What is capacitor? explain Construction of a capacitor.
1 Answer



  • Apart from resistors and insulators, a capacitor is also the other basic passive component commonly used in electrical circuits. Capacitor is a device which has the ability to store charges in the form of electrical energy, which neither a resistor nor an insulator can do.
  • An ideal capacitor may retain the charges stored in it for a long time, after power supply is removed from the circuit. That is, it can store charges for ever. This stored charge can discharge through a conductor (or) wire. This discharge can cause shock or damage to the connected equipment, during the misuse of capacitors in a circuit.

Construction of a capacitor :

  • Two similar metallic conductors separated by an insulator (or) dielectric medium forms a capacitor. Conductor – insulator – conductor sequence is the basic idea behind a capacitor.

The basic difference between insulator and dielectric medium is :

  • The materials which do not have free electrons in them are unable to conduct electricity and they are termed as insulators.

  • Some material like ceramic behaves as a dielectric medium. Charges are induced in the opposite faces of it, because of the external applied electric field. Such material is called dielectric.

  • All dielectric materials are insulators, but not all insulators make good dielectric materials.

  • The dielectric medium could be air, mica, ceramic, paper, polyester, Teflon, etc.

  • In the figure shown below two metallic conductors of equal area “A” separated by a dielectric medium, forms a two terminal device, named as Capacitor.

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  • The plates are kept perfectly parallel to each other. So it is called as parallel plate capacitor. The conducting plates of a capacitor can be either square or circular or rectangular or cylindrical or spherical in shape. Shape selection depends on its application and voltage rating.
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