 V/s Question

18

Correct Mark 1.00 out of 1.00 Flag question

Question text How much time is required for electromagnetic energy to travel one nautical mile and return to the source? Select one: a. 18.54 microseconds b. 12.36 microseconds c. 24.72 microseconds d. 6.18 microseconds Feedback The correct answer is: 12.36 microseconds Question Correct

19

Mark 1.00 out of 1.00 Flag question

Question text Three capacitors are connected in parallel. C1 = 10 uF; C2 = 15 uF; C3 = 20 uF. Calculate the total capacitance. Select one: a. 10 uF b. 4.167 uF c. 45 uF d. 20.35 uF Feedback The correct answer is: 45 uF Question

20

Correct Mark 1.00 out of 1.00 Flag question

Question text A simple electronic equipment which takes a 2 amperes current from a power source has a total load resistance of 100 ohms. How much power does it use? Select one: a. 100 watts b. 400 watts c. 200 watts d. 50 watts Feedback The correct answer is: 400 watts Question Incorrect

21

Mark 0.00 out of 1.00 Flag question

Question text Find the voltage drop developed across D Arsonval meter movement having an internal resistance of 1 kilo-ohms and full current of 150 micro amperes. Select one: a. 150 V b. 150 micro V c. 150 kV d. 150 mV Feedback The correct answer is: 150 V Question

22

Correct Mark 1.00 out of 1.00 Flag question

Question text An electric heater is rated at 120 volts, 1000 watts and is used to boil water. Calculate the time in minutes to raise the temperature of 1 liter of water from 15 degrees C to boiling. The heater has an over-all efficiency of 92%. Select one: a. 4.4 minutes b. 5.4 minutes c. 3.4 minutes d. 6.4 minutes Feedback The correct answer is: 6.4 minutes

Question

23

Correct Mark 1.00 out of 1.00 Flag question

Question text An R-L circuit has Z = (6 + j8) ohm. Its susceptance is ____ siemens. Select one: a. 0.06 b. 0.1 c. -0.08 d. 0.08 Feedback The correct answer is: -0.08 Question

24

Incorrect Mark 0.00 out of 1.00 Flag question

Question text A single-phase three wire, 60 Hz, 220 V, watthour meter has a disc constant of 1.2. Determine the energy recorder by the meter after 18,000 revolutions of the disc. Select one: a. 21.6 kW-hr b. 20.5 kW-hr c. 27.6 kW-hr d. 25.4 kW-hr Feedback The correct answer is: 21.6 kW-hr Question

25

Correct Mark 1.00 out of 1.00 Flag question

Question text A dc ammeter has an internal resistance of 0.1 ohm. A shunt of 1.010 x 10^-3 ohm is connected to the ammeter. What is the multiplier of the setup? Select one: a. 50 b. 100 c. 80 d. 10 Feedback The correct answer is: 100 Question

26

Incorrect Mark 0.00 out of 1.00 Flag question

Question text A capacitor with air between its plates has a capacitance of 3 uF. What is the capacitance when wax of dielectric constant 2.8 is between the plates? Select one: a. 8.40 uF b. 0.38 uF c. 1.07 uF d. 23.52 uF Feedback The correct answer is: 1.07 uF

Question

27

Correct Mark 1.00 out of 1.00 Flag question

Question text In an RL circuit, Kirchhoff law gives the following relation: E = Ldi/dt + Ri where: E = supply voltage (200 volts), R = resistance (20 ohms), L = inductance (1 Henry), t = time in seconds, i = current in amperes. If i = 0 when t = 0, find i when t = 0.02 second. Select one: a. 3.3 A b. 3.0 A c. 3.1 A d. 3.2 A Feedback The correct answer is: 3.3 A Question

28

Correct Mark 1.00 out of 1.00 Flag question

Question text A 20 uF capacitor is charged by a 12-V battery. What is the stored energy in the capacitor? Select one: a. 2.88 x 10^-2 J b. 1.07 x 10^-3 J c. 1.44 x 10^-3 J d. 2.88 x 10^-3 J Feedback

The correct answer is: 1.44 x 10^-3 J Question

29

Correct Mark 1.00 out of 1.00 Flag question

Question text The electric energy required to raise the temperature of a given amount of water is 1000 kWh. If heat losses are 25%, the total heating energy required is ____ kWh. Select one: a. 1500 b. 1250 c. 1000 d. 1333 Feedback The correct answer is: 1333 Question

30

Incorrect Mark 0.00 out of 1.00 Flag question

Question text A voltmeter using a 20 micro-amp meter movement has an ohm/V rating of Select one: a. 1 kilo-ohm/V b. 20 kilo-ohms/V c. 10 mega-ohms/V d. 50 kilo-ohms/V Feedback

The correct answer is: 50 kilo-ohms/V Question

31

Correct Mark 1.00 out of 1.00 Flag question

Question text A 15 ohm resistor connected in parallel with an impedance of 8 - j2 ohm across an AC source. The entire circuit takes a total average power of 2000 Watts. What is the average power in the 15 ohm resistor? Select one: a. 1277 W b. 2000 W c. 723 W d. 1500 W Feedback The correct answer is: 723 W Question

32

Correct Mark 1.00 out of 1.00 Flag question

Question text Two similar charges of 250 statC are situated on small spheres 15 cm apart. What is the potential at point midway between the spheres? Select one: a. 16.7 statV b. 66.7 statV c. 25 statV d. 33.3 statV Feedback

The correct answer is: 16.7 statV Question

33

Incorrect Mark 0.00 out of 1.00 Flag question

Question text An ammeter has a range of 0 - 10 amps. What is shunt resistance to be connected if the range is increased to 100 amps? The internal resistance of the ammeter is 0.10 ohms. Select one: a. 1.111 ohms b. 2.111 ohms c. 0.111 ohms d. 0.0111 ohms Feedback The correct answer is: 0.0111 ohms Question

34

Incorrect Mark 0.00 out of 1.00 Flag question

Question text The relative permeability of a certain silicon steel is 4500. A certain magnetic loop consists of a silicon steel of 10 cm square, 20 cm long and an air gap of 1/4 cm, what is the reluctance of the magnetic circuit? Select one: a. 2.54 x 10^-2 b. 2.54 x 10^-3 c. 6.44 x 10^-4 d. 6.44 x 10^-3

Feedback The correct answer is: 2.54 x 10^-2 Question

35

Correct Mark 1.00 out of 1.00 Flag question

Question text Two point charges Q1 = 50 microcoulombs and Q2 = 10 microcoulombs are located at (-1, 1, 3) and (3, 1, 0) meters respectively. Find the magnitude of the force on Q1. Select one: a. 0.018 N b. 4.9 N c. 74 N d. 124.5 N Feedback The correct answer is: 4.9 N Question

36

Correct Mark 1.00 out of 1.00 Flag question

Question text Three delta-connected resistors absorb 60 kW when connected to a 3phase line. If the resistors are connected in star, the power absorbed is Select one: a. 180 kW b. 60 kW c. 20 kW d. 40 kW

Feedback The correct answer is: 20 kW Question

37

Correct Mark 1.00 out of 1.00 Flag question

Question text Three loads, units A, B and C are connected in parallel and take currents that are respectively 12, 10 and 15 A respectively. Assuming Ia to be the reference phasor. Ib leads Ia by 30 deg and Ic lags behind Ia by 65 deg, calculate the total (resultant) current. Select one: a. 26.46 A b. 32.10 A c. 28.33 A d. 30.21 A Feedback The correct answer is: 28.33 A Question

38

Incorrect Mark 0.00 out of 1.00 Flag question

Question text A 50 mH inductance carries a current of 10 Amp which reverses in 5 milliseconds. What is the average voltage induced in the inductor because of this current reversal? Select one: a. 50 Volt b. 200 Volt

c. 100 Volt d. 400 Volt Feedback The correct answer is: 200 Volt Question

39

Incorrect Mark 0.00 out of 1.00 Flag question

Question text A wattmeter with its current coil in line 2 and potential coil across lines 2 and 3 is connected to a balanced 3-phase system. The only load supplied is a single phase one connected to lines 1 and 2. This load is known to be inductive. If the wattmeter reads zero watts, determine the power factor of the single-phase load. Select one: a. 0.866 b. 0.800 c. 0.707 d. 0.900 Feedback The correct answer is: 0.866 Question

40

Correct Mark 1.00 out of 1.00 Flag question

Question text Across a 230-V, 60 Hz power supply is a 15-ohm non-inductive resistor. What is the equation of the resulting current? Select one:

a. i = 26.56 sin 377t b. i = 21.68 sin 377t c. i = 28.16 sin 120t d. i = 15.33 sin 377t Feedback The correct answer is: i = 21.68 sin 377t Question

41

Correct Mark 1.00 out of 1.00 Flag question

Question text A 230 V single-phase meter has a constant load current of 4 amp passing through the meter for five hours at unity p.f. If the meter disk makes 1,104 revolutions during this period, solve for the meter constant in rev/kWh. Select one: a. 480 b. 240 c. 360 d. 120 Feedback The correct answer is: 240 Question

42

Correct Mark 1.00 out of 1.00 Flag question

Question text The r.m.s. value of the complex voltage given by v = 16*(2^1/2) sin wt + 12*(2^1/2) sin 3wt is

Select one: a. 28*(2^1/2) b. 192 c. 20 d. 20*(2^1/2) Feedback The correct answer is: 20 Question

43

Correct Mark 1.00 out of 1.00 Flag question

Question text A parallel plate capacitor has the following values: k = 81, d = 0.025 inches; A = 6 square inches. What is the capacitance of the capacitor? Select one: a. 43.72 picofarad b. 4.372 picofarad c. 437.2 picofarad d. 4372 picofarad Feedback The correct answer is: 4372 picofarad Question

44

Incorrect Mark 0.00 out of 1.00 Flag question

Question text The stator of a 440 V, 50 HP shunt motor is tested at 75 degrees C for its insulation resistance between terminals connected together and the ground frame. When a 50,000 ohm voltmeter is connected in series with

a 600 V DC source, the meter indicates 125 V. Calculate the insulation resistance. Select one: a. 170 kilo-ohms b. 200 kilo-ohms c. 190 kilo-ohms d. 180 kilo-ohms Feedback The correct answer is: 190 kilo-ohms Question

45

Correct Mark 1.00 out of 1.00 Flag question

Question text A series RLC circuit with R = 1 k-ohm, L = 1 H and C = 6.25 uF is suddenly connected across a 24 V dc source. At t = 0, i = 0 and q = 0. Determine the current after 0.01 sec. Select one: a. 5.05 mA b. 5.40 mA c. 4.61 mA d. 3.45 mA Feedback The correct answer is: 5.40 mA Question

46

Correct Mark 1.00 out of 1.00 Flag question

Question text

Find the required battery capacity needed to operate an equipment of 30 amperes at 5 hours. Select one: a. 6 b. 3 c. 30 d. 150 Feedback The correct answer is: 150 Question

47

Incorrect Mark 0.00 out of 1.00 Flag question

Question text Two spheres separated from each other by 10 m have charges of 0.001 Coulomb and 0.003 Coulomb, respectively. In between the two spheres is a point of zero electric field. What is its distance from the 0.001 Coulomb sphere? Select one: a. 6.34 m b. 2.24 m c. 3.66 m d. 7.78 m Feedback The correct answer is: 3.66 m Question

48

Correct Mark 1.00 out of 1.00 Flag question

Question text One ampere-turn is equivalent to _____ gilberts. Select one: a. 1.16 b. 1.36 c. 1.26 d. 1.46 Feedback The correct answer is: 1.26 Question

49

Correct Mark 1.00 out of 1.00 Flag question

Question text A circuit whose resistance is 20 ohms and inductance of 10 H has a steady state voltage of 100 volts suddenly applied to it. For the instant of 0.50 second after the voltage is applied, determine the total power input to the circuit. Select one: a. 200 watts b. 116 watts c. 316 watts d. 500 watts Feedback The correct answer is: 316 watts Question

50

Correct Mark 1.00 out of 1.00 Flag question

Question text A total of 0.8 kg of water at 20 degrees C is placed in a 1-kW electric kettle. How long a time in minute is needed to raise the temperature of the water to 100 degrees C? Select one: a. 4.56 min b. 5.32 min c. 4.46 min d. 5.34 min Feedback The correct answer is: 4.46 min

A. B.

Question Bank in AC Circuits A. 1.

SINUSOIDAL VOLTAGE AND CURRENT REE Board Exam September 2000 Find the average current during the half cycle given the instantaneous maximum value of 20 amperes. A. 12.73 amperes C. 20 amperes B. 14.14 amperes D. 10 amperes

2.

0.89 A 0.75 A

C. D.

0.91 A 0.84 A

8.

EE Board Exam April 1990 A 240-V, 25 Hz sinusoidal generator is connected to a 20 ohms resistor. Determine the instantaneous current when elapsed time is 0.01 second. A. 15.43 A C. 16.97 A B. 16.30 A D. 12.00 A

REE Board Exam April 1997 The phase shift between the current and voltage vectors us due to the following except one A. magnet coils C. power capacitors B. electric flat iron D. fluorescent lamp

9.

REE Board Exam April 1997 A wire carries a current i = 3 cos 314t amperes. What is the average current over 6 seconds? A. 0 A C. 1.5 A B. 3.0 A D. 0.532 A

3.

REE Board Exam April 2001 An alternating rectangular wave has a maximum value of 10 V and a frequency of 1 cycle per second. What is the average value of the wave? A. 5 V C. 0 B. 10 V D. 7.07 V

10. REE Board Exam April 1997 Across a 230-V, 60 Hz power supply is a 15-ohm non-inductive resistor. What is the equation of the resulting current? A. i = 21.68 sin 377t C. i = 15.33 sin 377t B. i = 26.56 sin 377t D. i = 28.16 sin 120t

4.

REE Board Exam October 2000 A sinusoidal current wave has a maximum value of 20 A. What is the average value of one-half cycle? A. 5 A C. 14.14 A B. 12.7 A D. 0

11. EE Board Exam April 1991 Determine the effective value of the circuit current of an emf of 151 sin 377t is connected in series with a DC emf of 110 volts. Both supply a load of 10 + j8 ohms. A. 10.3 A C. 13.8 A B. 12.5 A D. 11.4 A

5.

REE Board Exam October 1996 What is the wavelength of a carrier wave with frequency of 100 megahertz? A. 3.0 m C. 1.5 m B. 7.5 m D. 6.0 m

6.

REE Board Exam April 1997 A chart speed of a recording instrument is 25 mm/sec. One cycle of the signal being recorded extends over 5 mm. What is the frequency of the signal? A. 20 cps C. 50 cps B. 2 cps D. 5 cps

7.

EE Board Exam April 1992 Determine the rms value of the current drawn by a 2 μF condenser, which is connected across a source of potential. The potential has a third and fifth harmonic components, which are 30% and 20% respectively of the fundamental. The fundamental sinusoidal component has a peak value of 1000 volts and 60 Hz frequency.

12. EE Board Exam April 1994 An alternating current and a direct current flow simultaneously in the same conductor. If the effective of the alternating current is 5 A and the direct current is 10 A, what will an AC ammeter read when connected in the circuit? A. 7.5 A C. 11.18 A B. 15 A D. none of these 13. REE Board Exam April 1997 If e = 100 sin (ωt – 30°) – 50 cos 3ωt + 25 sin (5ωt + 150°) and i = 20 sin (ωt + 40°) + 10 sin (3ωt + 30°) – 5 sin (5ωt – 50°). Calculate the power in watts. A. 1177 C. 1043 B. 919 D. 1224 14. ECE Board Exam November 2001 It is the value of sine wave of voltage or current at one particular instant of time. A. average value C. rms value

B.

effective value

D.

instantaneous value

15. ECE Board Exam November 1998 If the combination of an ac voltage and a dc voltage has an instantaneous voltage that varies through a range from -2 V to +10 V, what is the peak ac voltage of the combination? A. 10 V C. 6 V B. 16 V D. 12 V 16. ECE Board Exam April 2001 Measured in Hertz, it is the number of cycles of alternating current per second. A. frequency C. peak to peak B. period D. wavelength 17. ECE Board Exam April 2000 If an ac signal has an average voltage of 18 V, what is the rms voltage? A. 16.2 V C. 25.38 V B. 19.98 V D. 12.73 V 18. ECE Board Exam April 2000 If an ac signal has a peak voltage of 55 V, what is the average value voltage? A. 61.05 V C. 34.98 V B. 38.86 V D. 86.35 V 19. ECE Board Exam April 1999 What is the phase relationship between current and voltage in an inductor? A. in phase B. current lags voltage by 90° C. voltage lags current by 90° D. current lags voltage by 180° 20. ECE Board Exam November 1995 If sine wave voltage varies from 0 to 200 V, how much is its instantaneous voltage at 90°? A. 100 V B. minimum voltage C. 200 V D. half of its maximum voltage 21. ECE Board Exam November 2000 How many degrees are there in one complete wave cycle? A. 360 degrees C. 180 degrees B. 90 degrees D. 720 degrees

22. ECE Board Exam April 1998 When comparing rms voltage and average voltages, which of the following statement is true, assuming sine waves? A. Either the rms voltage or the average voltage might be larger. B. The average voltage is always greater than the rms voltage. C. There will always be a very large difference between the rms voltage and the average voltage. D. The rms voltage is always greater than the average voltage. 23. ECE Board Exam November 1999 It is the maximum instantaneous value of a varying current, voltage, or power equal to 1.414 times the effective value of a sine wave. A. rms value C. effective value B. peak to peak value D. peak value 24. ECE Board Exam November 1999 It is the description of two sine waves that are in step with each other going through their maximum and minimum points at the same time and in same direction. A. stepped sine waves B. sine waves in coordination C. phased sine waves D. sine waves in phase 25. ECE Board Exam April 1999 What is the average voltage (Eave) output of a full wave rectifier with an output of 100 volts peak? A. 63.7 volts C. 141.4 volts B. 14.14 volts D. 6.37 volts 26. ECE Board Exam November 1997 The relation of the voltage across an inductor to it current is ____ A. Lagging the current by 90 degrees B. Leading the current by 90 degrees C. In phase with the current D. Leading the current by 180 degrees 27. ECE Board Exam April 1999 If two equal frequency ac signals of exactly 5 V each are combined with one of the signals 180 degrees out of phase with the other, what will be the value of the resultant voltage? A. 2.25 V C. 0 V B. 5 V D. 10 V

28. ECE Board Exam November 1998 Kind of electric current where amplitude drops to zero periodically normally produced by rectifier circuits A. alternating current B. varying direct current C. damped alternating current D. pulsating direct current 29. ECE Board Exam April 2000 If an ac signal has an average voltage of 18 V, what is the rms voltage? A. 16.2 V C. 25.38 V B. 19.98 V D. 12.726 V 30. ECE Board Exam April 2001 In electronic circuit the current that flows over a capacitor _____. A. In phase with the voltage B. Leads the voltage by 180 degrees C. Lags the voltage by 90 degrees D. Leads the voltage by 90 degrees 31. Two current sources deliver current to a common load. The first source delivers a current whose equation is 25 sin 100πt amperes while the second delivers a current whose equation is 15 cos 100πt amperes. What is the rms value of the current in the load? A. 29.15 A C. 20.6 A B. 40 A D. 10 A 32. Two alternators A and B delivers 100 A and 150 A, respectively to a load. If these currents are out of phase by 30 electrical degrees, determine the total current drawn by the load. A. 201.5 A C. 215.4 A B. 250.0 A D. 241.8 A 33. When using circuit laws and rules we must use A. maximum value C. effective value B. average value D. peak to peak value 34. A 60 Hz frequency would cause an electric light to A. turn on and off 120 times per second B. flicker noticeable C. turn on and off 180 times per second D. turn on and off 60 times per second 35. The relationship between frequency f, number of revolutions per second n and pair of poles p is given by

A. B.

f = n/p f = np

C. D.

f = n/2p f = 2np

36. The difference between the peak positive value and the peak negative of an a.c. voltage is called the A. maximum value C. average value B. effective value D. peak to peak value 37. The greatest value attained during one half of the cycle is called the A. peak value C. r.m.s. value B. average value D. effective value 38. The root mean square (r.m.s.) value of a.c. is the same as A. instantaneous value C. effective value B. average value D. maximum value 39. The r.m.s. value of a sine wave is equal to A. 0.637 maximum value C. 0.707 maximum value B. 0.506 maximum value D. 1.414 maximum value 40. Form factor is defined as A. r.m.s. value/peak value B. maximum value/r.m.s. value C. r.m.s. value/average value D. effective value/ r.m.s. value 41. The value of form factor for a pure sine wave is A. 1.414 C. 0.707 B. 0.637 D. 1.11 42. The value of peak factor for a pure sine wave is A. 1.414 C. 0.707 B. 0.637 D. 1.11 43. If the current and voltage are out of phase by 90, the power is A. 1.1 VI C. Maximum B. minimum D. zero 44. If e1 = A sin t and e2 = B sin (t - ) then A. e1 lags e2 by  C. e2 lags e1 by  B. e2 leads e1 by  D. e1 leads e2 by  45. Which of the following statements concerning the graph of figure below is most correct?

A. B.

3

infinite zero

C. D.

0.5 unity

2

54. The frequency of a sinusoidal signal shown in figure is

1 0 time

A. B. C. D.

it represents ac it represents dc it represents half-wave rectified ac it represents sum of ac and dc

46. Average value of a sine wave is √ times the maximum value A. True B. False 47. The equation for 25 cycles current sine wave having rms value of 30 amperes will be A. 30 sin 25t C. 30 sin 50t B. 42.4 sin 25πt D. 42.4 sin 50πt 48. The voltage v = 90 cos (ωt – 161.5°) may be represented as a sine function by A. 90 sin (ωt + 18.5°) C. 90 sin (ωt + 71.5°) B. 90 sin (ωt – 71.5°) D. 90 sin (ωt - 18.5°) 49. Which of the following frequencies has the longest period? A. 1 Hz C. 1 kHz B. 10 Hz D. 100 kHz 50. RMS value and the mean value is the same in case of A. square wave B. sine wave C. triangular wave D. half-wave rectified sine wave 51. If emf in a circuit is given by e = 100 sin 628t, the maximum value of voltage and frequency are A. 100 V, 50 Hz C. 100 V, 100 Hz B. 50√ V, 50 Hz D. 50√ V, 100 Hz 52. When the sole purpose of an alternating current is to produce heat, the selection of conductor is based on A. average value of current C. rms value of current B. peak value of current D. any of the above 53. The form factor of dc supply voltage is always

A. B.

500 Hz 1 kHz

C. D.

25 kHz 500 kHz

55. The period of the voltage 2 cos 4500πt + 7 sin 7500πt is A. 2.51 s C. 2.51 ms B. 2.51 ns D. 2.51 μs 56. The a.c. system is preferred to d.c. system because ____ A. a.c. voltages can easily be changed in magnitude B. d.c. motors do not have fine speed control C. high-voltage a.c. transmissions is less efficient D. d.c. voltage cannot be used for domestic appliances 57. In a.c. system, we generate sine wave form because ____ A. it can be easily drawn B. it produces lest disturbance in electrical circuits C. it is nature’s standard D. other waves cannot be produced easily 58. ____ will work only on d.c. supply. A. Electric lamp C. Heater B. Refrigerator D. Electroplating 59. ____ will produce a.c. voltage. A. Friction C. B. Photoelectric effect D.

Thermal energy Crystal

60. In Fig. 1.1, the component of flux that will contribute to e.m.f. in the coil is ____

Coil of N turns

ω rad/sec

φmax Figure 1.1

A. B.

max sin t max cos t

C. D.

68. An alternating current given by i = 10 sin 314t. Measuring time from t = 0, the time taken by the current to reach +10 A for the second time is ____. A. 0.05 second C. 0.025 second B. 0.1 second D. 0.02 second

max tan t max cot t

61. In Fig. 1.1, the maximum e.m.f. induced in the coil is ____.

Coil of N turns

ω rad/sec

φmax Figure 1.1

A. B.

N max  max

C. D.

67. A sinusoidal current has a magnitude of 3 A at 120. Its maximum value will be ____. A. √ A C. √ A B. √ A D. 6 A

N max sin t  N max

69. An a.c. generator having 10 poles and running at 600 r.p.m. will generate an alternating voltage of frequency _____ A. 25 Hz C. 50 Hz B. 100 Hz D. 200 Hz 70. We have assigned a frequency of 50 Hz to power system because it ____ A. can easily be obtained B. gives best result when used for operating both lights and machinery C. leads to easy calculation D. none of the above

62. A coil is rotating in the uniform field of an 8-pole generator. In one revolution of the coil, the number of cycles generated by the voltage is ____. A. one C. four B. two D. eight

71. An alternating voltage is given by v = 100 sin 314t volts. Its average value will be ____. A. 70.7 V C. 63.7 V B. 50 V D. 100 V

63. An alternating voltage is given by v = 20 sin 157t. The frequency of the alternating voltage is ____. A. 50 Hz C. 100 Hz B. 25 Hz D. 75 Hz

72. An alternating current whose average value is 1 A will produce ____ 1 A d.c. under similar conditions. A. less heat than C. the same heat as B. more heat than D. none of the above

64. An alternating current is given by i = 10 sin 314t. The time taken to generate two cycles of current is ____. A. 0.02 second C. 0.04 second B. 0.01 second D. 0.05 second

73. A sinusoidal alternating current has a maximum value of I m. Its average value will be ____. A. Im/ C. 2Im/ B. Im/2 D. none of the above

65. An alternating voltage is given by v = 30 sin 314t. The time taken by the voltage to reach –30 V for the first time is ____. A. 0.02 second C. 0.03 second B. 0.1 second D. 0.015 second

74. The area of a sinusoidal wave over a half-cycle is ____ A. max. value / 2 C. max. value /  B. 2 x max. value D. max. value / 2

66. A sine wave has a maximum value of 20 V. Its value at 135 is ____. A. 10 V C. 15 V B. 14.14 V D. 5 V

75. An alternating voltage is given by v = 200 sin 314t. Its r.m.s. value will be ____ A. 100 V C. 141.4 V B. 282.8 V D. 121.4 V

B. 76. The r.m.s. value of sinusoidally varying current is ____ that of its average value. A. more than C. same as B. less than D. none of the above 77. Alternating voltages and currents are expresses in r.m.s. values because ____ A. they can be easily determined B. calculations become very simple C. they give comparison with d.c. D. none of the above 2

78. The average value of sin  over a complete cycle is ____ A. +1 C. ½ B. -1 D. zero 79. The average value of sin over a complete cycle is ____. A. zero C. -1 B. +1 D. ½ 80. An alternating current is given by i = Im sin . The average value of squared wave of this current over a complete cycle is ____ A. Im/2 C. 2Im/ B. Im/ D. 2Im 81. The form factor a sinusoidal wave is ____ A. 1.414 C. 2 B. 1.11 D. 1.5 82. The filament of a vacuum tube requires 0.4 A d.c. to heat it. The r.m.s. value of a.c. required is ____. A. 0.4 x √ C. 0.8 / √ B. 0.4 / 2 A D. 0.4 A 83. A 100 V peak a.c. is as effective as ____ d.c. A. 100 V C. 70.7 V B. 50 V D. none of the above 84. The form factor of a ____ wave is 1. A. sinusoidal C. triangular B. square D. saw tooth 85. Out of the following ____ wave is the peakiest. A. sinusoidal C. rectangular

square

D.

triangular

86. The peak factor of a sine wave form is ____. A. 1.11 C. 2 B. 1.414 D. 1.5 87. When a 15-V square wave is connected across a 50-V a.c. voltmeter, it will read ____. A. 15 V C. 15 /√ B. 15 x √ D. none of the above 88. The breakdown voltage of an insulation depends upon ____ value of alternating voltage. A. average C. peak B. r.m.s. D. twice the r.m.s. 89. The peak factor of a half-wave rectified a.c. is ____. A. 1.57 C. 1.11 B. 2 D. 1.4142 90. The form factor of a half-wave rectified a.c. is ____ A. 2 C. 1.414 B. 1.11 D. 1.57 91. When 200 V sinusoidal peak-to-peak is connected across an a.c. voltmeter, it will read ____ A. 141.4 V C. 70.7 V B. 50 V D. none of the above 92. In Fig. 1.2, the wave that will produce maximum heat under the similar conditions is ____.

i 10 A

96. In Fig. 1.3, current is given by i = Im sin . The voltage equation will be ____.

i 10 A

0

0

t

t

A. B.

Vm sin  Vm sin ( + )

Vm sin ( - ) Vm sin ( - 2)

C. D.

-10 A

-10 A

i 10 A

97. The waveforms of voltage and current shown in Fig. 1.3 would exist in ____ circuit.

i 10 A

0

i

0

t

v

φ

θ

-10 A Figure 1.3

Figure 1.2

A. B.

square wave sinusoidal wave

C. D.

triangular wave saw tooth wave

93. In Fig. 1.2, ____ wave will have the highest average value. i 10 A 0

i 10 A 0

t

t

-10 A

-10 A

i 10 A

i 10 A

0

t

Figure 1.2

saw tooth square

a resistive a capacitive

C. D.

an inductive none of the above

98. An alternating voltage or current is a ____. A. scalar quantity C. phasor B. vector quantity D. none of the above 99. Three parallel circuits take the following currents: i1 = 5 sin 314t, i2 = 30 sin (314t + /2) and i3 = 25 sin (314t - /2). The expression for the resultant current is ____. A. 25 sin (314t + /3) C. 10 sin (314t - /6) B. 5 sin (314t + /2) D. 5√ sin (314t + /4) 100. The sum of the following two e.m.f’s will be ____ e1 = 10 sin t e2 = 10 cos t A. 10 C. 14.14 cos t B. 20 sin t D. 14.14 sin (t + /4)

0

-10 A

A. B.

A. B.

C. D.

triangular sinusoidal

94. The average value of a sinusoidal current is 100 A. Its r.m.s value is ____. A. 63.7 A C. 141.4 A B. 70.7 A D. 111 A 95. A current wave is given by i = 4 + 2√ sin 3 + 4√ sin 5. The r.m.s. value of current wave is ____. A. 10 A C. √ A B. 6 A D. 5 A

101. Each of the three coils generates an e.m.f. of 230 V. The e.m.f. of second leads that of the first 120 and the third lags behind the first by the same angle. The resultant e.m.f. across the series combination of the coils is ____. A. 0 V C. 690 V B. 230 V D. none of the above 102. In Fig. 1.4, I1 + I2 is equal to ____ 60° 6A

I1

I2 3A

Figure 1.4

I3 4A

A. B.

3A 4.33 A

C. D.

9A 3.43 A

103. In Fig. 1.4, I2 + I3 is equal to ____ I2

60° 6A

I3

3A

I1

4A

Figure 1.4

A. B.

7A √ A

108. In a pure resistive circuit, the instantaneous voltage and current are given by: v = 250 sin 314t volts i = 10 sin 314t amperes The average power in the circuit is A. 2500 W C. 25 W B. 250 W D. 1250 W

C. D.

5A none of the above

104. In Fig. 1.5, E1 + E2 + E3 + E4 is equal to E1 = 9 V

109. An alternating voltage current equation will be A. ⁄ ) B. (

is applied to a pure inductive circuit. The C. D.

( (

⁄ ) ⁄ )

110. The inductive reactance of a circuit is ____ frequency. A. directly proportional to C. independent of B. inversely proportional D. none of the above

E3 = 20 V E2 = 24 V E4 = 6 V Figure 1.5

A. B.

7V 5V

C. D.

20 V none of the above

105. In Fig. 1.5, ____ will have the least value. E1 = 9 V E3 = 20 V E2 = 24 V E4 = 6 V Figure 1.5

A. B.

E1 + E2 + E3 + E4 E1 + E2 + E3 – E4

C. D.

E1 + E2 - E3 – E4 -E1 + E4

106. In a pure resistive a.c. circuit, the frequency of power curve is ____ that of the circuit frequency. A. half C. thrice B. twice D. same as 107. In a pure resistive circuit, the instantaneous voltage and current are given by: v = 250 sin 314t volts i = 10 sin 314t amperes The peak power in the circuit is A. 1250 W C. 2500 W B. 25 W D. 250 W

111. Power absorbed in a pure inductive circuit is zero because A. reactive component of current is zero B. active component of current is maximum C. power factor of the circuit is zero D. reactive and active component of current cancel out 112. An alternating voltage current equation will be A. ⁄ ) B. (

is applied to a pure capacitive circuit. The C. D.

( (

⁄ ) ⁄ )

113. The capacitive reactance of a circuit is ____ frequency. A. independent of B. inversely proportional to C. directly proportional to D. none of the above 114. An a.c. current given by i = 14.14 sin (t + /6) has an rms value of ____ amperes and a phase of ____ degrees. A. 10, 30 C. 1.96 , -30 B. 14.14, 180 D. 7.07, 210 115. If e1 = A sin t and e2 = B sin (t – ), then A. e1 legs e2, by  C. e2 leads e1, by  B. e2 lags e1 by  D. e1 is in phase with e2 116. From the two voltage equations eA = Em sin 100t and eB = Em sin (100t + /6), it is obvious that

A. B. C. D.

eA leads eB 30 eB achieves its maximum value 1/600 second before e A does eB lags behind eA eA achieves its zero value 1/ 600 before eB

A. B.

119. The r.m.s. value of sinusoidal ac current is equal to its value at an angle of ____ degree. A. 60 C. 30 B. 45 D. 90 120. Two sinusoidal currents are given by the equations: i 1 = 10 sin (t + /3) and i2 = 15 sin (t - /4). The phase difference between them is ____ degrees. A. 105 C. 15 B. 75 D. 60 121. A sine wave has a frequency of 50 Hz. Its angular frequency is ____ radian/second. A. 50/ C. 50π B. 50/2 D. 100 122. An a.c. current is given by i = 100 sin 100. It will achieve a value of 50 A after ____ second. A. 1/600 C. 1/1800 B. 1/300 D. 1/900

C. D.

√ 5

125. The current through a resistor has a wave form as shown in Fig. 1.6. The reading shown by a moving coil ammeter will be ____ ampere.

117. The r.m.s. value a half-wave rectified current is 10 A, its value for full wave rectification would be ____ amperes. A. 20 C. 20/π B. 14.14 D. 40/ 118. A resultant current is made of two components: a 10 A d.c. components and a sinusoidal component of maximum value 14.14 A. The average value of the resultant current is ____ amperes and r.m.s. value is ____ amperes. A. 0, 10 C. 10, 14.14 B. 24, 24.14 D. 4.14, 100

10 0

5A i(t)

0

π

2π

3π

ωt

Fig. 1.6

A. B.

C. D.

√ √

5/π 0

126. A constant current of 2.8 exists in a resistor. The rms value of current is A. 2.8 A C. 1.4 A B. about 2 A D. undefined 127. The rms value of a half-wave rectified symmetrical square wave current of 2 A is A. √ A C. √ A B. 1 A D. √ A 128. The rms value of the voltage v(t) = 3 + 4 cos (3t) is A. √ V C. 7 V B. 5 V D. (3 + 2√ ) V 129. The rms value of the resultant current in a wire which carries a dc current of 10 A and a sinusoidal alternating current of peak value 20 A is A. 14.1 A C. 22.4 A B. 17.3 A D. 30.0 A 130. For the triangular waveform in the figure, the rms value of voltage s equal to v

123. The reactance offered by a capacitor to alternating current of frequency 50 Hz is 10 . If frequency is increased to 100 Hz reactance becomes ____ ohm. A. 20 C. 2.5 B. 5 D. 40 124. A complex current wave is given by i = 5 + 5 sin 100t ampere. Its average value is ____ ampere.

T/2

A. B.

√ √

V V

T

C. D.

3T/2

2T

5T/2

t

1/3 V V √

131. The rms value of the periodic waveform given in the figure is

i A

6A T/2

T

0

√ A √ A

T/2

-A

-6 A

A. B.

i A

C. D.

A √ 1.5 A

T

t

0

π

2π

0

t

t

-A Fig. b

Fig. a

A. B.

A

figure a and b figure b and c

C. D.

Fig. c

figure a and c none of the above

132. If i1 = 120 cos (100πt + 30°) and i1 = -0.1 cos (100πt + 100°) then i2 leads i1 by ____. A. -110 degrees C. -60 degrees B. 60 degrees D. 110 degrees

139. The length of time between a point in one cycle to the same point of the next cycle of an AC wave is the ____. A. frequency C. magnitude B. period D. polarity

133. If v1 = sin (ωt + 30°) and v2 = -5 sin (ωt - 15°) then v1 leads v2 by ____. A. 225 degrees C. 45 degrees B. 30 degrees D. none of the above

140. In an experiment, a sinusoidal wave form is observed to complete 8 cycles in 25 msec. Determine the frequency of the wave form. A. 320 Hz C. 200 Hz B. 40 Hz D. 64 Hz

134. The rms value of a rectangular wave of period T, having a value of +V for a duration, T1 (
A. B.

√ √

C. D.

√ √

138. Which of the waveforms are having unity peak factor?

141. If emf in a circuit is given by e = 100 sin 628t, the maximum value of voltage and frequency is ____. A. 100 V, 50 Hz C. √ V, 50 Hz B. 100 V, 100 Hz D. √ V, 100 Hz 142. A sinusoidal voltage wave has an RMS value of 70.71 V and a frequency of 60 Hz. Determine the value of the voltage 0.0014 second after the wave crosses the ωt axis. A. 70.71 V C. 50 V B. 100 V D. 141.42 V 143. An alternating current varying sinusoidally with frequency of 50 Hz has an RMS value of 20 A. At what time measured from the positive maximum value will the instantaneous current be 14.14 A? A. 1/600 sec C. 1/300 sec B. 1/200 sec D. 1/400 sec 144. The average value of the function i = 50 sin ωt + 30 sin 3ωt is equal to ____. A. 31.8 A C. 38.2 A B. 25 A D. 51.43 A 145. For 200 Vrms value triangular wave, the peak value is equal to ____. A. 200 V C. 282 V B. 222 V D. 346 V

146. Determine the rms value of a semi-circular current wave which has a maximum value of A. A. 0.816A C. 0.866A B. 0.23 A D. 0.707A 147. The rms value of a half-wave rectified current is 100 A. Its value for full-wave rectification would be ____ amperes. A. 141.4 A C. 200/π A B. 200 A D. 400/π A 148. A half-wave rectified sine wave has an average value of 100 amp. What is the effective value? A. 157 A C. 70.71 A B. 444 A D. 100 149. The form factor of a half-wave rectified alternating current is ____. A. 1.11 C. 1.73 B. 1.57 D. 1.0 150. Three alternating currents are (ωt + 90°) A; i3 = 20 cos (ωt current. A. 167.4 sin (ωt + 45.66°) B. 74.6 sin ωt

given by i1 = 141 sin (ωt + 45°) A; i2 = 30 sin – 120°) A. Find the equation of the resultant C. D.

143.8 sin (ωt + 51.4°) 64.7 sin (ωt – 30°)

151. The maximum value of a sine wave AC voltage which will produce heat in a resistor at the same average rate as 115 V of direct current is ____. A. 81.3 V C. 162.6 V B. 115 V D. 230 V 152. A sinusoidal voltage source has a peak value of 150 volts. What equivalent DC voltage source would produce the same heating effect in a 1-ohm resistor? A. 15 V C. 95 V B. 212 V D. 106 V 153. The effective value of v(t) = 100 + A sin ωt is known to be 103.1. The amplitude A of the sine term is ____. A. 25 C. 35.48 B. 4.85 D. 100 154. An alternating current and a direct current flow simultaneously in the same conductor. If the effective of the AC is 8 A and DC is 12 A, what will an AC ammeter read when connected in the circuit? A. 14.42 A C. 11.66 A

B.

12 A

D.

16.49 A

155. Find the reading of an AC voltmeter connected across the series source of 100 sin (ωt – π/2) and 100 sin ωt. A. 100 C. 170.71 B. 130.65 D. 184.78 156. A voltage is given be v = 100 sin 314t. How long does it take this wave to complete one fourth of a cycle? A. 20 ms C. 5 ms B. 10 ms D. 1 ms 157. When a 15 V square wave is connected across a 50 volt AC voltmeter, it will read ____. A. 21.21 V C. 15 V B. 10.61 V D. 9.55 V 158. Calculate the effective value of v(t) = 100 sin 400t + 50 sin 800t + 10 cos 1200t V. A. 79.5 V C. 112.25 V B. 57.9 V D. 121. 52 V 159. The magnetic field energy of an inductor changes from maximum value to minimum value in 5 ms when connected to an ac source. The frequency of the source is A. 20 Hz C. 200 Hz B. 50 Hz D. 500 Hz 160. Non-sinusoidal waveforms are made up of A. different sinusoidal waveforms B. fundamental and even harmonics C. fundamental and odd harmonics D. even and odd harmonics only 161. The positive and negative halves of a complex wave are symmetrical when A. it contains even harmonics B. phase difference between even harmonics and fundamental is 0 or π C. it contains odd harmonics D. phase difference between even harmonies and fundamental is either π/2 or 3π/2 162. The r.m.s. value of the complex voltage given by is √ A. C. √ √ B. 20 D. 192

√

163. In a 3-phase system, ____th harmonic has negative phase sequence of RBY. A. 9 C. 5 B. 13 D. 15 164. A complex current wave is given by the equation The r.m.s. value of the current is ____ ampere. A. 16 C. 10 B. 12 D. 8

.

165. When pure inductive coil is fed by a complex voltage wave, its current wave A. has larger harmonic content B. is more distorted C. is identical with voltage wave D. shows less distortion 166. A complex voltage wave is applied across a pure capacitor. As compared to the fundamental voltage, the reactance offered by the capacitor to the third harmonic voltage would be A. nine times C. one-third B. three times D. one-ninth 167. Which of the following harmonic voltage components in a 3-phase system would be in phase with each other? rd th th A. 3 , 9 , 15 etc. th th th B. 7 , 13 , 19 etc. th th th C. 5 , 11 , 17 etc. nd th th D. 2 , 4 , 6 etc. 168. An alternating voltage is one that A. varies continuously in magnitude B. reverses periodically in polarity C. never varies in magnitude D. both A and B 169. One complete revolution of a conductor loop through a magnetic field is called a(n) A. octave C. cycle B. decade D. alternation 170. For a sine wave, one half cycle is often called a(n) A. alternation C. octave B. harmonic D. period

171. For a sine wave, the number of complete cycles per second is called the A. period C. frequency B. wavelength D. phase angle 172. To compare the phase angle between two waveforms, both must have A. the same amplitude C. different frequency B. the same frequency D. both A and B 173. The value of alternating current or voltage that has the same heating effect as a corresponding dc value is known as the A. peak value C. rms value B. average value D. peak-to-peak value 174. For an ac waveform, the period refers to A. the number of complete cycles per second B. the length of time required to complete one cycle C. the time it takes for the waveform to reach its peak value D. none of the above 175. The wavelength of a radio wave is A. inversely proportional to its frequency B. directly proportional to its frequency C. inversely proportional to its amplitude D. unrelated to its frequency 176. Unless indicated otherwise, all sine wave ac measurements are in A. peak-to-peak values C. rms values B. peak values D. average values 177. A unit step voltage is applied across an inductor. The current through the inductor will be A. zero for all time B. a step function C. a ramp function D. a delta (impulse) function 178. A ramp current flowing through an initially relaxed capacitor will result in a voltage across it that A. varies inversely with time B. remains constant C. varies directly with time D. varies as the square of time 179. The voltage v(t) = t u(t) volts is connected across a 1 H inductor having an initial current of -1 A. The net current will be zero at time t equal to

A. B.

0

C. D.

√ seconds 1 seconds

180. A voltage waveform v (t) = 12t is applied across 1H Inductor for t ≥ 0, with initial current through it being zero. The current through the inductor for t ≥ 0 is given by 3 A. 12t C. 12t 3 B. 24t D. 4 t

B. SERIES CIRCUITS 186. REE Board Exam September 2003 The following are in series R = 1,000 Ω, L = .100 μH and C = 20,000 pF. The voltage across the circuit is 100 V, 60 kHz. What is the total impedance expressed in ohms? A. 1882 ohms C. 2132 ohms B. 1000 ohms D. 1885 ohms

181. It is desired to have a constant direct current i(t) through the ideal inductor L. The nature of the voltage source v(t) must A. constant voltage B. linearly increasing voltage C. an ideal impulse D. exponentially increasing voltage

187. REE Board Exam October 2000 A series circuit has an applied voltage of v = 220 sin (ωt + 30°) and draws a current of i = 10 sin (ωt - 30°). What is the average power and power factor of the circuit? A. 1,905 W, 86.6% lagging C. 2,200 W, 100% B. 1,905 W, 86.6% lagging D. 1,100 W, 50% lagging

√ seconds

2

182. For the current and voltage waveforms, identify the element & its value.

A. B.

L, 25 H C, 25 F

C. D.

L, 2 H C, 2 F

183. The voltage and current waveforms for an element are shown in the figure. Find the circuit element and its value.

A. B.

L and 25 H C and 25 F

C. D.

L and 1 H C and 1 F

184. What is the rms value of a square wave with an amplitude of 10 A and frequency of 1 Hz? A. 0 A C. 5 A B. 10 A D. 7.07 A 185. What is the frequency in kHz of a radio signal whose wavelength is 15 m? A. 10,000 C. 15,000 B. 20,000 D. 20,500

188. REE Board Exam September 2001 A coil has an impedance of 75.4 Ω when connected a across a source of 60 Hz. The same coil yields an impedance of 54.8 Ω when connected across a source having a different frequency of 30 Hz. What is the coil’s inductance? A. 245.7 mH C. 158.6 mH B. 512.8 mH D. 341.7 mH 189. REE Board Exam April 1996 A circuit consists of a 4 ohms resistor and a 300 μF capacitor in series. It is connected across a 60 Hz voltage source with a 500 V peak voltage. What is the phasor form of the current? A. A C. A B. A D. A 190. REE Board Exam September 2000 Find the power in a circuit if i(t) = 10 sin (ωt - 30) and v(t) = 220 sin (ωt + 30). A. 550 watts C. 1900 watts B. 2200 watts D. 1500 watts 191. REE Board Exam April 1997 A current of 2.5 A flows through a series circuit consisting of a 100 Ω resistor and an unknown capacitor across a source of 460 V, 50 Hz. What is the value of the capacitive reactance? A. XC = 91.86 Ω C. XC = 154.45 Ω B. XC = 39.19 Ω D. XC = 184.0 Ω 192. REE Board Exam April 1995

In a series RC circuit the voltage across the capacitor and the resistor are 60 volts and 80 volts respectively. The total voltage is A. 70 C. 140 B. none of these D. 100 193. EE Board Exam October 1984 An industrial coil has a resistance of 32 ohms and reactance of 24 ohms and rated 440 volts at 60 Hz. A factory will connect the coil to a 440 V, 50 Hz supply. Solve for the value of a series resistor needed to avoid over-current condition. A. 2.07 ohms C. 2.44 ohms B. 2.64 ohms D. 2.25 ohms 194. REE Board Exam October 1998 Two relays each with 20 ohms resistance and 0.16 H inductance are connected in series. What is the equivalent impedance? A. 20 + j102.2 Ω C. 40 + j120.63 Ω B. 20 + j95.32 Ω D. 40 + j25.32 Ω 195. EE Board Exam October 1990 An inductive coil takes a current of 2 A and consumes 160 W when connected to a 240 V ac supply. A second coil when connected across the same supply takes 3 A and 500 W. Find the total power when the two coils are connected in series to this supply, A. 144.56 W C. 150.22 W B. 134.31 W D. 128.35 W 196. EE Board Exam October 1985 A coil draws 1875 watts when connected to a 150 V dc source. It consumes 30.72 watts when use on a 240 V, 60 Hz ac source. Find the inductance of the coil. A. 0.0255 H C. 0.0153 H B. 0.0341 H D. 0.0240 H 197. REE Board Exam October 1994 A current of 10 A and a power factor of 0.8 lagging is taken form a single phase 250 volt supply. The reactive power of the system is A. 1500 vars C. 2500 vars B. 2000 vars D. none of these 198. REE Board Exam October 1996 The resistor of 6 Ω and unknown impedance coil in series draws 12 A from a 120 V, 60 Hz line. If the real power taken from the line is 1152 watts, what is the coil inductance? A. 15.9 mH C. 20 mH

B.

10 mH

D.

1.59 mH

199. REE Board Exam April 1997 Determine the power factor angle in the series circuit which consists of R = 25 Ω, L = 0.2 H, across a power supply of 200 V, 30 Hz. A. 36.4° C. 52.4° B. 46.4° D. 56.4° 200. EE Board Exam April 1993 The impedance coils absorbs 250 watts when connected across 220 V, 60 Hz mains. It is then connected across 110 V, 25 Hz mains and also absorbs 250 watts. What is the inductance of the coil? A. 0.125 H C. 0.154 H B. 0.149 H D. 0.163 H 201. REE Board Exam September 2001 In laboratory experiment, the impedance of the coil was obtained at 60 Hz and 30 Hz. These are 75.48 ohms and 57.44 ohms respectively. What is the inductance of the coil? A. 150 mH C. 42.5 mH B. 182.5 mH D. 2.1 mH 202. REE Board Exam September 2002 A 10 ohms inductive resistor is connected in series with an unknown capacitance. At 60 Hz the impedance of the circuit is 10 + j11.72 ohms. At 30 Hz the impedance of the circuit is 10 – j5 ohms. What is the value of L in millihenrys? A. 50 C. 100 B. 500 D. 250 203. REE Board Exam April 1995 An impedance coil takes 10 A and absorbs 250 W when connected across a 220 V, 60 Hz source. What power will it absorb when connected across 110 V, 25 Hz mains? A. 539 W C. 439 W B. 239 W D. 339 W 204. EE Board Exam October 1984 An industrial coil has a resistance of 32 ohms and a reactance of 24 ohms and rated 440 volts at 60 Hz. A factory will connect the coil to a 440 V, 50 Hz supply. How much percentage over-current will the coil suffer? A. 5% C. 6% B. 10% D. 8% 205. REE Board Exam March 1998

A 25 Ω resistor connected in series with a coil of 50 Ω resistance and 150 mH inductance. What is the power factor of the circuit? A. 85% C. 90% B. 80% D. 75% 206. REE Board Exam April 1997 A current of 2.5 A flows through a series circuit consisting of a 100 ohm resistor and an unknown capacitor across a source of 460 V, 50 Hz. What is the value of the capacitive reactance? A. XC = 91.86 Ω C. XC = 154.45 Ω B. XC = 39.19 Ω D. XC = 184 Ω 207. REE Board Exam October 1998 The ohmic resistance of a large magnetic contactor is measured to be 20 ohms. A 230 V is impressed on the contractor and the current is taken as 3.2 A. Neglecting core loss, determine the inductance of the contractor in mH? A. 261 C. 183 B. 315 D. 251 208. REE Board Exam March 1998 A load of 20 + j35 Ω is connected across a 220 V source. Determine the power factor and the VARS. A. 49.6%, 1042 vars C. 85.3%, 975 vars B. 52.2%, 1023 vars D. 42.3%, 1087 vars 209. EE Board Exam October 1990 Find the total impedance in rectangular form for the following three series impedances: ohm, ohm, 34 ohm. A. 66.52 + j23.46 Ω C. 74.31 + j21.56 Ω B. 68.34 + j20.54 Ω D. 67.70 + j22.04 Ω 210. REE Board Exam October 1997 An impedance draws a current i = 10 cos (ωt – 30°) A from a voltage, v = 220 sin (ωt + 30°) V. What is the impedance? A. 15.6 – j15.6 Ω C. 19.1 – j11.1 Ω B. 15.6 + j15.6 Ω D. 11.0 + j19.1 Ω 211. EE Board Exam April 1990 A series resistance-capacitance (R-C) circuit is connected to a 230 volt 60 cycle source. If the power taken by the circuit is 4,800 watts and the voltage drop across the resistor is 115 volts, calculate the capacitance of the capacitor. A. 540 μF C. 556 μF B. 530 μF D. 503 μF

212. REE Board Exam March 1998 A 50 μF and 100 μF capacitors are connected in series and across a 100 sin (ωt + 30°) voltage. Write the equation of the current. A. 1.26 sin (ωt + 120°) A C. 5.65 sin (ωt + 120°) A B. 1.26 sin (ωt + 90°) A D. 5.56 sin (ωt + 90°) A 213. EE Board Exam April 1993 A V, 120 Hz generator and a V, 60 Hz generator are connected in series with a 60 V battery and a coil. The resistance and inductance of the coil are 3  and 2.65 mH, respectively. Determine the rms current of the coil. A. 42.54 A C. 43.55 A B. 44.24 A D. 40.44 A 214. REE Board Exam October 1996 A series circuit composed of 100-ohm resistor and a 20-microfarad capacitor connected across a 240-V, 60 Hz line. Which of the following answers is WRONG? A. the impedance of the circuit is 167 ohms B. angle between the current and the voltage vectors is 53.1 degrees C. the resulting current is 0.723 ampere D. the voltage across the resistance is 144.6 volts 215. REE Board Exam April 1994 A capacitance is connected to a 115-V, 25 Hz mains and takes 5 A. What current will it take when the capacitance and the frequency are both doubled? A. 2.5 A C. 20 A B. 5 A D. 10 A 216. REE Board Exam October 1996 A capacitor is rated 100 kVAR, 380 V, 50 Hz, What will its rating be at 60 Hz, 220 V? A. 50 kVAR C. 90.9 kVAR B. 40 kVAR D. 57.7 kVAR 217. REE Board Exam October 1992 A resistor and a capacitor are connected in series across a supply of 250 V. When the supply frequency is 50 Hz the current in the circuit is 5 A. When the supply frequency is 60 Hz, the current is 5.8 A. Find the value of the capacitance. A. 58.3 μF C. 60.2 μF B. 69.1 μF D. 70.2 μF

218. EE Board Exam October 1993 A series circuit composed of a 0.2 Henry inductor and a 74-microfarad capacitor is connected to a 60 V variable frequency source. At what frequency is the current be 4 amperes with a lagging power factor? A. 50 Hz C. 48 Hz B. 51 Hz D. 49 Hz 219. REE Board Exam October 1998 The maximum instantaneous voltage and current output of an alternator are 300 V and 20 A, respectively. What is the power output in watts if the voltage leads the current by 30°? A. 2598 C. 5196 B. 3000 D. 6000 220. REE Board Exam October 1998 A 50-microfarad is connected in series with a coil having 50 ohms resistance and 150 mH inductance. The source voltage is 100 sin (ωt – 120°) V. What is the maximum power? A. 199 watts C. 212 watts B. 147 watts D. 165 watts 221. REE Board Exam October 1997 An impedance draws a current i = 10 cos (ωt – 30°) A from a voltage v = 220 sin ωt. What is the maximum power? A. 2200 watts C. 190.5 watts B. 1100 watts D. 1320 watts 222. REE Board Exam April 1995 An incandescent lamp load generally considered to be made up of resistors take 4.8 kW from a 120 V ac source. The instantaneous maximum value of power is A. 4800 W C. 480 W B. 2400 W D. 9600 W 223. ECE Board Exam November 1998 The term used for an out-of-phase, non-productive power associated with inductors and capacitors? A. peak envelope power C. true power B. effective power D. reactive power 224. ECE Board Exam November 2001 What is the capacitive reactance of a 33 microfarad capacitor at 6500 Hz? A. 7.4 0hms C. 0.74 ohms B. 96 0hms D. 1122 ohms

225. ECE Board Exam November 1999 The power dissipated across the resistance in an AC circuit. A. true power C. reactive power B. real power D. apparent power 226. ECE Board Exam April 2000 What is the capacitive reactance of a 33 microfarad capacitor at 500 Hz? A. 1,000,000 ohms C. 0 ohms B. 144 ohms D. 9.55 ohms 227. ECE Board Exam November 1998 What is the reactance of a 25 mH coil at 600 Hz? A. 0.011 ohm C. 785 ohms B. 94,000 ohms D. 94 ohms 228. ECE Board Exam April 1999 Ignoring capacitance effects, what is the impedance of a 250 mH coil with an internal resistance of 55 ohms at 60 Hz? A. 149.2 ohms C. 94.2 ohms B. 109 ohms D. 10,900 ohms 229. ECE Board Exam November 1999 Ignoring any inductive effects, what is the impedance of RC series capacitor made up of a 56 kilo ohms resistor and a 0.033 μF capacitor at a signal frequency of 450 Hz? A. 66,730  C. 10,730  B. 57,019  D. 45,270  230. ECE Board Exam April 2000 Assuming an ideal capacitor, with no leakage, what is the capacitive reactance of 10 microfarad capacitance of DC (0 Hz)? A. 0 ohms B. 16000 ohms C. 1,000,000 ohms D. infinite capacitive reactance 231. ECE Board Exam April 1998 The impedance in the study of electronics is represented by resistance and _____ A. Reactance B. Capacitance C. Inductance D. Inductance and capacitance 232. ECE Board Exam November 2000

One of the following satisfies the condition of Ohm’s Law A. Application to metals which heated up due to flow of current over them B. C. D.

Application to AC circuit having its impedance used in place of resistance Application to semiconductor Application to vacuum radio valves

233. The effective voltage across a circuit element is (20 + j10) and the effective current through the element is 4 – j3 A. Calculate the true and reactive power taken by the element. A. 50 watts & 100 vars lagging B. 50 watts & 100 vars leading C. 110 watts & 20 vars lagging D. 110 watts & 20 vars leading 234. The voltage across a given circuit is 75 + j50 V. What is the power supplied to the circuit if the current through it is (8 – j5) A? A. 850 W C. 750 W B. 550 W D. 350 W 235. Find average power in a resistance R = 10 ohms if the current in series form is i = 10 sin ωt + 5 sin 3ωt + 2 sin 5ωt amperes. A. 65.4 watts C. 546 watts B. 645 watts D. 5.46 watts 236. Across a 230-V, 60 Hz power supply is a 15-ohm non-inductive resistor. What is the equation of the voltage and resulting current? A. e = 398.4 sin 60t and i = 21.6 sin 60t B. e = 325.5 sin 377t and i = 21.6 sin 377t C. e = 230 sin 377t and i = 15.3 sin 377t D. e = 230 sin 120t and i = 15.3 sin 120t 237. A resistor R and a capacitor C are connected in series across a 100 V, 60 cycle source. The reading of an ammeter connected in the circuit is 2 A and the reading of a voltmeter connected across the capacitor is 80 V. Calculate the values of R and C. A. 66 Ω & 30 μF C. 30 Ω & 66 μF B. 30 Ω & 60 μF D. 36 Ω & 60 μF 238. A series circuit consisting of a 66.2 μF capacitor and a variable resistor. For what two values of resistance will the power taken by the circuit be 172.8 watts, if the impressed 60-cycle emf is 120 volts? A. 85.33 & 3.33 ohms C. 5.33 & 3.0 ohms B. 53.33 & 30 ohms D. 83.33 & 5.33 ohms

239. A series circuit composed of 0.2 H inductor and a 74 μF capacitor is connected to a 60 V variable frequency source. At what frequency will the current be 4 A with lagging power factor? A. 47.767 Hz C. 60 Hz B. 74.68 Hz D. 50 Hz 240. A 30 ohm resistor is connected in parallel with an inductor of inductive reactance XL. The combination is then connected in series with a capacitor of reactance XC. What is the value of XL and XC if the total impedance is 1.92 ohms? A. 7.84 and 7.34 C. 44.8 and 84.21 B. 47.4 and 47.3 D. 84.7 and 34.7 241. An impedance of 100 Ω resistance and an unknown inductance is connected across the capacitor. The resulting impedance is a pure resistance of 500 Ω 5 if ω = 10 rad/sec. Calculate the values of inductor and capacitor. A. 1 μF & 2 mH C. 7 μF & 3 mH B. 5 μF & 1 mH D. 0.04 μF & 2 mH 242. The voltage across the resistor, inductor and capacitor in series is 60 V, 90 V and 10 V respectively. What is the voltage across this circuit? A. 160 V C. 100 V B. 140 V D. 50 V 243. The open circuit voltage of an alternator is 127 V and its internal impedance is Ω. Find the voltage across a load of Ω. A. V C. V B. V D. V 244. The maximum values of alternating voltage and current are 400 V and 20 A, respectively. In a circuit connected to 50 Hz supply and these quantities are sinusoidal. The instantaneous values of voltage and current are 283 V and 10 A respectively at t = 0 both increasing positively. What is power factor of the circuit? A. 0.707 C. 0.85 B. 0.83 D. 0.965 245. The potential difference measured across a coil is 4.5 V, when it carries a direct current of 9 A. The same coil when carries an alternating current of 9 A at 25 Hz, the potential difference is 24 V. Find the power when it is supplied by 50 V, 50 Hz supply. A. 45 W C. 63 W B. 54 W D. 30 W

246. Two coils A and B are connected in series across a 240 V, 50 Hz supply. The resistance of A is 5 Ω and the inductance of B is 0.015 H. If the input from the supply is 3 kW and 2 kVAR, find the inductance of A and resistance of B. A. 0.0132 H & 8.3 Ω C. 0.026 H & 12 Ω B. 0.215 H & 3.8 Ω D. 0.031 H & 5.3 Ω

253. A coil has a resistance of 6 ohms and an inductance of 0.02 H. When a noninductive resistor is connected in series with the coil, the current drawn when connected to 220 V DC source is equal to the current drawn by the coil alone across a 220 V, 60 Hz source. Determine the resistance of the non-inductive resistor. A. 3.63 Ω C. 3.69 Ω B. 6.39 Ω D. 3.96 Ω

247. A current of 5 A flows through a non-inductive resistance in series with a choking coil when supplied at 250 V, 50 Hz. If the voltage across the resistance is 120 V and across the coil is 200 V, calculate the power absorbed by the coil in watts. A. 168.75 W C. 51.37 W B. 137.5 W D. 75.31 W

254. A series RL circuit has L = 0.02 H and an impedance of 17.85 Ω. When a sinusoidal voltage is applied, the current lags the voltage by 63.5°. What is the value of the angular frequency? A. 400 rad/sec C. 600 rad/sec B. 500 rad/sec D. 800 rad/sec

248. A single phase, 7.46 kW motor is supplied from a 400 V, 50 Hz AC mains. If its efficiency is 85% and the power factor is 0.8 lagging, find the reactive component of the input current. A. 16.46 A C. 27.43 A B. 21.95 A D. 21 A

255. A 50  resistance is connected in series with a coil having 25  resistance and 150 mH inductance. The circuit is connected to a voltage source of 200 sin t. Calculate the instantaneous current. A. 2.9 sin t C. 2.1 sin (t – 37) B. 1.7 sin (t + 37) D. 5.11 sin (t - 37)

249. A series RLC circuit consists of 20 ohms resistance, 0.2 H inductance and an unknown capacitance. What is the value of the capacitance if the circuit has a leading angle of 45° at 60 Hz? A. 35.18 μF C. 27.8 μF B. 47.9 μF D. 30.7 μF

256. A coil having a resistance of 25  and an inductance of 150 mH is connected in series with a 80 F capacitor across a voltage source of 200 sin 377t. What is its instantaneous current? A. 5.84 cos (377t - 43) C. 5.84 sin (377t + 43) B. 5.84 sin 377t D. 5.84 sin (377t - 43)

250. A 3 HP, 120 V, 60 Hz induction motor operating at 80% efficiency and 0.866 lagging power factor is to be used temporarily with 240 V, 60 Hz source. What resistance in series with the motor will be required for the motor to have 120 V across its terminals at full load? A. 6.68 Ω C. 13.76 Ω B. 4.77 Ω D. 9.54 Ω

257. A coil with a 15  resistance is connected in series with a capacitor. At 60 Hz source, the impedance is measured at 15 + j11.27  while in 30 Hz source it is measured as 15 – j7.24 . Calculate the inductance of the coil. A. 52.7 mH C. 41.2 mH B. 65.8 mH D. 11.27 mH

251. A circuit draws a current of (3 – j8) A from a source of (100 + j37) V. Find the true power of the circuit. A. 4 W C. 300 W B. 596 W D. 296 W

258. An impedance coil has a resistance and inductance of 20 ohms and 0.05 H respectively. What value of dc voltage can be applied to the coil in order that it will take the same power from a 220 V 60 Hz mains? A. 188 V C. 160 V B. 220 V D. 120 V

252. A resistor and a coil are connected in series with a voltage source. If the voltage across the coil is 10 sin (866t + 70°) V and the current flowing through the resistor is 2 cos (866t – 80°) A, what is the resistance of the coil? A. 4.92 Ω C. 5 Ω B. 2.5 Ω D. 4.33 Ω

259. A ½ HP, 110 V, 60 Hz, single-phase induction motor has an efficiency of 88% and a power factor of 0.707 lagging at rated load. This motor is to be connected temporarily on a 220 V, 60 Hz line. Determine the resistance required to be placed in series with the motor in order to prevent the machine from experiencing overcurrent? A. 25.2 ohms C. 19.5 ohms B. 23.5 ohms D. 27.6 ohms

D. 260. Two coils A and B known to have the same resistance are connected in series across a 110 V, 60 cycle line. The current and power delivered by the source are respectively 4.1 A and 300 W. If the voltage across coil A is twice that across coil B, calculate the inductance of coil B. A. 8.63 mH C. 9.02 mH B. 7.36 mH D. 4.49 mH 261. The total voltage in a series RL circuit ____ the current by an angle ____. A. lags, of 90 B. lags, between 0 and 90 C. leads, between 0 and 90 D. leads, between 90 and 180 262. In a series RL circuit, the inductor current ____ the resistor current. A. lags C. leads B. is equal D. is negative 263. The impedance triangle is similar to the ____ triangle with the resistance phasor in place of the ____ A. current, resistor current B. current, resistor voltage C. voltage, impedance D. voltage, resistor voltage 264. In the impedance triangle the inductive reactance and impedance phasor are analogous to the ____ and ____ phasor respectively in the voltage triangle. A. inductive voltage, total voltage B. inductive current, total current C. inductive voltage, resistive current D. inductive current, resistive current 265. In a series RL circuit, phasor diagram, total voltage may be represented by the ____ phasor and the resistor voltage may be represented by the ____ voltage. A. current, voltage B. impedance, resistance C. current, resistance D. impedance, inductance 266. The phase angle of a series RL circuit is the angle between the ____ phasor and the ____ phasor. A. resistance, inductive reactance B. resistance, impedance C. inductive reactance, impedance

none of the above

267. The phase angle of a series RL circuit may be computed ____ as ____ or ____. -1 -1 -1 A. cos R/XL, sin XL/R, tan R/Z -1 -1 -1 B. cos R/Z, sin XL/R, tan R/XL -1 -1 -1 C. cos Z/XL, sin R/Z, tan XL/R -1 -1 -1 D. cos R/Z, sin XL/Z, tan XL/R 268. In the circuit of figure shown the effective value of the resistor voltage is ____ volts. 5Ω

5Ω

Eeff. = 10 V

A. B.

5

√

C. D.

√ 10

269. A(n) ____ stores and returns energy to a circuit while a(n) ____ dissipates energy. A. resistor, impedance C. inductor, resistor B. resistor, inductor D. inductor, reactance 270. For an RL circuit, the power factor cannot be less than ____ or greater than ____. A. 0, 1 C. 0, -1 B. 1, 0 D. –1, 0 271. The voltage across a capacitor ____ the current through it by ____. A. lags, 45 C. leads, 0 B. lags, 90 D. leads, 90 272. If the resistance in a series RC circuit is increased the magnitude of the phase angle A. increases B. remains the same C. decreases D. changes to an indeterminate manner 273. In a series RC circuit, the current ____ the total voltage by an angle. A. lags, of 45 B. lags of 0 C. leads, between 0 and 90

D.

A. B.

leads, of 90

274. The resistance phasor for a series RC circuit points to the right. The capacitive reactance phasor points ____ while the diagonal of the rectangle having there two phasors as sides represents the ____. A. up, impedance C. down, impedance B. left, current D. up, total voltage 275. The phase angle for a series RC circuit is defined as the angle between the ____ and the ____ phasors. A. current, resistance voltage B. current, total voltage C. resistance voltage, capacitor voltage D. R, XC 276. The phase angle for a series RC circuit may be computed as the angle between the ____ and the ____ phasors. A. resistance, impedance B. resistance, reactance C. resistance, impedance D. none of the above 277. If a series RC circuit with 10 ohms and XC = 10 ohms carries a current of 1 ampere effective value the resistor voltage is ____ volts effective and the capacitor voltage is ____ volts effective. A. 10/√ , 10/√ C. 10√ , 10√ B. 10, 10 D. 5, 10 278. The power dissipated in a series RL circuit with R =10 ohms and X C = 10 ohms carrying an effective current of 3 amps is ____ watts. A. 30 C. 90 B. 30√ D. 90√ 279. The magnitude of the power factor of an RC circuit with R = 10 ohms, XC = 10 ohms. I = 2 amp effective is ____. A. 1 C. 0.707 B. 0.5 D. 0.0 280. The power dissipated in the circuit shown is ____ watts. 30 Ω

Eeff. = 100 V

40 Ω

60 80

C. D.

100 120

281. The net reactance in an RLC circuit is A. XL C. XC B. XC – XL D. XL - XC 282. The impedance of a series RLC circuit is ____. A.

√

C.

√

(

)

B.

√

D.

√

(

)

283. In a series RC circuit, the voltage across the capacitor and the resistor are 60 V and 80 V respectively. The input voltage should be A. V C. V B. V D. V 284. The transient current are due to A. voltage applied to circuit B. resistance of the circuit C. impedance of the circuit D. changes in stored energy in inductance and capacitance 285. To a highly inductive circuit, a small capacitance is added in series. The angle between voltage and current will A. increase B. decrease C. remain nearly the same D. become indeterminant 286. In a series R-L circuit. VL ____ VR by ____ degrees. A. lags, 45 C. leads, 90 B. lags, 90 D. leads, 45 287. The voltage applied across an R-L circuit is equal to ____ of VR and VL. A. arithmetic sum C. phasor sum B. algebraic sum D. sum of the squares 288. The power in an a.c. circuit is given by A. VI cos φ C. I² Z B. VI sin φ D. I² XL 289. The p.f. of an R-C circuit is A. often zero

B. C. D.

between zero and 1 always unity between zero and -1.0

298. An R-L-C circuit has R = 10 Ω, XL = 20 Ω and XC = 30 Ω. The impedance of the circuit is given by the expression. A. Z = 10 + j20 C. Z = 10 – j20 B. Z = 10 + j50 D. Z = -10 + j20

290. Which phasor diagram is correct for a series R-C circuit?

I Fig. 1 A. B.

Figure 1 Figure 2

V

V

I

V

Fig. 2 C. D.

I Fig. 3

I

V

Fig. 4

Figure 3 Figure 4

291. In an R-L-C circuit, v(t) = 20 sin (314t + 5π/6) and i(t) = 10 sin (314t + 2π/3). The p.f. of the circuit is ____ and power drawn is ____ watt. A. 0.5 lead, 200 C. 0.866 lead, 173.2 B. 0.886 lag, 186.6 D. 0.5 lag, 50 292. The input of an a.c. circuit having p.f. of 0.8 lagging is 20 kVA. The power drawn by the circuit is ____ kW. A. 12 C. 16 B. 20 D. 8 293. The power factor of an a.c. circuit is given by A. cosine of the phase angle B. tangent of the phase angle C. the ratio R/XL D. the ratio XL/Z 294. In series R-L-C circuit, R = 100 Ω, XL = 300 Ω and XC = 200 Ω. The phase angle Φ of the circuit is _____ degrees. A. 0 C. 45 B. 90 D. -45 295. The phase angle of a series R-L-C circuit is leading if A. XL = 0 C. XC > XL B. R = 0 D. XC < XL 296. In an a.c. circuit, the ratio of kW/kVA represents A. power factor C. form factor B. load factor D. diversity factor 297. If p.f. of a circuit is unity, its reactive power is A. a maximum C. zero B. equal to I²R D. a negative quantity

299. An alternating voltage e = 200 sin 314t is applied to a device which offers an ohmic resistance of 20 Ω to the flow of current in one direction while entirely preventing the flow in the opposite direction. The average value of current will be A. 5 A C. 1.57 A B. 3.18 A D. 1.10 A 300. A 10 mH inductor carries a sinusoidal current of 1 A rms at a frequency of 50 Hz. The average power dissipated by the inductor is A. 0 W C. 0.5 W B. 0.25 W D. 1.0 W 301. A circuit component that opposes the change in circuit voltage is A. resistance C. inductance B. capacitance D. all of the above 302. Power loss in an electrical circuit can take place in A. inductance only B. capacitance only C. inductance and resistance D. resistance only 303. A circuit of zero lagging power factor behaves as A. an inductive circuit C. R-L circuit B. a capacitive circuit D. R-C circuit 304. In an R-L series circuit the power factor is A. leading C. zero B. lagging D. unity 305. When a sinusoidal voltage is applied across an R-L series circuit having R = XL, the phase angle will be A. 90° C. 45° leading B. 45° lagging D. 90° leading 306. An ac source having voltage e = 110 sin (ωt + π/3) is connected in an ac circuit. If the current drawn from the circuit varies as i = 5 sin (ωt - π/3) the impedance of the circuit will be A. 22 Ω C. 30.8 Ω

B.

16 Ω

D.

none of these

307. Which are of the following true of the circuit shown in the given figure? 100 Ω

L

250 2 sin300 t

-

I

1. VR = 2. I = 2 A 3. L = 0.25 H √ V Select the correct answer using the codes given below: Codes: A. 2 and 3 C. 1 and 3 B. 1 and 2 D. 1, 2 and 3 308. The R-L circuit of the figure is fed from a constant magnitude variable frequency sinusoidal voltage source vin. At 100 Hz, the R and L element each has a voltage drop Vrms. If the frequency of the source is changes to 50 Hz, then new voltage drop across R is R

L

+ vin -

A. B.

√ √

Vrms Vrms

C. D.

5 W and 8.66 VAR 20 W and 60 VAR √ W and √ VAR

150 V

VR

+

B. C. D.

√ √

Vrms Vrms

312. In a two-element series circuit, the applied voltage and resultant current are 3 3 respectively, v(t) = 50 + 50 sin (5 x 10 t) and i(t) = 11.2 sin (5 x 10 t + 63.4°). The nature of the elements would be A. R-L C. L-C B. R-C D. neither R, nor L, nor C 313. A series circuit passive elements has the following current and applied voltage: v = 200 sin (2,000t + 50°), i = 4 cos (2,000t + 13.2°) The circuit elements A. must be resistance and capacitance B. must be resistance and inductance C. must be inductance, capacitance and resistance D. could be either resistance and capacitance or resistance, inductance and capacitance 314. A two terminal black box contains one of the R-L-C elements. The black box is connected to a 220 V ac supply. The current through the source is I. When a capacitance of 0.1 F is inserted in series between the source and the box, the current through the source is 2I. The element is A. a resistance B. an inductance C. a capacitance D. it is not possible to determine the element 315. In the following circuit, i(t) under steady state is

310. A square wave is fed to an R-C circuit. Then A. voltage across R is square and across C is not square B. voltage across C is square and across R is not square C. voltage across both R and C is square D. voltage across both R and C is not square 311. The voltage phasor of a circuit is V and the current phasor is A. The active and reactive powers in the circuit are A. 10 W and 17.32 VAR

2H

1Ω

309. An ac source of 200 Vrms supplies active power of 600 W and reactive power of 800 VAR. The rms current drawn from the source is A. 10 A C. 3.75 A B. 5 A D. 2.5 A

1F

5V 10 sin t

A. B.

zero 5

C. D.

i(t)

7.07 sin t 7.07 sin (t – 45°)

316. The source in the circuit is a sinusoidal source. The supply voltages across various elements are marked in the figure. The input voltage is

3V

14 V

321. In the case of the R-L-C circuit shown in the given figure, the voltage across the R, L and C would be respectively

10 V

R

A. B.

10 V 5V

C. D.

15 V (rms)

27 V 24 V

317. In the circuit shown in the given figure, if the power consumed by the 5 Ω resistor is 10 W, then the pf of the circuit is 5Ω

L

10 Ω

50 cos ωt

A. B. C. D.

L

C

V1 20 V (rms)

V2 9 V (rms)

12 V, 16 V and 7 V or 25 V 16 V, 12 V and 7 V or 25 V 7 V, 16 V and 12 V 16 V, 12 V and 25 V

322. Consider the following statements regarding the circuit shown in the figure. j15 / 3

5Ω

A. B.

0.8 0.6

C. D.

0.5 zero

10 6 V

318. In an RL circuit, supplied from an ac source, the reactive power is proportional to the A. the average energy stored in the electric field B. the average energy stored in the magnetic field C. sum of the average energy stored in the electric field and that stored in the magnetic field D. difference of the average energy stored in the electric field and that stored in the magnetic field 319. If a series RLC circuit excited by a voltage e = E sin ωt when LC < 1/ω A. current lags behind the applied voltage B. current leads the applied voltage C. current is in phase with the applied voltage D. voltage across L and C are equal

2

I

If the power consumed by 5 Ω resistor is 10 W then 1. |I| = √ A 2. the total impedance of the circuit is 5 Ω 3. cos θ = 0.866 Which of these statements is correct? A. 1 and 3 C. 1 and 2 B. 2 and 3 D. 1, 2 and 3 323. In an ac circuit if voltage V = (a + jb) and current I = (c + jd), then the power is given by A. ac + ad C. bc - ad B. ac + bd D. bc + ad 324. The reactive power drawn from the source in the network in the given figure is

320. The current in the circuit shown is

+j10 Ω

3Ω

10010 V

A. B.

5A 10 A

C. D.

10 Ω

15 A 25 A

A.

300 VAR

C.

100 VAR

-j10 Ω

B.

200 VAR

D.

zero

325. A series R-L-C circuit, consisting of R = 10 Ω, XL = 20 Ω, XC = 20 Ω is connected across an ac supply of 100 V (rms). The magnitude and phase angle (with reference to supply voltage) of the voltage across the inductive coil are respectively A. 100 V, 90° C. 200 V, -90° B. 100 V, -90° D. 200 V, 90° 326. For a capacitor in a sine wave ac circuit A. vC lags iC by 90° B. iC leads vC by 90° C. iC and vC have the same frequency D. all of the above 327. In a series RC circuit, A. VC leads VR by 90° B. VC and I are in phase

C. D.

VC lags VR by 90° both B and C

328. In a series RC circuit, A. VC and VR are in phase B. VT and I are always in phase C. VR and I are in phase D. VR leads I by 90° 329. When the frequency of the applied voltage increases in a series RC circuit A. the phase angle, θT, becomes more negative B. ZT increases C. ZT decreases D. both A and 330. Inductive reactance, XL A. applies only to non-sinusoidal waveforms or dc B. applies only to sine waves C. applies to either sinusoidal or non-sinusoidal waveforms D. is inversely proportional to frequency 331. For an inductor in a sine wave ac circuit A. VT leads iL by 90° C. VT and iL are in phase B. VT lags iL by 90° D. none of the above 332. In a series RL circuit, A. VT lags VR by 90° B. VT leads VR by 90°

C. D.

VR and I are in phase both B and C

333. In a series RL circuit where XL = R, the phase angle, θZ, is A. -45° C. 90° B. 0° D. 45° 334. In an ac circuit with only series resistances A. VT and I are in phase B. RT =R1 + R2 + R3 + … + etc. C. each voltage drop is in phase with the series current D. all of the above 335. The unit of apparent power is the A. volt-ampere (VA) B. watt (W) C. volt-ampere-reactive (VAR) D. joule (J) 336. In an ac circuit with only series capacitors A. VT leads I by 90° B. VT lags I by 90° C. each capacitor voltage drop leads I by 90° D. both A and C 337. The unit of real power is the A. watt (W) B. volt-ampere (VA) C. joule (J) D. volt-ampere-reactive (VAR) 338. In a series RLC circuit A. XL and XC are 180° out of phase B. IL and IC are 180° out of phase C. XL and XC are 90° out of phase D. XL and XC are in phase 339. The power factor of an ordinary electric bulb is A. zero B. unity C. slightly more than unity D. slightly less than unity 340. The power factor of an ac circuit is equal to A. cosine of the phase angle B. sine of the phase angle C. unity for a resistive circuit D. unity for a reactive circuit

341. If f(t) = sin t + sin √ t is passing through R = 1 ohm, what is the power dissipated in 1 ohm resistor? A. 1 W B. 2 W C. since f(t) in non-periodic, not possible to find power D. none of the above C. PARALLEL CIRCUITS 342. EE Board Exam October 1981 A circuit consists of XL = j5 ohms, XC = -j5 ohms and R = 5 ohms all are connected in parallel. Find the equivalent impedance. A. 5.5 Ω C. 4.8 Ω B. 5.0 Ω D. 5.2 Ω 343. EE Board Exam October 1985 Given: Z1 = -j2.5 ohms; Z2 = j4 ohms; Z3 = 5 ohms; Z4 = 1 + j5 ohms. If the four impedances are connected in parallel, find the equivalent impedance in ohms. A. 4.1 + j0.72 C. 4.2 + j0.35 B. 4.3 + j0.45 D. 4.0 + j0.97 344. EE Board Exam April 1984, April 1987 Three impedances Za = 3 + j4 ohms, Zc = 4 – j4 ohms and Zc = j3 ohms are connected in parallel. Solve for the pf of the combination. A. 0.653 leading C. 0.503 leading B. 0.554 lagging D. 0.620 lagging 345. EE Board Exam October 1993 -6 A pure capacitance of 530.515 x 10 farad and an inductance of 530.515 x -4 10 Henry are connected in parallel across an ac power source. Solve for the resultant impedance assuming that the frequency is 30 Hz. A. 10 Ω C. zero B. infinite D. undefined

A. B.

0.471 lagging 0.471 leading

C. D.

0.573 lagging 0.573 leading

348. REE Board Exam October 1997 A resistor of 50 ohms and an impedance of 100 + j50 ohms are connected in parallel across a 220 volts supply. What is the power factor of the load? A. 96% C. 98% B. 99% D. 95% 349. EE Board Exam October 1992 A capacitor of 3.18 microfarads is connected in parallel with a resistance of 2,000 ohms. The combination is further connected in series with an inductance of 795 mH and resistance of 100 ohms across a supply given by e = 400 sin wt + 80 sin (3wt + 60°). Assume w = 314 radians/sec. Determine the power dissipated. A. 74.66 W C. 80.28 W B. 78.05 W D. 75.66 W 350. EE Board Exam October 1992 A capacitor of 3.18 microfarads is connected in parallel with a resistance of 2,000 ohms. The combination is further connected in series with an inductance of 795 mH and resistance of 100 ohms across a supply given by e = 400 sin wt + 80 sin (3wt + 60°). Assume w = 314 radians/sec. Determine the circuit power factor. A. 0.702 C. 0.633 B. 0.650 D. 0.612 351. EE Board Exam April 1990 A capacitor, an electric resistance heater, and impedance are connected in parallel to a 120 V, 60 Hz system. The capacitor draws 50 var, the heater draws 100 W and the impedance coil draws 269 VA at a pf 0f 0.74 lagging. Determine the system power factor. A. 0.933 leading C. 0.916 lagging B. 0.928 lagging D. 0.911 lagging

346. REE Board Exam March 1998 A coil of a 50-ohm resistance and of 150 mH inductance is connected in parallel with a 50 μF capacitor. What is the power factor of the circuit? A. 80% C. 70% B. 50% D. 60%

352. REE Board Exam October 1996 A bank of capacitors is connected in parallel each rated at 10 kVAR, 380 volts. If one unit is shorted out, what would be the net capacitance of the bank? A. 330 μF C. 220 μF B. 440 μF D. 110 μF

347. EE Board Exam April 1982 Three impedances Za, Zb and Zc are connected in parallel. If at 60 Hz, Za = j8, Zb = -j2 and Zc = 5 ohms. Solve for the resultant power factor.

353. EE Board Exam October 1992 A capacitor of 3.18 microfarads is connected in parallel with a resistance of 2,000 ohms. The combination is further connected in series with an

inductance of 795 mH and resistance of 100 ohms across a supply given by e = 400 sin wt + 80 sin (3wt + 60°). Assume w = 314 radians/sec. Determine the rms value of the total current. A. 0.40 A C. 0.56 A B. 0.33 A D. 0.45 A 354. EE Board Exam June 1990 Three loads, units A, B and C are connected in parallel and take currents that are respectively 12, 10 and 15 A respectively. Assuming Ia to be the reference phasor. Ib leads Ia by 30° and Ic lags behind Ia by 65°, calculate the total (resultant) current. A. 28.33 A C. 26.46 A B. 30.21 A D. 32.10 A 355. EE Board Exam April 1992 Two single-phase motors are connected in parallel across a 120-volt, 60cycle source of supply. Motor A is a split-phase inductance type and motor B is a capacitor type: Motor A B

HP Output ¼ ½

Determine total power factor. A. 0.886 lag B. 0.864 lag

Efficiency 0.60 0.70

C. D.

pf 0.70 lag 0.95 lag

0.817 lag 0.825 lag

356. EE Board Exam April 1992 A 250 V, 30 Hz generator supplies power to a parallel circuit consisting of a 20 HP motor whose efficiency is 90% at 0.80 pf lagging and a second load that draws an apparent power of 7 kVA at unity pf. Determine the system power factor. A. 0.828 lagging C. 0.802 lagging B. 0.831 lagging D. 0.884 lagging 357. EE Board Exam April 1985 A resistance of 5 ohms is connected in series with a capacitor of 442.1 μF. The combination is then connected in parallel with an inductance of 21.22 mH. Solve for the resultant current if the circuit is connected across a 120 V, 60 Hz ac source. A. 9.44 A C. 11.29 A B. 10.68 A D. 10.34 A 358. EE Board Exam April 1993

An inductor L1 is connected in series with a parallel combination of inductor L2 and capacitor C. The impedance of the circuit w = 400 rad/sec is j100 ohms. The circuit is to yield infinite impedance at w = 1,000 rad/sec and zero impedance at w = 2,000 rad/sec. Determine the value of C. A. 1.28 μF C. 2.06 μF B. 1.67 μF D. 1.32 μF 359. EE Board Exam April 1992 A sinusoidal current source, 10 cos 1000t, is in parallel both with a 20-ohm resistor and the series combination of a 10-ohm resistor and a 10-mH inductor. Find the equation of the voltage across the 10-ohm resistor. A. 63.25 cos (1000t – 18.43°) B. 61.32 cos (1000t – 20.34°) C. 59.36 cos (1000t – 17.45°) D. 60.12 cos (1000t – 19.38°) 360. EE Board Exam April 1993 A 1-hp, 220 V, 60 Hz capacitor-start motor has main and auxiliary winding impedance at starting of 3.5 + j2.5 ohms and 8.6 + j2.5 ohms, respectively. Determine the value of the starting capacitance that will place the main and auxiliary winding currents 90 apart at starting, A. 186.75 μF C. 182.43 μF B. 174.35 μF D. 170.67 μF 361. EE Board Exam October 1990 Two impedances A and B are connected in parallel across a 120 V ac supply. The total current and the current in each impedance is adjusted to 20 A. The power drawn by A is doubled that of B and the power factor is lagging. Determine the power factor of A. A. 0.650 lagging C. 0.841 lagging B. 0.704 lagging D. 0.677 lagging 362. REE Board Exam March 1998 A coil of 50-ohm resistance and of 150-mH inductance is connected in parallel with a 50-μF capacitor. If the source voltage is 100 sin (ωt + 30°), what is the equation of the line current? A. 1.91 sin (ωt + 52.5°) C. 1.82 sin (ωt - 62°) B. 1.25 sin (ωt + 75.5°) D. 1.32 sin (ωt – 75.5°) 363. EE Board Exam October 1984 A resistor R is connected in parallel with a 10-ohm inductive reactance. The combination is then connected in series with a 4-ohm capacitive reactance. The whole combination is connected across a 100-volt, 60 Hz supply, How much is R if the angle between the supply voltage and the total current is 45 degrees?

A. B.

12 ohms 25 ohms

C. D.

16 ohms 20 ohms

364. EE Board Exam April 1980 Three impedances Z1 = 1 - j4 ohms, Z2 = – j6 ohms and Z3 = 4 + j3 ohms are connected in series-parallel. Z1 is connected in series with the parallel combination of Z2 and Z3. Determine the equivalent impedance of the combination. A. 4.32 – j1.21 ohms C. 6.76 – j5.68 ohms B. 2.23 – j3.32 ohms D. 5.42 – j7.21 ohms 365. EE Board Exam October 1984 A 5-ohm resistor is connected in parallel with a 10-ohm inductive reactance. The combination is then connected in series with a 4-ohm capacitive reactance. The whole combination is connected across a 100-volt, 60 Hz supply. How much is the total current drawn by the circuit? A. 22.36 A C. 23.16 A B. 20.45 A D. 19.89 A 366. EE Board Exam April 1983 A non-inductive resistor R is connected in parallel with an inductive reactance of 10 ohms. The combination is then connected in series with a capacitive reactance of 5 ohms. The whole combination is connected across a 100-volt, 60 Hz ac source. If R is equal to 5 ohms, solve for the voltage across the parallel combination. A. 87.53 V C. 89.44 V B. 88.34 V D. 91.87 V 367. EE Board Exam April 1980 Three impedances Z1 = 1 - j4 ohms, Z2 = – j6 ohms and Z3 = 4 + j3 ohms respectively are connected in series-parallel. Z1 is connected in series with the parallel combination of Z2 and Z3. If this circuit is connected across a 230 V, 60 Hz source, determine the voltage across the parallel combination of Z 2 and Z3. A. 156.3 V C. 135.7 V B. 146.8 V D. 163.2 V 368. EE Board Exam October 1980 Given three impedances: Z1 = 10 + j0 ohms, Z2 = 3 + j4 ohms and Z3 = 8 – j6 ohms. Impedance Z2 and Z3 are connected in parallel and the combination is connected in series with impedance Z1 across a 120 V single-phase 60 Hz source. Find the total power drawn by the impedance. A. 1008 W C. 1038 W B. 1204 W D. 1103 W

369. EE Board Exam October 1993 If admittance Y = 0.06 – j0.08 mho, then conductance G equals A. -0.06 C. 0.08 B. 0.06 D. -0.08 370. EE October 1986, April 1993 A parallel circuit consists of a resistor having a conductance of 4 mhos, an inductive reactor having a susceptance of 8 mhos and a capacitive reactor having a susceptance of 5 mhos. What is the impedance of the circuit? A. 0.11 + j0.13 ohms C. 0.12 + j0.16 ohms B. 0.13 + j0.11 ohms D. 0.16 + j0.12 ohms 371. REE Board Exam October 1994 A capacitor branch having a ratio of XC to R of 5 is paralleled with impedance consisting of a 4 Ω resistance and a 3 Ω inductive reactance. The power factor of the resulting circuit is 0.8 leading. Find the size of the capacitor in μF if the frequency is 60 Hz. A. 879.9 μF C. 978.9 μF B. 1078.9 μF D. 778.9 μF 372. ECE Board Exam November 2000 A parallel-LC circuit can store energy fed to it power source and produces an output which is a continuous A.C. wave. It is often called a ____. A. Tank circuit C. Storage circuit B. Store circuit D. Power circuit 373. ECE Board Exam November 2001 What is the impedance relationship between the output of one circuit and the input of another circuit will provide maximum power transfer? A. very low impedance C. lower impedance B. higher impedance D. equal impedance 374. The series circuit of R = 30 Ω & X = 4 Ω and a parallel circuit of R’ and X’ have the same impedance and power factor. Calculate the value of R’ and X’. A. 8.33 Ω and 6.25 Ω C. 7.47 Ω and 7.51 Ω B. 2.56 Ω and, 3.83 Ω D. 5.62 Ω and 9.84 Ω 375. A 25 Ω resistor, 2 mH inductor and 30 μF capacitor are connected in parallel across 100 sin (5000t + 45°) V source. Calculate the total current taken by the circuit. A. 4 sin (5000t + 45°) + 5 cos (5000t + 45°) B. 14 sin (5000t) + 15 sin (5000t + 45°) C. 40 sin (5000t + 30°) + 50 cos (5000t + 45°) D. 4 cos (5000t + 45°) + 5 cos (5000t + 45°)

376. A parallel circuit with one branch of R = 5 Ω and a single unknown element in the other branch has the following applied voltage and total current e = 10 cos (50t + 60°) V and i = 5.38 cos (50t – 8.23°) A. The unknown element is ____. A. L = 0.04 H C. C = 10 μF B. L = 0.02 H D. C = 5 μF 377. An impedance of 3 – j3 Ω is connected in parallel with 5 + j2 Ω. The voltmeter connected across 3 Ω resistance measures 45 V. Calculate the total current of the circuit. A. 22.4 A C. 13.4 A B. 41.3 A D. 7.91 A 378. Two impedances ZA = 4 + j6 Ω and ZB are connected in parallel. The apparent power for the impedance B is 1490 VA. Determine the total apparent power. A. 4250 VA C. 2652 VA B. 3290 VA D. 8031 VA 379. A feeder supplies two loads, one at 50 amperes at 50% power factor, the other 150 amperes at unity power factor. The total current supplied by the feeder is approximately ____. A. 180 A C. 175 A B. 200 A D. 150 A 380. A fluorescent lamp and its inductive ballast draw a 1.0 A current at 50% lagging power factor from a 120-V, 60-Hz source. What is the over-all power factor when a 26.5 μF capacitor is connected across the fixture? A. 0.832 lagging C. 0.5 leading B. 0.832 leading D. 0.5 lagging

383. Ten impedances connected in parallel draw the following individual current: , , , , , , , , , . What is the equivalent power factor of the circuit? A. 0.924 C. 0.707 B. 0.866 D. 0.876 384. Ten impedances connected in parallel draw the following individual current: , , , , , , , , , .What element should be connected across the circuit so that the current would be in phase with the source? A. 54 mH C. 13 mH B. 25.4 mH D. 31 mH 385. A small single-phase, 240 V induction motor is tested in parallel with 160 Ω resistor. The motor takes 2 amperes and the total current is 3 amperes. What is the power of the whole circuit? A. 800 W C. 220 W B. 360 W D. 580 W 386. A capacitor is placed in parallel with two inductive loads, one of 20 A at 30° lagging and another of 40 A at 60° lagging. What current in amperes should flow in the capacitor so that the circuit will have a unity power factor? A. 35.8 A C. 28.8 A B. 44.6 A D. 50.2 A 387. A coil of 10 Ω resistance and 0.1 H inductance is connected in parallel with a capacitor of unknown capacitance. If the total impedance of the combination is 100 Ω, determine the value of the capacitance. A. 50 μF C. 150 μF B. 100 μF D. 200 μF

381. Ten impedances connected in parallel draw the following individual current: , , , , , , , , , . What is the effective value of the total current? A. 48.444 A C. 25.345 A B. 34.255 A D. 84.389 A

388. An impedance equal to Ω is connected across a 220 V source. What should be the value of the second impedance in parallel with the first, if the total power delivered to the circuit is to be 16.5 kW and the overall power factor is to be unity? A. Ω C. Ω B. Ω D. Ω

382. Ten impedances connected in parallel draw the following individual current: , , , , , , , , , .What is the equivalent impedance that could replace the impedances if the source voltage is 100 sin 150t V? A. Ω C. Ω B. Ω D. Ω

389. An inductive reactance of 8 ohms is connected in parallel with a capacitive reactance of 18 ohms. This combination is then connected in series with a variable resistance. For what value of resistance will the power factor be 0.5? A. 8.314 Ω C. 13.81 Ω B. 3.318 Ω D. 1.381 Ω

390. Two impedances Z1 = 3 + j4 and Z2 = 5 – j8.66 ohms respectively are connected in parallel. If the combination is connected across a 240 V AC source, how much is the total current? A. 44.4 A C. 40.6 A B. 42.1 A D. 39.9 A

D.

398. The power taken by the circuit shown in Fig. 13.1 is IT

391. A resistance of 20 ohms and an unknown capacitance are connected in parallel across a 110 V, variable frequency AC source. When the frequency is 60 Hz, the current drawn by the circuit is 6 A. At what frequency will the current drawn fall to 5.8 A? A. 42. 33 Hz C. 46.02 Hz B. 50.12 Hz D. 44.18 Hz 392. Two parallel branches have admittances 0.3 + j0.4 and 0.2 – j0.25 S, respectively. If the current in the first branch is 10 A, determine the total current supplied to the parallel combination. A. 10.44 A C. 15.32 A B. 12.10 A D. 11.24 A

none of the above

Fig. 13.1

A. B.

470 W 1920 W

C. D.

396. Domestic appliances are connected in parallel across ac mains because A. it is a simple arrangement B. operation of each appliance becomes independent of each other C. appliances have same current ratings D. this arrangement occupies less space 397. When a parallel ac circuit contains a number of branches, then it is convenient to solve the circuit by A. phasor diagram B. phasor algebra C. equivalent impedance method

1200 W none of these

399. The active component of line current in Fig. 13.1 is IT

395. The impedances of two parallel branches of a circuit are (10 + j10) and (10 – j10) respectively. The impedance of the parallel combination is A. 20 + j0 C. 5 – j5 B. 10 + j0 D. 0 – j20

R= 30 Ω

XL = 30 Ω

240 V

393. An inductive reactance of 3 ohms is connected in parallel with a capacitive reactance of 4 ohms. If the combination is connected in series with a 4 ohm resistance, solve for the power factor of the whole combination. A. 0.333 C. 0.567 B. 0.409 D. 0.316 394. An R-L circuit has Z = (6 + j8) ohm. Its susceptance is ____ siemens. A. 0.06 C. 0.1 B. 0.08 D. -0.08

IR

IL

IR

IL

R= 30 Ω

XL = 30 Ω

240 V

Fig. 13.1

A. B.

8A 4A

C. D.

5.3 A none of these

400. The power factor of the circuit shown in Fig. 13.1 is IT 240 V

IR

IL

R= 30 Ω

XL = 30 Ω

Fig. 13.1

A. B.

0.707 lagging 0.5 lagging

C. D.

0.866 lagging none of these

401. The total line current drawn by the circuit shown in Fig. 13.1 is

IT

IT

IR

IL

R= 30 Ω

XL = 30 Ω

240 V

IL

XL = 40 Ω

240 V

√ A 16 A

C. D.

√ A none of these

402. The power consumed in the circuit shown in Fig. 13.2 is IT

A. B.

13 A 6A

C. D.

IR XL = 40 Ω

240 V

XC = 80 Ω

IC XC = 80 Ω

R= 60 Ω

5A none of these

405. The power factor of the circuit shown in Fig. 13.2 is IT

IL

IC R= 60 Ω

Fig. 13.2

Fig. 13.1

A. B.

IR

IL

IR XL = 40 Ω

240 V

IC R= 60 Ω

XC = 80 Ω

Fig. 13.2 Fig. 13.2

A. B.

480 W 960 W

C. D.

1200 W none of these

403. The active component of line current in Fig. 13.2 is IT 240 V

A. B.

0.8 0.5

C. D.

406. The impedance of the circuit shown in Fig. 13.2 is IT

IL

IR XL = 40 Ω

IC XC = 80 Ω

R= 60 Ω

0.707 none of these

IL

240 V

IR XL = 40 Ω

IC R= 60 Ω

XC = 80 Ω

Fig. 13.2 Fig. 13.2

A. B.

6A 3A

C. D.

13 A 4A

404. The line current drawn by the circuit shown in Fig. 13.2 is

A. B.

180 ohms 24 ohms

407. The circuit shown in Fig. 13.2 is

C. D.

48 ohms none of these

IT

IR

IL

XL = 40 Ω

240 V

IT

IC R= 60 Ω

I2 R1 = 4 Ω

XC = 80 Ω

120 V

R2 = 3 Ω

I1 XC = 4 Ω

XL = 3 Ω Fig. 13.2

A. B.

resistive capacitive

C. D.

Fig. 13.3

inductive in resonance

408. If in Fig. 13.2, XL is made equal to XC, the line current will be IT 240 V

IR

IL

XL = 40 Ω

A. B.

24 A 70 A

C. D.

411. The circuit shown in Fig. 13.3 is

IC

IT

XC = 80 Ω

R= 60 Ω

48 A 30 A

I2 R1 = 4 Ω

120 V

R2 = 3 Ω

I1 XC = 4 Ω

XL = 3 Ω Fig. 13.2

A. B.

10 A 6A

C. D.

4A none of these

Fig. 13.3

409. The power consumed in the circuit shown in Fig. 13.3 is IT 120 V

capacitive inductive

R2 = 3 Ω

resistive in resonance

IT

I1 XL = 3 Ω

C. D.

412. If the source frequency of Fig. 13.4 is low, then

I2 R1 = 4 Ω

A. B.

R

XC = 4 Ω

V

I1

I2

C

L

Fig. 13.3

A. B.

8400 W 3600 W

C. D.

4000 W none of these

410. If the circuit shown in Fig. 13.3 is connected to 120 V dc, the current drawn by the circuit is

Fig. 13.4

A. B. C. D.

coil takes a high lagging current coil takes a low lagging current capacitor takes a leading current circuit offers high impedance

413. If the source frequency of Fig. 13.4 is high, then

R=6Ω IT R V

I1

XL = 8 Ω

I2

C

L

Fig. 13.6

A. B.

Fig. 13.4

A. B. C. D.

coil takes a high lagging current capacitor takes a high leading current capacitor takes a low leading current circuit offers high impedance

10 S 14 S

C. D.

418. The conductance of the circuit shown in Fig. 13.6 is R=6Ω

414. The circuit shown in Fig. 13.5 is

XL = 8 Ω IT

100 V

R= 3Ω

I1

I2 XL = 4Ω

XC = 4Ω

Fig. 13.5

A. B.

in resonance resistive

C. D.

inductive capacitive

Fig. 13.6

A. B.

14 S 0.6 S

C. D.

100 V

R=6Ω XL = 8 Ω

R= 3Ω

I1

Fig. 13.6 I2

XL = 4Ω

XC = 4Ω

1200 W 2400 W

A. B.

8S 0.8 S

C. D.

0.08 S none of these

420. The circuit shown in Fig. 13.7 is

Fig. 13.5

A. B.

0.06 S none of these

419. The inductive susceptance of the circuit shown in Fig. 13.6 is

415. The circuit shown in Fig. 13.5 will consume a power of IT

0.1 S none of these

C. D.

500 W none of these

416. If the admittance of a parallel ac circuit is increased, the circuit current A. remains constant C. is increased B. is decreased D. none of these

100 V

417. The admittance of the circuit shown in Fig. 13.6 is

G= 0.01 S

-B

Fig. 13.7

A.

resistive

C.

capacitive

inductive

D.

none of these

421. The power loss in the circuit shown in Fig. 13.7 is

100 V

G= 0.01 S

-B

Fig. 13.7

A. B.

100 W 10,000 W

C. D.

10 W none of these

422. The conductance and susceptance components of admittance are A. series elements B. parallel elements C. series-parallel elements D. none of the above 423. The impedance of a circuit is 10 ohms. If the inductive susceptance is 1 siemen, then inductive reactance of the circuit is A. 10 ohms C. 100 ohms B. 1 ohm D. none of these 424. The conductance and inductive susceptance of a circuit have the same magnitude. The power factor of the circuit is A. 1 C. 0.707 B. 0.5 D. 0.866 425. The admittance of a circuit is (0.1 + j0.8) S. The circuit is A. resistive C. inductive B. capacitive D. none of these 426. In a parallel ac circuit, power loss is due to A. conductance alone B. susceptance alone C. both conductance and susceptance D. none of the above 427. The admittance of a parallel circuit is S. The circuit is A. inductive C. resistive B. capacitive D. none of these

428. A circuit have an impedance of (1 – j2) ohms. The susceptance of the circuit is A. 0.1 S C. 0.4 S B. 0.2 S D. none of these 429. A circuit has admittance of 0.1 S and conductance of 0.08 S. The power factor of the circuit is A. 0.1 C. 0.08 B. 0.8 D. none of these 430. When an sinusoidal voltage is applied across R-L parallel circuit so that R = XL the phase angle will be A. 45° lagging C. 90° lagging B. 45° leading D. 90° leading 431. In a parallel R-L circuit if IR is the current in resistor and IL is the current in the inductor, then A. IR lags IL by 90° C. IL leads IR by 270° B. IR leads IL by 270° D. IL lags IR by 90° 432. The current read by the ammeter A in the ac circuit shown is the given figure is A

1A

A. B.

9A 5A

C. D.

3A

5A

3A 1A

433. In the given figure, the admittance values of the elements in siemens are Y R = 0.5 + j0, YL = 0 – j1.5 and YC = 0 + j0.3 respectively. The value of I as a phasor when the voltage E across the elements is √ V is YR

I

A. B.

1.5 + j-.5 5 – j18

C. D.

YL

YC

E  100 V

B.

0.5 + j1.8 5 – j12

434. For the circuit shown in the figure, how much the voltage across the inductor leads the voltage across the capacitor?

L E ω = 2 rad/s

0.5 F

V  20

17/6 Ω

3Ω

1Ω

-j4 Ω

A. B.

45° 90°

C. D.

135° 180°

435. In the circuit shown in the figure, v = cos 2t, Z2 = 1 + j. C1 is chosen so that i = cos 2t. The value of C1 is I VS

C1

A. B.

6 + j0 Ω 7 + j0 Ω

C. D.

3Ω

j4 Ω

0 + j8 Ω 6 + j8 Ω

439. A resistance of 40 ohms and an inductive reactor of 30 ohms are joined in parallel to a 120 volts supply as shown in the figure. The power factor of the circuit is

Z2

I1

R = 40 Ω

I2

X = 30 Ω

I

A. B.

2F 1F

C. D.

0.5 F 0.25 F

120 volts

436. For the given ac circuit, what is the value of I? v(t) = 120 sin ωt

I

A. B.

A. B.

60

440. In a parallel RC circuit, A. IC lags IR by 90° B. IR and IC are in phase

C. D.

2-j 0 + j0

437. For the network shown in the given figure Z(0) = 3 Ω and Z(∞) = 2 Ω. The values of R1 and R2 will respectively be 1Ω

R1

A. B.

2 Ω, 1 Ω 1 Ω, 2 Ω

C. D.

0.8 unity

C. D.

IC leads IR by 90° IR leads IC by 90°

-j120 j60

1+j 1 + j0

Z(s)

0.6 0.7

1F

C. D.

R2

3 Ω, 2 Ω 2 Ω, 3 Ω

438. The total impedance Z(jω) of the circuit shown is

1F

441. In a parallel RC circuit, A. VC and IR are in phase B. VC and IC are in phase C. IC and IR are in phase D. VC and IR are 90° out of phase 442. When the frequency of the applied voltage increases in a parallel RC circuit A. the phase angle, θT, increases B. ZEQ increases C. ZEQ decreases D. both A and C 443. In a parallel RL circuit, A. iL lags iR by 90° B. iL leads iR by 90°

C. D.

iL and iR are in phase iR lags iL by 90°

444. In a parallel RL circuit, A. VT and IL are in phase B. IL and IR are in phase C. VT and IR are in phase D. VT and IR are 90° out of phase 445. When the frequency of the applied voltage decreases in a parallel RL circuit A. the phase angle, θI, becomes less negative B. ZEQ increases C. ZEQ decreases D. both A and B 446. When the frequency of the applied voltage increases in a parallel RL circuit A. θZ increases C. ZT increases B. ZT decreases D. both A and C 447. In an ac circuit with only parallel inductors A. IT lags VT by 90° C. VT and IT are in phase B. VT lags IT by 90° D. none of the above 448. In a parallel ac circuit with XL and XC A. IL and IC are 90° out of phase B. IL and IC are in phase C. IL and IC are 180° out of phase D. XL and XC are 90° out of phase D. RESONANCE 449. REE Board Exam October 2000 A series circuit consists of a 20-ohm resistance, a 150 mH inductance and an unknown capacitance. The circuit is supplied with a voltage v = 100 sin 377t. Find the value of capacitance at resonance. A. 42 μF C. 34.65 μF B. 47 μF D. 72.57 μF 450. REE Board Exam April 2001 A 5 mH pure inductance is connected in parallel with one microfarad capacitor. What frequency will the circuit be antiresonance? A. 250 Hz C. 60 Hz B. 2250 Hz D. 100 Hz 451. EE Board Exam April 1993

Capacitor of 30-microfarad capacitance is in series with a coil across an 8,000 cycle supply. What inductance is required for resonance? A. 13.34 μH C. 13.19 μH B. 10.45 μH D. 12.55 μH 452. REE Board Exam October 1998 -9 One leg of a radio tuned circuit has a capacitance of 1 x 10 F. It is tuned at 200 kHz. What is the inductance of the other leg in Henry? -4 -5 A. 6.33 x 10 C. 8.25 x 10 -3 -3 B. 20 x 10 D. 120 x 10 453. EE Board Exam April 1988 A loud speaker whose inductance through a condenser of 2 μF combination be resonant? A. 110 Hz C. B. 108 Hz D.

is 1.15 Henry is coupled to a power tube capacity. To what frequency will the 105 Hz 100 Hz

454. REE Board Exam April 1995 What capacitance must be placed in series with an inductance of 0.05 Henry so that at 100 Hz, the impedance becomes equal to the ohmic resistance? A. 50.7 μF C. 70.7 μF B. 35.5 μF D. 87.0 μF 455. EE Board Exam April 1989 A coil has a resistance of 50 ohms and a reactance of 100 ohms, is shunted by a capacitor, which has practically no losses in order that the voltage across the coil be in phase with the total current supplied to the parallel combination. What is the impedance of the parallel combination under the given condition? A. 250 ohms C. 230 ohms B. 200 ohms D. 220 ohms 456. EE Board Exam April 1983 A non-inductive resistor R is connected in parallel with an inductive reactance of 10 ohms. The combination is then connected in series with a capacitive reactance of 5 ohms. Solve for R at which the power factor of the given circuit would be unity. A. 10 Ω C. 13 Ω B. 12 Ω D. 11 Ω 457. EE Board Exam October 1982 Two impedances Z1 = 15 + j20 and Z2 = 5 – jXC are connected in parallel. Solve for the values of XC so that the total current drawn by the combination will be in phase with any supply voltage V.

A. B.

28.54  30.43 

C. D.

33.12  29.55 

458. EE Board Exam April 1985 A resistance of 5 ohms is connected in series with a capacitor of 442.1 μF. The combination is then connected in parallel with an inductance of 21.22 mH. Solve for the frequency of the impressed voltage with which the inductive reactance is equal to the capacitive reactance in magnitude. A. 50 Hz C. 52 Hz B. 51 Hz D. none of these 459. EE Board Exam April 1989 A coil has a resistance of 50 ohms and a reactance of 100 ohms, is shunted by a capacitor, which has practically no losses. What must be the reactance of the capacitor in order that the voltage across the coil is in phase with the total current supplied to the parallel combination? A. 120 ohms C. 125 ohms B. 127 ohms D. 132 ohms 460. EE Board Exam April 1982 Three impedances Za, Zb and Zc are connected in parallel. If at 60 Hz, Za = j8, Zb = -j2 and Zc = 5 ohms, Solve for the frequency at resonance. A. 30 Hz C. 36 Hz B. 34 Hz D. 28 Hz 461. EE Board Exam April 1981 A resistor R is connected in parallel with a 20-ohm inductive reactive. The combination is then connected in series with a 5-ohm capacitive reactance. Solve the value of R at which the power factor of the resultant impedance is unity. A. 10.05 ohms C. 11.55 ohms B. 9.15 ohms D. 10.73 ohms

464. EE Board Exam October 1998 In a series resonant RLC circuit, all of the following statements are correct EXCEPT one. Which one is this? A. The resonant frequency is dependent on the resistance of the circuit. B. The phase angle between the voltage and the current vectors is zero. C. The impedance is a minimum. D. The current is a maximum. 465. EE Board Exam April 1994, October 1993 The current in RLC series circuit at resonance is A. maximum C. minimum B. zero D. infinity 466. ECE Board Exam April 2001 Ignoring the capacitive effects, what is the impedance of a 100 mH coil (with an internal resistance of 45 ohms) in parallel with 4,700 ohms resistor at a frequency of 500 Hz? A. 317 ohms C. 5014 ohms B. 237 0hms D. 314 ohms 467. ECE Board Exam November 1996 ____ frequency is reached when the capacitive and inductive reactance in a tuned circuit are equal. A. zero C. infinite B. pulsating D. resonant 468. ECE Board Exam November 1998 Find the Q of a circuit when the resonant frequency is 4.468 MHz, the inductance is 47 microhenry and the resistance is 180 ohms parallel. A. 0.136 C. 0.00735 B. 13.30 D. 7.35

462. EE Board Exam October 1998 A coil has a resistance of 50 ohms and a reactance of 70 ohms. A capacitor is connected in parallel to produce resonance. The source voltage is 120 V. What is the power drawn by the circuit? A. 162 W C. 132 W B. 97 W D. 52 W

469. ECE Board Exam November 2000 In an “IDEAL” resonant circuit, what is the relationship between the current and the impedance? A. current high, impedance low B. current low, impedance low C. current low, impedance high D. current high, impedance high

463. EE Board Exam April 1995 A coil is supplied with 200 volts and takes a current (rms) of 2 amperes at 0.707 lagging. The quality factor (Q) of the coil is A. 25 C. 10 B. 1 D. 100

470. ECE Board Exam November 1997 What condition does resonance occurs in an electrical circuit? A. When the power factor is at minimum

B. C. D.

When the square root of the sum of the capacitive and inductive reactances is to the resonant frequency When the inductive and capacitive reactances are equal none of the above

471. ECE Board Exam November 2001 What is the relationship between frequency and the value of XC? A. frequency has no effect B. XC varies directly with frequency C. XC varies inversely with frequency D. XC varies indirectly with frequency 472. ECE Board Exam April 2001 When is the line current minimum in a parallel LC circuit? A. at the broadcast frequency B. at the circuit frequency C. at the resonant frequency D. at the highest frequency 473. ECE Board Exam November 1999 Find the half-power bandwidth of a parallel resonant circuit which has a resonant frequency of 7.1 MHz and Q of 150. A. 16.5 kHz C. 21.1 kHz B. 211 kHz D. 47.3 kHz 474. ECE Board Exam November 1997 It is the term for the phenomena which occurs in an electrical circuit when the inductive reactance balances with the capacitive reactance. A. reactive equilibrium C. reactive quiescence B. resonance D. high Q 475. ECE Board Exam April 1998 What is the resonant frequency of a circuit when L of 25 microhenrys and C of 10 picofarads are in parallel? A. 68.7 kHz C. 68.7 MHz B. 10.1 kHz D. 10.1 MHz

If you need an LC circuit to be resonant at 2,500 Hz and use a 150 mH coil, what should the capacitance value be? A. 0.015 μF C. 27 μF B. 0.15 μF D. 0.027 μF 478. ECE Board Exam April 1999 What is the resonant frequency of a circuit when L is 40 microhenrys and C is 6 picofarads are in series? A. 6.63 MHz C. 6.63 kHz B. 10.3 MHZ D. 10.3 kHz 479. ECE Board Exam April 1998 What is the resonant frequency of a circuit when L of 3 microhenrys and C of 40 picofarads are in series? A. 14.5 MHz C. 1.33 kHz B. 1.33 MHz D. 14.5 kHz 480. ECE Board Exam November 2001 ____ refers to reactive power. A. power consumed in circuit Q B. power consumed in wire resistance in an inductor C. wattles, non-productive power D. power lost because of capacitor leakage 481. ECE Board Exam November 1998 How do you call the nature of a circuit during series resonance? A. unstable C. resistive B. capacitive D. inductive 482. ECE Board Exam April 1999 What is the resonant frequency of a circuit when L is 200 microhenrys and C is 10 picofarads are in series? A. 7.96 MHz C. 3.56 MHz B. 6 MHz D. 7.96 kHz

476. ECE March 1996 What is the effect in terms of bandwidth when the Q of a single-tuned stage is doubled? A. halved C. doubled B. the same D. four times

483. ECE Board Exam April 2000 In a series resonant LC circuit, what is the impedance at resonant frequency? A. Infinity B. Determined solely by the dc resistance C. The maximum impedance value D. Zero

477. ECE Board Exam November 1999

484. ECE Board Exam April 1999

What is the characteristic of the current flow in a parallel R-L-C circuit at resonance? A. The current circulating in the parallel elements is dc B. The current circulating in the parallel elements is zero C. The current circulating in the parallel elements is at a maximum D. The current circulating in the parallel elements is at a minimum 485. ECE Board Exam March 1996 What is the responsible for the phenomenon when voltages across reactances in series can often be larger than the voltage applied to them? A. Capacitance C. Conductance B. Resistance D. Resonance 486. ECE Board Exam March 1996 Term used for resonance in an electrical circuit. A. The frequency at which power factor is at a minimum B. The frequency at which capacitive reactance equals inductive reactances C. The highest frequency that will pass current D. The lowest frequency that will pass current 487. ECE Board Exam November 1998 Ignoring any effects of dc resistance, what is the total reactance of a 250 mH coil in series with a 4.7 F capacitor at a signal frequency of 1000 Hz? A. 1604  C. 1536  B. 35  D. 1570  488. ECE Board Exam November 1996 The _____ the Q of a circuit, the narrower is its bandwidth. A. Lower C. Higher B. Broader D. Selective

Find the half-power bandwidth of a parallel resonant circuit which has a resonant frequency of 3.6 MHz and a Q of 218. A. 58.7 kHz C. 16.5 kHz B. 606 kHz D. 47.3 kHz 492. ECE Board Exam November 1998 What is the resonant frequency of a circuit when L is 3 microhenrys and C is 40 picofarads are in parallel? A. 14.5 kHz C. 14.5 MHz B. 13.1 kHz D. 13.1 MHz 493. ECE Board Exam November 1998 What is the resonant frequency of a circuit when L is 15 microhenry and C is 5 picofarads are in series? A. 2.12 kHz C. 18.4 kHz B. 18.4 MHz D. 2.12 MHz 494. ECE Board Exam November 1998 What is the resonant frequency of a circuit when L is 2 microhenry and C is 15 picofarads are in series? A. 29.1 MHz C. 29.1 kHz B. 5.31 MHz D. 5.31 kHz 495. ECE Board Exam April 1998 Characteristic of the current flow in a series R-L-C circuit at resonance A. it is zero B. it is dc C. it is at a maximum D. it is at a minimum

489. ECE Board Exam March 1996 Find the half-power bandwidth of a resonant circuit which has a resonant frequency of 1.8 MHz and a Q of 95. A. 58.7 kHz C. 189 Hz B. 18.9 kHz D. 1.89 kHz

496. ECE Board Exam April 2001 What is the term for the number of times per second that a tank circuit energy is stored in the inductor of capacitor? A. Non-resonant frequency B. Broadcast frequency C. Circuit frequency D. Resonant frequency

490. ECE Board Exam November 1998 What is the resonant frequency of a circuit when L is 5 microhenrys and C is 9 picofarads are in series? A. 23.7 kHz C. 23.7 MHz B. 3.54 kHz D. 3.54 MHz

497. ECE Board Exam November 1995 An LC circuit resonates at 2000 kHz, and has a Q of 100. Find the lower and upper cut-off frequencies. A. 1950 kHz, 2050 kHz C. 1980 kHz, 2020 kHz B. 1990 kHz, 2010 kHz D. 1900 kHz, 2100 kHz

491. ECE Board Exam April 1998

498. ECE Board Exam November 1998

What is the resonant frequency of a circuit when L is 50 microhenrys and C is 10 picofarads are in parallel? A. 3.18 kHz C. 7.12 MHz B. 3.18 MHz D. 7.12 kHz 499. ECE Board Exam November 1999 What is the cause of a minimum Q on a single-tuned LC circuit? A. Decreased shunt resistor B. Decreased capacitance C. Increased shunt resistor D. Decreased series resistor 500. ECE Board Exam November 1998 ____ is another term for quality factor or Q of the resonant circuit. A. Noise factor C. White noise B. Noise figure D. Figure of merit 501. ECE Board Exam November 2000 What is the biggest advantage of using crystals in resonant circuits? A. less fragile B. cost C. size D. greater accuracy and stability 502. ECE Board Exam April 2001 What is the impedance of a crystal at its resonant frequency when it is used in the parallel mode? A. 70 percent C. minimum B. 50 percent D. maximum 503. ECE Board Exam April 1998 _____ is a parallel LC circuit. A. Hartley circuit B. Static circuit C. Tank circuit D. Parallel resisting circuit 504. There will ____ be a frequency, called the ____ frequency at which ____. A. sometimes, natural; XL = XC B. always, natural; R = 0 C. always, resonant; XL = XC D. sometimes, resonant; R = 0 505. The formula for the resonant frequency is f = ____. A. √ C. √

B.

√

D.

√

506. For a series RLC circuit, a circuit at resonance the current amplitude is ____ for a fixed voltage amplitude and the power factor is ____. A. minimum, zero C. maximum, zero B. minimum, unity D. maximum, unity 507. In an RLC circuit, the impedance at resonance is A. maximum C. infinity B. minimum D. zero 508. The current in RLC series circuit, i.e., at resonance is A. maximum C. infinity B. minimum D. zero 509. In RLC circuits, the current at resonance is A. the maximum in series circuit and minimum in parallel circuit B. maximum in parallel circuit and minimum in series circuit C. maximum in both the circuits D. minimum in both the circuits 510. A series resonant circuit is capacitive at f = 100 Hz. The circuit will be inductive somewhere at A. f = 100 Hz B. f > 100 Hz C. f = 100 Hz by increasing the value of the resistance D. none of these 511. At a frequency less than the resonant frequency A. series circuit is capacitive and parallel circuit is inductive B. series circuit is inductive and parallel circuit is capacitive C. both circuits are inductive D. both circuits are capacitive 512. In series as well as parallel resonant circuits, increasing the value of resistance would lead to A. increase in the bandwidth of both the circuits B. decrease in the bandwidth of both the circuits C. increase in bandwidth in series circuit and decrease in parallel circuit D. decrease in bandwidth in series circuit and increase in parallel circuit 513. The value of current at resonance in a series RLC circuit is affected by the value of A. R C. C B. L D. all of these

514. In resonant circuits, the power factor at resonance is A. zero C. 1 B. 0.5 D. 0.707

A.

C.

B.

D.

515. Which of the following statements is true for a series RLC circuit tuned at resonant frequency? A. the voltage across C > applied voltage B. the voltage across L > applied voltage C. the voltage across L and C > applied voltage D. the voltage across L and C = applied voltage

520. To a series RLC circuit, a voltage of 10 V is applied. If Q of the coil at resonant frequency is 20, the voltage across the inductor at resonant frequency will be A. 200 V C. 75 V B. 100 V D. 50 V

516. At anti-resonance for the given circuit, the frequency is given by

521. The currents flowing in L and C at parallel resonance are A. zero C. infinite B. equal D. different

A. B.

√

√

√

√

R1

R2

L

C

C. D.

522. The exact natural frequency of free oscillation in an oscillatory circuit with capacitance of 0.055 μF, inductance 2 μH and resistance 1 ohm will be A. 478 kHz C. 272 kHz B. 337 kHz D. 192 kHz √ √

√ √

517. The frequency at which maximum voltage occurs the inductance in RLC series circuits is A. B.

√ √

C. √

D. √

518. The frequency at which maximum voltage occurs across the capacitance in RLC series circuits is A.

√

B.

C. √

D. √

√

519. If f1 and f2 are half power frequencies and f0 be resonance frequency, the selectivity of RLC series circuit is given by

523. A coil with large distributed capacitance has a A. low resistance B. low Q C. low resonant frequency D. high resonant frequency 524. In a series R-L-C circuit, resonance occurs when A. R = XL - XC C. XL = 10 XC or more B. XL = XC D. net X > R 525. The p.f. of a series R-L-C circuit at its half-power point is A. unity C. leading B. lagging D. either B and C 526. A resonance curve for a series circuit is a plot of frequency versus ____. A. voltage C. current B. impedance D. reactance 527. At half-power points of a resonance curve, the current is ____ times the maximum current. A. 2 C. √ B. D. 1/2 √ 528. Higher the Q of a series circuit, A. greater its bandwidth

B. C. D.

sharper its resonance broader its resonance curve narrower its pass band

529. As the Q-factor of a circuit ____, its selectivity becomes ____. A. increases, better C. decreases, better B. increases, worse D. decreases, narrower 530. An R-L-C circuit has a resonance frequency of 160 kHz and a Q-factor of 100. Its bandwidth is A. 1.6 kHz C. 16 MHz B. 0.625 kHz D. none of the above 531. In a parallel resonant circuit there is practically no difference between the condition for unity power factor and the condition for maximum impedance so long as Q is A. very small of the order of 5 B. small of the order of 20 C. large of the order of 1000 D. none of these 532. A parallel AC circuit in resonance will A. act like a resistor of low value B. have a high impedance C. have current in each section equal to the line current D. have a high voltage developed across each inductive and capacitive section 533. A parallel resonant circuit can be used A. to amplify certain frequencies B. to reject a small band of frequencies C. as a high impedance D. both B and C 534. The Q-factor of a 2-branched parallel circuit is given by the ratio A. Ic/IL C. I/IL B. I/Ic D. L/C 535. Like a resonant R-L-C, a parallel resonant circuit also A. has a power factor of unity B. offers minimum impedance C. draws maximum current D. magnifies current

536. At resonant frequency an R-L-C circuit draws maximum current due to the reason that A. the difference between capacitive reactance and inductive reactance B. C. D.

the impedance is more than resistance the voltage across the capacitor equals the applied voltage the power factor is less than unity

537. Consider the following statements with respect to a series R-L-C circuit under resonance condition: 1. All the applied voltage appears across R. 2. There is no voltage across either L or C. 3. The voltage across L and C is equal and equal to their maximum values. Of these statement A. 1 alone is correct C. 1 and 3 are correct B. 2 alone is correct D. 1 and 2 are correct 538. A series R-L-C circuit will have unity power factor if operated at a frequency of 2 A. 1/LC C. 1/ω LC B. D. √ √ 539. A series resonant circuit implies A. zero pf and maximum current B. unity pf and maximum current C. unity pf and minimum current D. zero pf and minimum current 540. Consider the following statements: In a network of resonance: 1. the admittance is maximum 2. the power factor is unity irrespective of the network 3. the Q of a series RLC resonant circuit is independent of R Of these statements A. 1 and 3 are correct C. 2 and 3 are correct B. 1 and 2 are correct D. 1 alone is correct 541. A circuit with a resistor, inductor and capacitor in series is resonant at f 0 Hz. If all the component values are now doubled the new resonant frequency is A. 2f0 C. f0/4 B. still f0 D. f0/2 542. If the resonant frequency of the circuit shown in Fig. 1 is 1 kHz, the resonant frequency of the circuit shown in Fig. 2 will be

100 Ω

L

547. The resonant frequency of the given series circuit is

C

M=1H Fig. 1 R

L

2H

C L

A. B.

4 kHz 2 kHz

C. D.

0.5 kHz 0.25 kHz

543. In the circuit shown in the given figure, the magnitude of V L and VC are twice that of VR. The inductance of the coil is VR

VL

VC

5Ω

L

C

50 V

A. B.

2.14 mH 5.30 mH

√

2H

Hz

C.

Hz

D.

√ √

Hz Hz

C

Fig. 2

A. B.

√

2F

C. D.

31.8 mH 1.32 mH

544. In a series RLC circuit at resonance, the magnitude of voltage developed across the capacitor A. is always zero B. can never be greater than the input voltage C. can be greater than the input voltage however it is 90° out of phase with the input voltage D. can be greater than the input voltage and is in phase with the input voltage 545. A coil having a resistance of 5 Ω and inductance of 0.1 H is connected in series with a capacitor of capacitance 50 μF. A constant alternating voltage of 200 V is applied to the circuit. The voltage across the coil at resonance is A. 200 volts C. 1,800 volts B. 1,788 volts D. 2,000 volts 546. A series R-L-C circuit, excited by a 100 V variable frequency supply, has a resistance of 10 Ω and an inductive reactance of 50 Ω at 100 Hz. If the resonance frequency is 500 Hz, what is the voltage across the capacitor at resonance? A. 100 V C. 2,500 V B. 500 V D. 5,000 V

548. In a series R-L-C circuit, the maximum voltage across the capacitor occurs at a frequency A. double the resonant frequency B. equal to the resonant frequency C. √ times the resonant frequency D. below the resonant frequency 549. For a series RLC circuit, the power factor at the lower power frequency is A. 0.5 lagging C. unity B. 0.5 leading D. 0.707 leading 550. Q-factor of a series RLC circuit possessing resonant frequency of 10 Hz and bandwidth of 5 Hz is A. 0.5 C. 2.5 B. 2 D. 50 551. The quality factor of RLC circuit will increase if A. R decreases B. R increases C. voltage increases D. voltage decreases 552. When Q-factor of a circuit is high, then A. power factor of the circuit is high B. impedance of the circuit is high C. bandwidth is large D. none of these 553. Consider the following statements regarding the frequency response curve of a series RLC circuit: 1. At half-power frequencies, the current in the circuit is one half of the current at resonant frequencies 2. At half-power frequencies, the power factor angle of the circuit is 45° 3. At resonant frequency, the power factor angle of the circuit is 90° 4. Maximum power occurs at resonant frequency

2 and 4 are correct 1 and 4 are correct

10 Ω

554. An RLC series circuit has f1 and f2 as the half power frequencies and f0 as the resonant frequency. The Q-factor of the circuit is given by: A. C. A. B.

D.

555. Resonant frequency fr of a series RLC circuit is related to half power frequencies f1 and f2 as A. C. B.

√

D.

√

√

556. A series RLC circuit has R = 50 Ω, L = 100 μH and C = 1 μF. The lower half power frequency of the circuit is A. 30.55 kHz C. 51.92 kHz B. 3.055 kHz D. 1.92 kHz 557. For a series RLC resonant circuit, what is the total reactance at the lower half power frequency? A. √ C. R B. √ D. -R 558. A series RLC circuit when excited by a 10 V sinusoidal voltage source of variable frequency, exhibits resonance at 100 Hz and has a 3 dB bandwidth of 5 Hz. The voltage across the inductor L at resonance is A. 10 V C. √ B. D. 200 V √ V 559. An RLC resonant circuit has a resonant frequency of 1.5 MHz and a bandwidth of 10 kHz. If C = 150 pF, then the effective resistance of the circuit will be A. 29.5 Ω C. 9.4 Ω B. 14.75 Ω D. 4.7 Ω 560. The following circuit resonates at

1F +

all frequencies 0.5 rad/s

C. D.

-

5 rad/s 1 rad/s

561. A choke coil of inductance L and series resistance R is shunted by a capacitor. The dynamic impedance of the resonant circuit would be A. R/(LC) C. L/(RC) B. C/(RL) D. 1/(RLC) 562. For the following circuit, the current source is sinusoidal with frequency equal to the resonant frequency of the circuit. What is the value of current through resistor?

I

A. B.

0 0.11

0.1 H

C. D.

10 Ω

0.1 F

1 10.1

563. In the given circuit, at resonance IR amperes is equal to

0.5 H

B.

1F

4H

C. D.

5A

A. B.

0A 10 A

C. D.

R IR

50 μF

Of these statements A. 1, 2 and 4 are correct B. 1, 2 and 3 are correct

5A 0.5 A

564. A circuit has two parallel branches. In one branch, R and L are connected in series while in the other R and C are connected in series. If , which √ of the following is not correct? A. The circuit is in resonance. B. The two branch currents are in quadrature. C. The circuit has an impedance independent of its frequency.

D.

The two branch currents are in phase.

565. A parallel circuit consists of two branches. One branch has R L and L connected in series and the other branch has RC and C connected in series. Consider the following statements: 1. The two branch currents will be in quadrature if RLRC = L/C. 2. The impedance of the whole circuit is independent of frequency, if RL = RC and √ . 3. The circuit is in resonance for all the frequencies if RL = RC. 4. The two branch currents will be in phase at √ . Which of the above statements are correct? A. 1 and 2 C. 1 and 3 B. 2 and 3 D. 3 and 4 566. The value of Z in given figure which is most appropriate to cause parallel resonance at 500 Hz is

5Ω 2H

A. B.

125 mH 304.2 μF

C. D.

Z

2 μF 0.05 μF

567. The value of the capacitance ‘C’ in the given ac circuit to make it a constant resistance circuit or for the supply current to be independent of its frequency is

A. B.

1/16 F 1/12 F

C. D.

4Ω

4Ω

1H

C

1/8 F 1/4 F

568. A coil takes apparent power and reactive power of 100 VA and 80 VAR, respectively. What is the Q factor of the coil? A. 1.33 C. 8 B. 10 D. 6

569. A 50 Ω resistance, a 30 Ω inductive reactance and a 25 Ω capacitive reactance are connected in series across a 100 V, 60 Hz supply. What will be its resonant frequency? A. 65.726 Hz C. 25 Hz B. 53 Hz D. 54.77 Hz 570. A coil having a Q factor of 5 is connected in series with an ideal capacitor across ac source of 60 V. Calculate the voltage across the capacitor at resonance. A. 150 V C. 12 V B. 300 V D. 65 V 571. A coil having an inductance of 50 mH and a resistance 10 Ω is connected in series with a 25 μF capacitor across a 200 V ac supply. Find the value of Q factor? A. 7.4 C. 3.54 B. 4.53 D. 4.47 572. The following data are given connected in parallel: XL = 15 the circuit be in resonance? A. 169 ohms B. 916 ohms

for a series RL and a series RC which are Ω, XC = 25 Ω, RC = 15 Ω. For value of RL will C. D.

16.9 ohms 91.6 ohms

573. A circuit consisting of a capacitor in series with a resistance of 10 ohms is connected in parallel with a coil having a reactance and resistance of 17.32 ohms and 10 ohms respectively. What is the reactance of the capacitor that will draw minimum current from a 230-V, 60 Hz supply? A. 17.32 Ω C. 6.78 Ω B. 10.32 Ω D. 22.18 Ω 574. Series circuit consists of a 20-ohm resistance, a 150 mH inductance and an unknown capacitance. The circuit is supplied with a voltage v = 100 sin 377t. Find the value of capacitance at resonance. A. 42 μF C. 47 μF B. 72.567 μF D. 34.65 μF 575. A coil having a resistance of 0.5 ohm and an inductance of 5.25 mH is connected in parallel with a capacitor across a 220 volt, 60 Hz source. Calculate the value of the capacitance at resonance. A. 125 microfarad C. 125 millifarad B. 1.25 microfarad D. 1.25 millifarad 576. The current in an RL and C parallel circuit at resonance is A. maximum C. minimum

B.

zero

D.

infinity

577. A circuit draws 25 A when connected across a source of frequency f1. Determine the current drawn by the same circuit at resonance if f 1 is half the resonant frequency. A. 12.5 A C. 35.35 A B. 17.68 A D. 50 A 578. A series RLC circuit is connected across a 120-V, 60 Hz source and draws a leading current of 5 A. Determine the voltage across the capacitor at resonance if R = 5 Ω and L = 25 mH. A. 47.12 V C. 236.6 V B. 164.5 V D. 422.6 V 579. The best definition of Q-factor of a coil is A. The ratio of its maximum energy stored to its energy dissipated per cycle B. Its power factor C. The reciprocal of its reactive factor D. The ratio of its resistance to its inductive reactance 580. A coil is to be wound with Q-factor of 8. A lamp rated 120 V, 480 W is connected in series with the coil and connected across 230 V, 60 Hz source. What is the impedance of the coil if the voltage across the lamp is maintained at 120 V? A. Ω C. Ω B. Ω D. Ω 581. An inductive coil having a resistance of 25 ohms and inductance of 0.2 H is connected in parallel with a 100 μF capacitor. Find the frequency at which the total current taken is in phase with the supply voltage. A. 35.6 Hz C. 29.5 Hz B. 46.5 Hz D. 52.9 Hz 582. The resonant frequency of an LC circuit is the frequency where A. XL = 0 Ω and XC = 0 Ω B. XL = XC C. XL and rS of the coil are equal D. XL and XC are in phase 583. The impedance of a series LC circuit at resonance is A. maximum C. minimum B. nearly infinite D. both A and B 584. The total line current, IT, of a parallel LC circuit at resonance is

A. B. C. D.

minimum maximum equal to IL and IC Q times larger than IL or IC

585. The current at resonance in a series LC circuit is A. zero B. minimum C. different in each component D. maximum 586. The impedance of a parallel LC circuit at resonance is A. zero B. maximum C. minimum D. equal to the rS of the coil 587. The phase angle of an LC circuit at resonance is A. 0° C. 180° B. 90° D. -90° 588. Below resonance, a series LC circuit appears A. inductive C. capacitive B. resistive D. none of the above 589. Above resonance, a parallel LC circuit appears A. inductive C. capacitive B. resistive D. none of the above 590. When either L or C is increased, the resonant frequency of an LC circuit A. decreases B. increases C. doesn’t change D. This is impossible to determine. 591. In a low Q parallel resonant circuit, when XL = XC A. IL = IC C. IC is less than IL B. IL is less than IC D. IL is more than IC 592. To double the resonant frequency of an LC circuit with a fixed value of L, the capacitance, C, must be A. doubled B. quadrupled C. reduced by one-half D. reduced by one-quarter

B. 593. A higher Q for a resonant frequency provides a A. dampened response curve B. wider bandwidth C. narrower bandwidth D. none of the above 594. The Q of a parallel resonant circuit can be lowered by A. placing a resistor in parallel with the tank B. adding more resistance in series with the coil C. decreasing the value of L or C D. both A and B 595. The ability of an LC circuit to supply complete sine waves when the input to the tank is only a pulse is called A. tuning C. anti-resonance B. the flywheel effect D. its Q 596. Which of the following can provide a higher Q? A. a higher L/C ratio B. a lower L/C ratio C. more resistance in series with the coil D. either B or C 597. A resonance curve for a series circuit is a plot of frequency versus ____. A. voltage C. current B. impedance D. reactance 598. At half-power points of a resonance curve, the current is ____ times the maximum current. A. 2 C. √ B. D. 1/2 √ 599. A parallel resonant circuit can be used A. to amplify certain frequencies B. to reject a small band of frequencies C. as a high impedance D. both B and C 600. As the Q-factor of a circuit ____, its selectivity becomes ____. A. increases, better C. decreases, better B. increases, worse D. decreases, narrower 601. The half – power frequency of, series RC circuit is A. 1/RC C. R/C

RC

D.

C/R

602. For the given parallel resonant circuit, match the following: A. I at resonance 1. W/R B. IL 2. In phase with voltage C. Dynamic impedance 3. L/CR 4. Lags the applied voltage ABC ABC A. 4 2 3 C. 4 2 1 B. 2 4 3 D. 2 4 1 603. To increase the Q- factor of an inductor, it can be with A. Thicker wire B. Thinner wire C. Longer wire D. Wire with heavy insulation 604. Given Z = jωL + 1/jωC; the magnitude of Z curve will be

A. B.

Figure a Figure b

C. D.

Figure c none of the above

605. The bandwidth of R.C series circuit is A. 1/RC C. ∞ B. RC D. none of the above 606. Consider the following statements: In a series RLC resonant circuit, the bandwidth is 1. directly proportional to resonant frequency 2. Inversely proportional to resonant frequency 3. directly proportional to quality factor 4. Inversely proportional to quality factor A. 2 & 3 are correct C. 1 & 3 are correct B. 2 & 4 are correct D. 1 & 4 are correct 607. An RLC parallel resonant circuit has a resonance frequency of 1.5 MHz and a bandwidth of 1 kHz. If C = 150 pF, then the effective resistance of the circuit will be A. 2.96 MΩ C. 9.5 Ω B. 14.75 Ω D. 4.7 Ω

608. The parallel RL circuit is having quality factor of Q1, when it is connected in series with R, the new quality factor Q2 will be A. Q2 > Q1 C. Q2 = Q1 B. Q2 < Q1 D. none of the above 609. In a series RLC circuit, as R increases 1. Bandwidth decreases 2. Bandwidth increases 3. Resonance frequency increases 4. Lower 3 dB decreases 5. Upper 3 dB increases A. 2, 4 & 5 are correct C. 2, 3, 4 are correct B. 1, 4 & 5 are correct D. none of the above

616. The half power frequency of series RL circuit is A. R/L C. 2R/L B. L/R D. 2L/R 617. In a series RLC circuit, the value of current at resonance is affected by the value of A. only L C. both L & C B. only C D. only R

610. In a series RLC circuit, given R = 10 Ω, L = 14 H, C = 1 F. Find damping ratio. A. 1.33 C. 0.5 B. 0.187 D. none of the above

618. In a series RLC circuit at resonance with Q = 10, and with applied voltage of 100 mV at resonance frequency voltage across capacitor is A. 100 mV C. 10 mV B. 1 volt D. 10 volts 619. Find fR in the circuit shown.

611. The power factor of parallel RLC circuit at W > Wo is A. < 1 C. > 1 B. =1 D. 0 612. The phase of even symmetric signal is A. +90° C. 0° B. –90° D. 0° or ±180°

A. B.

613. The power in a series R-L-C circuit will be half of that at resonance when the magnitude of current is equal to A. V/2R C. V/√ R B. V/√ R D. √ V/R 614. In a series RLC high Q circuit, the current peaks at a frequency A. f = fo C. f < fo B. f > fo D. none of these 615. The given series resonant circuit frequency of 20 MHz. It will A. By pass all signals of 20 B. permit flow of signal of 20 time C. Not produce any effect at 20 D. cause moderate attenuation MHz

resonance

at

MHz MHz along the MHz of signal at 20

all frequencies 0.5 rad/ sec

C. D.

5 rad / sec 1 rad/ sec

620. The parallel RLC circuit shown is in resonance.

A. B.

|IR| < 1 mA |IR + IL| >1 mA

C. D.

|IR + IC| < 1 mA |IL + IC| > 1 mA

621. A series RLC ckt has a Q of 100 and an impedance of (100 + j0) Ω at its resonance angular frequency of 107 rad| sec. The values of R & L are A. R = 100 Ω; L = 1 mH C. R = 100 Ω; L = 10 mH B. R = 10 Ω; L = 10 mH D. none of the above 622. The parallel RLC circuit having damping ratio δp is connected in series with same values, then series circuit damping ratio δs is

A. B.

4δp 2δp

C. D.

δp/4 δp/2

C. D.

623. A series LCR circuit consisting of R = 10Ω, |XL| = 20 Ω & |XC| = 20 Ω is connected across an a.c supply of 200 V rms. The rms voltage across the capacitor is A. 200 -90° C. 400 +90 B. 200 +90° D. 400 -90 624. At fR what is K?

A. B.

0.25 0.5

C. D.

0.999 1.0

625. Find Zin at resonance.

A. B.

1.28 Ω 12.8 Ω

628. A series RLC circuit when existed by a 10 V sinusoidal voltage source of variable frequency, exhibits resonance at 100 HZ and has a 3dB band width of 5 Hz. The voltage across the inductor L at resonance is A. 10 V C. 10/√ V B. 10√ V D. 200 V 629. A circuit with a resistor, inductor and capacitor in series is resonant at fR Hz. If all the component values are now doubled, the new resonant frequency is A. 2 fR C. fR/4 B. still fR D. fR/2 630. A coil (series RL) has been designed for high Q performance at a rated voltage and a specific frequency. If the frequency of operation is doubled, and the coil is operated at the same rated voltage, then the Q factor and the active power P consumed by the coil will be affected as follows A. P is doubled, Q is halved B. P is halved, Q is doubled C. P remain constant, Q is doubled D. P decreases 4 times, Q is doubled

C. D.

2Ω 128 Ω

626. For the series RLC circuit, the partial phasor diagram at a certain frequency is shown, the operating frequency of the circuit is

A. B. C. D.

can be greater than the input voltage however, it is 90° out of phase with the input voltage can be greater than the input voltage and is in phase with the input voltage.

631. A series RLC circuit has the following parameter values R = 10 Ω, L = 0.01 H, C = 100 µF. The Q factor of the circuit at resonance is A. 1 C. 0.1 B. 10 D. none of the above 632. At resonance, the parallel circuit of given figure constituted by an iron-cored coil and a capacitor, behaves like.

Equal to resonant frequency less than resonant frequency Greater than resonant frequency none of the above

627. In a series RLC circuit at resonance, the magnitude of the voltage developed across the capacitor A. is always zero B. can never be greater than the input voltage

A. B.

open circuit short

C. D.

pure resistance = R pure resistance > R

633. Find L & C of a parallel RLC circuit to resonate at 1 rad/sec with a Q of 5 and resistance of 1 ohm. A. 1/5 H, 5 F C. 1 H, 1 F B. 5 H, 1/5 F D. 5 H, 5 F 634. In a parallel RLC resonant circuit R = 10 kΩ, C = 0. 47 µF, the bandwidth will be. A. 212.76 rad/sec C. 100 rad/sec 10 B. 2.12 x 10 rad/sec D. none of the above 635. A parallel resonate circuit (RP, L, &C) and a series resonant circuit (RS, L & C) have the same Q. Find the relation between RP & RS 2 A. RS = Q Rp C. RP = RS 2 B. RP = Q RS D. none of the above 636. In a parallel resonant circuit, as R increases, the selectivity will be A. Decreasing C. Constant B. Increasing D. none of the above 637. In a series RLC circuit, the phasor form at some frequency is as shown, then the frequency is

A. B.

R/L L/RC

C. D.

1/RC ω0L/R

641. The Q of a parallel RLC circuit at its resonance frequency ω0 is A. ω0L/R C. ω0RC B. R/ω0C D. ω0LR 642. In a series R-L-C circuit below resonance, the current A. lags behind the applied voltage B. leads the applied voltage C. is in phase with the voltage D. leads or lags behind the applied voltage depending upon the actual values of L and C 643. A high Q coil has A. large bandwidth B. high losses

C. D.

low losses flat response

644. At a frequency below the resonant frequency ____ circuit is capacitive and ____ circuit. A. series, parallel C. parallel, parallel B. parallel, series D. series, series 645. In the following parallel circuit, resonance will never occur, if:

A. B. C. D.

Less than W0 More than W0 equal to W0 none of the above

638. In a series RLC circuit, let Qc be the Q of the coil at resonance and let Qs = (resonance frequency)/bandwidth, then A. Qc and Qs are not related to each other B. Qc > Qs C. Qc < Qs D. Qc = Qs 639. A coil is represented by an inductance L in parallel with a resistance R. The Q of the coil at frequency w is A. R/(ωL) C. ωLR B. ωL/ R D. 1/(ωLR) 640. The half power bandwidth of a series RCL circuit is

A. B. C. D.

2

2

R1 = R2 = L/C 2 R1 < L/C 2 2 R2 > L/C and R1 < L/C 2 2 R1 > L/C and R2 > L/C

646. The circulating current in a parallel LC circuit at any resonant frequency is A. Directly proportional to frequency B. Inversely proportional to frequency C. Independent of frequency D. none of the above 2

647. In series RLC circuit excited by a voltage, e = E sin ωt, where LC < (1/ω ) A. Current lags the applied voltage B. current leads the applied voltage C. current is in phase with the applied voltage D. voltages across L and C are equal

648. A series RLC circuit has a resonance frequency of 1 kHz and a quality factor Q = 100. If each of R, L and C is doubled from its original value, the new Q of the circuit is A. 25 C. 100 B. 50 D. 200

A. B.

R√ R√

C. D.

1/R√ 1/R√

656. A practical inductor can be replaced by the following equivalent circuit at low to medium frequency.

649. What is the bandwidth of parallel RLC circuit at resonance? A. RC C. R/C B. 1/RC D. C/R 650. The current bandwidth of RC series circuit is A. 1/RC C. ∞ B. RC D. none of the above 651. The circuit shown acts as an ideal current source with respect to terminals AB, when the frequency is

A. B.

zero 1 rad/sec

C. D.

4 rad/sec 16 rad/sec

652. A series RLC circuit is excited by an ac voltage v(t) = sin t. If L = 10 H and C = 0.1 F, then the peak value of the voltage across R will be A. 0.707 B. 1 C. 1.414 D. indeterminate as the value of R is not given

A. B.

Figure a Figure b

C. D.

Figure c Figure d

657. A coil of wire has inductive impedance. At high frequencies the impedance will be represented by

A. B.

Figure a Figure b

C. D.

Figure c Figure d

658. In a series RLC circuit R= 2 kΩ, L = 1 H, and C = 1/ 400 microfarads. The resonant frequency is 4 4 A. 2 x 10 Hz C. 10 Hz 4 4 B. (1/π) x 10 Hz D. 2π x 10 Hz 659. In the circuit shown in the figure, Vs = Vm sin 2t and Z2 = 1 – j. The value of C is shown such that the current I is in phase with Vs. The value of C in farad is

653. In a parallel RLC circuit, the current source (I) lags voltage across circuit (V) if A. wL > 1/wC C. R > [wL + 1/wC] B. wL < 1/wC D. none of the above 654. At lower half power frequency the total reactance of the series RLC circuit is A. –R C. √ -45° B. √ 45° D. none of the above 655. In a parallel RLC circuit, the quality factor at a resonance is given by

A. B.

1/4 1/2√

C. D.

2 4

660. The circuit shown has i(t) = 10 sin (120πt). The power (time average power) dissipated in R is when L = 1/120π H, C = 1/60π H, R = 1 ohm.

A. B.

A. B.

25 watts 100 watts

C. D.

10/√ watts 50 watts

661. The value of the capacitance C in the given ac circuit to make it a constant resistance circuit or for the supply current to be independent of its frequency is

A. B.

1/16 F 1/12 F

C. D.

1/8 F ¼F

662. A parallel RLC circuit has half power frequencies at 105 M rad/s and 95 M rad/s. Then Q is given by A. 10.5 C. 100 B. 9.5 D. 10 2

663. The system function H(s) = s/(s + 2s + 100). The resonant frequency and the bandwidth in rad/s are given, respectively, by A. 10, 1 C. 100, 2 B. 10, 2 D. 100, 1 E. POWER FACTOR CORRECTION (1-PHASE) 664. EE Board Exam October 1990 A single phase inductive load takes 50 kVA at 0.60 power factor lagging. Solve for the kVAR of a capacitor required to improve the power factor to 1.0. A. 30 kVAR C. 22.5 kVAR B. 20 kVAR D. 40 KVAR 665. REE Board Exam March 1998 A single phase induction motor is rated 5 hp, 75% power factor and 220 volts. What approximate size of capacitor is necessary to raise the power factor to about 95%?

3 kVAR 2 kVAR

C. D.

2.5 kVAR 3.5 Kvar

666. EE Board Exam April 1984 A plant has a load of 290 kilowatt with an average power factor of 70%. The owner requests you to correct the power factor to reduce its power consumption. How much capacitor kVAR is required to increase the power factor to 90%? A. 152.46 C. 150.34 B. 155.39 D. 154.58 667. REE Board Exam October 1996 A single-phase, 60 Hz, 5 hp squirrel cage induction motor draws a current of 53 A at 117 V. If it has a 78.5% electrical to mechanical conversion efficiency, what capacitance should be connected at the terminals of the motor in order to increase the power factor of the load combination to 92%? A. 480 μF C. 320 μF B. 380 μF D. 420 μF 668. EE Board Exam April 1997 A load of 10,000 kVA, 80% pf lagging is connected to a 13,200 volts line. How much capacitive reactive power is needed to correct the power factor to 0.97 lagging? A. 5,156 kVAR C. 2,547 kVAR B. 3,138 kVAR D. 4,395 kVAR 669. In a pure reactive circuit, the power factor is A. lagging C. leading B. zero D. unity 670. Power factor is defined as the ratio of A. volt ampere to watts B. watts to volt amperes C. volt amperes reactive to watts D. watts to volt amperes reactive 671. In a series circuit consisting of resistance and reactance, power factor is defined as the ratio of A. resistance to impedance B. resistance to reactance C. reactance to impedance D. none of these 672. For a parallel circuit consisting of resistance and reactance the value of power factor is the ratio of

A. B. C. D.

impedance to reactance reactance to impedance resistance to impedance impedance to resistance

C. D.

673. It is not easy to find the value of impedance for a parallel circuit but power factor can easily be obtained as a ratio of A. active current to line current B. reactive current to line current C. line current to active current D. none of these 674. The power factor of a.c. circuit containing both a resistor and a conductor is A. more than unity C. between 0 -1 leading B. leading by 90° D. none of these 675. In an a.c. circuits, a low value of reactive volt-ampere compared with watts indicates A. high power factor C. leading power factor B. unity power factor D. none of these 676. In a given circuit when power factor is unity the reactive power is A. a maximum C. zero 2 B. equal to I R D. none of these 677. The capacitor of power factor correction are rated in terms of A. voltage C. kW B. VA D. kVAR 678. Poor power factor results in all of the following except A. overloading of transformers B. overloading of alternators C. reduction in power losses D. reduction in load handling capacity of electrical system 679. Power factor of an inductive circuit can be improved capacitor to it in A. series B. parallel C. either series or parallel D. depends on the value of the capacitor 680. For the same load, if the power factor is reduced, it will A. draw more current B. draw less current

by connecting a

draw same current but less power draw less current but more power

681. The power factor of incandescent bulb is A. 0.8 lagging C. unity B. 0.8 leading D. zero 682. Power factor of the magnetizing component of a transformer is A. unity C. always leading B. 0.8 lagging D. zero 683. One of the reasons for improving the power factor is A. to increase the reactive power B. to decrease the reactive power C. to increase the real power D. to decrease the real power 684. Another reason for improving the power factor is A. to avoid poor voltage regulation B. to keep voltage regulation constant C. to increase the voltage regulation D. to decrease the voltage regulation 685. Power factor improvement may be achieved by the use of A. synchronous motor C. long transmission line B. induction motor D. short transmission line 686. The advantage of using static capacitor to improve the power factor is because they A. are not variable B. are almost loss free C. provide continuous change of power factor D. none of these 687. Many industrial tariffs penalize consumers whose power factor falls A. below 0.8 C. between 0.8 to 0.95 B. below unity D. none of these 688. A factory takes a load of 1000 KW and has a reactive power of 1000 KVAR. Its power factor is A. 0.6 C. 0.8 B. unity D. 0.7 689. A current of 10 amperes at a power factor of 0.8 lagging is taken from 250 V a.c. supply. The reactive power of the system is

2000 watts 2000 VA

C. D.

1500 watts 1500 VAR

695. Consider the following statements: In the circuit shown in the figure, if the equivalent impedance x – x is Zeq then

690. A resistance ‘R’ Ω and inductance ‘L’ H are connected across 240 V, 50 Hz supply. Power dissipated in the circuit is 100 W and the voltage across R is 100 V. In order to improve the pf to unity, the capacitor that is to be connected in series should have a value of A. 43.7 μF C. 437 μF B. 4.37 μF D. 4.37 mF 691. What size of condenser must be placed across an inductance having a resistance of 10 ohms and reactance of 20 ohms to draw minimum current from the line when the combination is connected across a 60-cycle line? (Assume a condenser of negligible resistance). A. 20 μF C. 10 μF B. 106 μF D. 6.33 μF F. AC NETWORK ANALYSIS 692. A segment of a circuit figure VR = 5 V, VC = 4 voltage VL is given by A. 3 – 8 cos 2t B. 32 sin 2t C. 16 sin 2t D. 16 cos 2t 693. Three currents i1, i2 and approaching a node. If + 60°) A and i2 = 10 sin (400t - 60°) A, then i3 is A. 0 C. -10 sin 400t A B. 10 sin 400t A D. √ (

i3 are i1 = 10 sin (400t )A

I1

4Ω

j10 Ω

1. Zeq = 2 + j5 2. Zeq = 2 + j3 Of these statements A. 1 alone is true B. 2 and 4 are correct

3. 4.

I1 = -I2 I1 = I2

C. D.

2 and 3 are correct none of the above

j3 Ω

A

A. B.

j2 Ω

j5.33 V 5.33 V

C. D.

V2

A. B.

0° 45°

C. D.

-45° -90°

B

j4 Ω

-j5.33 V j3.33 V

697. In the circuit shown in given figure, ( ) √ ( ) and ( ) ( ). What is the voltage v(t) across the 1 ohm grounded √ resistor? 1Ω

1Ω

+

+ 1Ω

e1(t)

A. B. C. D.

V (

) V

j1 V

(

e2(t) -

I j10 Ω

j10 Ω

j4 Ω

-

10 Ω

4Ω

696. For the network shown in the figure, the voltage VB will be

694. The phase angle of the current ‘I’ with respect to the V 1 in the circuit shown in the figure is V1 = 100 (1 + j); V2 = 100(1 – j)

V1

I2

x

1A

shown in given sin 2t. The

x

2A

A. B.

)V

698. If all elements in a particular network are linear, then the superposition theorem would hold when the excitation is A. dc only C. either ac or dc B. ac only D. an impulse 699. For the network shown in given figure, the Thevenin equivalent impedance across terminals CD is given by A. B.

[

]

[

]

C. (

D.

700. In the given figure Thevenin impedance seen from X-Y is A. C. B. D.

,

)

,

.

701. In the figure the current source is A, R = 1 ohm, the impedances are ZC = -j ohm, and ZL = j2 ohm, The Thevenin equivalent circuit looking into the circuit across X-Y is A. √ V, (1 + j2) Ω C. V, (1 + j) Ω B. V, (1 + j2) Ω D. √ V, (1 + j) Ω 702. The circuit shown in Fig. 1 is replaced by its Norton’s equivalent circuit in Fig. 2. The value of I will be A. A C. A B. A D. A 703. Consider the following statements: The transfer impedance and admittance of a network remain constant when the position of excitation and response are interchanged if the network 1. is linear 2. consists of bilateral elements 3. has high impedance or admittance as the case may be 4. is resonant Of these statements A. 1 and 2 are correct C. 2 and 4 are correct B. 1, 3 and 4 are correct D. all are correct 704. In a linear network, the ratio of voltage excitation to current response is unaltered when the position of excitation and response are interchanged. The assertions stems from the A. principle of duality B. reciprocity theorem

C. D.

principle of superposition equivalence theorem

705. A certain network N feeds a load resistance as shown in Fig. 1. It consumes a power of ‘P’. If an indicated network is added as shown in Fig. 2. The power consumed by R will be A. less than P C. between P and 4P B. equal to P D. more than 4P 706. In the circuit shown in the figure, the current source I = 1 A, the voltage source V = 5 V, R1 = R2 = R3 = 1 Ω, L1 = L2 = L3 = 1 H, C1 = C2 = 1 F. The currents (in A) through R3 and the voltage source V respectively will be A. 1, 4 C. 5, 2 B. 5, 1 D. 5, 4 707. For loop (1) of the network shown in the given figure, the correct loop equation is A. C. B. D. 708. An ac source of voltage ES and an internal impedance of ZS = (RS + jXS) is connected to a load of impedance ZL = (RL + jXL). Consider the following conditions in this regard. 1. XL = XS if only XL is varied 2. XL = -XS if only XL is varied √ 3. ( ) if only RL is varied 4. |ZL| = |ZS| if the magnitude of ZL is varied, keeping the phase angle fixed Among these conditions, those which are to be satisfied for maximum power transfer from the source to the load would include A. 2 and 3 C. 1, 2 and 4 B. 1 and 3 D. 2, 3 and 4 709. Under the conditions of maximum power transfer from an ac source to a variable load A. the load impedance must be inductive, if the generator impedance is inductive B. the sum of the source and the load impedances is zero C. the sum of the source reactance and the load reactance is zero D. the load impedance has the same phase angle as the generator impedance 710. If the combined generator and line impedance is (5 + j10) Ω, then for the maximum power transfer to a load impedance from a generator of constant generated voltage, the load impedance is given be which of the following?

A. B.

(5 + j10) Ω (5 – j10) Ω

C. D.

(5 + j5) Ω 5Ω

A. B.

1,905 W 3,300 W

C. D.

5,716 W 3,810 W

711. A voltage source having an internal impedance of 8 + j6 Ω supplies power to a resistive load. What should be load resistance for maximum power transferred to it? A. 8 Ω C. 10 Ω B. 6 Ω D. √ Ω

718. REE Board Exam April 1997 A 170 kV, 3-phase electric source delivers 200 MVA to a balanced load, which has a power factor of 90% lagging. What is the line current? A. 257 A C. 402 A B. 502 A D. 679 A

712. The Thevenin equivalent circuit of a network is as shown in the given figure. For maximum power transfer to the variable and purely resistive load R L, its resistance should be A. 60 Ω C. 100 Ω B. 80 Ω D. infinity

719. REE Board Exam October 1997 A three-phase motor is rated 50 hp, 440 volts and 85% power factor. What is its rated current? A. 61.5 A C. 55 A B. 57.5 A D. 59 A

713. Two ac sources fed a common variable load as shown in the given figure. Under the maximum power transfer condition, the power absorbed by the load resistance RL is A. 2200 W C. 1000 W B. 1250 W D. 625 W

720. EE Board Exam April 1985 A balanced 3-phase load draws 120 amperes line current at 230 volts line to line, 0.848 pf lagging. Solve for the real power. A. 40.54 kW C. 41.45 kW B. 42.35 kW D. 43.15 kW

714. REE Board Exam March 1998 Three impedances, -j10, j10 and 10 ohms are wye-connected. Determine the impedance of an equivalent delta. A. 12.5, j12.5, -12.5 Ω C. j8.5, -j12.5, 8 Ω B. 10, j10, -j10 Ω D. 5, j5, -j5 Ω

721. REE Board Exam March 1998 A generator supplies three-phase power to balanced load. The voltage is 230 volts, the current is 18 A and the power factor is 85%. What is the power? A. 3.6 kW C. 6.1 kW B. 1.6 kW D. 1.4 kW

715. A telephone circuit makes power available at a pair of terminals. The open circuit voltage across the terminals is 1 volt and the impedance looking into the terminals is 500 – j500 Ω. What is the maximum power that can be drawn from the circuit? A. 0.002 W C. 0.001 W B. 0.0005 W D. 0.0014 W

722. EE Board Exam April 1984 A balanced 3-phase load draws 75 amperes line current at 230 volts line to line, 0.848 pf lagging. Solve for the reactive power being drawn. A. 15.83 kVAR C. 15.35 kVAR B. 15.26 kVAR D. 15.94 kVAR

G. BALANCED POLYPHASE SYSTEM 716. REE Board Exam April 2002 In a balanced three-phase system, the phase A voltage is 132.8 cis 0°, what is the line to line voltage VCA? A. 230 cis 30° C. 230 cis (-60°) B. 230 cis (-30°) D. 132.8 cis 120°

723. EE Board Exam April 1990 The input power factor to a three-phase, 6-poles, 460 volts., 60 Hz, 50 hp induction motor is 0.62 as 20 A is drawn by the motor. Find the power input to the motor. A. 9,880 W C. 9,895 W B. 9,675 W D. 9,478 W

717. REE Board Exam September 2001 The phase B line voltage and the phase A line current of a balanced three phase system are v = 220 sin (ωt + 210°) and i = 10 sin (ωt + 180°) amperes, respectively. What is the power of the system?

724. EE Board Exam April 1992 A 460 volt, three-phase motor draws 208 A with a power factor of 0.91 lagging. Calculate the kW input to the motor. A. 150.8 C. 152.4

B.

156.3

D.

160.3

725. EE Board Exam April 1993 A wye-connected load has a ohm impedance per phase and is connected across a 120-V three-phase source. Calculate the line current. A. 24 A C. 41.56 A B. 13.85 A D. 15.45 A

731. EE Board Exam June 1990 Two parallel connected loads A and B are supplied by a 440 V, 3-phase, 60 Hz generator. Load A draws an apparent power of 100 kVA at 0.80 pf lagging and load B draws an apparent power of 70 kVA at unity pf. Determine the feeder current. A. 208 A C. 214 A B. 212 A D. 202 A

726. EE Board Exam April 1993 Three condensers, each having capacity of 75 microfarads are connected in star to a 440 volts, 3-phase, 50 cycles supply. Calculate the capacitance of each of the three condensers so that when they are connected in delta to the same supply the line current remains the same. A. 20 μF C. 25 μF B. 28 μF D. 30 μF

732. EE Board Exam April 1990 A three-phase motor takes 10 kVA at 0.67 pf lagging from a source of 230 volts. It is in parallel with a balanced delta load having 16 ohms resistance and 12 ohms capacitive reactance in series in each phase. Determine the total power factor. A. 0.966 lagging C. 0.917 lagging B. 0.896 lagging D. 0.967 lagging

727. EE April 1993 A balanced three-phase load is wye-connected and has an impedance Zp = 4 – j3 ohms per phase. Find the line current if this load is connected across a 220 V three-phase source. A. 25.4 A C. 20.5 A B. 22.3 A D. 26.7 A

733. REE Board Exam March 1998 The phase b line voltage and the phase a line current of a balanced threephase system are v = 220 (sin wt + 210) and i = 10 sin (wt - 30), respectively. What is the power of the system? A. 1905 W C. 5716 W B. 3300 W D. 3810 W

728. REE Board Exam October 1998 Three 10-ohm resistances are connected delta on a balanced three-phase source. If the equation of the phase Van =120 sin ωt. What is the equation of the line current in line a? A. 20.78 sin (ωt + 30°) C. 12 sin (ωt – 56.56°) B. 13.15 sin (ωt - 30°) D. 36 sin ωt

734. EE Board Exam April 1985 A balanced 3-phase load draws 120 amperes line current at 230 volts line to line, 0.848 pf lagging current. Solve for the readings of the two wattmeters used to measure the 3-phase power. A. 25.543 kW, 15.087 kW B. 28.155 kW, 12.385 kW C. 24.365 kW, 16.175 kW D. 27.583 kW, 12.957 kW

729. EE Board Exam October 1994 Three resistors 10, 15 and 30 ohmic values are connected in wyeconfiguration to a balanced 208 volt three-phase supply. Calculate the total power of the system. A. 2644 W C. 3080 W B. 2880 W D. 3280 W 730. REE Board Exam March 1998 Three impedances each 10 + j5 ohms are connected delta on a balanced three-phase source. If the equation of the phase Van =120 sin ωt. What is the equation of the line current through the impedance connected across phase A and B? A. 20.02 sin (ωt - 22°) C. 16.21 sin (ωt + 56.56°) B. 18.59 sin (ωt + 3.44°) D. 21.32 sin (ωt – 8.15°)

735. EE Board Exam April 1988 MERALCO used two wattmeters to measure the balanced 3-phase dynatron elevator motor drive. The coils of the wattmeters are connected to the current transformers, which are lines 1 and 2 respectively. The potential coils are connected to potential transformers, which are across lines 2 and 3 and lines 3 and 1, respectively. The line potentials are 230 V and the line currents are each 150 A. The wattmeters each indicate 19.6 kW. Assume load is wye connected. What is the total power supplied? A. 49.175 kW C. 45.461 kW B. 48.236 kW D. 47.350 kW 736. EE Board Exam April 1992

A 460-volt three-phase motor draws 208 A with a power factor of 0.91 lagging. Calculate the indication of W1 and W2 for the given condition. A. 75.40 kW, 75.40 kW C. 89.56 kW, 61.25 kW B. 91.23 kW, 59.58 kW D. 95.24 kW, 55.57 kW 737. EE Board Exam June 1990 Two wattmeter method is used to test a 25 HP, 230 volt, 1800 rpm, 60 cycle, 3-phase induction motor. When the line voltages are 230 volts, one wattmeter reads +13,400 watts and the other +7,400 watts. Determine motor power factor. A. 0.961 C. 0.894 B. 0.886 D. 0.807 738. In a balanced three phase star connected circuit the line voltages are equal A. to the line current B. to the phase voltage C. and so are line currents D. but the line currents are unequal

743. The advantages of star connections over delta connections for the same voltage is that it gives A. step down current B. extra step up voltage C. extra step up current D. extra step up power 744. Power in a three phase star system is equal to A. √ x VL x IL x power factor B. 3 x Vph x IL x power factor C. √ x VL X Iph X power factor D. 3 x Vph x Iph x power factor 745. Power in a three phase delta system with balanced load is equal to A. √ x VL x IL x power factor B. √ x Vph X Iph X power factor C. 3 x Vph x IL x power factor D. 3 x VL x IL x power factor

739. The type of a.c. distribution system commonly used to supply both light and power is the A. open delta system B. three phase delta system C. three phase star system with neutral wire D. three phase star system without neutral wire

746. In a delta connected system the line current is A. 1.414 times the phase current B. phasor sum of the two phase currents C. equal to the phase current D. 1.732 times the phase current

740. The phase displacement between phasors in polyphase system is always A. 90 degrees B. 120 degrees C. 360 degrees divided by the number of phases D. none of the above

747. Power in star connected system is A. equal to that of delta system B. √ times the delta system C. √ times the delta system D. 3 times of a delta system

741. In a balanced three phase star connected system the line voltage is A. the phasor difference of the two phase voltages B. the phasor sum of the two phase voltages C. 0.707 times the phase voltage D. 1.414 times the phase voltage

748. Electric power is almost exclusively generated, transmitted and distributed, by three phase system because it A. it is more efficient B. uses less material for a given capacity C. costs less than single-phase apparatus D. all of the above

742. In a star connected system line current is A. 0.707 times the phase current B. 1.735 times the phase current C. equal to the phase current D. 1.414 times the phase current

749. The voltages induced in the three windings of a three-phase alternator are ____ degree apart in time phase. A. 120 C. 90 B. 60 D. 30

750. If positive phase sequence of a 3 – phase load is a-b-c the negative sequence would be A. b-a-c C. a-c-b B. c-b-a D. all of the above 751. In the balanced 3-phase voltage system generated by a Y-connected alternator, VYB lags ER by ____ electrical degrees. A. 90 B. 120 C. 60 D. 30 752. The power taken by 3-phase load is given by the expression A. 3 VL IL cos φ C. 3 VL IL sin φ B. √ VL IL cos φ D. √ VL IL sin φ 753. In a balanced 3-phase voltage generator, the difference phase voltages reach their maximum values ____ degree apart. A. 120 C. 240 B. 60 D. 30 754. If the B-phase, Y-connected alternator become reverse connected by mistake, it will not affect. A. V Y B C. V B R B. V R Y D. V B Y 755. Three equal impedances are first connected in star across a balanced 3phase supply. If connected in delta across the same supply. A. phase current will be tripled B. phase current will be doubled C. line current will become one-third D. power consumed will increase three-fold 756. A 3-phase, 4-wire, 230/440-V system is supplying lamp load at 230 V. If a 3phase motor is now switched on across the same supply then, A. neutral current will increase B. all line currents will decrease C. neutral current will remain unchanged D. power factor will be improved 757. Power factor improvement A. does not affect the performance characteristics of the original load B. employs series resonance C. increase the active power drawn by the load D. increases the reactive power taken by the load 758. The chief disadvantage of a low power factor is that

A. B. C. D.

more power is consumed by the load current required for a given load power is higher active power developed by a generator exceeds its rated output capacity heat generated is more than the desired amount

759. In the 2-wattmeter method of measuring 3-phase power, the two wattmeter’s indicate equal and opposite readings when load power factor angle is ____ degrees lagging. A. 60 C. 30 B. 0 D. 90 760. When phase sequence at the 3-phase load is reversed A. phase powers are changed B. phase currents are changed C. phase currents change in angle but not in magnitude D. total power consumed in changed 761. Phase reversal of a 4-wire unbalanced load supplied from a balanced 3phase supply changes A. magnitude of phase currents B. magnitudes as well as phase angle of neutral current C. the power consumed D. only the magnitude of neutral current 762. In a two-phase generator, the electrical displacement between two phase or windings is ____ electrical degrees. A. 120 C. 180 B. 90 D. none of the above 763. In a six-phase generator, the electrical displacement between different phases or windings is ____ electrical degrees. A. 60 C. 120 B. 90 D. 45 764. The torque on the rotor if a 3-phase motor is more constant than that of a single motor because A. single phase motors are not self-starting B. single phase motors are small in size C. 3-phase power is of constant value D. none of the above 765. For the same rating, the size of a 3-phase motor will be ____ single phase motor. A. less than that of C. same as that of B. more than that of D. none of the above

770. The advantage of star-connected supply system is that A. line current is equal to phase current B. two voltages can be used C. phase sequence can easily be changed D. it is a simple arrangement

767. The phase sequence of a three-phase system is RYB. The other possible phase sequence can be A. B R Y C. R B Y B. Y R B D. none of the above

771. In a balanced star connected, line voltages are ____ ahead of their respective phase voltages. A. 30 C. 120 B. 60 D. none of the above

768. If in Fig. 14.1, the phase sequence is RYB, then

772. In a star-connected system, the relation between the line voltage V L and phase voltage Vph is A. C. √ B. D. none of the above √

3-phase line

766. To transmit the same amount of power over a fixed distance at a given voltage, the 3-phase system requires ____the weight of copper required for the single-phase system. A. 3 times C. 1.5 times B. 3/4 times D. 0.5 times

R

60 W

Y

60 W

L1

L2

773. Fig 14.2 shows a balanced star-connected system. The line voltage VRY is given by

R

C B

A. B. C. D.

N

L1 will burn more brightly than L2 L2 will burn more brightly than L1 both lamps will be equally bright none of the above

B

3-phase line

769. If the phase sequence of the 3-phase line in Fig 14.1 is reversed R

60 W

Y

60 W

L1

L2

C B Fig. 14.1

A. B. C. D.

L1 will be brighter than L2 L2 will be brighter than L1 both lamps will be equally bright none of the above

IR

ERN

Fig. 14.1

EBN

EYN Y

VRY IY IB

VBR VYB

Fig. 14.2 A. B. C. D.

VRY = ERN – ENY …..phasor sum VRY = ERN – EYN.....phasor difference VRY = ENR + EYN …..phasor sum none of the above

774. If the load connected to the 3-phase generator shown in Fig. 14.2 has a lagging p.f. of cos , then angle between VRY and IR is

777. The power delivered by the 3-phase system shown in Fig. 14.2 is . Here θ is the phase difference between √

R IR

ERN N B

EYN

EBN

Y

R

VRY VBR

IY

N VYB

IB

B

EYN

EBN

Y

Fig. 14.2 A. B.

30 + ϕ 30 - ϕ

C. D.

60 + ϕ 120 – ϕ

R N B

IR

EYN

EBN

Y

VRY VBR

IY

VYB

IB

90 – ϕ 90 + ϕ

C. D.

60 + ϕ 30 - ϕ

776. Each phase voltage in Fig. 14.2 is 230 V. If connections of phase B are reversed then

A. B. C. D.

B

R

EYN

EBN

Y

VRY = 230 V VRY > 230 V

C. D.

1

IB IR

VRY VBR

IY

2 B

IB

VRY < 230 V VRY = 0 V

Y

IY

VYB

3 Fig. 14.3

Fig. 14.2 A. B.

line voltage and corresponding line current phase voltage and corresponding phase current phase current and line current none of the above

780. Fig. 14.3 shows a balanced delta-connected supply system. The current in line 1 is

IR

ERN

VYB

778. A 3-phase load is balanced if all the three phases have the same A. impedance B. power factor C. impedance and power factor D. none of the above

R N

IB

VBR

779. Three 50-ohm resistors are connected in star across 400 V, 3-phase supply. If one of the resistors is disconnected, then line current will be A. 8 A C. √ A B. 4 A D. √ A

Fig. 14.2 A. B.

VRY IY

Fig. 14.2

775. If the load connected to the 3-phase generator shown in Fig. 14.2 has a leading p.f. of cos , then angle between VRY and IR is

ERN

IR

ERN

A. B. C. D.

IR - IB..... phasor difference IB - IR ….. phasor difference IY - IR - IB ….. phasor difference none of the above

781. In Fig. 14.3, line currents are ____ behind the respective phase currents.

R IB

10 Ω

400 V

1

10 Ω

400 V

IR

10 Ω N

400 V

2 B

Y

IY

Fig. 14.4

3 Fig. 14.3

A. B.

60 30

C. D.

120 none of the above

A. B.

400 V √ V

2 3 Fig. 14.3 A. B.

200 V √ V

C. D.

10 Ω N

400 V Fig. 14.4

Y

IY

10 Ω

400 V

IR B

10 Ω

400 V

1

IB

230 V none of the above

786. The power rating of each resistor in Fig. 14.4 is

782. The delta-connected generator shown in Fig. 14.3 has phase voltage of 200 V on no load. If a connection of one of the phases is reversed then resultant voltage across the mesh is

R

C. D.

A. B.

4000 W 2300 W

C. D.

787. If one of the resistors in Fig. 14.4 were open-circuited, then power consumed in the circuit is

400 V none of the above

785. The voltage rating of each resistor in Fig. 14.4 should be

10 Ω

400 V 10 Ω

400 V

783. If one line conductor of a 3-phase line is cut, the load is then supplied by the ____ voltage. A. single phase C. three phase B. two phase D. none of the above 784. The resistance between any two terminals of a balanced star connected load is 12 . The resistance of each phase is A. 12  C. 6  B. 18  D. 36 

4600 W 5290 W

10 Ω N

400 V Fig. 14.4

A. B.

8000 W 4000 W

C. D.

16000 W none of the above

788. The power consumed in the star-connected load shown in Fig. 14.5 is 690 W. The line current is

8Ω

6Ω

400 V

8Ω

6Ω

400 V

8Ω

6Ω

10 Ω

400 V 10 Ω

400 V

10 Ω

400 V

N

400 V Fig. 14.4

A. B.

2.5 A 1A

C. D.

1.725 A none of the above

789. If one of the resistors in Fig. 14.5 is open-circuited, power consumption will be

R

R

Fig. 14.6 A. B.

184 V 138 V

C. D.

792. The power consumed in each phase of the circuit shown in Fig. 14.6 is

8Ω

6Ω

400 V

8Ω

6Ω

400 V

8Ω

6Ω

400 V 400 V

R

Y 400 V

B A. B.

400 V R

Fig. 14.5 C. 345 W D. none of the above

200 W 300 W

790. The power factor of the star-connected load shown in Fig. 14.6 is

8Ω

6Ω

400 V

8Ω

6Ω

400 V

8Ω

6Ω

400 V

Fig. 14.6 A. B.

0.8 lagging 0.6 lagging

C. D.

400 V none of the above

0.75 lagging none of the above

791. The voltage drop across each inductor in Fig. 14.6 is

Fig. 14.6 A. B.

2300 W 4000 W

C. D.

3174 W none of the above

793. Three identical resistances connected in star consume 4000 W. If the resistances are connected in delta across the same supply, the power consumed will be A. 4000 W C. 8000 W B. 6000 W D. 12000 W 794. Three identical resistances, each of 15 , are connected in delta across 400 V, 3-phase supply. The value of resistance in each leg of the equivalent starconnected load would be A. 15  C. 5  B. 7.5  D. 30  795. Three identical capacitances, each of 450 F, are connected in star. The value of capacitance in each phase of the equivalent delta-connected load would be

C. D.

225 F 900 F

802. If the p.f. of the load shown in Fig. 14.7 (phase sequence is RYB) is zero, then

796. Three identical resistances connected in star carry a line current of 12 A. If the same resistances are connected in delta across the same supply, the line current will be A. 12 A C. 8 A B. 4 A D. 36 A

Z

N

W2

W1 will read zero W2 will read zero both W1 and W2 will read zero W1 and W2 will read equal and opposite

Z

Z

W2

IL

Y

VL IL

± ±

C. D.

√ √

( (

IL

Y

B

± ±

Z

Z

Z

) )

VL N

VL ± ±

IL

Fig. 14.7

A. B. C. D.

W1 will give more reading than W2 both W1 and W2 will give equal and positive reading W2 will give more reading than W1 none of the above

804. If the p.f. of the load (phase sequence is RYB) is Fig. 14.7 is 0.5, then

Fig. 14.7

( (

± ±

IL

N

A. B.

W1

R

VL

W2

± ±

803. If the p.f. of the load (phase sequence is RYB) in Fig. 14.7 is unity, then

IL

B

VL IL

Fig. 14.7

A. B. C. D.

801. In the circuit shown in Fig. 14.7, the phase sequence is RYB. If the load p.f. is cos  lagging, then reading of wattmeter W2 will be R

IL

Y

B

800. A wattmeter measures ____ power. A. instantaneous C. reactive B. apparent D. average

W1

VL

Z

799. In order to measure power in a 3-phase,4-wire unbalanced load, the minimum number of wattmeters required would be A. 1 C. 4 B. 2 D. 3

± ±

IL

797. Three delta-connected resistors absorb 60 kW when connected to a 3phase line. If the resistors are connected in star, the power absorbed is A. 60 kW C. 40 kW B. 20 kW D. 180 kW 798. If a balanced delta load has an impedance of (6 + j9) ohms per phase, then impedance of each phase of equivalent star load is A. (6 + j9) ohms C. (12 + j18) ohms B. (2 + j3) ohms D. (3 + j4.5) ohms

W1

R

Z

150 F 450 F

Z

A. B.

) )

W1

R

± ±

W1

R

± ±

IL Z

Z

IL VL

N

Z

Z

W2

Z

IL

Y

B

IL

W2

Fig. 14.7

A. B. C. D.

VL ± ±

IL

Fig. 14.7

W2 will give total power W1 will give total power both W1 and W2 will read equal W2 will give negative reading

A. B. C. D.

805. If the p.f. of the load (phase sequence is RYB) is Fig. 14.7 is 0.4, then W1

R

IL

Y

B

VL ± ±

Z

N

VL

± ±

Z

IL VL

total power drawn will change total power drawn will not change power factor of the load remains same none of the above

807. In two wattmeter method, the algebraic sum of the readings of two wattmeters will indicate true power only if A. the load is balanced B. phase sequence remains unchanged C. there is no source unbalance D. neutral wire available does not carry any current

N IL

Z

Y

Z

B

W2

VL ± ±

IL

Fig. 14.7

A. B. C. D.

W2 will give negative reading both W1 and W2 will give negative reading W1 will give negative reading both W1 and W2 will give positive reading

806. If capacitors of equal capacitance are shunted across each phase in Fig. 14.7, then

808. Three-wattmeter method is not used to measure power in a 3-phase circuit because A. it is complicated B. generally neutral is not available or delta load cannot be opened C. it requires three wattmeters D. none of the above 809. Three resistors having the same resistances are connected in star and across 480 V 3-phase lines. To what value should the line voltage be changed to obtain the same line currents with the resistors delta-connected? A. 230 V C. 160 V B. 133 V D. 240 V 810. In the circuit shown in Fig. 14.8, the wattmeter reads 1000 W. The total reactive power drawn by the balanced 3-phase load is

W R

± ±

Z

IR

N Z

Y

Z

B

IY IB

Fig. 14.8

A. B.

1000 VAR 2000 VAR

C. D.

1732 VAR none of the above

811. The most difficult unbalanced 3-phase load to deal with is A. 4-wire star connected unbalanced load B. unbalanced -connected load C. unbalanced 3-wire, Y-connected load D. none of the above 812. In a balanced three-phase system, the line to line voltages are displaced from each other by ____. A. 0° C. 90° B. 30° D. 120° 813. When phase sequence of the three-phase system is reversed ____. A. Phase currents change in angle not in magnitude B. Phase currents are changed C. Total Power consumed is changed D. Phase power are changed 814. A three-phase load is balanced if all the three phases have the same ____. A. Impedance B. Impedance & power factor C. Power factor D. Power 815. In balanced star (wye) connected system, the line voltage is A. 0.707 times the phase voltage B. 1.414 times the phase voltage C. phasor sum of the two phase voltage D. phasor difference of the two phase voltage

816. The phase sequence of a three-phase system is BCA. The other possible phase sequence can be ____. A. CBA C. ACB B. CAB D. none of these 817. Find the line voltage Vab is A. V B. V

C. D.

V and the sequence is BCA. V V

818. Line B of a 230 V ungrounded-wye system touches the ground. What is the voltage between line A and ground? A. 230 V C. 0 B. 115 V D. 132.79 V 819. A system consists of three equal resistors connected in wye and is fed from a balanced three-phase supply. How much power is reduced if one of the resistors is disconnected? A. 33% C. 25% B. 50% D. 0% 820. Three identical wye-connected resistances consume 1,000 watts. If the resistances are connected in delta across the same supply, the power consumed will be ____. A. 3,000 W C. 1,000 W B. 6,000 W D. 333 W 821. A balanced delta connected load draws 10 A of line current and 3 kW at 220 V. The reactance of each phase of the load is ____. A. 38.1 Ω C. 23.5 Ω B. 30 Ω D. 22 Ω 822. A 50-HP, three-phase induction motor with full load efficiency of 85% and power factor of 0.80 is connected to a three phase, 480 V system. The equivalent star connected impedance that can replace this motor is ____ A. C. B. D. 823. Three equal impedances of (20 + j20) ohms re connected in delta to 240 V, three-phase, 60 Hz line. Determine the capacitance of an ideal condenser in wye so that the overall power factor is 0.8 lagging. A. 16.58 μF C. 38.53 μF B. 49.74 μF D. 83.74 μF

824. Find the average power absorbed by a balance three phase load in an ACB circuit in which one line voltage is V and one line current to the load is A. A. 1337 W C. 1719 W B. 1122 W D. 1122 W

831. A 100 KVA balanced three phase load operates at 0.65 power factor lagging at 450 V. If power is measured by two wattmeters, what will be the reading of each wattmeter? A. 20,000 W & 45,000 W C. 10,563 W & 54,437 W B. 25,000 W & 40,000 W D. 65,000 W & 0 W

825. A balanced delta connected load having impedance per phase of ohms is supplied from a balanced 3-phase, 240 V source. Determine the total real power. A. 6824 W C. 7416 W B. 6912 W D. 6740 W

832. The two wattmeter method is applied to a three phase, three-wire, 100 V, ABC system with the meters in lines B and C, W B = 836 watts and WC = 224 watts. What is the impedance of the balanced delta-connected load? A. C. B. D.

826. A balanced three-phase load draws 20 kW at 0.447 pf lagging from a 230 V, 60 Hz three phase transmission line. Find the readings of the two wattmeters properly connected to measure power. A. 18.45 kW, 1.55 kW C. 21.55 kW, -1.55 kW B. 14.25 kW, 5.75 kW D. 25.75 kW, -5.75 kW

833. Two wattmeters are connected are for the two wattmeter method with current coils in lines A and B of a 208 V, ABC circuit that has a balanced delta load. If the meter readings arte 6 kW and -3 kW respectively, find the load impedance per phase. A. C. B. D.

827. A 25 HP induction motor is operating at rated load from a three phase 450 V, 60 Hz system. The efficiency and power factor of the motor are 87% and 90%, respectively. The apparent power in kVA drawn by the motor is ____. A. 23.82 C. 21.44 B. 27.78 D. 19.30 828. A balanced star connected load is supplied from a symmetrical three phase, 400 volts ABC system. The current in each phase is 30 amperes and lags 30° behind the line voltage. What is the total power? A. 18,000 W C. 20,785 W B. 10,393 W D. 31.177 W 829. A balanced delta load with impedances of 15 – j9 ohms is connected to a three phase source by three wires each of which has 2 + j5 ohms impedance. The load phase voltage is 120 V. Find the line voltages of the source. A. 69 V C. 259 V B. 208 V D. 87 V 830. Two-wattmeter method is applied to a three-phase motor running at full load. The two wattmeters indicate 85.5 kW and 34.7 kW, respectively. What is the operating power factor of the motor? A. 87.45% C. 89.49% B. 80.69% D. 94.76%

834. Three equal impedances, each represented by a series R-L circuit are connected to a three phase source. A total power of 7630 watts is measured by the two-wattmeter method. If one wattmeter gives zero deflection, determine the values of R and XL for a line voltage of 230 V. A. 3.2, 10 Ω C. 3.2, 9 Ω B. 5.2, 10 Ω D. 5.2, 9 Ω 835. Three equal impedances of (25 + j30) Ω are connected in wye to 240 V, 60 Hz, three-phase source. Determine the value of the capacitor to be connected in parallel with the load so that the total current drawn by the load is 3 amperes. A. 90 μF C. 70 μF B. 80 μF D. 60 μF 836. A delta-connected load draws 17.28 kW from 240-V, balanced three-phase supply. What is the resistance of the load if the reactance is equal to 5 ohms? A. 5 Ω C. 10 Ω B. 7.5 Ω D. 2.5 Ω 837. Three identical impedances of ohms are connected in star to a threephase, three-wire, 240 V system. The lines between the supply and the load have an impedance 2 + j1 ohms. Find the magnitude of the line voltage at the load. A. 123 V C. 416 V B. 240 V D. 213 V

838. A delta connected load having an impedance of (300 + j210) per phase is supplied from 480 V, three-phase supply through a line having an impedance of (4 + j8) per wire. What is the total power supplied to the load? A. 1418 W C. 454 W B. 473 W D. 1363 W 839. A certain load takes 300 kW at 400 V. A three-phase capacitor bank rated 15 kVA per phase is connected in parallel with the load to raise the power factor of the load to 90% lagging. What is the power factor of the load before correction? A. 99% C. 95% B. 92% D. 88% 840. A factory load draws 100 kW at 75% lagging power factor from a 480 V source. To increase the power factor to 90% lagging, a synchronous motor operating at 80% leading power factor is connected to the load. What is the rating of the motor if it has an efficiency of 80%? A. 54 HP C. 33 HP B. 43 HP D. 35 HP 841. A three-phase, wye-connected induction motor is connected to a 480 V, three-phase supply. It draws a current of 15 amperes at 80% power factor. A delta connected reactance is connected in parallel with the motor and the combination draws 15 amperes. What is the value of the element? A. 57.4 μF C. 28.7 μF B. 122.5 μF D. 245.0 μF 842. A three-phase balanced load is connected across 220 V, three-phase, ACB source. A wattmeter with its current coil in line A and voltage coil across liens A and B reads 800 W. The potential coil is then connected across liens A and C with the current coil in the same line. What is the power factor of the load if the meter reads -800 W? A. 0.5 lagging C. 0.87 lagging B. 0.5 leading D. 0.87 leading 843. In two-wattmeter method, the readings of the wattmeter will be identical when _____. A. load in one of the two phases is zero B. power factor is unity C. power factor is 0.5 D. neutral is earthed 844. A wye-connected, balanced three-phase load draws 75 A from 230 V, 60 Hz source. To measure the total power, two wattmeters are connected in lines A

and C and reads 8,625 W and 17,250 W, respectively. Determine the impedance of the balanced load. A. C. B. D. 845. Two wattmeters are used to measure the power drawn by a balanced threephase load from a 440 V, three-phase source. The wattmeters are connected in lines A and B and reads 10 kW and -2.5 kW. When a capacitor in parallel with the load and the wattmeters reconnected in lines B and C, the wattmeter in line B reads 7.5 kW. What is the power factor of the combined load? A. 33% C. 28% B. 50% D. 72% 846. The ratio of the readings of wattmeters connected to measure the power delivered to an inductive load is 0.75. If the load draws 75 kVA from 440-V supply, determine the impedance per phase of the delta-connected load? A. C. B. D. 847. A balanced three-phase, three-wire, 480 V supply has two loads. The first load is delta connected and takes 30 kW at 80% lagging power factor. The second load is delta connected and uses 24 kVA at 90% leading power factor. Find the readings of the two wattmeters connected in lines A and C. A. 28,940 & 22,660 W C. 30,000 & 21,600 W B. 20,400 & 31,200 W D. 32,680 & 18,920 W H. POWER FACTOR CORRECTION (3-PHASE) 848. EE Board Exam April 1989, October 1989 A three-phase, 60 Hz, 2200 volts induction motor develops 500 HP, 0.8 lagging pf and efficiency of 94%. The power factor is raised to 0.90 lagging by connecting a bank of condensers in delta across the lines. If each of the capacitance unit is built up of four similar 550 V condensers, calculate the required capacitance of each condenser. A. 77.04 μF C. 76.12 μF B. 75.42 μF D. 72.30 μF 849. EE Board Exam October 1987, October 1982 Installed in one of the customer CEPALCO are two single phase transformers each rated 75 kVA are connected V or open delta to serve a 3phase load of 120 kW at 0.8 p.f. lagging. To prevent the overloading of the transformers, determine the size of the capacitor in kVAR. A. 40 C. 39 B. 41 D. 42

850. EE Board Exam October 1983 Three single-phase transformers each rated 75 kVA are banked in delta and supplying a three-phase load drawing 160 kVA at 0.8 lagging power factor. If one transformer is removed for repairs, solve for the minimum amount in kVAR of a capacitor needed to prevent overloading of the remaining units. A. 70.32 C. 72.46 B. 73.64 D. 73.28 851. EE Board Exam October 1982 Two single-phase transformers each rated 75 kVA are connected in V or open delta to serve a 3-phase load of 120 W at 0.8 power factor lagging. Determine the size in kVAR of the capacitor needed to prevent overloading of the transformers. A. 40.25 C. 45.24 B. 41.28 D. 43.50 852. EE Board Exam October 1982 A 150 kVA transformer bank will serve a load expected to draw 135 kW at 0.80 lagging power factor. Solve for the size of the capacitor bank needed to be added in order to prevent overloading of the transformer bank. A. 32.506 kVAR C. 40.391 kVAR B. 35.866 kVAR D. 28.266 kVAR 853. EE Board Exam October 1981 A 3-phase generator has the following 3-phase loads: an inductive load drawing 400 kVA at 0.60 pf power factor and a resistive load drawing 80 kVA at 1.00 power factor. Solve for the size in kVAR of the capacitor bank needed to improve the power factor of the combined loads to 0.85 lagging. A. 120.58 kVAR C. 124.54 kVAR B. 121.68 kVAR D. 122.82 kVAR 854. EE Board Exam April 1986 A short, 3-phase, 3-wire transmission line has a receiving end voltage of 4,160 V phase to neutral and serving a balanced 3-phase load of 998.400 volt-amperes at 0.82 pf lagging. At the receiving end the voltage is 4600 V., phase to neutral and the pf is 0.77 lagging. Solve for the size in kVAR of a capacitor needed to improve the receiving end pf to 0.9 lagging maintaining 4160 V. A. 181 C. 172 B. 175 D. 178 855. REE Board Exam October 1996 A 132 kV line, three-phase system delivers 70.7 MVA of a balanced delta load of power factor 70.7%. Determine the reactance necessary in order to attain unity power factor.

A. 1,092 Ω B. 965 Ω

C. D.

1,142 Ω 1,045 Ω

856. EE Board Exam October 1980 A balanced 500 kVA, 3-phase, 440 volt, 60 Hz, inductive load operates at a pf of 75%. Determine the total capacitive kVAR required improving the pf to 95%. A. 207.46 C. 210.75 B. 176.42 D. 192.21 857. EE Board Exam October 1984 A balanced 3-phase load draws 150 A phase current at 7.5 kV phase to neutral, 0.891 power factor lagging. It is desired to raise the power factor to 0.96 leading. Solve for the amount of capacitor kVAR needed to achieve such pf. A. 2273 kVAR C. 2509 kVAR B. 2409 kVAR D. 2365 kVAR 858. EE Board Exam April 1981 A 3-phase, 3-wire, short transmission line has a resistance of 3 ohms and a reactance of 8 ohms per wire. At the receiving end, a balanced 3-phase load draws a line current of 60 A, at 13,500 volts line to line, 0.90 power factor lagging. Assuming the receiving end voltage is maintained at 13,500 V, solve for the size in kVAR of capacitors needed to raise the power factor at the receiving end to 0.95 leading. A. 1043.5 C. 1026.5 B. 1154.2 D. 1232.2 859. EE Board Exam April 1981 A three-phase balanced load draws a line current of 80 A at 0.90 lagging power factor. Solve for the minimum size in kVAR of the capacitor bank needed to raise the power factor to 0.96 leading, if the line to line voltage is 13,200 volts. A. 1310.15 C. 1247.54 B. 1338.25 D. 1430.12 860. EE Board Exam October 1990 Two Y-connected, 50° rise induction motors are fed by a 4160 V, line to line, 3-phase 60 Hz motor-control center 20 feet away. Motor 1 drives a 600-hp compressor. The efficiency of this motor is 90% and its power factor is 0.5. Instruments of motor 2 indicate 1730 kW, 277 amperes. Determine the capacity in microfarads per phase of a wye-connected bank that is required to correct the power factor of the load to 0.966 lagging. A. 172.4 μF C. 167.2 μF B. 193.8 μF D. 182.1 μF

861. EE Board Exam April 1993 A star-connected 400 HP (metric), 2000 V, 50 c/s motor works at a power factor of 0.7 lagging. A bank of mesh-connected condensers is used to raise the power factor to 0.93 lagging. Calculate the capacitance of each unit required if each is rated 500 V, 50 c/s. The motor efficiency is 85%. A. 194 μF C. 302 μF B. 225 μF D. 233 μF 862. A delta connected induction motor takes 20 kW at 0.8 pf from a 500 V 60 Hz mains. Three delta connected capacitors are used to raise the pf to 0.95. What is the capacitance of each capacitor in F? A. 22.3 F C. 29.8 F B. 28.7 F D. 38.9 F 863. A three-phase induction motor delivers 150 HP while operating at 80% efficiency and a power factor of 0.8 lagging from 480 V lines. A wye connected power factor correction capacitor is to be installed to improve the overall power factor to 0.9 lagging. Determine the capacitance required per phase. A. 428 μF C. 1283 μF B. 142.6 μF D. 3850 μF G. UNBALANCED POLYPHASE SYSTEMS 864. EE Board Exam April 1982 Given a balanced 3-wire, three-phase system serving the following loads:

Determine the current on line b A. 20.34 A C. B. 22.04 A D.

24.36 A 21.57 A

865. EE Board Exam April 1982 Given the following line voltages and two load impedances:

Solve for the current in line c. A. 17.41 A B. 17.95 A

C. D.

16.62 A 18.46 A

866. EE Board Exam April 1988 Three unequal single-phase loads so connected across the lines of a balanced, 3-phase, 230 volts circuit. The first takes 106 A at 0.78 pf lagging

and is connected across lines 1 & 2. The second takes 142 A, at 0.82 pf lagging and is connected across lines 2 & 3. And the third takes 28.4 kW at 0.77 pf lagging and is connected across lines 3 & 1. Find the three line currents. A. 254.40 A, 211.38 A, 252 A B. 231.26 A, 215.20 A, 268 A C. 254.40 A, 215.20 A, 252 A D. 231.26 A, 211.38 A, 268 A 867. EE Board Exam October 1992 A 120-V per phase, three-phase Y-connected source delivers power to the following delta-connected load:

Solve for the three line currents. A. 12.45 A, 9 A, 22.45 A B. 13.49 A, 9 A, 22.45 A C. 13.49 A, 10 A. 20.22 A D. 12.45 A, 10 A, 20.22 A 868. EE Board Exam October 1985 Given:

Solve for the three line currents Ia, Ib and Ic. A. Ia = 45 A, Ib = 43 A, Ic = 20 A B. Ia = 48 A, Ib = 42 A, Ic = 24 A C. Ia = 45 A, Ib = 42 A, Ic = 20 A D. Ia = 48 A, Ib = 43 A, Ic = 24 A 869. EE Board Exam April 1985 A three phase 230-V circuit serves two single-phase loads, A and B. Load A is an induction motor rated 8 hp, 230 V, 0.70 pf, 0.90 efficiency, which is connected across lines a and b. Load B draws 5 kW at 1.0 pf and is connected across lines b and c. Assume a sequence of a-b-c, solve for the current on line b. A. 42.19 A C. 41.08 A B. 27.74 A D. 34.46 A 870. EE Board Exam April 1980 A factory is supplied by a three-phase, 3-wire system with the following characteristics:

B. Find the line current Ib. A. 145.3 A B. 163.3 A

C. D.

184.6 A 166.5 A

871. EE Board Exam April 1988 Three unequal single-phase loads so connected across the lines of a balanced, 3-phase, 230 volts circuit. The first takes 106 A at 0.78 pf lagging and is connected across lines 1 & 2. The second takes 142 A at 0.82 pf lagging and is connected across 2 & 3. And the third takes 28.4 kW at 0.77 pf lagging. Determine total apparent power. A. 94 kVA C. 78 kVA B. 83 kVA D. 101 kVA 872. REE Board Exam October 1996 The following information is given for a delta-connected load of three numerically equal impedances that differ in power factor. Line voltage = 120 volts. , and . Phase sequence of voltages is a-b-c. Using the phase sequence as a guide, calculate the total power drawn by the load. A. 2,624 W C. 2,564 W B. 2,472 W D. 2,731 W 873. EE Board Exam April 1993 In AC circuit, find the total power in kW in an unbalanced three-phase circuit loaded as follows: Phase I = 120 V, 100 A, unity pf. Phase II = 100 V, 230 A, 80% pf and phase III = 110 V, 85 A, 77% pf. A. 37.6 kW C. 32.8 kW B. 35.3 kW D. 38.2 kW 874. EE Board Exam April 1983 Two single-phase transformers are connected in V (open delta) and serving a delta connected impedance load. Each impedance is equal to . If the transformer voltages impressed on the impedances are , , . Solve for the total kVA drawn by the load. A. 6.23 C. 10.8 B. 8.31 D. 11.3 875. EE Board Exam October 1980, October 1982 Three impedances Zan = 20 + j0, Zbn = 16 + j12, Zcn = 5 – j15 ohms, are connected in wye across a 230 V (line to line), 3-phase, 4-wire source. The phase sequence is a-b-c, counterclockwise. Determine the current passing thru the neutral. A. 7.54 A C. 8.81 A

9.12 A

D.

8.02 A

876. EE April 1981 A wye-connected transformer with neutral connection has balanced voltages of 265 V between lines and neutral. The transformer is serving two single phase motors. Motor A (rated 4 hp, 0.90 efficiency, 0.80 power factor lagging) is connected across line a and neutral. Motor B (rated 3 hp, 0.85 efficiency, 0.85 power factor lagging) is connected across line b and neutral. Solve for the neutral current, using Van as reference vector. A. 20.42 A C. 22.45 A B. 25.37 A D. 23.14 A 877. REE Board Exam October 1998 The loads of a wye connected transformer are: Ia = 10 cis (-30°); Ib = 12 cis 215°; Ic = 15 cis 82°. What is the neutral current? A. 1.04 cis 72.8° C. 0.92 cis 62.5° B. 2.21 cis (-30°) D. 3.11 cis 72.6° 878. EE Board Exam April 1980 A factory is supplied by a three-phase, 3-wire system with the following characteristics: Determine the power consumed by the load. A. 42.75 kW C. 40.23 kW B. 48.78 kW D. 45.12 kW 879. EE Board Exam April 1981 The following voltages and line currents were measured to a 3-phase, 3-wire feeder serving a commercial building: Solve for the real power in kW drawn by the commercial building. A. 402.2 C. 419.5 B. 404.5 D. 421.5 880. EE Board Exam October 1981 A 3-phase, 3-wire load draws the following line currents: , and . If the voltages impressed on the load are balanced 3-phase, having a magnitude of 4140 volts line to line, solve for the total power in kW. A. 556.16 C. 536.54 B. 506.85 D. 520.18 881. EE Board Exam October 1983

Given the following load impedances in delta and the impressed voltages as follows:

What will be the reading of the two wattmeters connected to measure total power. Use line a as the common potential point. A. 3.869 kW, 9.031 kW C. 3.125 kW, 6.778 kW B. 2.546 kW, 8.357 kW D. 4.055 kW, 9.848 kW 882. EE Board Exam October 1984 The 3-phase power supply to a factory has the following measurements:

Solve for the total power drawn. A. 60.2 kW C. B. 56.5 kW D.

58.8 kW 62.4 kW

883. EE Board Exam April 1985 A three-phase 230-V circuit serves two single-phase loads, A and B. Load A is an induction motor rated 8 hp, 230 V, 0.70 pf, 0.90 efficiency, which is connected across lines a and b. Load B draws 5 kW at 1.0 pf and is connected across lines b and c. Assume a sequence of a-b-c, solve for the total power factor of the load. A. 0.907 C. 0.864 B. 0.704 D. 0.886 884. EE Board Exam October 1987 A wound rotor motor, 7.5 HP, 230 volts, 3-phase takes a line current of 18.4 ampere, when operating at rated output at an efficiency of 88%. Calculate the indication on the wattmeter when this is inserted to measure power by the T-method. A. 3.179 kW C. 3.361 kW B. 4.401 kW D. 4.042 kW 885. EE Board Exam October 1994 A wattmeter with its current coil in line 2 and potential coil across lines 2 and 3 is connected to a balanced 3-phase system. The only load supplied is a single phase one connected to lines 1 and 2. This load is known to be inductive. If the wattmeter reads zero watts, determine the power factor of the single-phase load. A. 0.707 C. 0.800 B. 0.866 D. 0.900

886. EE Board Exam April 1984 A balanced 3-phase load draws 75 amperes line current at 230 volts line to line and 0.848 lagging power factor. If the two-wattmeter is used, solve for the readings of the two wattmeters. A. 15.32 kW, 10.02 kW C. 16.42 kW, 8.92 kW B. 17.86 kW, 7.48 kW D. 17.24 kW, 8.10 kW 887. EE Board Exam October 1980 Three equal impedances, each having a resistance of 8 ohms and an inductive reactance of 7 ohms are connected in delta to lines a, b and c of a 240 V, 3-phase, 3-wire line, phase sequence a-b-c. What is the reading of a single-phase wattmeter connected with its current coil in line a and the potential coil across lines b and c? A. 6,180 W C. 6,561 W B. 6,324 W D. 6,004 W 888. EE Board Exam October 1992 A 3-phase feeder carries two lagging balanced loads. The power observed by each is measured by two wattmeter method, giving the following readings: First Load: W1 = 160 kW W2 = 96 kW Second Load: W1 = 90 kW W2 = 48 kW What is the combined kVA load on the feeder? A. 434.68 C. 504.35 B. 462.35 D. 420.12 889. EE Board Exam October 1992 National Power Corporation used two wattmeters to measure 3-phase power of a balanced Y-connected lagging power factor motor loads. Each wattmeter indicates 15.4 kW. The voltage coils are connected across lines 2 and 3, and across lines 1 and 3, respectively. The line to line voltages are 230 volts with V12 leading V23 and the line currents are each 120 A. Calculate the total power supplied. A. 37.44 kW C. 39.67 kW B. 30.72 kW D. 34.88 kW 890. EE Board Exam April 1980 A factory is supplied by a three-phase, 3-wire system with the following characteristics: A. B.

0.934 lagging 0.908 lagging

C. D.

0.892 lagging 0.866 lagging

891. EE Board Exam October 1981 A 3-phase, 3-wire load draws the following line currents:

, and . If the voltages impressed on the load are balanced 3-phase, having a magnitude of 4140 volts line to line, solve for the power factor of the load. A. 0.976 C. 0.982 B. 0.999 D. 0.906 892. EE Board Exam April 1995 Three unequal single-phase induction motor loads are connected across the lines and neutral conductor of a balanced, 3-phase, 350 volts circuit. The line to neutral voltages is each 202 volts. The first load takes 20 kW at 0.82 power factor, the second takes 28 kW at 0.75 power factor, and the third takes 36 kW at 0.80 power factor. What is the current in the neutral conductor? A. 105.5 amps C. 125.4 amps B. 86.6 amps D. none of these 893. For an unbalanced load which connection is suitable A. 3 wire open delta B. 4 wire star connection C. 3 wire delta connection D. 3 wire star connection 894. What is the minimum number of wattmeters required for measuring power of a three phase balanced load? A. two C. one B. four D. three 895. The power is to be measured for a balanced delta connected load whose terminals cannot be opened. How many wattmeters do you need? A. four C. two B. one D. three 896. What is the minimum number of wattmeters required to measure unbalanced power for a three-phase system? A. two C. three B. four D. one 897. In two wattmeter method, the readings of the wattmeter will be identical when A. load in one of the phases is zero B. power factor is unity C. power factor is 0.5 D. neutral is earthed 898. Two wattmeters can be used to measure 3-phase for a

A. B. C. D.

balanced and unbalanced load unbalanced load only balanced load only unity power factor only

899. In 2 wattmeter method, the reading of one of the wattmeter will be zero when A. power factor is unity B. power factor is 0.5 C. load in one of the phases is zero D. a neutral wire is not provided 900. For a 3 phase unbalanced load A. the power factor of each phase will be in proportional to the load B. the power factor of each phase will be the same C. the power factor of at least one of the phase must be leading D. the power factor of each phase may be different 901. A wattmeter is installed in a balanced 3-phase system. The wattmeter will measure R Y B

A. B.

total power real power

C. D.

active power reactive power

902. A three-phase, three-wire, 240 V, CBA system supplies power a wyeconnected load with impedances of , . Find the total power. A. 1,553 W C. 1,883 W B. 2,589 W D. 2,104 W 903. A 100 V, balanced three-phase source has two single-phase loads. The first load has an impedance of (5 + jX) ohms and connected across lines A and B. The second load is connected across B and C and has an impedance of (R – j2) ohms. Determine the values of R and X, if the current in line B is A and the ratio of X to R is 1.5. A. 2 Ω, 3 Ω C. 4 Ω, 6 Ω B. 3 Ω, 4.5 Ω D. 5 Ω, 7.5 Ω 904. Three – single phase loads are connected between lines of a 280 V, balanced three phase source. The currents measured in lines B and C are:

A, component of the currents? A. A B. A

A. What is the negative sequence C. D.

A A

905. Two of the three unbalanced currents are given for an unbalanced, threephase system. Find the positive sequence of phase B current of the neutral current is A. A. A C. B. A D. A 906. The phase b voltage and the phase b current of a balanced 3-phase system are: V = 220 sin (t + 210°) and I = 10 sin (t – 180°). What is the power of the system? A. 3300 W C. 1905 W B. 5716 W D. 3810 W 907. Two voltage generators are in series. The voltage being generated are V ab = 50 sin(t - 30°) and Vbc = 100 sin(t + 60°). What is the output voltage Vac? A. 111.83 cis 33.5° C. 145.5 cis 50.1° B. 50 cis 30° D. 150 cis 30°

The two-port network is A. Non reciprocal & passive B. Non-reciprocal & active C. Reciprocal & passive D. reciprocal & active 913. If the two port network is reciprocal, then A. Z12 / Y12 = Z122 – Z11 Z12 B. Z12 = 1/Y22 C. h12 = -h21 D. AD-BC = 0 914. Two networks are cascaded through an ideal buffer. If tr1 & tr2 are the rise times of two networks, then the over-all rise time of the two networks together will be A. √ tr1 tr2 C. tr1 + tr2 B. √ (tr12 +tr22) D. (tr1 + tr2 )/ 2 915. Which one of the following combinations of open circuit voltage and Thevenin’s equivalent resistance represents the Thevenin’s equivalent of the circuit shown in the given figure?

TWO PORT NETWORKS

908. As the poles of a network shift away from the axis, the response A. remain constant C. becomes more oscillating B. becomes less oscillating D. none of these 909. The response of a network is decided by the location of A. Its zeros C. both zeros & poles B. Its poles D. neither zeros nor poles 910. The pole-zero configuration of a network function is shown. The magnitude of the transfer function will A. B. C. D.

Decrease with frequency increase with frequency Initially increase and then decreases with frequency Be independent of frequency

911. Given I1 = 2V1 + V2 and I2 = V1 + V2 the Z-parameters are given by A. 2, 1, 1, 1 C. 1, 1, 1, 2 B. 1, -1, -1, 2 D. 2, -1, 1, 1 912. The short – circuit admittance matrix of a two-port network is as shown

A. B.

1 V, 10 Ω 1 V, 1 kΩ

C. D.

1 mV, 1 kΩ 1 mV, 10 Ω

D. Symmetrical Components 916. REE Board Exam October 1998 If the loads of a wye-connected transformer are: Ia = 10 cis (-30°) Ib = 12 cis 215° Ic = 15 cis 82° What is the phase b positive sequence component? A. 13.4 cis (-32.2°) C. 12.27 cis 208.4° B. 10.2 cis 240° D. 12.27 cis (-31.6°) 917. REE Board Exam March 1998, September 2001 The three unbalanced currents are: Ia = 10 cis (-30°)

Ib = 0 Ic = 10 cis 150° Find the negative sequence current of phase a. A. 8.66 cis 30° C. -5.77 B. 5.77 cis (-60°) D. 5.77

Positive sequence current = 18.4 cis (-31.6°) Negative sequence current = 3.23 cis 168.2° Determine the phase b current. A. 18 cis 215° C. 19 cis 220° B. 15 cis 240° D. 20 cis 225°

918. EE Board Exam October 1984 Given the following currents: Ia = 60 + j0 A Ib = -36 – j48 A Ic = -48 + j36 A Solve for the negative sequence component Ia. A. 8.641 – j1.543 C. 9.751 – j1.464 B. 9.436 + j1.346 D. 8.354 + j1.034

923. REE Board Exam March 1998 The sequence components of phase a current are: Zero sequence current = 0.47 + j1.49 Positive sequence current = 18.4 cis (-31.6°) Negative sequence current = 3.23 cis 168.2° Determine the phase c current. A. 17.5 cis 91° C. 22.5 cis 82° B. 18 cis 215° D. 15 cis 100°

919. REE Board Exam October 1998 The three unbalanced currents are: Ia = 10 cis (-30°) Ib = 0 Ic = 10 cis 150° Find the zero sequence current. A. 3.33 cis 30° C. 5.77 B. 0 D. 3.33

924. EE Board Exam April 1992 Determine the symmetrical components of the line current in line ‘a’ if one of the in-phase impedance of its delta connected load connected across lines ‘ca’ is removed. The delta load with impedance of ohms per phase is supplied from a 220 volts, 60 cycle, 3-phase source. Assume a phase sequence of a-b-c. A. Ia1 = 11 A, Ia2 = 11 A, Ia0 = 0 A B. Ia1 = 7.33 A, Ia2 = 7.33 A, Ia0 = 7.33 A C. Ia1 = 22 A, Ia2 = 22 A, Ia0 = 22 A D. Ia1 = 25.4 A, Ia2 = 12.7 A, Ia0 = 0 A

920. EE Board Exam October 1984 Given the following currents: Ia = 60 + j0 A Ib = -36 – j48 A Ic = -48 + j36 A Solve for the zero component of Ia. A. 10 + j4 C. -8 – j4 B. 8 – j6 D. 12 – j6 921. REE Board Exam October 1997 The sequence currents of phase a current are as follows: Zero sequence current = Positive sequence current = Negative sequence current = Determine the phase a current. A. C. B. D. 922. REE Board Exam October 1998 The sequence components of phase a current are: Zero sequence current = 0.47 + j1.49

925. EE Board Exam April 1991 A star-connected balanced load takes 75 A from a balanced 3-phase, 4-wire supply. If the two supply lines of the fuses are removed determine the symmetrical components of the lines after the fuses are removed. A. I1 = 25 A, I2 = 25 A, I3 = 25 A B. I1 = 25 A, I2 = 50 A, I3 = 0 A C. I1 = 75 A, I2 = 75 A, I3 = 75 A D. I1 = 75 A, I2 = 0 A, I3 = 0 A 926. REE Board Exam September 2000 If the loads of a wye-connected transformer are: Ia = 10 cis (-30°) Ib = 12 cis 215° Ic = 15 cis 82° Find the positive sequence component of phase a current. A. 13.4 cis (-32.2°) C. 12.27 cis 208.4° B. 10.2 cis 240° D. 12.27 cis (-31.6°) 927. The method of symmetrical components is very useful for

A. B. C. D.

solving unbalanced polyphase circuits analyzing the performance of 3-phase electrical machinery calculating currents resulting from unbalanced faults all of the above

928. An unbalanced system of 3-phase voltages having RYB sequence actually consists of A. a positive-sequence component B. a negative-sequence component C. a zero-sequence component D. all of the above 929. The zero-sequence component of the unbalanced 3-phase system of vectors VA, VB and VC is of their vector sum. A. one-third C. two-third B. one-half D. one-fourth 930. In the case of an unbalanced star-connected load supplied from an unbalanced 3-, 3 wire system, load currents will consists of A. positive-sequence components B. negative-sequence components C. zero-sequence components D. only A and B 2

931. In symmetrical components, what is the vector sum of 1 + a + a ? A. 1 C. -1 B. 0 D. infinity 932. REE Board Exam October 1997 The sequence currents of a three phase current are: Zero sequence current = 14.13 cis 17.34° Positive sequence current = 708.26 cis (-31°) Negative sequence current = 2.98 cis 10.06° Determine the phase a current. A. 720 cis (-30°) C. 710 cis 88° B. 730 cis (-15.2°) D. 695 cis 15.2° 933. REE Board Exam April 2001 The three unbalanced currents are: Ia = 10 cis (-30°) Ib = 0 Ic = 10 cis 150° Find the phase B positive sequence current. A. 8.66 A C. 5.77 A B. 5.77 cis 240° A D. 8.66 cis 120° A

934. REE Board Exam September 2002 The phase currents of a three-phase system are: Ia = 100 cis 0° Ib = 80 cis 240° Ic = 91.8 cis 130.9° Find the zero sequence current. A. 90.23 cis 3.68° A B. 270.7 cis 3.68° A C. 34.68 cis (-30.24°) A D. none of the above 935. Given three unbalanced three-phase voltages: Va = 150 + j0 V Vb = -90 – j120 V Vc = -120 + j90 V Determine Va1 A. 142.43 + j12.35 B. 135.32 – j 1.34 C. 145.62 + j13.66 D. 140.23 – j9.32 936.

A. B.

C. D.