In an A.C. circuit, Irms and I₀ are related as (a) Irms = p I₀ (b) Irms = 2 I₀ (c) Irms = I₀/p (d) Irms =I₀ / 2

A 40 mF capacitor is connected to a 200 V, 50 Hz ac supply. The r.m.s value of the current in the circuit is, nearly (a) 1.7 A (b) 2.05 A (c) 2.5 A (d) 25.1 A

Two cables of copper are of equal lengths. One of them has a single wire of area of cross- section A, while other has 10 wires of cross-sectional area A/10 each. Give their suitability for transporting A.C. and D.C. (a) only multiple strands for A.C., either for D.C. (b) only multiple strands for A.C., only single strand for D.C. (c) only single strand for D.C., either for A.C. (d) only single strand for A.C., either for D.C.

A small signal voltage V(t) = V₀ sin(ωt) is applied across an ideal capacitor C (a) Current I(t) is in phase with voltage V(t). (b) Current I(t) leads voltage V(t) by 180°. (c) Current I(t), lags voltage V(t) by 90°. (d) Over a full cycle the capacitor C does not consume any energy from the voltage source

A capacitor of capacity C has reactance X. If capacitance and frequency become double then reactance will be (a) 4X (b) X/2 (c) X/4 (d) 2X

A transformer having efficiency of 90% is working on 200 V and 3 kW power supply. If the current in the secondary coil is 6 A, the voltage across the secondary coil and the current in the primary coil respectively are (a) 300 V, 15 A (b) 450 V, 15 A (c) 450 V, 13.5 A (d) 600 V, 5 A

The core of a transformer is laminated because (a) ratio of voltage in primary and secondary may be increased (b) energy losses due to eddy currents may be minimized (c) the weight of the transformer may be reduced (d) rusting of the core may be prevented

An AC voltage source of variable angular frequency ω and fixed amplitude V connected in series with a capacitance C and an electric bulb of resistance R (inductance zero). When ω is increased (a) The bulb glows dimmer (b) The bulb glows brighter (c) Net impedance of circuit is unchanged (d) Total impedance of the circuit increases

In electric arc furnace Cu or Iron is melted due to variation of (a) current (b) magnetic field (c) voltage (d) electric field

High voltage transmission line is preferred as (a) Its appliances are less costly (b) Thin power cables are required (c) Idle current very low (d) Power loss is very less

In a purely resistive a.c. circuit, the current (a) is in phase with the e.m.f. (b) leads the e.m.f. by a difference of π radians phase (c) leads the e.m.f. by a phase difference of π/2 radians (d) lags behind the e.m.f. by a phase difference of π/4 radians

In highly inductive load circuit, it is more dangerous when (a) we close the switch (b) open the switch (c) increasing the resistance (d) decreasing the resistance

An alternating e.m.f. of angular frequency ω is applied across an inductance. The instantaneous power developed across it has an angular frequency (a) ω/4 (b) ω/2 (c) ω (d) 2 ω

In series R-L-C circuit, quality factor can be improved by (a) decreasing L (b) increasing C (c) decreasing R (d) decreasing R & L

Define capacitive reactance. Write its S.I. unit.