Question: 22: As the temperature increases, the electrical resistance
(1) Increases for conductors but decreases for semiconductors
(2) Decreases for conductors but increases for semiconductors
(3) Increases for both conductors and semiconductors
(4) Decreases for both conductors and semiconductors
Answer: Option (1)
Explanation:
In metallic conductors, electric current is due to the flow of free electrons.
When the temperature increases, the lattice ions of the conductor vibrate more vigorously.
These increased vibrations cause more frequent collisions of electrons with the lattice ions,
which reduces the drift velocity of electrons.
As a result, the electrical resistance of conductors increases with increase in temperature.
In semiconductors, charge carriers are electrons and holes. When temperature increases,
more electrons gain sufficient energy to jump from the valence band to the conduction band.
This increases the number of charge carriers available for conduction.
Since electrical conductivity increases with temperature,
the electrical resistance of semiconductors decreases as temperature rises.
Hence, resistance increases for conductors but decreases for semiconductors with increase in temperature.