Q. The electric bulbs have tungsten filaments of same length. If one of then gives $60\ watt$ and other $100\ watt,$ then
A) $100\ watt$ bulb has thicker filament
B) $60\ watt$ bulb has thicker filament
C) Both filaments are of same thickness
D) It is possible to get different wattage unless the lengths are different
Explanation
(a) $P_{Rated} \propto \frac{1}{R}\ and\ R \propto \frac{1}{\lbrack Thickness\ of\ filament\rbrack^{2}}$
So$\ P_{Rated} \propto (Thickness\ of\ filament)^{2}$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.