Q. In a wire of circular cross-section with radius $r,$ free electrons travel with a drift velocity $V$ when a current $I$ flows through the wire. What is the current in another wire of half the radius and of the same material when the drift velocity is $2V$
A) $2I$
B) $I$
C) $I/2$
D) $I/4$
Explanation
(c) From $v_{d} = \frac{i}{neA} \Rightarrow i \propto v_{d}A \Rightarrow i \propto v_{d}r^{2}$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.