§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.
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.
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.
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. є 8.1) - it is self-maintained
§5. Contact of electrical and hole semiconductors (semiconductor transition) (l.w. є8.7) - it is self-maintained§6. Point-contact diodes and transistors (l.w. є8.7) - it is self-maintained