Question

a piece of silk cloth rubber is found to have a positive charge of 2μc. estimate the number of electrons transferred to rubber

Answer 1

If the silk cloth charge is +2μC, then the same, but negative charge was transferred to rubber: $q = -2μC$ .The charge of one electron is $e = -1.6\times10^{-19}C$. Thus, the number of electrons will be:

$$n = \dfrac{q}{e} = \dfrac{-2\times10^{-6}C}{-1.6\times10^{-19}C} = 1.25\times10^{13}$$

Answer. $1.25\times10^{13}$ electrons.