Question

On increasing the temperature of a conductor, its resistance increases because

• A. Electron density decreases
• B. Relaxation time increases
• C. Number of collisions between electrons decreases
• D. Relaxation time decreases

Hint:

As temperature increases, the atomic vibrations in the conductor increase, leading to more collisions between electrons and atoms, which decreases the relaxation time and increases resistance.

Answer 1

The Correct Option is D

The resistance of a conductor increases with temperature primarily because of the increased collision frequency between the free electrons and the atoms of the conductor. As the temperature increases, the atoms vibrate more, which leads to more frequent collisions with electrons, reducing the relaxation time, which is the time between these collisions. The increased collision rate results in a higher resistance. 
Therefore, the correct reason for the increase in resistance is that the relaxation time decreases as temperature increases.