Engineering Physics

5.4 Fermi-Dirac distribution

In a metallic crystal, the free electrons possess different energies except the restriction put forward by Pauli’s exclusion principle. According to quantum theory, at absolute zero of temperature, the free electrons occupy different energy levels continuously without any vacancy in between filled states. This can be understood by dropping the free electrons of a metal one by one into the potential well. The first electron dropped would occupy the lowest available energy, E₀ (say), and the next electron dropped also occupy the same energy level. The third electron dropped would occupy the next energy level. That is, the third electron dropped would occupy the energy level E₁ (>E₀) and so on because of Pauli’s exclusion ...