A copper wire of cross-sectional area `1 mm^2` carries a current of 0.21A Find the drift velocity of free electrons. Given density of free electrons in copper `=8.84 times 10^(24)m^-3` and electronic charge `e=1.6 times 10^-19 C`.

Explanation

Current in copper wire `I=0.21A` electronic charge `e=1.6 times 10^(-19)C`, density of free electrons in copper `n=8.84 times 10^(24)m^-3` , cross sectional area of copper wire `A=1mm^2=10^-6m^2`
`therefore` Drift velocity
`v_d=1/(n eA)=0.21/((8.84times10^24)times(1.6times10^-19)times10^-6)`
`=0.148m.s^-1`