Question

The resistance of a semiconductor material (germanium or silicon) _______ with rise in temperature.
A. Increases
B. Decreases
C. Remains the same
D. First increases then decreases

Answer 1

Hint: In this question remember the basic properties of semiconductor also use the term temperature coefficient of semiconductor to find the correct option.

Complete Step-by-Step solution:
We know that temperature coefficient of resistance for conductor is positive due to which with the rise in temperature the resistance of the conductor increases but for the semiconductor we know that temperature coefficient of resistance for semiconductor is negative. So, by the above statement we can say that resistance is indirectly proportional to temperature.
Therefore the resistance decreases with the increase in the temperature.
Hence, option B is the correct option.

Note: In the answer we have said that the temperature coefficient of the semiconductor is negative let’s find out how we got this statement; in semiconductor the number of free electrons increases with increase in temperature. Because at higher temperature, due to sufficient heat energy supplied to the crystal more numbers of covalent bonds are broken due to which more free electrons are created. This means if temperature increases, more number of electrons comes to the conduction bands from the valence band by crossing the forbidden energy gap so as the number of free electrons increases, the resistance of this type of non-metallic substance decreases with increase of temperature.
Hence, the temperature coefficient of resistance for semiconductors is negative.