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` is given by
`J = (I)/(A) =(4.8 xx10^(-3))/((4 xx10^(-3))(25 xx 10^(-5))) = (4.8 xx 10^(-3))/(10^(-6))`
The drift velocity `v_(d)` given by
`v_(d)=(J)/(n e)=(4800)/(10^(22) xx 1.6 xx 10^(-19)) = 3m//s`
The time taken 't' given by
`t =(L)/(v_(d)) =(6 xx 10^(-2))/(3) = 0.02 sec`.