Question

If the conductance of a material decreases with an increase in temperature, what temperature coefficient of conductance does it have?

a.Exponential

b.Positive

c.Negative

d.Zero​

Answer 1

Answer:

At given temperature, resistivity of any material depends on number of free electrons and drift speed of electrons in the material. The drift speed of electrons is determined by how often electrons collide with each other and other atoms in the material.

For semiconductors, resistivity decreases with increase in temperature because more free charge carriers (electrons and/ or holes) are available for conduction. Therefore, they have negative temperature coefficient.

Whereas, as temperature increases resistivity increases as electrons collide more frequently with vibrating atoms in conductor. This reduces drift speed of electrons (and thus current reduces) and gives them positive temperature coefficient of resistance.