Electrical And Electronics Engineering

Set No.1

Code No: RR12302

I B.Tech. Regular Examinations, June -2005 ELECTRICAL AND ELECTRONICS ENGINEERING (Bio-Technology) Time: 3 hours Max Marks: 80 Answer any FIVE Questions All Questions carry equal marks ????? 1. (a) State RMS value of a voltage waveform and find the RMS value and crest factor of the waveform v(t) of figure.1 below

Figure 1: (b) What is potential difference? (c) An electric heater takes 3KW at 240 volts. Calculate the current and resistance of the heating element. 2. (a) Why is the core of the transformer laminated? (b) What are the various losses in a transformer? And how do these losses vary? (c) A single phase 50HZ transformer has 100 turns on the primary and 400 turns on the secondary. The cross sectional area of the core is 250 cm2 . The primary winding is connected to 230 volts. Determine i. E.M.F induced in the secondary winding. ii. The maximum value of the flux density in the core. 3. (a) Shown that for circuit show in the figure 2 below, the output voltage is 5V when either V1 or V2 or both is 5V. Assume the ideal behaviour of the diode. (b) Determine Vo and ID for the networks shown in the figure 3. 4. (a) A full wave bridge rectifier is fed with 220v, 50Hz, through a step-down transformer of turns ratio 11:1. Assuming ideal diode find the i. d.c. output voltage ii. peak inverse voltage iii. Rectifier efficiency. The load resistance is 100Ω. (b) What is ripple factor? Show that the ripple factor for full wave rectifier is 0.482. 5. (a) Compare the merits and drawbacks of FET and BJT. 1 of 2

Set No.1

Code No: RR12302

Figure 2:

Figure 3:

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Set No.1

Code No: RR12302 (b) Sketch the basic structure of an n-channel JFET.

(c) Define the pinch off voltage VP and sketch the depletion region before and after pinch-off and explain the reason. 6. (a) Draw the circuit diagram of an emitter follower circuit and its h-parameter model. (b) For the given component values Rs = 1KΩ, RL = 3KΩ and for the given hparameters hf e = 100, hie = 2KΩ, hre = 2.5 x 10−4 , hoe = 10µA/V. Calculate AI , RI , Avs , Avs and R0 . 7. Define the following terms with reference to OP-AMPs: (a) i/p bias current (b) i/p offset current (c) open loop gain (d) i/p off set voltage (e) o/p offset voltage (f) CMRR (g) PSSR (h) Slew rate. 8. (a) Realize NAND gate using minimum number of NOR gates. (b) Explain the principle of basic shift registers. (c) Distinguish between asynchronous and synchronous counters. (d) Distinguish between Ring and Twisted Ring counters. ?????

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Set No.2

Code No: RR12302

I B.Tech. Regular Examinations, June -2005 ELECTRICAL AND ELECTRONICS ENGINEERING (Bio-Technology) Time: 3 hours Max Marks: 80 Answer any FIVE Questions All Questions carry equal marks ????? 1. (a) Derive the voltage current relations (between line and phase) values for a star − and − delta connected systems. (b) A 3-phase, 4 wire 208V system supplies power to a star connected load each arm with impedance equal to (17.32 − J10) ohms (per phase) find the line currents, power consumed, and the power factor of the load. 2. (a) Why is the core of the transformer laminated? (b) What are the various losses in a transformer? And how do these losses vary? (c) A single phase 50HZ transformer has 100 turns on the primary and 400 turns on the secondary. The cross sectional area of the core is 250 cm2 . The primary winding is connected to 230 volts. Determine i. E.M.F induced in the secondary winding. ii. The maximum value of the flux density in the core. 3. (a) Determine the range of input voltage that maintains an output voltage of 10V at the output for the regulator shown in the figure 4 below.

Figure 4: (b) Explain the applications of Zener diode. (c) Explain static and Dynamic Resistance of a diode. 4. (a) Draw the circuit diagram of half wave rectifier and explain its operation. (b) A half wave rectifier is fed by 220V, 50Hz via a step down transformer of turns ratio 11:1 find i. the output d.c. and 1 of 2

Set No.2

Code No: RR12302 ii. peak inverse voltage under no load condition. 5. (a) Compare the merits and drawbacks of FET and BJT. (b) Sketch the basic structure of an n-channel JFET.

(c) Define the pinch off voltage VP and sketch the depletion region before and after pinch-off and explain the reason. 6. (a) Compare the differences between voltage amplifiers and power amplifiers. (b) Show that the maximum theoretical efficiency of class B push-pull amplifiers is 78.5%. (c) Draw the circuit of a transformer coupled power amplifier and explain its operations with help of load-line analysis. 7. (a) Explain the effect of temperature on i. i/p bias current ii. i/p off set current iii. i/p offset voltage. (b) Explain in brief the applications of OP AMP. 8. (a) Convert the following numbers: i. (1431)10 to base 2. ii. (53.1575)10 to base 2. (b) Implement AB+C0 D0 = F with three NAND gates. Draw the logic circuit. (c) Prove that the NAND Gate is a universal gate. ?????

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Set No.3

Code No: RR12302

I B.Tech. Regular Examinations, June -2005 ELECTRICAL AND ELECTRONICS ENGINEERING (Bio-Technology) Time: 3 hours Max Marks: 80 Answer any FIVE Questions All Questions carry equal marks ????? 1. Consider a general A.C circuit in which the current leads the applied voltage by an angle φ. Write the equation for the voltage and current and hence derive the equation for the power. Also plot the voltage, current and power wave forms. 2. (a) Discuss the classification of d.c generators with suitable diagrams, and give the practical applications of each generator. (b) A 10Kw shunt generator supplies load at a terminal voltage of 200 volts. The shunt field resistance is 100 ohms and armature resistance is 0.1 ohm. Calculate the e.m.f induced in the generator. 3. (a) Explain the Law of junction for p-n diode. (b) Explain Avalanche and Zener break downs and compare. (c) Derive Diode current equation. 4. (a) What are the principle feature of a bridge rectifier. Explain its operation with neat circuit diagram. (b) Describe the characteristics of a triac. 5. (a) Sketch the input and output characteristics of CB configuration for an n-p-n transistor, Explain the shape of the curves qualitatively. (b) For the circuit in figure:5 shown below if α = 0.98 VBE = 0.7V find R1 in the circuit for an emitter current of IE = -2mA. Neglect the reverse saturation current.

Figure 5: 6. (a) Draw the h-parameter small signal low-frequency BJT model and what are the dimensions of each parameter.

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Set No.3

Code No: RR12302

(b) Draw the approximate h-parameter model for common collector configuration and derive expressions for current gain, Input Resistance voltage gain and output resistance. 7. (a) Find the resistance R and hf e for the transistor to provide a resonating frequency of 5kHz of a transistorized phase shift oscillator. The biasing resistances are 25kΩ and 47kΩ. The load resistance is 10Ω. The capacitor in the tank circuit is 1000pF which hie of the transistor is 2kΩ. (b) Explain the role of commutating capacitors in multivibrator circuits. (c) Design an Astable multivibrator circuit with 50% duty cycle and f=2KHz, VCC =10v, VBE(Sat) = 0.6v, VCE(Sat) = 0.3v. Using NPN Si transistors. 8. (a) Realize Exclusive-OR gate using minimum number of NAND gates. (b) Realize SR flip-flop using NAND gates. (c) Explain the principle of decade counter and realize it using JK-flipflops. (d) Realize exclusive −OR gate using basic gates. ?????

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Set No.4

Code No: RR12302

I B.Tech. Regular Examinations, June -2005 ELECTRICAL AND ELECTRONICS ENGINEERING (Bio-Technology) Time: 3 hours Max Marks: 80 Answer any FIVE Questions All Questions carry equal marks ????? 1. (a) Derive an expression for the total power in a 3-phase circuit in terms of line voltages and line currents. Show that the power is same whether the load is delta connected or star connected. (b) A 3-phase balanced star-connected load consists of 100 ohms resistance connected across a 220V, 3-phase supply. Determine the line currents and total power consumed. 2. (a) Does the induction motor have any similarities with the transformer? Compare the similarities and differences between them. (b) A 20h.p, 400V, 50HZ, 3-phase induction motor has an efficiency of 80% and working at 0.7p.f. The motor is connected to 400 volts, 3-phase supply calculate the current drawn by the motor from the mains. 3. (a) Give the specifications of Zener diode. (b) Explain the terms: i. ii. iii. iv. v.

Space-charge region Transition region. Barrier potential. Donar impurities, Acceptor impurities.

4. (a) Draw the circuit diagram of half wave rectifier and explain its operation. (b) A half wave rectifier is fed by 220V, 50Hz via a step down transformer of turns ratio 11:1 find i. the output d.c. and ii. peak inverse voltage under no load condition. 5. (a) Draw the circuit of a transistor (n-p-n) in the CB configuration. Sketch the input & output characteristics and explain the shape of the curves qualitatively. (b) For the circuit in figure 6 shown below for n-p-n transistor, calculate the collector and base currents. Assume hF E = 50. Explain Q point. 6. (a) Draw the circuit of a current shunt feedback amplifier and explain. (b) An amplifier has a gain of 10,000 without feedback. The gain is reduced to 50 with negative feedback. Find the feedback factor. 1 of 2

Set No.4

Code No: RR12302

Figure 6: (c) Explain the principle of operations of Tuned amplifiers. 7. (a) Explain the working principle of Colpitt’s oscillator and derive the formula for the O/P signal frequency. What is the basic difference between RC phase shift oscillator and Hartley oscillator? (b) Explain the principle of operation of self-bias binary circuit. 8. (a) Explain with a block diagram the major blocks of a digital computer. (b) Implement the following with either NAND or NOR gates. Use only 4 gates only the normal inputs are available. F = w0 xz + w0 yz + x0 yz0 + wxy0 z. (c) With a circuit diagram, explain Counter type A-to-D converter. ?????

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