Q. Two wires of the same material but of different diameters carry the same current $i$. If ratio of their diameters is 1:2, then the corresponding ratio of their mean drift velocities will be
A) $4:1$
B) $1:1$
C) $1:2$
D) $1:4$
Explanation
(d) $v_{d} = \frac{i}{nAe} = \frac{i \times 4}{n\pi D^{2}e}ie,\ v_{d} \propto \frac{1}{D^{2}}$
$\therefore\ \ \frac{vd_{1}}{vd_{2}} = \frac{D_{2}^{2}}{D_{1}^{2}} = \left( \frac{1}{2} \right)^{2} = \frac{1}{4}$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.