A current of 0.2 A passes through a metal wire for 20 s.calculate the number of electrons passing through the cross section of wire during this time.(The charge on an electron = -1.6? 10 -19C)
Now ,by quantization of charge
Q= ne
Total charge= number of electrons x charge on 1 electron
so,Q= 4C
e=-1.6x10^19c
n=?
so,4 = n x -1.6x10^-19C
or n = 25 x 10^18