A capacitor is a very common electrical circuit device that can store electrical energy as charge. It works based on the idea that you can have a separation between two conductive plates and store a charge on the surface of these plates. However, if too much electricity is stored in the plates, it can jump across the gap causing less energy to be stored. The amount of charge stored in the capacitor can be increased by putting a dielectric material between the plates; air plays this role if no other material is present. This helps to prevent the charge from crossing the gap between the two electrodes, which allows more charge to be stored in this manner. 