Question

what is the effect of rise in temperature on conductivity of copper and silicon

Answer 1

Conductivity of copper decreases and conductivity of silicon increases. The difference is in the mechanism of conductivity.


Copper is a typical conductor with some constant density of charge carriers. Thermal motion of atoms in the crystal lattice increases with rise of a temperature and troubles in electron's motion increase. It observes as decrease of copper's conductivity.


Silicon is a semiconductor. There are valence and conduction electrons. First of them are bonded with crystal lattice (lower energy) and second ones are free (higher energy). There is a some energy gap between valence and conduction electrons. Temperature gives additional energy to valence electrons (Delta E = kT, where k is the Boltzmann constant and T is a temperature in Kelvins), they "jump" to some higher energy levels and become conduction electrons. Because the carrier density increases with rise of temperature, conduction of silicon increases.