When a.c.passes through pure inductor then

(a) e.m.f.leads the current by `pi/2`

(b) e.m.f.lags the current by `pi/2`

(c) e.m.f.leads the current by `pi/4`

(d) e.m.f.and current are in the same phase

When current in a coil changes with time, how is the back e.m.f. induced in the coil related to it ?

When a resistance of 2 ohm is connected across terminals of a cell, the current is 0.5 A . When the resistance is increased to 5 ohm, the current is 0.25 A The e.m.f. of the cell is

Show that the current leads the voltage in phase by pi//2 in an a.c. circuit containing an ideal capacitor.

Assertion : At resonance, LCR series circuit have a minimum current. Reason : At resonance, in LCR series circuit, the current and e.m.f. are not in phase with each other.

An electric motor runs a D.C. source of e.m.f. 200 V and draws a current of 10A . If the efficiency is 40% , then ressistance of the armature is:

Prove that the current flowing through an ideal inductor connected across a.c. source, lags the voltage in phase by pi/2 .

In an LCR circuit R=100 ohm . When capacitance C is removed, the current lags behind the voltage by pi//3 . When inductance L is removed, the current leads the voltage by pi//3 . The impedence of the circuit is

An e.m.f. of 12 "volts" is induced in a given coil when the current in it changes at the rate of 48 amperes per minute. The self-inductance of the coil is

In the figure shown. Find the e.m.f. varepsilon for which charge on 2mu F capacitor is 4 mu C.

A cell of e.m.f. E and internal resistance r is used to send current to an external resistance R. Write expressions for (a) the total resistance of circuit, (b) the current drawn from the cell, (c) the p.d. across the cell, and (d) voltage drop inside the cell.