Explain temperature dependence of electrical conductivity and resistivity in conductors.

When the temperature is increased, there is a greater thermal motion in atoms that reduces the regularity in the atoms spacing along with a consequent reduces in the mobility of the electrons. Therefore the resistivity of most of the conductors increases along with an increase in the temperature. Because the number and the energy of the electrons at top of the Fermi distribution curve vary insignificantly along with temperature, change in temperature should be related with a change in the mean free path. Within a perfectly regular lattice, all electrons will exist in a particular energy state and they will have a fixed velocity. Basically in practical way metals do not have a perfect lattice due to impurities and deviations of the atoms about their mean positions because of lattice oscillations. Because the lattice oscillations decreases at low temperature the scattering of electron waves falls and therefore the conductivity increases quickly as the temperature reaches absolute zero. There is a limiting value beyond that the conductivity will not increase. Generally, purer the specimen higher is the conductivity. The conductivity of several conductors decreases linearly as the temperature is raised above the room temperature but below that temperature the conductivity raises markedly.