The capability of storing energy as electric charge is called electric capacitor. The capacitor is the mechanical device designed to sustain the capacitance. Capacitor stores energy from a source such as electric cell and again uses it. An electric capacitor is made by placing an insulating material such as air, glass, plastic etc. Therefore, the mechanical process of storing energy as electric charges by placing an insulating medium in between two nearby conductors is called capacitor.
A simple capacitor is made by placing two insulating metal plates parallel to each other. When a battery is connected to its two plates (Fig) then electrons may flow to a plate from its negative rod and is charged negatively. Electrons flow to the positive rod of the battery from the other plate of the capacitor. As a result that plate is charged positively. The amount of charge deposited in the plates depends on the voltage of the battery.
Capacitors are used in radio, television, record player and the circuits of other electronic devices widely.