History of the discovery of the thermoelectric effect

Beginning in 1794, Volta repeatedly carried out this experiment: he placed a frog prepared by the method of Galvani, so that its hind legs were lowered into the water of one can, and the back and spine were immersed in another jar of water. If the chain was closed with an iron wire, one end of which dropped for several minutes into boiling water, then strong frog convulsions were observed, continuing until the end of the wire cooled.

Thomas Seebek This experience went unnoticed, and Thomas Seebeck (1770 - 1831) probably did not know anything about him either, who spoke in 1821 with reports at the Berlin Academy of Sciences. On the basis of these reports, Seebeck subsequently wrote a well-known work, published only in 1825. The phenomenon that he discovered now is well known.

Seebeck himself describes one of his many experiments as follows. A small piece of bismuth was soldered from both ends to a copper spiral. If one end was heated by a lamp, the other remained cold, then the magnetic needle enclosed inside the support turned to indicate the passage of the current, which in the cold junction went from copper to bismuth.

This phenomenon became known in 1823 due to Oersted, who gave him the name, rooted to the present day. In the same year 1823 Fourier and Oersted proved that the thermoelectric effect possesses the property of superposition and built the first thermoelectric battery consisting of three plates of antimony alternating with three bismuth plates and welded at the ends so that they formed a hexagon.

This battery was significantly improved in 1829 by Nobili, who arranged the bimetallic sticks, combining them not with butts, but with planes, "in an oblique position, almost vertically, along the edges of the cylindrical surface and placed in a vessel filled with gum, so that one group of junctions was Immersed in the gum, and the other protruded outward.

Further improvements were made after a year by Melloni, who designed a prismatic model, which is still in use. Based on the Melloni battery and the galvanometer of its design, Nobili constructed in the same year 1830 a thermomultiplier of such sensitivity that he reacted to the heat of the human body at a distance of 18 to 20 cubits.

History of the discovery of the thermoelectric effect

In 1834, during the experimental studies of the conductivity of antimony and bismuth, Jean Charles Peltier (1785 - 1845) intended to determine how the temperature varies along a homogeneous or dissimilar conductor, but to which the current passes. In this connection, Peltier investigated the temperature at different points in the thermoelectric circuit using a thermocouple connected to a galvanometer, and found that in the junctions of different metals the temperature changes sharply, there are even cases of cooling. The greatest effect was achieved with a pair of bismuth-antimony. Thus, the electric current can also cause cooling.

Becquerel, De la Reeve, and other physicists reacted with distrust to Peltier's experiments, in part, probably because he was in science, so to speak, an accidental man - up to thirty years Peltier was a watchmaker. To exclude all doubts, Peltier confirmed the phenomenon discovered by him directly using an air thermometer. This method is now described in textbooks.

In other of his experiments, Peltier welded two pieces of metal through a cross, then, connecting a galvanometer, passed through two successive ends of the cross and through a galvanometer a thermoelectric current, and after a while the chain disconnected and connected the same galvanometer, but to the other two ends of the cross - and the galvanometer showed A current caused either by heating or by cooling the junction of the cross.

In which cases the heating is obtained, and in what cooling at the junction, Puggendorf was determined in 1838 and independent of him in 1840 by Luigi Paciniotti (1807-1889), the father of Antonio Pacinotti, the inventor of a constant-current dynamo.

Mario Lezzi "History of Physics"