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Thomas Johann Seebeck

 
Scientist: Thomas Johann Seebeck

Estonian–German physicist (1770–1831)

Seebeck was born into a wealthy family in Tallinn, the Estonian capital, and moved to Germany at the age of 17. He studied medicine in Berlin and in 1802 received an MD from the University of Göttingen. More interested in science than medical practice, he was wealthy enough to be able to devote his time to scientific research. In the early years of the 19th century he moved to Jena, where he became acquainted with an important intellectual circle of scientists and philosophers. His subsequent researches made him one of the most distinguished experimental physicists of his day.

Seebeck made investigations into photoluminescence (the luminescent emission from certain materials excited by light), the heating and chemical effects of different parts of the solar spectrum, polarization, and the magnetic character of electric currents. His most important work however came in 1822, after he had moved to Berlin. His discovery of thermoelectricity (the Seebeck effect) showed that electric currents could be produced by temperature differences. Seebeck joined two wires of different metals to form a closed circuit and applied heat to one of the junctions; a nearby magnetic needle behaved as if an electric current flowed around the circuit. He called this effect ‘thermomagnetism’ (and later objected to the term thermoelectricity).

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Thomas Johann Seebeck

Born 9 April 1770 (1770-04-09)
Reval
Died 10 December 1831 (1831-12-11)
Berlin[1]
Ethnicity Baltic German
Fields Physics
Known for Discovered the thermoelectric effect

Thomas Johann Seebeck (9 April 1770 – 10 December 1831) was a physicist who in 1821 discovered the thermoelectric effect.

Seebeck was born in Reval (today Tallinn, Estonia) to a wealthy Baltic German merchant family. He received a medical degree in 1802 from the University of Göttingen, but preferred to study physics. In 1821 he discovered the thermoelectric effect, where a junction of dissimilar metals produces an electric current when exposed to a temperature gradient. This is now called the Peltier–Seebeck effect and is the basis of thermocouples and thermopiles.

Contents

Seebeck effect

In 1821 Thomas Johann Seebeck found that a circuit made from two dissimilar metals, with junctions at different temperatures would deflect a compass magnet. Seebeck initially believed this was due to magnetism induced by the temperature difference. However, it was quickly realized that it was an electrical current that is induced, which by Ampere's law deflects the magnet. More specifically, the temperature difference, produces an electric potential (voltage) which can drive an electric current in a closed circuit. Today, this effect is known as the Peltier–Seebeck effect.

The voltage produced is proportional to the temperature difference between the two junctions. The proportionality constant (a) is known as the Seebeck coefficient, and often referred to as the thermoelectric power or thermopower. The Seebeck voltage does not depend on the distribution of temperature along the metals between the junctions. This effect is the physical basis for a thermocouple, which is used often for temperature measurement.

V = a(T_h - T_c)\,\!

The voltage difference, V, produced across the terminals of an open circuit made from a pair of dissimilar metals, A and B, whose two junctions are held at different temperatures, is directly proportional to the difference between the hot and cold junction temperatures, Th - Tc.

Precursors to color photography

In 1810, at Jena, Seebeck described the action of the spectrum of light on the chloride of silver. He observed that the exposed chemical would sometimes take on a pale version of the color of light that exposed it, and also reported the action of light for a considerable distance beyond the violet end of the spectrum.[2] Seebeck also worked on the theory of color with Johann Wolfgang von Goethe.

Other achievements

In 1808, Seebeck was first to produce and describe the amalgam of potassium. In 1810, he observed the magnetic properties of nickel and cobalt. In 1818, Seebeck discovered the optical activity of the solutions of sugar.

References

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