Why do resistivity and conductivity change with temperature?

[jawad hussain]

why resistivity of a metal increases with increase of temperature and conductivity of a semiconductor increases with increase in temperature??​

 

[Drakkith]

The simple explanation is that in conductors an increase in temperature increases the chance that a charge will collide with ions or other electrons and lose energy. In semiconductors increasing the temperature increases the number of available charge carriers by exciting electrons into the conduction band. This puts more electrons in the conduction band and leaves behind a hole, both of which decrease the resistance of the semiconductor.

For a much more detailed explanation, see here: http://en.wikipedia.org/wiki/Electrical_resistivity_and_conductivity#Temperature_dependence

 

[jawad hussain]

Got it...Thanks