Suppose you repeat the charging (starting again with uncharged rod and fur), but this time you rub longer and twice as much charge accumulates at each point on the two objects. How do the following quantities compare to what they were after the first charging: (i) the direction and magnitude of the electric field at point \(\mathrm{P}\) in Figure 26.1a; (ii) the potential difference between two fixed points on the rod and the fur; and (iii) the electric potential energy in the rod-fur system?

Figure 26.1 When we charge a rubber rod and a piece of fur by rub- bing them together, we do work to separate charge and hence increase the electric potential energy of the system comprising the rod and fur. (a) Rubber rod and piece of fur: before rubbing after rubbing (b) Energy diagram for system of rod and fur AK AU , W