Question

The resistance of insulators __________

(a) Increases with an increase in temperature

(b) Decreases with an increase in temperature

(c) Remains the same with an increase in temperature

(d) Becomes zero with an increase in temperature

The question was asked in a job interview.

Enquiry is from Temperature Coefficient of Resistance topic in division Simple DC Networks of Basic Electrical Engineering

Answer 1

The correct answer is (b) Decreases with an increase in temperature

Explanation: In the case of an insulator, the energy gap between the conduction band and the valence band is very large. When the temperature is increased, the electrons move from the conduction band to the valence band and hence it starts conducting. When conductance increases, resistance decreases, since C=1/R. Thus, when the temperature increases, resistance decreases in insulators.