Seebeck Effect

Seebeck discovered that in a closed circuit made from two DISSIMILAR metals joined at two junctions, if those two junctions are maintained at different temperatures, an emf (a potential difference) develops across the loop. The current that this emf drives around the loop is called the thermoelectric current, and the two-metal, two-junction loop itself is called a thermocouple (Figure 2.35). If the hot and cold junctions are interchanged (i.e. whichever junction was hot is now made cold, and vice versa), the direction of the induced current reverses as well -- so the Seebeck effect is fully reversible.

The magnitude of the emf a given thermocouple develops depends on exactly two things: (i) which particular pair of metals makes up the thermocouple, and (ii) how large the temperature difference between the two junctions actually is. This direct, predictable dependence on temperature difference is precisely what makes the Seebeck effect so practically useful. Its applications include: thermoelectric generators (Seebeck generators), used in power plants to convert otherwise-wasted heat directly into usable electricity; automotive thermoelectric generators, fitted to vehicles specifically to recover exhaust heat and improve overall fuel ef …