With the help of energy bands explain how conduction takes place in insulators.

Insulators: Substance as wood, glass, that do not permit the passage of current through them is termed as insulators. The valence band of these substances is full while the conduction band is fully empty. The forbidden energy gap among valence band and conduction band is very large (8ev) as demonstrated in the figure. Thus, a large amount of energy that is a very high electric field is needed to push the valence electrons to the conduction band. It is the reason, why such materials under ordinary conditions do not conduct at all and are designated like insulators.

Energy Band Diagrams