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As we have shown, the physical cause of the thermoelectric potential is the thermodiffusion of the conduction electrons. Under conditions of zero current the current due to thermodiffusion must be compensated by a gradient of the electrochemical potential, which leads to the thermoelectric potential field. Although in general the electrochemical potential is the sum of the electric potential and a non-electric contribution (usually called the chemical potential), the potential measured in a thermoelectric circuit is of purely electrostatic origin. The electric charges generating this potential under stationary conditions are located at the interfaces between the two metals in contact and on the surfaces. Under non-stationary conditions, when temperature gradients relax via heat conduction, (weak) space charges and electric currents exist transiently inside the conductors.

Klaus Froboese 2000-11-07