Question

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

(a) 2.4 W

(b) 3.4 W

(c) 2.2 W

(d) 3.2 W

I had been asked this question in semester exam.

The question is from Methods of Starting Electric Motors topic in chapter Starting of Electric Drives

Answer 1

Right option is (d) 3.2 W

The best I can explain: 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 90°. P=I^2R=2×2×.8=3.2 MW.