In terms of band theory, what is the difference between
a. a condcutor and an insulator
b. a conductor and a semiconductor

Explanation

(i) The energy gap betweeen the valence band and conduction band in an insulation is very large wheras in a conductor , the energy gap is very small or there is overlapping between valance band and conduction band. (ii) In a conductor, there is very small, energy gap or there is overlapping between valance band and conduction band but in a semiconductor, there is always a small energy between them.