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Copper and silicon are cooled from 300 K to 60 K, the specific resistance : -
A
Decreases in copper but increases in silicon
B
Increases in copper but decreases in silicon
C
Increases in both
D
Decreases in both
Detailed Solution
Copper is a metal with a positive temperature coefficient of resistance. On cooling, lattice vibrations decrease, electrons collide less often, and resistivity decreases.
Silicon is a semiconductor with a negative temperature coefficient. On cooling, fewer electrons are thermally excited into the conduction band, so the number of charge carriers falls and resistivity increases.
So the specific resistance decreases in copper but increases in silicon.
Silicon is a semiconductor with a negative temperature coefficient. On cooling, fewer electrons are thermally excited into the conduction band, so the number of charge carriers falls and resistivity increases.
So the specific resistance decreases in copper but increases in silicon.