Question

What is mean by drift velocity? A current of $0.5$ ampere flows in a wire of radius $0.5mm$. If the number of free electrons in the wire be $4\times {10}^{28}$ per $m^3$, calculate their drift velocity.

Answer 1

Here,

$I=0.5amp$

$n=4\times {10}^{28}/m^3$

$r=0.5mm$

$\therefore A=\pi r^2=0.78\times {10}^{-6}m$

$q=1.6\times {10}^{-19}C$

Drift velocity of electrons of current carrying wire is given by ,

$V_d=\frac{I}{nAq}$

$\therefore V_d=\frac{0.5}{4\times {10}^{28}\times 0.78\times {10}^{-6}\times 1.6\times {10}^{-19}}$

$\therefore V_d=9.95\times {10}^{-5}m/s$