Question

Calculate the active power in a 2 Ω resistor with 8 A current flowing through it.

(a) 125 W

(b) 128 W

(c) 123 W

(d) 126 W

This question was addressed to me in an internship interview.

Asked question is from Speed Control of Series Motor topic in portion Speed Control of Direct Current Motors & Induction Motors of Electric Drives

Answer 1

Right option is (b) 128 W

Explanation: The 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 0°. P=I^2R=8×8×2=128 W.