ELECTRICAL AND ELECTRONICS ENGINEERING-SUPLY2K5

Code No: RR12302 Set No. 1
I B.Tech Supplementary Examinations, November/December 2005
ELECTRICAL AND ELECTRONICS ENGINEERING
(Bio-Technology)
Time: 3 hours Max Marks: 80
Answer any FIVE Questions
All Questions carry equal marks
⋆ ⋆ ⋆ ⋆ ⋆
1. (a) Determine the effective resistance between the nodes A and B in the circuit
shown in the figure 1 below (all values are in ohms).
Figure 1:
(b) Find the Vc and IL from the circuit shown in Figure 2under steady state
conditions. [10+6]
Figure 2:
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. [4+8+4]
3. (a) Explain how an n-type semiconductor is formed. Name different donor impu-
rities used.
(b) i. Find the conductivity of intrinsic silicon at 3000K.
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Code No: RR12302 Set No. 1
ii. If donor impurity is added to the extent of 1 impurity atom in 108 silicon
atoms, find the conductivity. It is given that at 3000K,
ni = 1.5 × 1010/Cm3, μp = 500Cm2/v − s, μn = 1300Cm2/V − S..
[4+4+8]
4. (a) Describe the basic structure of DIAC. Draw its volt-ampere characteristics
and explain.
(b) Define and explain the following terms of SCR
i. Turn-on-time
ii. Turn-off-time
(c) Draw the two transistor representation of SCR and explain. [8+4+4]
5. (a) Compare and contrast of FET and BJT.
(b) Give the constructional features of JFET and explain its operation with the
help of the drain characteristics.
(c) From the drain characteristics derive mutual characteristic and explain the
shape of the curve qualitatively. [6+6+4]
6. (a) Compare the three transistor amplifier configurations with related to AI , Av,
Ri and R0.
(b) For the circuit shown calculate AI , AV , Ri and R0, using approximate h-
parameter model. Assume hfe = 50, hie = 1100, hoe = 25 μA/V, hre = 2.5
× 10−4 as shown in the figure 3 below.
[6+10]
Figure 3:
7. (a) Explain the operation of monostable multi vibrator with relevant waveforms.
(b) How Frequency stability can be improved in the oscillators? Explain.
(c) For phase shift oscillator, the feedback network uses R=6k and C=1500pF.
The transistorized amplifier used, has a collector resistance of 18k. Calcu-
late the frequency of oscillations and minimum value of hfe of the transistor.
[6+4+6]
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Code No: RR12302 Set No. 1
8. (a) Realize Full-adder using logic gates.
(b) Explain the principle of operation of D-to-A converter.
(c) Simplify the following functions
i. A′BC′ + A′C′D + A′B′D′ + AC + BCD′
ii. A′B′D′ + A′CD + A′BC. [4 +4+8]
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Code No: RR12302 Set No. 2
I B.Tech Supplementary Examinations, November/December 2005
ELECTRICAL AND ELECTRONICS ENGINEERING
(Bio-Technology)
Time: 3 hours Max Marks: 80
Answer any FIVE Questions
All Questions carry equal marks
⋆ ⋆ ⋆ ⋆ ⋆
1. (a) Explain the principle of operation of single-phase energy meter.
(b) A single phase energy meter is used to measure the energy consumption of
factory. The factory load is 100KW and is in continuous use for 6000 hrs
per annum. If the meter constant is 600 revolutions per KWhr, how many
revolutions the disc of the energy meter makes. [6+10]
2. (a) Discuss the torque − armature current characteristics of various types of d.c
motors and give the practical applications of each type of motor.
(b) Discuss classification of d.c motors with suitable diagrams. [8+8]
3. (a) i. Find the resistivity of intrinsic silicon at 3000K. It is given the ni at 3000K
in silicon is 1.5×1010/Cm3 andμp = 500Cm2/V −S, μn = 1300Cm2/V −
S.
ii. If an acceptor impurity is added to the extent of 1 imputrity atom in
2 × 108 silicon atoms, find its resistivity.
iii. If a donor impurity is added to the extent of 1 impurity atom in 5 × 107
silicon atoms, find its resistivity.
(b) Prove that the concentration of free electron in an intrinsic semiconductor is
given by n = Nce−(Ec−Ef )/KT [12+4]
4. (a) Describe the basic structure of DIAC. Draw its volt-ampere characteristics
and explain.
(b) Define and explain the following terms of SCR
i. Turn-on-time
ii. Turn-off-time
(c) Draw the two transistor representation of SCR and explain. [8+4+4]
5. (a) Draw a family of drain characteristics and mutual characteristics of an n-
channel FET and explain the shape of the curves qualitatively.
(b) Define FET parameters and derive the relationship between them. [8+8]
6. (a) Compare the three transistor amplifier configurations with related to AI , Av,
Ri and R0.
(b) For the circuit shown calculate AI , AV , Ri and R0, using approximate h-
parameter model. Assume hfe = 50, hie = 1100, hoe = 25 μA/V, hre = 2.5
× 10−4 as shown in the figure 1 below.
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Code No: RR12302 Set No. 2
[6+10]
Figure 1:
7. (a) Draw the circuit diagram of wien bridge oscillator using BJT. Show that the
gain of the amplifier must be at least 3 for the oscillations to occur.
(b) For the fixed-bias Ge transistor, npn type, the junction voltages at saturation
and cutoff one in active region, may be assumed to zero. This circuit operate
properly over the temperature range -50oC to 75oC and to just start malfunc-
tioning at these extremes. The various circuit specifications are: VCC = 4.5v,
VBB = 3v, hFE=40 at -50oC, and hFE=60 at 75oC, ICBO = 4μA at 25oC and
doubles every 10oC. Collector current is 10μA. Design the values of Rc1, R1
and R2.. [8+8]
8. (a) Distinguish between positive and negative logic.
(b) Represent the decimal number 8620 in binary.
(c) How do you convert an RS flip-flop into a T-flipflop?
(d) Distinguish between Truth table and excitation table.. [4+4+4+4]
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Code No: RR12302 Set No. 3
I B.Tech Supplementary Examinations, November/December 2005
ELECTRICAL AND ELECTRONICS ENGINEERING
(Bio-Technology)
Time: 3 hours Max Marks: 80
Answer any FIVE Questions
All Questions carry equal marks
⋆ ⋆ ⋆ ⋆ ⋆
1. (a) Determine the effective resistance between the nodes A and B in the circuit
shown in the figure 1 below (all values are in ohms).
Figure 1:
(b) Find the Vc and IL from the circuit shown in Figure 2under steady state
conditions. [10+6]
Figure 2:
2. (a) Show that single phase induction motors are not self starting.
(b) Explain the construction and working principle of any type of 1-phase induc-
tion motor. [8+8]
3. (a) Give the electronics configurations of Silicon and Germanium.
(b) What is the difference between intrinsic and extrinsic semi-conductors.
(c) Draw energy band diagrams of
i. Insulator
ii. Semiconductor and
iii. Metal, and hence explain the difference in their conductivities. [4+4+8]
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Code No: RR12302 Set No. 3
4. (a) The half wave rectifier shown in the figure:3 below is fed with a sinusoidal
voltage v=20sin100t.
i. Sketch the output waveform.
ii. Determine the d.c. output voltage assuming ideal diode behaviour.
iii. Repeat the calculations assuming the simplified diode (silicon) model.
Figure 3:
(b) Draw the circuit diagram of full wave rectifier having two diodes and explain
its operation. [8+8]
5. (a) Define different stability factors of biasing circuits using BJT.
(b) List out different transistor biasing methods and compare their merits and
demerits.
(c) Write short notes on
i. Thermal runaway
ii. Early effect [6+6+4]
6. (a) Draw the circuit of a transformer coupled amplifier and explain its operations.
(b) Draw the circuit of a class B push-pull amplifier and derive expression for the
output power. [8+8]
7. (a) Draw the circuit diagram of wien bridge oscillator using BJT. Show that the
gain of the amplifier must be at least 3 for the oscillations to occur.
(b) For the fixed-bias Ge transistor, npn type, the junction voltages at saturation
and cutoff one in active region, may be assumed to zero. This circuit operate
properly over the temperature range -50oC to 75oC and to just start malfunc-
tioning at these extremes. The various circuit specifications are: VCC = 4.5v,
VBB = 3v, hFE=40 at -50oC, and hFE=60 at 75oC, ICBO = 4μA at 25oC and
doubles every 10oC. Collector current is 10μA. Design the values of Rc1, R1
and R2.. [8+8]
8. (a) Explain how a shift register is used as a Ring counter. Draw the O/P waveform
from each flip-flop of a 3-stage unit.
(b) Prove that if w′x + yz = 0, then wx + y′ (w′+z′) = wx + xz + x′z′ + w′y′z.
(c) Represent the given negative numbers in sign-magnetude, 1’S and 2’S com-
plement representation in 12-bit format.
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Code No: RR12302 Set No. 3
i. -64
ii. -512.. [6+6+4]
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3 of 3
Code No: RR12302 Set No. 4
I B.Tech Supplementary Examinations, November/December 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 consumed in a 3-phase, delta con-
nected load, connected to 3-phase balanced supply.
(b) Three equal impedances of (6+J8) ohm are connected in delta fashion across
400V, 3-phase balanced supply. Calculate the phase current, line current and
total power consumed by the load. [8+8]
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.. [8+8]
3. (a) Explain how an n-type semiconductor is formed. Name different donor impu-
rities used.
(b) i. Find the conductivity of intrinsic silicon at 3000K.
ii. If donor impurity is added to the extent of 1 impurity atom in 108 silicon
atoms, find the conductivity. It is given that at 3000K,
ni = 1.5 × 1010/Cm3, μp = 500Cm2/v − s, μn = 1300Cm2/V − S..
[4+4+8]
4. (a) A sinusoidal voltage of peak value 40V and frequency 50Hz is applied to HWR
using PN diode. The total load resistor is 800. Neglecting cut in voltage and
using idealized characteristic for the diode with Rf=8 and Rr=α calculate
i. Peak d.c and RMS values of load current
ii. d.c. and a.c. output power
iii. Rectifier efficiency
iv. Ripple factor.
(b) Derive the formulas used in the above problem. [8+8]
5. (a) Sketch a family of drain and mutual characteristics and explain the shape of
the curves qualitatively for a JFET.
(b) For a source self-bias circuit if ID = 0.8 mA, IDSS = 1.65 mA and VP = -2V
find VGS. [8+8]
6. (a) Define class A, B, AB, B and C operation of amplifiers.
(b) Draw the circuit diagram of a push-pull amplifier and explain how even har-
monics are eliminated.
(c) Derive the relation between gain with feed back and without feedback.[6+6+4]
7. (a) With the help of neat circuit diagram, explain the following applications of
OP-AMP.
i. Multiplier
ii. differentiator
iii. Subtractor.
(b) Design a scaling adder circuit using OP-AMP, to give the output voltage
Vo = −(3V 1 +4V 2 +5V 3),where V1, V2 and V3 are the input voltages given to
the circuit.. [10+6]
8. (a) Explain how a shift register is used as a Ring counter. Draw the O/P waveform
from each flip-flop of a 3-stage unit.
(b) Prove that if w′x + yz = 0, then wx + y′ (w′+z′) = wx + xz + x′z′ + w′y′z.
(c) Represent the given negative numbers in sign-magnetude, 1’S and 2’S com-
plement representation in 12-bit format.
i. -64
ii. -512.. [6+6+4]