Q. When a current flows in a conductor, the order of magnitude of drift velocity of electrons through it is :

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A

$10^{10} cm / s$

B

$10^{4} cm / s$

C

$10^{-2} cm / s$

D

$10^{-7} cm / s$

Solution:

If in general we consider in a copper wire of cross sectional area $1 mm ^{2}$ carrying a current of $1 A$, the drift velocity is given as
$v_{ d }=\frac{J}{n e}=\frac{1 / 10^{-6}}{8.5 \times 10^{28} \times 1.6 \times 10^{-19}}$
$ \approx 10^{-4} m / s =10^{-2} \,cm / s$

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