Q 1471034826.     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 intE^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^2 V`

A charge `q_1` is placed at the centre of a spherical conducting shell of radius `R`.
Conducting shell has a total charge `q_2` . Electrostatic potential energy of the
system is: