The Drude model was proposed in 1990 by Paul Drude to explain the transport properties of electrons in materials (especially metals).The free electron theory aims to explain structure and properties of solids by their electronic structure.They consider valence electrons to form an electron gas surrounding the ion cores and are free to move anywhere in the metals. Basic assumptions of Drude model: Electrons in a metal behave like particle in an ideal gas. (i.e. No coulombian interaction and collision between particles). This is called independent electron approximation. The effect of electron-electron and electron-ion interaction is ignored. Mean free time between collisions is τ. It is independent of electrons position and velocity. Electrons achieve thermal equilibrium by collisions with ions and their mean kinetic energy can be given by 12 m V2 = 3 KB T. Mean free time between collisions is τ. It is independent of electrons position and velocity. After the collisions, they move in random directions with a speed that depends on the temperature of the region where collision occurred i.e., hotter the region higher is the speed of emerging electrons.
