Et(gautam)

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ET - 2nd MID -

-

JNTU ONLINE EXAMINATIONS [Mid 2 - ET]

1.

Which of the following determines the direction of the induced emf in the stator just before it begins rotate? a. Fleming's right hand rule b. Kirchoff's law c. Lenz's law d. Ohm's law

2.

The rotating field caused by the stator current induces EMF in the rotor by a. Transformer action b. DC machine action c. Synchronous machine action d. AC machine action

3.

Induction motor works on the principle of a. Mutual induction b. Ampere's law c. Lenz's law d. Ohm's law

4.

The magnitude of rotating magnetic field is equals to a. 1.5 X maximum flux density b. 3X maximum flux density c. 2 X maximum flux density d. Maximum flux density

5.

The rotor speed of induction motor is always slightly a. Less than synchronous speed b. More than synchronous speed c. Less than slip speed d. More than slip speed

6.

The operating speed of induction motor never be equal to a. Synchronous speed b. Slip speed c. Stator speed d. Speed of magnetic field

7.

The induction motor draws balanced three phase current, when it is connected across a a. Balanced three phase ac supply b. Balanced single phase ac supply c. Balanced three phase dc supply d. Balanced dc supply

8.

The direction of rotation of rotating magnetic field gets reversed, when a. Interchanging any two terminals of stator windings b. Interchanging any three terminals of stator windings c. Interchanging any two terminals of rotor windings d. Applying supply voltage to rotor windings

9.

The magnitude of rotating magnetic field is a. Constant b. Not constant c. Varying d. Rotating

10.

An a. b. c. d.

Induction motor is Self-starting with low torque Self-starting with zero torque Self-starting with high torque Non- Self starting

11.

The skewed at a desired angle of the rotor slots in squirrel cage induction motor results a. uniform torque and avoid magnetic locking b. non uniform torque and avoid magnetic locking c. uniform torque and magnetic locking

ET - 2nd MID -

d.

-

non uniform torque and magnetic locking

12.

The skewed at a desired angle of the rotor slots in squirrel cage induction motor results a. Reduce humming noise b. increase humming noise c. Non uniform torque d. un avoid magnetic locking

13.

The coil wound rotor must be wound for the same number of poles as that of a. stator b. rotor c. armature d. field

14.

The rotor winding of a squirrel cage induction motor is a. solid un insulated conductors b. similar to the stator winding c. solid insulated conductors d. laminated base conductors

15.

The starting torque of three-phase slip ring induction motor is high because a. Rotor is phase wound b. Rotor resistance is low c. Rotor resistance is zero d. Rotor has short - circuited

16.

The number of slip rings on a squirrel cage induction motor is usually a. Zero b. Two c. Three d. Four

17.

The windings of wound rotors are similar to a. stator windings b. rotor windings c. armature winding d. field winding

18.

The rotor of the squirrel cage induction motor is also called a. Short circuited rotor b. Open circuited rotor c. Open ended rotor d. Stationary rotor

19.

In a. b. c. d.

20.

The three phase winding on the rotor of slip ring induction motor is connected in a. Star b. Delta c. Series d. Parallel

21.

The speed near to the synchronous speed the torque-speed and torque-slip curves are approximately a. Straight line b. Parabola c. Hyperbola d. A curve

22.

The maximum torque in an induction motor depends on a. Square of the supply voltage, frequency, rotor reactance b. Square of the supply current, frequency, rotor reactance c. Square of the supply voltage, frequency, rotor resistance d. Square of the supply current, rotor reactance

a squirrel cage induction motor, the stationary current is 5 to 7 times the rated current Equal to the rated current Double the rated current Half the rated current

ET - 2nd MID -

-

23.

For a slip greater than 0.1 Pu, torque T varies inversely as a. slip b. rotor resistance c. stator resistance d. rotor reactance

24.

The maximum running torque is a. Independent of rotor resistance b. Dependent of rotor resistance c. Dependent on slip d. Independent of rotor frequency

25.

The maximum torque is also called a. Pull-out torque b. Starting torque c. Running torque d. Stator torque

26.

In a. b. c. d.

27.

The torque T developed by induction motor is directly proportional to a. slip, for lower values of S b. slip for higher values of S c. rotor resistance d. stator resistance

28.

The condition for the maximum torque occurs when the slip is equal to a. ratio of rotor resistance and leakage reactance b. ratio of leakage reactance to rotor reactance c. rotor resistance d. leakage reactance

29.

The torque is zero, when a. Slip is zero b. Slip is unity c. Slip is infinity d. Slip is 0.5

30.

The value of the maximum torque is independent of a. rotor resistance b. stator resistance c. rotor reactance d. leakage reactance

31.

The power developed at the shaft is equal to a. Difference of gross mechanical power and mechanical losses b. Difference of input power and output power c. Difference of input power and mechanical power d. Difference of input power and mechanical losses

32.

A 420v, 50Hz, 6-pole, 3- phase induction motor has rotor power input of 80kw. The slip is 3.3 %, then the mechanical power developed is a. 77.33kw b. 154.66kw c. 2.64kw d. 26.4kw

33.

The power input to a 6-pole, 3-Ø, 50Hz induction motor is 40kw. Stator loss is 11kw, and the slip is 45. Then the rotor copper losses are a. 1.56kw b. 1.6kw c. 15.6kw d. 16kw

34.

The rotor core loss is negligible, because

case of induction motor the torque is Directly proportional to slip Inversely proportional to slip Directly proportional to square of the slip Inversely proportional to square of the slip

ET - 2nd MID -

a. b. c. d.

-

The frequency of rotor current is small under running conditions The frequency of rotor current is high under running conditions The frequency of stator current is small under running conditions The frequency of stator current is high under running conditions

35.

The power factor of three - phase induction motor at no - load is a. 0.1 b. 0.5 c. 0.6 d. Unity

36.

In a. b. c. d.

37.

The slip of the induction motor is also defined as the ratio of a. Rotor copper loss to rotor input b. Rotor input to rotor copper loss c. Air gap power to rotor input d. Stator copper loss to rotor input

38.

The fractional slip of an induction motor is the ratio of a. Rotor copper loss to rotor input b. Stator copper loss to stator input c. Rotor copper loss to rotor output d. Rotor copper loss to stator copper loss

39.

The input power to the rotor is usually called a. Air gap power b. input power c. out put power d. mechanical power

40.

In a. b. c. d.

41.

In case of star- delta starter, the voltage applied across the winding is a. 1/ times the line voltage

an induction motor the core losses occur mainly in Stator core Armature core Slip rings Brushes

induction motor, the maximum efficiency occurs, when Variable losses equal to constant losses Variable losses are equal to zero Constant losses are equal to zero The total losses equal to zero

b. c. d. 42.

times the line voltage 3 times the line voltage 1/3 times the line voltage

In case of star- delta starter, the starting torque is a. 1/3 times the full-load torque b. 1/ times the full-load torque c. d.

3 times the full-load torque

43.

In a. b. c. d.

case of induction motor, the starting current drawn from the supply is about Four to seven times the full-load current Ten to twelve times the full load current Four to seven times the no load current Ten to twelve times the no load current

44.

In case of auto transformer starting transformation ratio K=1/

times the full-load torque

starting method corresponds to a. Star-delta starting b. DOL starting c. Resistance starter d. Rotor resistance starter 45.

The rotor resistance starter reduces

, this

ET - 2nd MID -

a. b. c. d.

-

The magnitude of starting current The magnitude of applied voltage The magnitude of starting speed The magnitude of starting torque

46.

The induction motor is a a. Self starting motor b. Not self starting motor c. Coupled to other drive d. Coupled to other drive

47.

The Rotor resistance starter improves the a. Starting power factor b. Starting current c. Starting voltage d. Starting resistance

48.

The three-phase induction motors up to 5hp can be started by a. Direct on line starter b. Star-delta starter c. Auto transformer starter d. Resistance starter

49.

The star- delta starter is used for a. Squirrel-case Induction motor b. Slip-ring Induction motor c. Phase-wound Induction motor d. Double cage Induction motor

50.

n an squirrel cage induction motor, the starting torque is very low because a. The rotor resistance is small b. The rotor reactance is small c. The rotor resistance is high d. The rotor reactance is high

51.

The salient pole construction is employed for synchronous machines having a comparatively a. Low output and slow speeds b. Large output and slow speeds c. Low output and high speeds d. Large output and high speeds

52.

Three-phase alternators are usually star connected a. To save on copper b. To reduce windage losses c. To reduce conductor size d. To obtain higher terminal voltage

53.

The stator of alternator is made of high permeability laminated steel stampings in order to reduce a. Hysterisis and eddy current losses b. Copper losses c. Mechanical losses d. Friction and wind age losses

54.

The salient type rotor is also called a. Projected type b. Cylindrical type c. Conical type d. Spherical

55.

The function of the winding on the rotor of an alternator is a. To produce flux in the air gap b. To produce torque in the air gap c. To produce induced EMF in the air gap d. To produce current in the air gap

56.

The non-salient type rotor is also called a. Cylindrical type b. Projected type c. Conical type

ET - 2nd MID -

d.

-

Spherical type

57.

The rotor of alternator is constructed from laminated high permeability steel in order to reduce a. Eddy-current losses b. Hysterisis losses c. Copper losses d. Friction and wind age losses

58.

The coupling between the electric and mechanical systems is through the medium of a. Electromagnetic field b. Electric field c. Mechanical field d. Electrostatic field

59.

In a. b. c. d.

60.

The speed of a 4-pole 60Hz synchronous machine will be a. 1800rpm b. 1500rpm c. 3000rpm d. 3600rpm

61.

The number of cycles of the induced EMF depends on a. The number of poles b. Number of conductors c. Number of slots d. Number of rotations

62.

The integral number of slots per pole is often used in order to eliminate a. Harmonics in the wave form b. Copper loss c. Core loss d. Friction and wind age loss

63.

An a. b. c. d.

64.

Synchronous generators are used to generate a. Only alternating current b. Only direct current c. Both alternating and direct current d. Either alternating and direct current

65.

The EMF generated in an alternator is a. Average value b. Maximum value c. RMS value d. Virtual value

66.

In a. b. c. d.

67.

EMF generated in an alternator depends upon a. Flux per pole, no. of conductors b. Slip and no. of conductors c. Slip and rated speed d. Flux per mole and rated speed

68.

a rotary machine the purpose of an air gap is to Reduce the mmf required Provide a path for the flux Allow for rotation of the rotor Improve the reluctance

exciter is nothing but a DC shunt generator DC series motor DC shunt motor DC series generator

a Non-salient pole machine The rotor is cylindrical and air gap is uniform The rotor is cylindrical and air gap is non-uniform The rotor is Non-cylindrical and air gap is uniform The rotor is Non-cylindrical and air gap is non-uniform

In an alternator

ET - 2nd MID -

a. b. c. d.

-

The conductors are stationary and field is rotating The conductors are rotating and field is also rotating The conductors are stationary and field is also stationary The conductors are rotating and field is stationary

69.

The alternators work on the principle of a. Electromagnetic induction b. Electrostatic induction c. Lenz's law d. Ampere's law

70.

Alternator will convert a. Mechanical energy into electrical energy b. Electrical energy into Mechanical energy c. Mechanical energy into rotating energy d. Mechanical energy into heat energy

71.

Turbo-alternators are generally used to turn at a. 3000rpm b. 1500rpm c. 5000rpm d. 15000rpm

72.

The open type of slots are preferable for use in alternators because a. They easily accommodate the winding b. Their use is less costlier c. They provide wave form d. Their use gives uniform flux distribution

73.

The salient pole type of alternator is also called a. Projected pole type b. Non-salient type c. Cylindrical type d. Un projected type

74.

Salient pole alternators are generally used on a. Low and medium speed prime movers b. Low voltage alternators c. Hydrogen cooled prime movers d. High speed prime movers

75.

In a. b. c. d.

76.

The cylindrical type of alternator is also called a. Non-salient type b. Salient type c. Projected pole type d. Un projected type

77.

Salient pole alternations are used, when a. The speed of the alternator is low b. The power required is large c. The speed of the alternator is high d. The voltage to be generated is high

78.

The advantage of cylindrical type rotor of an alternator is a. Low wind age losses and better balance b. Low copper losses and better balance c. Smooth operation and low core losses d. Less air friction and low variable losses

79.

The rotor preferred for alternators applied to hydraulic turbines are a. Salient pole type b. Cylindrical pole type c. Solid rotor type

a Non-Salient pole machine, the rotor is Cylindrical and air gap is uniform Cylindrical and air gap is non-uniform Non-Cylindrical and air gap is uniform Non-Cylindrical and air gap is non-uniform

ET - 2nd MID -

d.

-

Non-salient type

80.

The cylindrical rotor machines have always a. Horizontal configuration b. Vertical configuration c. Both Horizontal and Vertical configurations d. Either Horizontal or Vertical configurations

81.

In a. b. c. d.

which coil the harmonic component of the generated EMF will be more? Full pitch coil Short pitch coil Long pitch coil Same in all coil

82.

In a. b. c. d.

an alternator, if the air gap flux density is non-sinusoidal, then the EMF generated contains Harmonics Composite wave form of voltage and current Only current wave form Only voltage wave form

83.

By to a. b. c. d.

distributing the winding of an alternator into number of slots, the generated EMF can be made

84.

In a. b. c. d.

an alternator the resultant EMF per turn will be Twice the EMF induced in a conductor Equals the EMF induced in a conductor Half the EMF induced in a conductor Thrice the EMF induced in a conductor

85.

To a. b. c. d.

generate sinusoidal EMF's, the special flux distribution in the air gap must be sinusoidal Rectangular Triangular Elliptical

86.

In a. b. c. d.

an alternator the average EMF per phase is equal to 4.44 f Ø T volts 4.44 B T volts 4.44 f B volts 4.44 f T

87.

The EMF equation of an alternator( if the winding for each phase under each pole is distributed) is a. 4.44 f Ø T kc k d volts b. c. d.

Reduce Increase No change Reduce or increase

4.44 f Ø T volts 4.44 f Ø T k c volts 4.44 f Ø T kd volts

88.

A 4 pole, 1500rpm alternator will generate EMF at the frequency of a. 50 Hz b. 60 Hz c. 40 Hz d. 25 Hz

89.

If a. b. c. d.

the speed of alternator is increased the EMF generated will Increase Decrease Remains same No change

90.

In a. b. c.

an alternator, the EMF generated is due to Rate of change flux linkages Transformer action Relative motion between conductors and the field

ET - 2nd MID -

d.

-

Electro static induction

91.

The pitch factor is defined as the ratio of the voltage generated in a a. Short pitch coil to the voltage generated in a full pitch coil b. Long pitch coil to the voltage generated in a full pitch coil c. Short pitch coil to the voltage generated half pitch coil d. Long pitch coil to the voltage generated half pitch coil

92.

The advantage of a full-pitched coil span is that it provides a. Higher generated EMF b. Lower armature current c. Lower terminal current d. Higher full-load current

93.

The winding factor is equal to a. Product of distribution and power factors b. Ratio of distribution and power factors c. Ratio of power and distribution factors d. Sum of distribution and power factors

94.

The coil span is defined as a. The separation between coil sides of the same coil b. Separation between two consecutive coils c. Separation between coil ends of the same coil d. Separation between coil ends of different coils

95.

For short pitch and distributed winding, coil span factor and distribution factor are always a. Less than unity b. Greater than unity c. Equals to unity d. Equals to zero

96.

The short-pitched coil means a. The coil span is less than full pitch b. The coil span is less than half pitch c. The coil span is less than quarter pitch d. The coil span is equal to full pitch

97.

Short-pitched coils are employed to a. Save conductor material and reduce high frequency harmonic content b. Save conductor material and increase high frequency harmonic content c. Increase overhang d. Improve the wave form of the generated phase voltage

98.

The voltage generated in a full pitch coil is equal to a. Twice the coil side voltage b. Thrice the coil side voltage c. Coil side voltage d. Half the coil side voltage

99.

The breadth factor is also named as a. Distribution factor b. Pitch factor c. Power factor d. Loss factor

100.

The distribution factor is always a. Less than unity b. Greater than unity c. Equals to unity d. Equals to zero

101.

In a. b. c. d.

102.

In case of synchronous impedance method the synchronous impedance determined at short

synchronous impedance method, the armature reaction effect is replaced by Equivalent voltage drop Equivalent mmf Equivalent reactance drop Equivalent resistance drop

ET - 2nd MID -

-

circuit condition is too large due to a. Low degree of saturation b. High degree of saturation c. Medium degree of saturation d. No saturation 103.

The synchronous impedance method can be used for a. Very high capacity alternators b. High capacity alternators c. Low capacity alternators d. Medium capacity alternators

104.

The synchronous reactance of an alternator a. Equivalent reactance representing the armature reaction and leakage reactance b. A false reactance c. A reactance which is fictitious d. Equivalent leakage reactance

105.

The regulation obtained by synchronous impedance method is generally a. Higher than the actual value b. Lower than the actual value c. Equal to actual value d. equal to zero

106.

The synchronous impedance method is used to determine a. Regulation of cylindrical rotor synchronous machine b. Regulation of salient pole synchronous machine c. Regulation of projected type synchronous machine d. Regulation of DC machine

107.

The synchronous impedance method is a. Pessimistic method b. Optimistic method c. Equality method d. Used for salient pole machines

108.

The synchronous impedance method is also called a. EMF method b. Ampere method c. MMF method d. Zero power factor method

109.

When there is no saturation, the synchronous impedance is a. Constant b. Reduces c. Increases d. Varies

110.

The synchronous impedance varies with a. Load and power factor conditions b. Only load conditions c. Only power factor conditions d. Terminal voltage conditions

111.

The open circuit characteristics of an alternator resembles a. B-H curve of magnetic material b. B-H curve of insulating material c. Speed torque characteristics of DC motor d. Load characteristics of DC generator

112.

The following test results are not affected by the variation in the speed of an alternator a. Short circuit test b. Open circuit test c. Short circuit and Open circuit tests d. Synchronous impedance method

113.

The synchronous impedance of an alternator is high at a. Lower excitations b. Higher excitations

ET - 2nd MID -

c. d.

-

Zero excitation Very high excitations

114.

The synchronous impedance of an alternator is low at a. Higher excitations b. Lower excitations c. Zero excitation d. Very low excitations

115.

The regulation of an alternator can be predetermined by conducting a. Open circuit and short circuit tests b. Open circuit test only c. Short circuit test only d. Load test

116.

The open circuit and short circuit tests are performed on a three-phase generator to determine a. Synchronous reactance b. Synchronous resistance c. Field resistance d. Field reactance

117.

The open circuit characteristic is plotted with a. Field current Vs phase voltage b. Field current Vs Line voltage c. Field current Vs phase current d. Field current Vs line current

118.

The short circuit characteristics of an alternator is a a. Straight line b. Parabola c. Hyperbola d. Semi-circle

119.

The magnetization characteristic of the generator is also called as a. Open circuit characteristics b. Short circuit characteristics c. Load characteristics d. Starting characteristics

120.

The short circuit ratio is a. Inversely proportional to the synchronous reactance b. Directly proportional to the synchronous reactance c. Inversely proportional to the synchronous resistance d. Directly proportional to the synchronous resistance

121.

The single-phase induction motors are not self-starting, because a. There is no relative motion between the stator and motor magnetic fields b. The magnitude of the flux produced in stator is low c. No voltage is induced in the rotor circuit d. Zero magnetic flux in rotor

122.

In a. b. c. d.

123.

The backward rotor slip in an induction motor is equal to a. (2-S) b. (1-S) c. S d. (S-1)

124.

In a. b. c. d.

case of double revolving field theory, a field can be resolved into two equal fields Rotating in opposite directions with equal angular velocities Rotating in same directions with equal angular velocities Rotating in opposite directions with unequal angular velocities Rotating in same directions with unequal angular velocities

case of single coil carrying an alternating current, the flux in air gap is Pulsating Rotating Constant Revolving

ET - 2nd MID -

-

125.

Single phase induction motor has no self- starting because a. The transformer EMF is induced in the rotor at stand still producing zero net torque b. Stator flux is pulsating c. No revolving field in the rotor d. No EMF induced in the motor

126.

The starting characteristics of single phase induction motors are described qualitatively by a. Double revolving field theory b. Rotating field theory c. Static field theory d. Magnetic field theory

127.

In case of single phase induction motor the torque produced by the forward and backward fields are a. Equal and opposite b. Equal c. Unequal and opposite d. Unequal

128.

The speed of rotation of the two magnetic fields is a. 120 f/p b. 240f/p c. 120p/f d. 240 p/f

129.

The torque developed by a single phase motor at starting is a. Zero b. More than the rated torque c. Less than the rated torque d. Rated torque

130.

The single-phase induction motor operate at a. Low power factor b. High power factor c. Unity power factor d. Medium power factor

131.

The single phase induction motor used in ceiling fan and table fan is a. Capacitor start and run motor b. Capacitor start motor c. Capacitor run motor d. Split phase motor

132.

If a. b. c. d.

133.

The capacitor start motors produce a. Very high starting torque b. Low starting torque c. Minimum starting torque d. Starting torque is zero

134.

In a. b. c. d.

135.

The capacitor in the starting winding of the single phase induction motor improves a. The power factor b. The starting current c. The starting voltage d. The starting reactance

136.

The main advantages of a capacitor run motor is a. It not only provides starting torque and also improves the power factor

the capacitor of a single phase motor is short circuited The motor will not start The motor will burn The motor will run in reverse direction The motor will run in the same direction at reduced rpm

case of capacitor start and capacitor run motors Capacitor remains in the circuit permanently Capacitor remains in the circuit temporarily Inductor remains in the auxiliary winding Resistor remains in the auxiliary winding

ET - 2nd MID -

-

b. c. d.

It is cheap It provides the starting torque It is easy to manufacture

137.

In a. b. c. d.

case of capacitor start single phase induction motor A capacitor of high value is only used for starting A capacitor of low value is only used for starting A capacitor of high value is only used for improving power factor A capacitor of low value is only used for improving power factor

138.

The stator winding of single phase induction motor is also called a. Main winding b. Auxiliary winding c. Starting winding d. Rotor winding

139.

The auxiliary winding of single phase induction motor is also called a. Starting winding b. Main winding c. Rotor winding d. Stator winding

140.

In case of capacitor start induction motors the phase difference between main current and starting current a. Almost 900 b. Less than 600 c. Equal to zero d. Between 200 to 40 0

141.

The A.C. servo motor is basically a. Two-phase induction motor b. Single phase induction motor c. Three phase induction motor d. DC motor

142.

In a. b. c. d.

143.

The main difference between a control transmitter (CX) and a control transformer (CT) is a. Electrical angle is different in addition to the air gap being uniform b. Air gap is less in the case of CT c. Air gap is more or less uniform in the case of a CT d. Electrical angle is different

144.

Permanent magnet tachometers are a. Compact, efficient and reliable b. Bulky, efficient and reliable c. Compact, low efficient and reliable d. Compact, efficient and non-reliable

145.

In a. b. c. d.

DC Tachometer, the high inertia of the rotor can be reduced by Iron less rotor Iron rotors Iron less stator Iron stator

146.

AC a. b. c. d.

serve motors are best suited for Low power applications High power applications Medium power applications Very high power applications

147.

Servo motors work on the principle of a. Transformer b. An induction motor

case of photo electric tachometer the number of pulses generated depends up on The number of holes in the disc and speed The speed only The applied voltage The input power

ET - 2nd MID -

-

c. d.

Lenz's law Ampere's circuit law

148.

In a. b. c. d.

servo system the output is A mechanical variable, like position, velocity or acceleration An electrical variable, like voltage, current or power An electrical variable, like, charge, flux or resistance A mechanical variable, like length, time or precision

149.

Ac a. b. c. d.

servo motors are not suited for High power applications Low power applications Very low power applications Medium low power applications

150.

An electro mechanical unit which generates an electrical output proportional to the speed of the shaft is called a. Tachometer b. Servo motor c. Synchro d. Single phase commutator motor

151.

A machine has a distributed 3-phase winding on stator and a Two-pole single phase winding on rotor is called a. Synchro b. Ac servo motor c. Dc motor d. Induction motor

152.

The holding torque of the stepper motor a. Increases with the exciting current b. Decreases with the exciting current c. Increases with the speed d. Decreases with the voltage

153.

The synchros are a. Self - Synchronizing machines b. Dc machines c. Induction machines d. Static machines

154.

The motor used in computer printers is a. Stepper motor b. Dc shunt motor c. Dc series motor d. Induction motor

155.

The motors used for adding and subtracting rotary speeds are a. Synchros b. Tacho generators c. Dc motors d. Ac motors

156.

A stepper motor a. Does not rotate continuously b. Does rotate continuously c. Runs at very high speeds d. Runs at very low speeds

157.

The following motor is an incremental motion motor a. Stepper motor b. Induction motor c. Dc motor d. Ac motor

158.

The stepper motor is a special type of a. Synchronous motor b. Dc motor c. Hysterisis motor

ET - 2nd MID -

d.

-

Repulsion motor

159.

A synchro is a. Miniature Dc machine b. Miniature Ac static machine c. Miniature Ac induction machine d. Miniature Ac Dynamic

160.

The synchros are used for a. Error detection b. servo mechanism for voltage Transmission c. Rotating speeds d. current detection

161.

The frequency of two phase AC servo motors varies from a. 50 Hz to 400 Hz b. 1 Hz to 50 Hz c. 400 Hz to 700 Hz d. 700 Hz to 1000 Hz

162.

The following motor have the slope of Torque- Speed characteristic is negative a. Ac servo motor b. Dc motor c. Induction motor d. Synchronous motor

163.

The servo motor has characteristic of a. High torque at all speeds including zero speed b. low torque at all speeds including zero speed c. Medium torque at all speeds including zero speed d. No torque at all speeds including zero speed

164.

The torque- speed characteristic of Ac servo motor is a. Linear b. Non- Linear c. Parabolic d. Hyperbola

165.

The servo motors consume power from a. A fraction of watt up to a few 100watts b. A fraction of watt up to a 1 watt c. 1000 watts to 1 mega watt d. 100 watts to 1000walts

166.

The Ac servo motors are working on the principle of a. Induction motor b. Synchronous motor c. Dc motor d. Transformer

167.

The servo motors are a. Able to reverse directions quickly b. Not able to accelerate quickly c. Not able to decelerate quickly d. Over heat at stand still

168.

The control winding in case of AC servo motor is excited by a. Variable voltage b. Fixed voltage c. High voltage d. Low voltage

169.

In case of AC servo motor the phase angle between the voltage applied to control winding and voltage applied to the reference winding is a. 900 b. 180 0 c. 270 0 d. 360 0

ET - 2nd MID -

-

170.

The Ac servo motor does a. Not require brushes and slip rings b. Require brushes and slip rings c. Not require main winding d. Require control winding only

171.

The main function of damping torque in an indicating measuring instrument is a. To bring the pointer to rest quickly b. To make pointer move quickly c. To slow down the movement of pointer d. To keeps on moving the pointer

172.

In a. b. c. d.

case of recording instruments the drum rotates Very slowly perpendicular to the direction of pointer Very fastly perpendicular to the direction of pointer Very slowly along the direction of pointer Very fastly along the direction of pointer

173.

If a. b. c. d.

there is no controlling torque the pointer Deflects continuously with out stoppage deflects continuously with stoppage Does not deflect Deflects in stepped manner

174.

The integrating instruments consists of a. Registering mechanism b. Pointer c. Inked pointer d. Graph sheet

175.

The essential requirements of measuring instruments are a. Controlling, deflecting and damping torques b. Controlling and deflecting torques c. Deflecting and damping torques d. Breaking torque

176.

The absolute instruments are also called as a. Standard instruments b. Substandard instruments c. Commercial instruments d. Secondary instruments

177.

Tangent galvanometer is a a. Absolute instrument b. Secondary instrument c. Substandard instrument d. Commercial instrument

178.

The standard instruments are used to a. Calibrate secondary instruments b. Calibrate absolute instruments c. Calibrate angle of deflection d. Calibrate number of turns

179.

The secondary instruments are also called as a. Substandard instruments b. Standard instruments c. Absolute instruments d. Tangent galvano meter

180.

The instruments which indicate the values at that instant are called a. Indicating instruments b. Integrating instruments c. Recording instruments d. Absolute instruments

181.

In moving coil type an iron core is placed in the air gap of the coil to a. Increase flux density b. Decrease flux density

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c. d.

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Increase current density Decrease current density

182.

The moving coil instruments possess a. High torque and weight ratio b. Low torque and weight ratio c. High weight and torque ratio d. Low weight and torque ratio

183.

In a. b. c. d.

184.

The dynamometer type of moving coil instruments are used for a. Both Ac and Dc measurements b. Ac measurements c. Dc measurements d. Steady state measurements

185.

The moving coil instruments have a. No hysterisis loss b. No eddy current loss c. No mechanical loss d. No copper loss

186.

In a. b. c. d.

moving coil instruments the control torque in produced by Hair springs Eddy currents Iron core magnets Air gap

187.

In a. b. c. d.

moving coil instruments the damping torque is produced by Eddy currents Hair springs Iron core Air gap

188.

In a. b. c. d.

moving coil instruments the deflecting torque is proportional to current proportional to voltage proportional to energy proportional to flux density

189.

The moving coil instruments can not be used for a. Ac measurements b. Dc measurements c. Both Ac and Dc measurements d. steady state measurements

190.

The following instruments have uniform scale a. Moving coil b. Moving iron c. Attraction type moving iron d. Repulsion type moving iron

191.

In a. b. c. d.

moving iron instruments the readings are higher for descending values is mainly due to Hysterisis loss Stray fields Copper loss Eddy current loss

192.

In a. b. c. d.

moving iron instruments the readings are lower for ascending values is mainly due to Hysterisis loss Stray fields Copper loss Eddy current loss

moving coil instruments the deflecting torque is Hair springs Eddy currents Iron core air gap

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193.

In a. b. c. d.

case of moving iron instruments the defecting torque is Proportional to square of the current Proportional to the current Inversely to the square of the current Inversely to the current

194.

In a. b. c. d.

case of moving iron instruments the controlling torque is Proportional to Sinθ Proportional to Cosθ Inversely to Sinθ Inversely to Cosθ

195.

In a. b. c. d.

moving iron instruments changes of frequency produce Change in eddy currents Change in hysterisis currents Change in load currents Change in magnetic currents

196.

In a. b. c. d.

case of moving iron instruments scale is not uniform Scale is uniform Scale is zig - zag Scale is circular

197.

In a. b. c. d.

case of moving iron instruments Soft iron moves in the magnetic field Coil moves in the magnetic field Soft iron moves in the electric field Coil moves in the electric field

198.

The power consumption is higher in a. Moving iron instruments b. Moving coil instruments c. Electro - magnetic instruments d. Dynamometer instruments

199.

The moving iron instruments can be used to a. Both DC and AC measurements b. AC measurements only c. DC measurements d. Flow measurements only.

200.

In a. b. c. d.

moving iron instruments the changes of frequency produce Change in impedance of the coil Change in resistance of the coil Change in conductance of the coil Change in resonance frequency of the coil

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