Q. The drift velocity of free electrons in a conductor is $'v'$ when a current $'i'$ is flowing in it. If both the radius and current are doubled, then drift velocity will be
A) $v$
B) $\frac{v}{2}$
C) $\frac{v}{4}$
D) $\frac{v}{8}$
Explanation
(b) $v_{d} = \frac{i}{ne\pi r^{2}} \Rightarrow v_{d} \propto \frac{i}{r^{2}} \Rightarrow \frac{v}{v^{'}} = \frac{i_{1}}{i_{2}} \times \left( \frac{r_{2}}{r_{1}} \right)^{2} \Rightarrow v^{'} = \frac{v}{2}$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.