A resistor R draws power P from an AC source. If an inductor is added in series, giving a total impedance Z, find the new average power drawn from the same AC source.
Options

Question

A resistor R draws power P from an AC source. If an inductor is added in series, giving a total impedance Z, find the new average power drawn from the same AC source.

G1 Physics · Accepted Answer

Step 1: Pure resistor dissipates P=V(RMS)²/R. Step 2: After adding inductor the series current becomes I=V(RMS)/Z, but real heating still occurs only in R. Step 3: P′=I²R=V(RMS)²R/Z²=P(R/Z)². Answer A. Final answer: (A) P(R/Z)².