A capacitor can quickly store a small amount of electrical energy. It's then said to be charged.
Inside, are two surfaces, separated by insulating material. When the capacitor is charged, one surface is positively charged, the other is negative.
When a circuit is closed between its terminals, the capacitor releases charge. It is then said to be discharged.
A typical capacitor stores the charge on thin sheets of foil, with sheets of insulation between them. These are rolled together to form a protective canister.
A capacitor's 'capacitance' (C) is a measure of the amount of charge (Q) stored on each plate for a given potential difference or voltage (V) which appears between the plates. In general, as the capacitance and voltage rating of the capacitor increase, the physical size of the capacitor increases.
