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RGPV First Year Engineering (Set B) (Semester 2)
Basic Electricals & Electronics Engg.
December 2011
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

Answer any one question from Q1 and Q2
1 (a) What do you understand by dependent and independent source? Explain with neat sketches.
7 M
1 (b) State superposition theorem. In the given network, marketing use of superposition theorem, determine the current in resistors R1, R2 and R3 and also the current in voltage source E.
7 M

2 (a) Voltage v(t)v0cos (?r+?) is applied to a series circuit containing resistor R, inductor L and capacitor C. Obtain expression for the steady state current.
7 M
2 (b) Describe star connecting method for interconnection of 3-phase supply.
7 M

Answer any one question from Q3 and Q4
3 (a) i) State Faraday's Law of electromagnetism.
ii) What is meant by turn ratio in transformer?
iii) What is megneto-motive force?
iv) Mention the two important electrical performances of transformer.
7 M
3 (b) Explain the principle of operation of transformer with suitable sketches.
7 M

4 (a) The O.C. and S.C. tests on 5kVA. 230/110 V. 50 Hz transformer gave the following data:
O.C. test (H.V. side) - 230 V, 0.6 A, 80W
S.C. test (L.V. side) - 6V, 15 A, 20W
Calculate percentage efficiency and regulation of a transformer on full load at 0.8 p.f. lagging.
7 M
4 (b) Derive the condition for maximum efficiency of a transformer.
7 M

Answer any one question from Q5 and Q6
5 (a) Derive the expression for generated voltage in D.C. machine.
7 M
5 (b) Draw and explain the construction of a single-phase induction motor with neat sketches.
7 M

6 (a) Obtain an expression for e.m.f. equation of 3-phase induction motor.
7 M
6 (b) What are the different methods of speed control in D.C. motor? Discuss in details.
7 M

Answer any one question from Q7 and Q8
7 (a) Convert the following numbers into decimal:
i) (11111111)2
ii) (100)8
iii) (FFFF)16
iv) (01010101)2
v) (100-100)2
7 M
7 (b) Give the logic symbol ad truth table for the following logic gates (any two):
i) NAND
ii) NOR
iii) NOT
iv) EX-OR
7 M

8 (a) Distinguish between combinational and sequential logic circuits giving example of each.
7 M
8 (b) Draw the circuit diagram of a half adder and derive its truth table.
7 M

9 (a) (i) Name any three materials which are most widely used as semiconductor.
7 M
9 (a) (ii) What type of semiconductor results when silion is doped with (a) donor impurities (b) acceptor impurities?
7 M
9 (a) (iii) What is doping?
7 M
9 (a) (iv) What is intrinsic semiconductor?
7 M
9 (a) (v) What is operating points?
7 M
9 (b) Explain the forward and reverse bias operating and voltage-current characteristics of a PN junction diode.
7 M

10 (a) Explain the working of Bipolar junction transistor in common emitter configuration.
7 M
10 (b) Explain how a BJT can be used as (i) An amplifier (ii) 2 switch
7 M

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