Jawaharlal Nehru Technological University, Hyderabad B.Tech Computer Science and Engineering Basic Electrical Engineering 2008 B.tech Question paper

Code No: 07A1EC07

Set No. 1

I B.Tech Regular Examinations, May/Jun 2008
BASIC ELECTRICAL ENGINEERING
( Common to Computer Science & Engineering, Information Technology and Computer Science & Systems Engineering)

Time: 3 hours Answer any FIVE Questions

All Questions carry equal marks

1. Explain the following terms:
(a) Charge
(b) Electric potential
(c) Potential difference
(d) Electric current
(e) Resistance
(f) Conductance
(g) Power
(h) Electrical energy.
[2+2+2+2+2+2+2+2]

2. Using Thevenin's theorem, find the current through the 7O resistor as shown in [16]

3.(a) State and explain faraday's laws of electromagnetic induction.
(b) Write short notes on Lenz's law.
(c) A coil of 1000 turns of wire uniformly wound on a non-magnetic ring of mean diameter 40 cm and cross-sectional area 20 sq.cm. Calculate
i. The inductance of the coil.
ii. The energy stored in the magnetic field when the coil is carrying a current of 15A.
iii. The emf induced in the coil if this current is completely interrupted in 0.01 second. [5+3+8]

4.(a) Explain the terms:
i. In-phase vectors
ii. Lead-Lag vectors.
(b)Calculate the current, power, power factor and voltage across the resistor of 8 O in series with a inductor of 20H and a capacitor of 14 µF excited by an AC supply of 110 V. [6+10]

5.(a) The full load voltage drop in a single phase transformer is 3% and 6% re-spectively due to resistance and leakage reactance. The full load ohmic loss is equal to the iron loss. Calculate:
i. The efficiency on full load at unity p.f
ii. The full load p.f at which the voltage drop is maximum iii. The load p.f at which the voltage drop is zero.
(b) A 200 / 400V, 50Hz 1 phase transformer on test gave following readings:
O.C (l.v): 200V, 0.7A, 70W, S.C (h.v): 15V, 10A, 80W. Find voltage regulation at 0.8 p.f lagging at full load. [8+8]

6. (a) What are the differences between a DC shunt motor and a DC series motor.
(b) Why a DC series motor cannot be started on no load? Explain.
(c) Explain the principle of torque production in a DC motor. [6+5+5]

7. (a) Give the constructional features of a synchronous motor.
(b) Explain the working of a synchronous motor. [8+8]

8. (a) Bring out the advantages and disadvantages of MI and MC instrument.
(b)Bring out the differences between various methods of producing controlling torque. [8+8]