Q. An electric bulb is rated 220 V-100 W. The power consumed by it when operated on 110 V will be
A) 75 W
B) 40 W
C) 25 W
D) 50 W
Explanation
(c) Resistance of bulb $R = \frac{V^{2}}{P} = \frac{220 \times 220}{100} = 484\Omega$
Power when the bulb of operated on a voltage
$V^{'} = 110V\ will\ be\ P^{'} = \frac{V^{'2}}{R} = \frac{110 \times 110}{484} = 25W$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.