## Physics for Scientists and Engineers: A Strategic Approach with Modern Physics (4th 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. The charge on the rod changes by +5.0 nC, so a charge of -5.0 nC was removed from the rod. In this case, we can assume that electrons have been removed from the rod and transferred to the sphere. (b) A total 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 transferred. $\frac{-5.0\times 10^{-9}~C}{-1.6\times 10^{-19}~C} = 3.1\times 10^{10}~electrons$ $3.1\times 10^{10}$ electrons were transferred.