Thermodynamic model for the quantitative description of the electromotive force in a thermocouple has been developed. Thermodynamic
equilibrium was applied to the system of electrons in two metals in a contact, contrary to the consideration of the dynamics
of electrons in a metal under external temperature gradient in the previous classical (Drude) and quantum (Sommerfeld) approaches.
The new model has two parameters, the ‘universal’ sensitivity ɛ0 and the characteristic temperature of a particular thermocouple Θv, and quite simple expression for the emf ΔU=ɛ0(T−Θvln(1+T/Θv) and sensitivity ɛ(T)=ɛ0T/(Θv+T). The model is shown to fit the experimental data very well at low temperatures. At high temperatures, the model is less
The characteristic temperature Θv depends on the difference between the electron heat capacity coefficients γ1−γ2 of two metals in the thermocouple. The greater the difference, the higher the sensitivity of the thermocouple.