Assertion: If the temperature of a semiconductor is increased then its resistance decreases.
Reason: The energy gap between conduction band and valence band is very small

Options

A. If both assertion and reason are true and the reason is the correct explanation of the assertion.
B. If both assertion and reason are true but reason is not the correct explanation of the assertion.
C. If assertion is true but reason is false.
D. If the assertion and reason both are false.

Answer

A

Explanation

In semiconductors the energy gap between conduction band and valence band is small `(~~ 1 eV)`. Due to temperature rise, electron in the valence band gain thermal energy and may jump across the small energy gap, (to the conduction band). Thus, conductivity increases and hence resistance decreases.