conductivity of metals decreases on increasing temperature. why?
Conductivity in metals is caused by the presence of electrons at the low energy level (the upper one), which is closed to so-called the Fermi level. Since they have similar energy for each atom these levels are spread via material to form ‘bands’ of levels. At this level electrons can move in the crystalline pack from one to another atom upon performing electrical field. Therefore an increase in temperature leads to increase in thermal vibration of atoms resulting in the distraction or change of ‘band of levels’ expended through the matter. Some electrons can’t move, which causes the lower electrical conductivity.