A current 4.0 A exist in a wire of cross-sectional area `2.0 mm^(2)`. If each cubic metre of the wire contains `12.0xx10^(28)` free electrons, then the drift spped is

Options

A. `2xx10^(-8) ms^(-1)`
B. `0.5xx10^(-3)ms^(-1)`
C. `1.04xx10^(-4)ms^(-1)`
D. None of these

Answer

C

Explanation

The current density in the wire is given by
`J = (i)/(A)=(4)/(2xx10^(-6))=2xx10^(6)Am^(-2)`
The drift speed is given by
`v=(j)/("ne")=(2xx10^(6))/(12xx10^(28)xx1.6xx10^(-19))`
`=(10^(6))/(6xx1.6xx10^(9))=1.04xx10^(-4)ms^(-1)`