You rub a plastic comb through your hair and it now carries a charge of $-4\times {10}^{-10}\mathrm{C}$. What is the charge on your hair?

The given data is listed below as,

The charge carried by the plastic comb is, $e=-4\times {10}^{-10}\mathrm{C}$.

According to the concept of charging by induction, initially both the bodies are neutral, after rubbing one body gets one charge and another body gets an opposite charge of the same amount.

Initially, both the bodies (hair and comb) are neutral, then according to the concept of charging by induction, when the plastic comb gets rubbed on the hair then, the plastic comb gets the negative charge and the hair gets the opposite charge of the same amount.

Now, the hair also gets the same charge but the opposite in nature. So, the charge on the hair will be positive but the value is equal in magnitude to that of the comb.

Thus, the charge on your hair is $4\times {10}^{-10}\mathrm{C}$.