ELECTRICAL AND ELECTRONICS ENGINEERING -JUN 2K5REG

Code No: RR12302 Set No.1
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 ¯nd the RMS value and crest
factor of the waveform v(t) of ¯gure.1 below
Figure 1:
(b) What is potential di®erence?
(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 °ux density in the core.
3. (a) Shown that for circuit show in the ¯gure 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 IDfor the networks shown in the ¯gure 3.
4. (a) A full wave bridge recti¯er is fed with 220v, 50Hz, through a step-down trans-
former of turns ratio 11:1. Assuming ideal diode ¯nd the
i. d.c. output voltage
ii. peak inverse voltage
iii. Recti¯er e±ciency. The load resistance is 100­.
(b) What is ripple factor? Show that the ripple factor for full wave recti¯er is
0.482.
5. (a) Compare the merits and drawbacks of FET and BJT.
1 of 2
Code No: RR12302 Set No.1
Figure 2:
Figure 3:
2 of 2
Code No: RR12302 Set No.1
(b) Sketch the basic structure of an n-channel JFET.
(c) De¯ne the pinch o® voltage VP and sketch the depletion region before and
after pinch-o® 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 = 1K­, RL = 3K­ and for the given h-
parameters hfe = 100, hie = 2K­, hre = 2.5 x 10¡4, hoe = 10¹A/V. Calculate
AI , RI , Avs, Avs and R0.
7. De¯ne the following terms with reference to OP-AMPs:
(a) i/p bias current
(b) i/p o®set current
(c) open loop gain
(d) i/p o® set voltage
(e) o/p o®set 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.
? ? ? ? ?
3 of 2
Code No: RR12302 Set No.2
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) ¯nd 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 °ux 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 ¯gure 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 recti¯er and explain its operation.
(b) A half wave recti¯er is fed by 220V, 50Hz via a step down transformer of turns
ratio 11:1 ¯nd
i. the output d.c. and
1 of 2
Code No: RR12302 Set No.2
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) De¯ne the pinch o® voltage VP and sketch the depletion region before and
after pinch-o® and explain the reason.
6. (a) Compare the di®erences between voltage ampli¯ers and power ampli¯ers.
(b) Show that the maximum theoretical e±ciency of class B push-pull ampli¯ers
is 78.5%.
(c) Draw the circuit of a transformer coupled power ampli¯er and explain its
operations with help of load-line analysis.
7. (a) Explain the e®ect of temperature on
i. i/p bias current
ii. i/p o® set current
iii. i/p o®set 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+C0D0 = F with three NAND gates. Draw the logic circuit.
(c) Prove that the NAND Gate is a universal gate.
? ? ? ? ?
2 of 2
Code No: RR12302 Set No.3
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 Á. 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 classi¯cation 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 ¯eld 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 recti¯er. Explain its operation with
neat circuit diagram.
(b) Describe the characteristics of a triac.
5. (a) Sketch the input and output characteristics of CB con¯guration for an n-p-n
transistor, Explain the shape of the curves qualitatively.
(b) For the circuit in ¯gure:5 shown below if ® = 0.98 VBE = 0.7V ¯nd 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.
1 of 2
Code No: RR12302 Set No.3
(b) Draw the approximate h-parameter model for common collector con¯guration
and derive expressions for current gain, Input Resistance voltage gain and
output resistance.
7. (a) Find the resistance R and hfe for the transistor to provide a resonating fre-
quency of 5kHz of a transistorized phase shift oscillator. The biasing resis-
tances are 25k­ and 47k­. The load resistance is 10­. The capacitor in the
tank circuit is 1000pF which hie of the transistor is 2k­.
(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 °ip-°op using NAND gates.
(c) Explain the principle of decade counter and realize it using JK-°ip°ops.
(d) Realize exclusive ¡OR gate using basic gates.
? ? ? ? ?
2 of 2
Code No: RR12302 Set No.4
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 con-
nected 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? Com-
pare the similarities and di®erences between them.
(b) A 20h.p, 400V, 50HZ, 3-phase induction motor has an e±ciency of 80% and
working at 0.7p.f. The motor is connected to 400 volts, 3-phase supply calcu-
late the current drawn by the motor from the mains.
3. (a) Give the speci¯cations of Zener diode.
(b) Explain the terms:
i. Space-charge region
ii. Transition region.
iii. Barrier potential.
iv. Donar impurities,
v. Acceptor impurities.
4. (a) Draw the circuit diagram of half wave recti¯er and explain its operation.
(b) A half wave recti¯er is fed by 220V, 50Hz via a step down transformer of turns
ratio 11:1 ¯nd
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 con¯guration. Sketch the
input & output characteristics and explain the shape of the curves qualita-
tively.
(b) For the circuit in ¯gure 6 shown below for n-p-n transistor, calculate the
collector and base currents. Assume hFE = 50. Explain Q point.
6. (a) Draw the circuit of a current shunt feedback ampli¯er and explain.
(b) An ampli¯er has a gain of 10,000 without feedback. The gain is reduced to 50
with negative feedback. Find the feedback factor.
Figure 6:

(c) Explain the principle of operations of Tuned ampli¯ers.
7. (a) Explain the working principle of Colpitt's oscillator and derive the formula
for the O/P signal frequency. What is the basic di®erence 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 = w0xz + w0yz + x0yz0 + wxy0z.
(c) With a circuit diagram, explain Counter type A-to-D converter.
? ? ? ? ?