Question

The electrical conductivity of semiconductors:
A.Increases with temperature
B.Decreases with temperature
C.Remains constants on heating
D.All the above

Answer 1

Hint: The electrical conductivity of any substance be it a conductor, an insulator or semiconductor depends purely on the number of free electrons present. More the number of free electrons present more is the conductivity of the material.

Complete step-by-step answer:The electrical conductivity of semiconductors increases with rise in temperature as with rise in temperature more electrons can jump into the conduction band by taking energy from increased temperature.
From our previous knowledge we know that the conductivity of material depends on free electron concentration.
The concentration of free electrons in semiconductors is less than conductors and more than insulators. Because of this, the conductivity of semiconductors is of moderate level (not high like conductors and not low as insulators).
The normality of a semiconductor is that the valence electrons present are not free as they are present in conductors, here these valence electrons are present as bonds between two atoms. Germanium and silicon are very common examples of semiconductors.
So the correct option is (A) i.e. the electrical conductivity of semiconductor increases with temperature.
Option (B) is wrong as metal’s conductivity decreases with temperature not of semiconductor’s.
Option(C) and (D) are again wrong for semiconductors.

Additional information: Semiconductors are of two types: one is intrinsic and other is extrinsic semiconductors.
Intrinsic semiconductor is undoped semiconductor and extrinsic semiconductor is doped semiconductor. Extrinsic semiconductors are again of two types: one is n type semiconductor and other is p type semiconductor. In n type semiconductor the semiconductor is doped with pentavalent impurities and these pentavalent impurities are of group fifteen
In p type semiconductors, semiconductors are doped with trivalent impurities and these trivalent impurities are of group thirteen. Semiconductors like silicon, germanium, etc are generally of group fourteen.

Thus the correct answer for the given question is option A.

Note: In good conductors there is presence of a large number of free electrons and in insulators free electrons concentration is nearly negligible. The conductors have high conductance value or we can say that they have low resistance value as resistance and conductance are inversely proportional.