A 100-µF parallel-plate capacitor is charged to 500 V. It is then disconnected from the charging source and insulated.
(a) How much energy is stored on the capacitor?
(b) If the plates are pulled apart to a separation that is twice their initial separation, what energy is stored on the capacitor?
(c) If the answers are not identical, account for their difference.
See attached file for full problem description.
The energy of a capacitor is: E = 0.5 * C * V^2
The charge on a capacitor is: Q = C * V
The energy stored on the capacitor = 0.5 * (100 * 10^-6) * 500^2 = 12.5 J.
Before the plates were pulled ...
This solution looks at the energy stored in a capacitor.