Question

A piece of copper and another of germanium are cooled from room temperature to $80\text{K}$. The resistance of

• A. copper increases, germanium decreases.
• B. copper decreases, germanium increases.
• C. each of them increases.
• D. each of them decreases.

Answer 1

The correct option is B copper decreases, germanium increases.

The resistance of a conductor is directly proportional to the temperature, and that of a semiconductor is inversely proportional to the temperature.

As Copper is a conductor and Germanium is a semiconductor,

When cooled, the resistance of copper decreases and that of germanium increases.

Hence, option $\left(B\right)$ is correct.