Review of potential energy and electrical potential energy... Electrical potential energy is the energy a charge has due to its position in an electric field.. The difference in electrical potential energy and electric potential was restated and shown to be the total electrical p.e./amount of charge. It is joules/coulomb and measured in units called volts. The electric potential is called voltage. What a capacitor is, and how it works, and how it differs from a battery was discussed and a short video was used to demonstrate its uses and explain how it is charged. How a difference in voltage will affect the brightness of a bulb was also shown, and explained in terms of electrons /sec passing through the bulb.