Q 1451134924.     The potential energy of a charged conductor or a capacitor is stored in electric field. The energy per unit volume is called the energy density (u). Energy density in a dielectric media is given by

`U=(1)/(2) epsilon_0 KE^2`

This relation shows that the energy stored per unit volume depends on `E^2`. If E is the electric field in a space of volume dV, then total stored energy in an electrostatic field is given by

`U= (1)/(2) epsilon_0 K int E^2 dV`

and if E is uniform throughout the volume, then total energy stored can be given by

`U= (1)/(2) K epsilon_0 E^2V`



Let `U_a` and `U_b` represent the energy density in air and in a dielectric respectively, for the same field in both. Let K = dielectric constant. Then :