The Big Idea
When current flows through wires and resistors in a circuit as a result of a difference in electric potential, charge does not build up significantly anywhere on its path. Capacitors are devices placed in electric circuits where charge can build up. The amount of charge a capacitor can store before it “fills up” depends on its geometry and how much electric potential is applied. The ratio of charge stored in a capacitor to the voltage applied is called its capacitance, measured in Farads . The larger the electric potential in volts, the stronger the electric field that is used to “cram” the charge into the device. Any capacitor will fill up with enough charge and voltage. Capacitors store energy when charged, and release it when they discharge.