Chapter 29, Problem 9Q

To determine

Increase in resistivity of metal where as decrease in resistivity of semiconductor with increase in temperature.

Explanation of Solution

In case of semiconductors when we increase temperature more number of electrons can move from valence band to conduction band as they get energy to overcome the forbidden energy gap hence there is decrease in resistivity of semiconductors with increase in temperature

In case of metals or conductor when we increase temperature thermal speed of free electrons increases consequently the free electrons collide more frequently with the metal ions hence mean relaxation time decreases and resistivity of metals will increase.