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AU First Year Engineering (Semester 2)
Basic Electrical and Electronic Engineering
May 2013
Total marks: --
Total time: --
INSTRUCTIONS
(1) Assume appropriate data and state your reasons
(2) Marks are given to the right of every question
(3) Draw neat diagrams wherever necessary

1 A 120 ? resistor has a specified maximum power dissipation of 1W. Calculate the maximum current level.
2 M

2 Three inductive coils each with resistance of 15? and an inductance of 0.03 H are connected in star to a 3? 400 V, 50 Hz supply. Calculate the phase voltages.
2 M

3 A dc shunt generator supplies a load of 10 kW at 220 V through feeders of resistance 0.1?, The resistance of armature and shunt field windings is 0.05? and 100 ? respectively. Calculate the terminal voltage.
2 M

4 In a single phase transformer, Np=350 turns, Ns=1050 turns, Ep=400 V. Find Eg.
2 M

5 Write ant two salient points on a p-n junction.
2 M

6 When should a transistor be biased? Name two common biasing circuits.
2 M

7 Find the following binary difference:
1011010-0101110
2 M

8 An active high S-R latch has a '1' on the S-input and 'o' on the 'R' input. What state is the latch in?
2 M

9 As related to amplitude modulation, what is overmodulation, undermodulation and 100% modulation?
2 M

10 Why are digital signals said to be noise immune?
2 M

Answer any one question from Q11 (a) & Q11 (b)
11 (a) (i) State and explain Kirchoffs laws.
4 M
11 (a) (i) A sinusoidal current wave is given by i=50 sin (100 ?t). Determine the root mean square value.
4 M
11 (a) (ii) Write short notes on moving Iron Measuring Instruments under the following headings:
(1) Operating principle
(2) Classification
8 M
11 (b) (i) 3?, 200 kW, 50 Hz delta connected induction motor is supplied from a 3?, 400 V, 50 Hz supply system. The efficiency and power factor of 3? induction motor are 91% and 0.86 respectively. Calculate:
(1) (A) Current in each motor phse
(B) Line current
(2) Phasor diagram of the circuit
8 M
11 (b) (ii) Find the current in the 8? resistor in the following circuit using Kirchoff's laws.

8 M

Answer any one question from Q12 (a) & Q12 (b)
12 (a) (i) Write short notes on the types of DC machines.
8 M
12 (a) (ii) With neat diagrams explain the construction and principle of operation of a single phase transformer. What are the characteristics of an ideal transformer?
8 M
12 (b) (i) Explain the basic nature of the emf induced in the armature of a d.c. machine.
4 M
12 (b) (i) How can the alternating current waveform in the armature be converted into a dc waveform?
4 M
12 (b) (ii) A 200 V dc shunt motor takes a total current of 100 A and runs at 750 rpm. The resistance of the armature winding and of shunt field winding is 0.1 and 40? respectively. Find the torque developed by the armature.
8 M

Answer any one question from Q13 (a) & Q13 (b)
13 (a) (i) With neat diagrams explain how a voltage regulator circuit regulates the output voltage under the following conditions:
(2) Input voltage decreases.
8 M
13 (a) (ii) Using the two diode analogy explain why the base-emitter junction has to be forward biased to provide collector current.
4 M
13 (a) (ii) Sketch a common emitter amplifier circuit with an NPN transistor.
4 M
13 (b) (i) Explain the avalanche effect that accounts for the reverse breakdown voltage (PIV) of a diode.
4 M
13 (b) (i) What is the effect on capacitance of a PN junction diode as forward and reverse bias are applied?
4 M
13 (b) (ii) Explain the amplifying action of a transistor.
6 M
13 (b) (ii) In a CE IB changes from 100 ?A to 150 ?A which causes a change in IC from 5mA to 7.5 mA. If VCE is held constant at 10 V, find ?ac (hfc)
2 M

Answer any one question from Q14 (a) & Q14 (b)
14 (a) (i) Reduce the following expressions using Boolean algebra postulates:
? a'b'c'+a'b'c+ab'c'+abc
? [(A+B)'+C']'
4 M
14 (a) (i) Realise the give expession using only NAND gates and inverters:
xyz+x'y'z
4 M
14 (a) (ii) Design a full adder, construct the truth table, simplify the output equations and draw the logic diagram.
8 M
14 (b) (i) Draw the logic diagram for a four bit parallel input parallel output register. Indicate inputs, outputs and a negative edge trigerred clock.
4 M
14 (b) (i) Draw a simple ring counter and briefly describe its counting action.
4 M
14 (b) (ii) Give a brief explanation of an A/D conversion and the need for the A/D conversions.
4 M
14 (b) (ii) Convert 95.062510 to binary.
4 M

Answer any one question from Q15 (a) & Q15 (b)
15 (a) (i) Draw a typical television video signal. Explain how this is converted to an image on a TV screen
6 M
15 (a) (ii) What is the need for modulation? Explain the principles behind amplitude modulation and frequency modulation. Compare and contrast the two types of modulation.
10 M
15 (b) (i) With neat diagrams explain any one method of amplitude modulation and its corresponding demodulation.
8 M
15 (b) (ii) Write short notes on the following modes of communication:
(1) Microwave
(2) Optical fibre
8 M

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