given:
charge to be produced =125 nc or 125*10^-9 c.
to find:
Number of electrons required to produce a charge of 125 nc.
solution:
the charge of an electron is 1.602 x 10^-19 C:
Then, number of electrons = 125 x 10^-9 / (1.602 x 10^-19)
= 78 x 10 ^ 10 electrons
so, 78 x 10^10 electrons must be transferred to a body to produce a charge of 125nc.