Question

If you pass a comb through your hair and it acquires a charge of -0.1 μC, how many excess electrons does it carry? What conclusions can you reach by applying the law of conservation of charge to this situation?

Answer 1

How many excess electrons carries:

$$n=\frac qe=\frac{0.1\cdot10^{-9}}{1.602\cdot10^{-19}}=624150974.$$

We conclude that all acquired charges are made of electrons.