Peltier Effects

Consider a copper-iron thermocouple. When a current is allowed to pass through the thermocouple in the direction of arrows (from A to B), heat is absorbed at the junction B and generated at the junction A. The absorption or evolution of heat at a junction when a current of heat at a junction when a current is sent through thermocouple is called Peltier effect. The Peltier effect is a reversible phenomenon. If the direction of the current is reversed, then there will be cooling at the junction A and heating at the junction B.

When an electric current is passed through a closed circuit made up of two different metals, one junction is heated and the other junction is heated and the other junction is cooled. This is known as Peltier effect.

The amount of heat H absorbed or evolved at a junction is proportional to the charge q passing through the junction. i.e.,
        H ∞ q or H ∞ It
 or            H = π It
 where π is a constant called Peltier coefficient.
When I = 1A and t = 1s, then H = π.

It is expressed is joule/coulomb i.e., volt. The Peltier coefficient is not constant but depends on the temperature of the junction.



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