Q. If $R_{1}$ and $R_{2}$ are respectively the filament resistances of a $200\ watt$ bulb and $100\ watt$ bulb designed to operate on the same voltage, then
A) $R_{1}$ is two times $R_{2}$
B) $R_{2}$ is two times $R_{1}$
C) $R_{2}$ is four times $R_{1}$
D) $R_{1}$ is four times $R_{2}$
Explanation
(b) $P \propto \frac{1}{R} \Rightarrow \frac{P_{1}}{P_{2}} = \frac{R_{2}}{R_{1}} \Rightarrow \frac{200}{100} = \frac{R_{2}}{R_{1}} \Rightarrow R_{2} = 2R_{1}$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.