Q. The resistance of an incandescent lamp is
A) Greater when switched off
B) Smaller when switched on
C) Greater when switched on
D) The same whether it is switched off or switched on
Explanation
(c) $R \propto \frac{1}{\tau}$;where $\tau =$ Relaxation time
When lamp is switched on, temperature of filament increases, hence $\tau$ decreases so $R$ increases
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.