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