Thermopower

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The thermopower, thermoelectric power, or Seebeck coefficient of a material describes how it functions thermoelectrically.

The Seebeck coefficients, represented as <math>S</math>, are non-linear, and depend on the conductors' absolute temperature, material, and molecular structure.

If the temperature difference between the two nodes of a thermocouple is small,

<math>

T_2 = T_1 + \Delta T \, </math>

and a voltage ΔV is seen at the terminals, then the thermopower of the entire thermocouple is defined as:

<math>

S_{AB} = S_B-S_A = \lim_{\Delta T \to 0} {\Delta V \over \Delta T} </math>

This can also be written in relation to the electric field <math>E</math> and the temperature gradient <math>\nabla T</math>, by the equation

<math>

S = {E \over \left | \nabla T \right |} </math>

Superconductors have zero thermopower, and can be used to make thermocouples. This allows a direct measurement of the thermopower of the other material, since it is the thermopower of the entire thermocouple as well. In addition, a measurement of the Thompson coefficient, <math>\mu</math>, of a material can also yield the thermopower through the relation: <math>S = \int {\mu \over T} dT</math>

In semiconductors the sign of the thermopower is used to determine whether the charge carriers are electrons or holes.

it:Potere termoelettrico