Principle of a capacitor

A capacitor is a device to store charges and electrostatic energy. In the simplest form, a capacitor consists of two parallel metal plates separated by a layer of air or a dielectric.
Above figure shows that two parallel plates in which one plate A having positive charge which induces negative charge on other plate B, then the equal amount of positive charge on outside of plate B. The induced charge on the plate B gets neutralized due to earthing. While the induced negative charge on inner side of B is held in position by the attraction of positive charge on A. As this negative charge on B lowers the potential of A.
The principle of a capacitor is to increase the capacitance of a conductor by bringing an uncharged conductor near to it and earthing the outside of the uncharged conductor.
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