A current of 1.0 A exists in a copper wire of cross-section `1.0mm^(2)`.Assuming one free electron per atom calculate the drift speed of the free electrons in the wire.The density of copper is `9000kgm^(-3)`.

Explanation

`i=1A,
` A = 1 mm^2, = 1 xx (10^-6)(m^2)`
` f_cu = 9000 kg/m^3`
Molecular mass has `N_0` atoms
`= m kg has (N_0/m) atoms. `
` = ((N_0)A/9000)/63.5 xx (10^-3)`
No. of atoms = No. of electrons.
n= Number of electrons /Unit Volume
` = (N.p./m.l) = (N_0 p/M)`
` = (6 xx (10^23) xx 9000/ 63.5 xx (10^-3))`
` i= V_d nAe `
` V_d = (1/ 6 xx (10^23) xx 9000/ 63.5 xx (10^-3)) xx (10^-6) xx 1.6 xx (10^-19)`
` = (63.5 xx (10^-3)/ 6 xx (10^23) xx9000 xx (10^-6) xx 1.6 xx (10^-19))`
= (63.5 xx (10^-3)/ 6 xx (10^23) xx 9 xx (10^-6) xx 1.6 xx ( 10^-19) ) `
` (63.5 xx (10^-3)/ 6 xx 9 xx 16)`
` = 0.073 xx (10^-3) m/s = 0.073 mm/s` .