A parallel-plate air capacitor has a capacitance of 920 pF. The charge on each plate is 2.55C.

Question:

A parallel-plate air capacitor has a capacitance of 920 pF. The charge on each plate is 2.55µC.
(a) What is the potential difference between the plates?
(b) If the charge is kept constant, what will be the potential difference between the plates if the separation is doubled?
(c) How much work is required to double the separation?