2 January 2018

Capacitor ( Function of capacitor )

  • The capacitor is defined as the conducting plates separated by dielectric material.
  • The function of capacitor is to store electricity in which excess electrons on one plate and deficit electrons on other plate. 
  • When direct voltage is given to capacitor, charge is stored in the dielectric material. The stored charge is directly proportional to applied voltage.

       q a V
       q = CV
       C = q / V
          Where q = Charge
                    V = Applied voltage
                    C = Constant, a capacitance


  • Therefore the capacitance is defined as the charge per unit voltage. Its unit is coulomb per voltage or farad in SI unit.

        Capacitance C = eA / d
              d = Distance between two plates
             A = Area of plates
              e = Permittivity of material
  • The capacitance of capacitor depends upon area of plate and distance between two plates.  
  • As the distance between two plates increases, the capacitance decreases and vice versa. The permittivity of air is taken as unity.

          e = eoer
        eo = Absolute permittivity
         er = Relative permittivity
  • The relative permittivity of any material is defined as the ratio of permittivity of any material to the permittivity of air.

         er = e / eo

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