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.
