Answer to Question #36972 in Electric Circuits for gagan
what is the effect of rise in temperature on conductivity of copper and silicon
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.