There are `8.4xx10^(22)` free electrons per `cm^(3)` in copper. The current in the wire is `0.21A` (e=`1.6xx10^(-19)C`). Then the drifts velocity of electrns in a copper wire of `1mm^(2)` cross section, will be:-

Options

A. `0.6 xx 10^-5`
B. `0.8 xx 10^-5`
C. `1.0 xx 10^-5`
D. `1.56 xx 10^-5`

Answer

A

Explanation

`v = v ln ((m)/(m_(0))) - g t = 20 ln[(4)/(3)] - g t = 20 (0.28) - 5`
`= 5.6 - 5 = 0.6m//s`