Postulates Of Classical Free Electron Theory Of Metals

Drude and Lorentz developed the classical free electron theory, based on the following assumptions. 

• Metal atoms have some of the valence electrons freely moving about in the body of the metal. These electrons are called free electrons or conduction electrons, as they contribute to conduction in the metal. 

• The force between the free electrons and the ionic core electrons is negligible. 

• The electric potential due to the ionic core is constant throughout the body of the metal. 

• The free electrons move about identical with the motion of gas molecules and hence assumed to obey the kinetic theory of gases.                                                                                    In the absence of external electric field they are at random motion and their average kinetic energy is 1⁄2 mvth2 = 3/2 k T,                                                                                                                            where vth is the thermal velocity, k, Boltzmann’s constant and T is temperature.