Assume that each atom of copper contributes one free electron, If the current flowing through a copper wire of 1 mm diameter is 1.1 A, the drift velocity of electrons will be [density of Cu = 9gcm -3, At. wt. of Cu = 63)

The number of atoms in 63g of copper is equal to Avogadro's number = 6 .0 x 1023Volume of 63g copper  63 density =639=7cm3∴ n=6⋅02×10237 per cm3=6⋅02×1029/7 per m3A=πr2=π0⋅5×10−32m2The drift velocity, vd=i/(neA)∴vd=1⋅16⋅02×1029/7×1⋅6×10−19×π0⋅5×10−32=0⋅1×10−3m/s=0⋅1mm/s