A capacitor is a device that functions to conserve energy in an electric field. It is constructed by separating at least two conductors by an insulator. This insulator must be a dielectric so that it can become polarized by the voltage difference between the two plates. Unlike in a conductor in which the electric charge flows through the material, when the dielectric insulator becomes polarized by the voltage difference between the two plates of the conductor an electric field forms in the insulator where the energy is stored.
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