Question
Fri December 16, 2011 By: Ashik Kumar

why on cooling a piece of copper and another of germanium from room temperature to 80*K increases the resistance of germanium while decreases that of copper.

Mon December 19, 2011
on decreasing temperature, there will be less collision  in the free electrons of copper. so resistance will decrease.current will increase.
but in germenium, there will be less number of electrons available for flow. so current will be less.resistance will increase.

in semiconductors, as temperature increases, more and more electrons will be available in the lattice for conduction.as more electrons will be going to conduction level from valence energy band.
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