The effect of increase in temperature on the number of electrons in conduction band () and resistance of a semiconductor will be:
Both and resistance decrease
Both and resistance increase
increases, resistance decreases
decreases, resistance increases
Correct answer:C
Standard Method
Given: The question asks the effect of increase in temperature on the number of electrons in conduction band and the resistance of a semiconductor.
Find: How and resistance change when temperature increases.
In a semiconductor, as temperature increases, more electrons gain sufficient thermal energy to move to the conduction band. Therefore, the number of free charge carriers increases.
Since conductivity increases when the number of charge carriers increases, the resistance decreases.
Therefore, increases and resistance decreases. The correct option is C.
Confusing semiconductors with metallic conductors. In metals, resistance usually increases with temperature, but in semiconductors the increase in charge carriers dominates. Use semiconductor carrier behavior, not metallic resistance trends.
Assuming that higher temperature always means higher resistance. That rule is not universal. For semiconductors, temperature raises the number of conduction electrons, so resistance decreases.
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