A `N`-type silicon sample of width `4xx10^(-3)m`, thickness and length `6xx10^(-2)m` carriers a current of `4.8mA`, when the voltage is applied across the length of the sample. The free electron density is `10^(22)m^(-3)`

Explanation

The current density
`j=(i)/(A)=(4.8xx10^(-3))/(6xx10^(-2)xx4xx10^(-3))=20A//m^(2)`
The drift speed
`v_(d)=(j)/(n e)=(20)/(10^(22)xx1.6xx10^(-19))=12.5xx10^(-3)m//sec`
Time `t=(l)/(v_(d))=(6xx10^(-2))/(12.5xx10^(-3))=4.8sec`