Question

Calculate the total heat dissipated in a rotor resistor of 14.23 Ω when .65 A current flows through it.

(a) 6.45 W

(b) 6.01 W

(c) 6.78 W

(d) 6.98 W

I got this question in final exam.

This intriguing question comes from Induction Motors Speed Control in chapter Speed Control of Direct Current Motors & Induction Motors of Electric Drives

Answer 1

The correct choice is (b) 6.01 W

To explain: The rotor resistor is a linear element. It only absorbs real power and dissipates it in the form of heat. The voltage and current are in the same phase in case of the resistor so the angle between V & I is 90°. P=I^2R=.65×.65×14.23=6.01 W.