How do you with a simple model explain the temperature dependence of the electrical conductivity. If you use the Drude model you get for the electrical conductivity sigma = ne^2t / m where n is the density of mobile electrons and t is the relaxation time. t is the time between collisions and must be the only variabel here that depends on temperature. How can you estimate t(T). Maybe there is a better model that describes the temperature dependence of the electrical conductivity.