Explain the working principle of a parallel plate capacitor.

Explanation

To understand the principle of a capacitor consider an insulated conductor plate A and give charge Q to it [Fig. ] so that it acquires a potential `V_1`. Now bring another metallic plate B of same size near A. As shown in Fig. equal amount of -ve and +ve charges are induced on plate B. Induced + ve charge on B tends to raise the potential of plate A but induced – ve charge tends to lower the potential of A.
However, if plate B is earthed [Fig.] then induced positive charge, being free, passes to earth. Now due to - ve charge of B electric potential of A is lowered by a large value to V (say) and consequently its capacitance is raised appreciably. It is the basic principle of a capacitor.