Thermostatic electron gas
Thermoelectricity - Thermodynamics and applications

The operation of a thermoelectric cell can be described schematically by analogy with an enclosure containing a thermodynamic working fluid. In this case, the working fluid is the electron gas, which can be likened to a perfect gas. The condition of a perfect gas is understood here as that of a gas with no interaction between particles, with the exception of elastic collisions, which ensure a microscopic velocity distribution compatible with the definition of a temperature, i.e. a stable thermal velocity spectrum. The electrochemical electron potential μ takes the place of the partial pressure for the electron gas. We can then write: