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§3. Thermoelectric phenomenas.
If the temperature of contacts of various metals is not identical, in a
chain there is an electric current termed as the thermoelectric. The phenomenon of occurrence of a thermoelectric current (the phenomenon of Th. Seebeck) and as a J. Peltier effect and Thomson, it is termed as thermoelectric phenomenas.
- phenomenon of Seebeck
(the German physicist) 1821 y. - thermoelectric current occurrence (or
thermoE.M.F.) in a closed circuit of consistently joined diverse
conductors contacts between which have various temperature.
In a closed circuit thermoE.M.F. ~ differences of temperatures.
ε = a(T1-T2)
Occurrence explanation thermoE.M.F.:
EF depends on temperature ⇒
if the temperature of crystals is various, intrinsic-contact potential
differences will be different also. Thus the total of leap of
potentials is distinct from zero and ⇒
arises in a chain thermoE.M.F. The Electron diffusion at a temperature
lapse rate in a chain also leads to occurrence thermoE.M.F.
The phenomenon of Seebeck is used for measuring of temperatures - thermoelectric couples - represent two diverse metals which contacts are at different temperatures.
- Peltier effect (the French physicist) 1834 y.: (the return to the phenomenon of Seebeck,
at current passage through contact of two diverse metals depending on
its voltage except Joule heat (heating of conductors) is oozed (at one
voltage of a current) or is immersed (at other voltage of a current)
additional warmth.
Q Joule heat ∼I2, QPeltier∼I; QPeltier> 0 at I→ and Q Joule heat < 0 at I←
Peltier effect explanation:
Electrons on the different leg of junction possess various medial energy. If electrons, moving clockwise, transit junction B and will get to field with smaller energy they will donate surplus of the energy to a crystalline lattice and junction B will heat up. In junction A
electrons transfer in field with greater energy, take away a part of
energy from a crystalline lattice for alignment of the temperature with
temperature of a crystalline lattice. Thus junction A will be cooled.
The Peltier effect is used in thermoelectric semiconductor cooler
bodies.
- Thomson's phenomenon (1856)
At current passage on non-uniformly warming a conductor there should
be an additional allocation (or uptake) warmth to similar warmth of
Peltier.
Explanation of the phenomenon of Thomson:
As
in warming parts of a conductor electrons have major medial energy,
than in less warming moving to a direction of decrease of temperature,
they donate a part of the energy to a lattice therefore there is an
allocation of warmth of Thomson. At a motion of electrons in the
opposite direction there is an energy absorption (warmth) of Thomson.
§4. Contact metal - the semiconductor (l.w. № 8.1) - it is self-maintained
§5. Contact of electrical and hole semiconductors (semiconductor transition) (l.w. №8.7) - it is self-maintained
§6. Point-contact diodes and transistors (l.w. №8.7) - it is self-maintained
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