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Q.
A piece of copper and another of germanium are cooled from room temperature to $77^{\circ} K$. The resistance of
TS EAMCET 2020
Solution:
Copper is a metal and germanium is a semiconductor.
On cooling resistance of copper decreases as atomic vibrations decreases and causes a reduction in electronic collisions.
Whereas on cooling germanium, number of electrons and holes decreases and hence its resistance increases.