A n-type silicon sample of width `4xx10^(-3)m`, thickness `25xx10^(-5)m` and length `6xx10^(-2)m` carries a current of 4.8 mA when the voltage is applied across the length of the sample. If the free electron density is `10^(22)m^(-3)`, then find how much time does it take for the electrons to travel the full length of the sample? Given that charge on an electron `e=1.6xx10^(-19)C`

Explanation

The current density J is given by
`J=(i)/(A)=(4.8xx10^(-3))/((4xx10^(-3))(25xx10^(-5)))=(4.8xx10^(-3))/(10^(-6))`
The drift velocity `v_(d)` is given by
`V_(d)=(J)/(n e)=(4800)/(10^(22)xx1.6xx10^(-19))=3m//s`
The time takent is given by `t=(L)/(u_(d))=(6xx10^(-2))/(3)="0.02 sec"`