A current of 3 A is flowing through a wire of length 2 m and cross- sectional area `1mm^(2)`. If wire contains `10^(29) "electrons"//m^(3)`, calculate the average time taken by an electron to cross the length of the wire.

Answer

`3.36 xx 10^(4)s`

Explanation

Here, `I = 2A ,l = 1 m, A = 2 mm^(2) = 2 xx 10^(-6) m^(2)`,
`n = 8.5 xx 10^(28) m^(-1)`
Driff speed `upsilon_(d) = (I)/(n A e)`
`= (2)/((8.5 xx 10^(28)) xx (2 xx 10^(-6)) xx (1.6 xx 10^(-19))`
` = 7.35 xx 10^(-5)ms^(-1)`
Time taken, `t = (l)/(upsilon_(d)) = (1)/(7.35 xx 10^(-5)) = 3.36 xx 10^(4)s`