A current of 10 A exists in a wire of cross-sectional area of  5 mm2 with a drift velocity of 2×10−3ms−1 . The number of free electrons in each cubic meter of the wire is____

The relation between current, number of electrons per unit volume, area of cross section and drift velocity is i=ne  A   Vd ∴n=ieAVd=101.6×10−19×510−32×2×10−3=0.625×1028=625×1025 per m3