Why does conductivity of metallic conductor decrease with an increase in temperature, wheras in case of electrolytic conductors the conductivity increases with an increase in temperature ?

Explanation

With an increase in temperature the degree of disosciation of an electrolyte increases, thus more number of ions is produced and rate of migration of ions towards respective electrodes also increases due to increase in the mobility of ions. Therefore, conductivity increases. However, conductivity decreases with decrease in temperature in case of metallic conductors because as temperature increases the vibration of positive kernels and free electrons increases but there is net increase in the KE of electrons, thereby the speed or flow of electrons is hindered or obstructed by increased movement of positive kernels. The obstruction caused by positive kernels to the flow of electrons is called resistance and due to the increase in resistance with increase in temperature, conductivity of a metal decreases.