The number of free electrons per 100 mm of ordinary copper wire is `2xx10^(21)`. The average drift speed of electorn is `0.25 mm//s`. What is the current flowing?

Answer

`1.6 A`

Explanation

If A is the area of cross-section of the wire, then number of electron per unit volume of copper wire is
`n = (2xx 10^(21))/(A xx (5xx 10^(-2))) m^(-3)`
`I = nAe upsilon_(d)`
`= (2xx 10^(21))/(A xx(5 xx10^(-2))) xx A xx (1.6 xx 10^(-19)) xx (0.25 xx 10^(-3))`
`= 1.6 A`