Those materials which cannot pass electricity are known as non-conductors. They do not pass electricity because they do not have free electrons and ions to help in flow of current. Non-conductors have large resistance and zero conductivity. If we consider energy bands of a non-conductor there is a large forbidden energy band but a very small conduction band. They are widely used in coating of electric wires. They are also used as dielectric in the capacitors to increase the capacitance of capacitors. Plastic, glass, rubbers, ceramic are examples of non conductors. Moreover, they are also known as insulators.