Q. In India electricity is supplied for domestic use at 220 V. It is supplied at 110 V in USA. If the resistance of a 60 W bulb for use in India is $R$,the resistance of a 60 W bulb for use in USA will be
A) $R$
B) 2 $R$
C) $R/4$
D) $R/2$
Explanation
(c) In India, power, $P_{1} = \frac{V^{2}}{R} = \frac{220^{2}}{R}$
In USA, power, ${\ P}_{2} = \frac{V^{'2}}{R^{'}} = \frac{(110)^{2}}{R^{'}}$
As $P_{1} = P_{2},\ so\frac{220^{2}}{R} = \frac{(110)^{2}}{R^{'}}$
or $R^{'} = \frac{(110)^{2}}{(220)^{2}}R = \frac{R}{4}$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.