concept of density

Using the concept of energy density, find the total energy stored in a a. parallel plate capacitor b. charged spherical conductor.

Using the concept of energy density , show that the total energy stored by a shell of radius R and charge Q is (Q^(2))/( 8 pi epsilon_(0)R)

A charge Q is filled in a spherical volume of Radius R . Use the concept of energy density , find energy stored inside the charge volume.

Concepts

Briefly explain the concept of heat and concept of temperature.