A wire carrying a current of 4A  and its cross-sectional area10−8 m2 . If the free electron density in wire is1028 m−3 , the drift velocity is (in m/s)

current i=4 A cross-sectional area A=10−8 m2 number of electrons n=1028 m−3 charge e=1.6×10−19 drift velocity Vd=? Vd=ineA       =41028×1.6×10−19×10−8 ∴  Vd=0.25 m/s