Question

Calculate the active power in a .89 H inductor.

(a) 1.535 W

(b) 0 W

(c) 2.484 W

(d) 1.598 W

The question was asked in an interview.

Asked question is from Induction Motors Speed Control in chapter Speed Control of Direct Current Motors & Induction Motors of Electric Drives

Answer 1

Right choice is (b) 0 W

To explain I would say: The inductor is a linear element. It only absorbs reactive power and stores it in the form of oscillating energy. The voltage and current are 90° in phase in case of the inductor so the angle between V & I is 90°. P=VIcos90° = 0 W.