Describe how a capacitor works.

If you think of electrons as tennis balls being passed around by a circle of people, then a capacitor occurs when there is a gap between 2 people which is too large for the ball/electron to be passed on. This effectively causes a blockage so that loads of electrons/balls build up on one side of the gap/capacitor. Because elections are negative and on the other side of the gap there are also negative electrons, knowing that the same charged particulate repel, we can work out that the electrons are going to repelled from the other side of the gap, hence leaving more protons than electrons there and causing a positively charged side. These sides are called plates. A capacitor therefore consists of a gap in an electric circuit with one positively charged and one negatively charger plate.