Q.No.219: - Distinguish between conductors insulators and semi conductors on the basis of energy band theory also draw diagrams.

Q.No.219: - Distinguish between conductors insulators and semi conductors on the basis of energy band theory also draw diagrams.

Ans: - According to the energy band theory the insulators are those materials in which there is a large energy difference between valence and conduction band. The conduction band is empty, and the electrons in the valence band acquire a large amount of energy to jump in conduction band and become free. The forbidden gap is very large between valence and conduction band. That’s why the insulators did not conduct. The electric current is defined as the flow charge and there are no free electrons or holes in insulators so no current flows.

Conductors are those materials in which there is no difference of energy between valence and conduction band, or these two bands are overlapped. Electrons can easily jump from valence and conduction band. In conductors the conduction band is partially filled than those of insulators. As there are electrons is conduction band so such materials are good conductors of electricity. There is no forbidden gap between valence and conduction band in conductors.

Semiconductors are those materials in which there is a very small energy difference between valence and conduction bands and electrons and can easily jump by acquiring a small amount of energy. In semiconductors the there is a very small forbidden gap between valence and conduction bands.