A conductor wire having `10^(29)` free electrons/`m^(3)` carries a current of 20 A.If the cross-section of the wire is 1 `mm^(2)`,then the drift velocity of electrons will be (e=`1.6xx10^(-19)C`)

Options

A. `1.25xx10^(-4)m s^(-1)`
B. `1.25xx10^(-3)m S^(-1)`
C. `1.25 xx10^(-5) m s^(-1)`
D. `6.25 xx10^(-3)m s^(-1)`

Answer

B

Explanation

Here ,I=20 A,n`=10^(29) m^(-3)`
A=1 `mm^(2)=10^(-6) m^(2),e=1.6xx10^(-19)`C
Drift velocity,`v_(d)=(I)/(nAe)`
`=(20A)/(10^(29)m^(-3)xx10^(-6)m^(2)xx1.6xx10^(-19)C)`
=1.25xx`10^(-3)ms^(-1)`