In considering thermoelectric effects, we have to realize that we are dealing with a non-equilibrium SITUATION. A general theory of non-equilibrium is beyond our means, suffice it to say that Lars Onsager, with a paper ENTITLED” reciprocal relations in irreversible processes” induced some fundamental insights as late as 1930; he received the Nobel Prize for his contribution to non-equilibrium THERMODYNAMICS in 1968-for chemistry, of all things. However, what we should aware of, is the ESSENTIAL statement of non-equilibrium theory:

1. As long as there is no equilibrium, we always have currents of something trying to establish equilibrium by reducing a gradient in something else that is the actual cause of the non-equilibrium. A gradient in the electrical potential, e.g., cause out well-known electrical currents, and a gradient in a CONCENTRATION causes diffusion currents.
2. But we must abstract even more, and consider things like entropy currents as well as all kinds of combinations of gradients and currents

While Onsager discovered some quite general relations between gradients and currents, we will not delve into details here, but only look a bit more closely at what causes some thermoelectric effects of current.

In considering thermoelectric effects, we have to realize that we are dealing with a non-equilibrium situation. A general theory of non-equilibrium is beyond our means, suffice it to say that Lars Onsager, with a paper entitled” reciprocal relations in irreversible processes” induced some fundamental insights as late as 1930; he received the Nobel Prize for his contribution to non-equilibrium thermodynamics in 1968-for chemistry, of all things. However, what we should aware of, is the essential statement of non-equilibrium theory:

While Onsager discovered some quite general relations between gradients and currents, we will not delve into details here, but only look a bit more closely at what causes some thermoelectric effects of current.