## Physics for Scientists and Engineers: A Strategic Approach with Modern Physics (3rd Edition)

(a) Electrons have been removed from the rod and transferred to the sphere. (b) $3.1\times 10^{10}$ electrons were transferred.
(a) Since it is normally quite easy for electrons to move, we can assume that it is the electrons which are transferred when there is a transfer of charge. In this case, we can assume that electrons have been removed from the rod and transferred to the sphere. (b) The change in the charge of the rod is $+5.0~nC$, so a charge of $-5.0~nC$ was removed from the rod. Each electron has a charge of $-1.6\times 10^{-19}~C$. We can find the number of electrons that were removed. $\frac{-5.0\times 10^{-9}~C}{-1.6\times 10^{-19}~C} = 3.1\times 10^{10}~electrons$ $3.1\times 10^{10}$ electrons were transferred.