CSVTU Question Papers
Basic Electrical Engineering May 2009
Q.1 (a) Why are electrical machine made of magnetic materials?
(b) State and explain super position theorem.
(c) Determine the equivalent resistance between the terminals X and Y of the circuit shown.
(d) A steel ring of 25 cm in diameter and of circular section 3 cm in diameter has an air gap of 1.5 mm length. If is would uniformly with 750 turns of wire carrying a current of 2.1 A.
(i) Magneto motive force.
(ii) Flux density in air gap.
(iii) Magnetic flux.
(iv) Relative permeability of steel ring.
Assume that iron path takes about 35% of the total miff.
Q.2 (a) Show that power consumed in a 1 – ?.
Ac circuit is-given by VI coos ?.
(b) Derive the expression for the band width in series RLC circuit.
(c) A circuit consist of R = 35 ohms in series with an unknown impedance Z. For a sinusoidal current of 2 A, the observed voltages are 200 volte across R and z together , 150 volts across impendence Z. Find the impedance Z.
(d) Show that: tan ? = (W2 – W1)
W1 + W2
Unit – III
Q.3 (a) The efficiency of a transformer is high compared to other electrical machines. Give reasons .
(b) Write short note on no load and short circuit tests.
(c) What do you mean by efficiency of a transformer ? Derive the condition for maximum efficiency.
(d) A 200 kava transformer has an efficiency of 98% at full load. If the maximum efficiency occurs at 75% of lull load, calculate the efficiency at half load. Assume negligible magnetizing current and pf at 0.8 atall load.
Q.4 (a) A series motor should never be started with our load on if Give reasons .
(b) A 120 V decent motor has an armature resistance of 02 ohrr and a field resistance of 60 ohms. It runs at 1800 rpm it is taking a full load current of 40A. Find the speed of the moto when it is operating at half full load.
(c) With usual notations, derive the torque equation of a 0.1 motor.
(d) Derive the expression for developed torque in a 3 phase in diction motor.
Q.5 (a) How do you extend the rate of an ammeter?
(b) What is the principle of a moving iron voltmeter?
(c) Explain the operation of a single phase energy meter.
(d) A single phase K who meter makes 500 revolutions per K Who. It is found in testing as making 40 revolutions in 58.1 seconds at 5 kW full load find out the percentage error.