ABSTRACT
In 1821 T. J. Seebeck discovered that when a temperature gradient is established between the two junctions of a loop made of two different metals, a magnetic field is generated. Later on, in 1834, J. Peltier discovered that a temperature difference appears between the junctions of two different materials under the flow of an electrical current and in 1838 H. Lenz showed that heat is liberated or absorbed depending on the direction of the electrical current. In 1851, soon after starting establishing the first rules of thermodynamics, W. Thomson (also known as Lord Kelvin) demonstrated that the coupling between electrical current and heat flux through a material, the Thomson effect, is the origin of both Seebeck and Peltier effects. The magnetic field measured by Seebeck was actually the consequence of an electrical current generated by the temperature gradient. He also showed that Seebeck and
Peltier effects actually appear in each of the individual materials, the properties of a junction being the coupling of the individual effects. It was decades before was discovered what an electrical current is made of: electrons.
