Explain the effect of temperature on electrical conductivity of metals.

As the temperature is increased, there is a greater thermal motion of atoms which decreases the regularity in the atom spacing with a consequent decrease in the mobility of the electrons. The resistivity of most metals therefore increases with an increase in the temperature. Since the number and the energy of the electrons at top of the Fermi distribution curve vary insignificantly with temperature, the change in temperature must be associated with a change in the mean free path. In a perfectly regular lattice, each electron will exist in a particular energy state and will have a fixed velocity. Practical metals do not have a perfect lattice because of impurities and because of deviation of atoms about their mean position due lattice oscillations. Since the lattice oscillations decrease at low temperature the scattering of electron waves falls and the conductivity therefore increases rapidly. As the temperature, approaches absolute zero. There is a limiting value beyond which the conductivity will not increase. In general purer the specimen higher is the limiting conductivity. The conductivity of many metals decreases linearly as the temperature is increased above the room temperature but below this temperature the conductivity increases markedly.