If the resistivity of copper is 1.7×10−6Ω cm, then the mobility of electrons in copper, if each atom of copper contributes one free electron for conduction, is [The atomic weight of copper is 63.54 and its density is 8.96 g/cc]:

Mobility of electron μ=σne-(1)also resistivity ρ=1σFrom Eqs. (i) and (ii) , we get μ=1neρHere, n = number of free electrons per unit volume n=N0×d atomic weight n=6.023×1023×8.9663.54=8.5×1022From Eqs. (iii) and (iv) , we get μ=18.5×1022×1.6×10−19×1.7×10−6∴μ=43.25cm2/Vs