Q. When a current $I$flows through a wire, the drift velocity of the electrons is $v.$ When current $2I$ flows through another wire of the same material having double the length and double the area of cross-section, the drift velocity of the electrons will be
A) $\frac{v}{8}$
B) $\frac{v}{4}$
C) $\frac{v}{2}$
D) $v$
Explanation
(d) $\ \ \ \ \ \ \ \ I = neAv_{d}$
$or\ \ v_{d} = \frac{1}{neA}$
$or\ \ v_{d} \propto \frac{I}{A}\ $
$\therefore\frac{v^{'}d}{vd} = \frac{I^{'}/A'}{I/A} = \frac{2I/2A}{I/A} = 1$
$or\ \ \ \ \ \ \ \ \ \ \ \ v^{'}d = v_{d} = v$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.