A Conductor wire having $10^{29} $ per electron per $m^3$ carries a current of 20A.If the crosssection of wire is $1 mm^2$, then drift velocity of the electron will be ($ e = 1.6 \times 10^{-19} C$)

$1.25\times 10^{-4}m/s$ $1.25\times 10^{-3}m/s$ $1.25\times 10^{-5}m/s$ $6.25\times 10^{-3}m/s$

$1.25\times 10^{-3}m/s$

$ I = nA V_de$ $\Rightarrow V_d = \frac{I}{nAe} = \frac{20}{10^{29}\times 10^{-6} \times 1.6 \times 10^{-19}} = 1.25\times 10^{-3}m/s$