16.If resistance is 20 Q. and inductance is 27 in a R-L series circuit, then time constant of this circuit will be

17.Pure inductive circuit takes power from the A.C. line when

18.If a sinusoidal wave has frequency of 50 Hz with 30 A r.m.s. current which of the following equation represents this wave ?

19.What will be the phase angle between two alternating waves of equal frequency, when one wave attains maximum value the other is at zero value ?

20.A pure inductance connected across 250 V, 50 Hz supply consumes 100 W. This consumption can be attributed to