There is a conducting sphere $S_1$ of radius 'r' mounted on an insulating handle. The sphere is given a charge Q. Another uncharged conducting sphere $S_2$ of radius R mounted on an insulating handle is now brought in contact with S1 for sufficient time and then removed. $S_1$ is again given a charge Q and $S_2$ is again brought in contact with it and then removed. The process is repeated 'n'times. The purpose is to find the charge on $S_2$ after n times and for the special case where n tends to infinity.
However the solution does not considers the potential at the centre of $S_1$ due to $S_2$ and at the centre of $S_2$ due to $S_1$. Why?