Question

There is a current of 40A in a wire of 10^-2 m area of cross section. If the number of free electrons per cubic metre is 10^29 then drift velocity is?

Answer 1

$v=\frac{I}{neA}$
where I is current = 40 A
n is number of electrons = 10²⁹
A is cross sectional area = 10^-2
e is charge on an electron = 1.6 ☓ 10^-19
$\Rightarrow v=\frac{40}{{10}^{29}\times 1.6\times {10}^{-19}\times {10}^{-2}}=25\times {10}^8\mathrm{m}/\mathrm{s}$
The drift velocity of the electrons is 25 ☓ 10⁸ m/s