ELECTRICAL AND ELECTRONICS ENGINEERING-REG 2K4

Code No:RR12302
I B.Tech Regular Examination, May/June 2004
ELECTRICAL AND ELECTRONICS ENGINEERING
(Bio Technology)
Time: 3 hours. Max.Marks:80
Answer any FIVE questions.
All questions carry equal marks.
- - -
1. a) Write down the expression for the instantaneous power, and hence derive the
equation for the average power.
b) A series R-L-C circuit consists of 100 ohms resistor and an inductor of 0.318
Henry and a capacitor of unknown value. This circuit is supplied by 230V, 50 HZ
supply and draws a current of 2.3 ohms, and the current is in phase with the
supply voltage. Find i) the value of the capacitance, and the power supplied by the
source.
2.a) Derive the equation for the voltage generated in a d.c generator.
b) A 2 pole d.c generator has 200 conductors on its armature. It is driven by a
prime mover at a constant speed of 600 r.p.m. If the flux per pole is 0.1 wb,
calculate the emf generated.
3.a) Prove that the Fermi level for p-type semiconductor is given by
. ln  


 


= +
A
V
F V N
N
E E KT
b) In a p-type semiconductor, if the concentration of acceptor atoms is increased by a
factor 10, find the shift in the position of Fermi level. Assume KT=0.03ev.
4.a) A HWR has a load of 3.5KW. If the diode resistance and secondary coil
resistance together have a resistance of 800W and the input voltage has a signal
voltage of peak value 240v, Calculate
i) Peak, average and RMS value of current flowing.
ii) dc power output
iii) AC power input
iv) Efficiency of the rectifier.
b) Compare Half wave, Center tapped full wave and Bridge rectifiers.
5.a) Draw a self bias circuit using n-p-n transistor and derive expression for stability
factor S'.
b) A transistor with b = 100 is to be used in a CE configuration with collector-tobase
bias. If RC = 1KW and Va = 10V. Assume VBE = 0 and it is required to have
a quiescent collector-to-emitter voltage is 4V. Find the value of RB and the
stability factors S and S'.
Contd….2
Set No:
1
Code No:RR12302 -2- Set No:1
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) Draw the internal diagram of OP-AMP. Explain the function of each block.
b) What do you understand about the term “Virtual ground”? Give the circuit
diagram for differentiate circuit using OP-AMP and prove that a triangular
waveform with frequency 5KHz is converted into rectangular waveform of the
same frequency.
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.
***********
Code No:RR12302
I B.Tech Regular Examination, May/June 2004
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 f . 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) Explain the process of voltage build up in a self-excited d.c machine.
b) List out the various conditions to be satisfied for voltage build up process in a
self-excited machine, and write down remedies if the conditions fail.
3.a) Draw the V-I characteristics of p-n diode and explain.
b) (i) What is the current in the diode shown in the fig.
(ii) Calculate the load voltage load power, diode power and total power in the
above circuit.
c) Explain how p-n junction diode act as a rectifier.
4.a) In a bridge rectifier, the transformer is connected to 220V, 60Hz mains and the
turns ratio of the step down transformer is 11:1. Load resistance is 800 W.
Assuming the diode is ideal, find
i) Idc
ii) Voltage across the load
iii) PIV
b) Explain the following terms:
i) Ripple factor ii) Peak Inverse voltage iii) Efficiency
iv) TUF v) Form factor vi) Peak factor.
Contd….2
Set No:
2
Code No:RR12302 -2- Set No:2
5.a) Define the following BJT switching times with suitable sketches..
i) Delay time, ii) Turn-on Time iii) Storage Time
iv) Fall time v) turn-off time
b) What are the bias compensation techniques? Explain the operation of one among
them.
c) An n-p-n transistor with b = 50 is used in a CE circuit with VCC = 10V, and RC =
2KW. The bias is obtained by connecting a 100KW resistance from collector to
base. Assume VBE=0V. Find the Quiescent point.
6. a) List out different distortions that occur in amplifiers and discuss.
b) Enumerate the effect of negative feedback on the various characteristics of the
amplifier.
Draw the circuit diagram of an emitter follower circuit and mention what type of
feedback is employed? Justify your answer.
7.a) Give the circuit diagram of a scale changer circuit using OP-AMP and explain its
operation.
b) Design an astable multivibrator circuit using, silicon BJTs for the given
specifications: Vcc = 15V,
FEmin h = 40,
Csat I = 2mA, tON = tOFF = 200msec. Assume
necessary data.
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.
**********
Code No:RR12302
I B.Tech Regular Examination, May/June 2004
ELECTRICAL AND ELECTRONICS ENGINEERING
(Bio Technology)
Time: 3 hours. Max.Marks:80
Answer any FIVE questions.
All questions carry equal marks.
- - -
1. a) Define the terms i) active power ii) reactive power and iii) apparent power,
and give the expressions for the same.
b) A single phase motor operating at 440V, 50 HZ supply is developing 10Kw
with an efficiency of 84% and power factor 0.7 lag. Calculate (a) the input KVA
and active power, and reactive power.
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) Determine the currents I1,I2 and I3 for the circuit shown below.
b) What are the specifications of any p-n diode.
c) Explain current components in a diode.
4.a) Sketch typical SCR forward and reverse characteristics.
b) Identify all regions of the characteristics and all important current and voltage
levels.
c) Explain the shape of the curves in terms of the SCR two transistor equivalent
Circuit.
d) Explain why always silicon but not Germanium is used in the construction of
SCR.
e) Obtain the expression for total current through SCR and Triac.
Contd….2
Set No:
3
Code No:RR12302 -2- Set No:3
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. a) Give the advantages of negative feedback amplifier.
b) Draw the circuit of a voltage shunt feedback amplifier and explain.
c) When the negative feedback is applied to an amplifier of gain 100, the overall
gain falls to 50. Calculate (i) the feedback factor ‘b’ (ii) If the same feedback
factor is maintained, find the value of amplifier gain required if the overall gain is
to be 75.
7.a) Derive an expression for the O/P voltage of OP AMP integrator circuit.
b) Explain the principle of operation of transistorized RC phase shift oscillator.
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 = w¢xz + w¢yz + x¢yz¢ + wxy¢z.
c) With a circuit diagram, explain Counter type A-to-D converter.
**********
Code No:RR12302
I B.Tech Regular Examination, May/June 2004
ELECTRICAL AND ELECTRONICS ENGINEERING
(Bio Technology)
Time: 3 hours. Max.Marks:80
Answer any FIVE questions.
All questions carry equal marks.
- - -
1.a) Explain what do you understand by
i) unidirectional current ii) alternating current iii) sinusoidal a.c. current
b) Define the terms i) R.M.S value ii) time period iii) frequency iv) average value.
c) Find out average value and root mean square value of output waveform of full
wave rectifier circuit. Assume the waveform has maximum voltage of 24V with
100Hz frequency.
2.a) Derive the torque equation of a d.c motor.
b) A 4-pole wave wound d.c armature has 294 conductors. Find (a) Flux per pole
to generate 230V at 1500 r.p.m. (b) Electromagnetic torque at this flux when
armature current is 120 A.
3.a) Explain how an n-type semiconductor is formed. Name different donor impurities
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, m p = 500Cm2 / v - s, m n = 1300Cm2 /V - S.
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.
5.a) Draw the static drain characteristics and transfer characteristics of an N-channel
MOSFET and explain the shape of the curves qualitatively.
b) Explain the following
i) BJT Switching times with suitable sketches.
ii) Early effect and its consequences.
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.
c) Explain the principle of operations of Tuned amplifiers.
7.a) A FET phase shift oscillator has gm = 500ms, and rd = 30kW. The feedback
resistance is 100kW, and the capacitor value is 64.97pF. Calculate the frequency
of oscillations and the value of RD. Draw the corresponding circuit diagram.
b) Explain about symmetrical and asymmetrical triggering methods in
mutlivibrators.
8.a) Give the Boolean functions: F= xy + x¢y¢ +y¢z
(i) Implement with only OR and NOT gates.
(ii) Implement with only AND and NOT gates.
b) Explain the principle of master-slave JK flip-flop.
c) Find the complement of given function and reduce it to a minimum number of
literals. (BC¢+A¢D) (AB¢+CD¢)
***********