Charge carrier diffusion if electrons move from hot to cold, then a positive immobile nucleus is left at hot side to conserve charge. So this gives rise to a voltage. Phonon Drag: Similar, P has holes while N has excess by running current the incoming electrons distort nearby electrons thus causing a degradation in mobility and thus a lower temperature.
Thermo Couples used to be only two different metals but now you have p and n type Used to be metal not p and n semiconductors2000 degress Celsiusseries
P type has a deficiency of charge carriers and n types have an excess
Thermo power is measured across the material
The thermo electric effect
THE THERMO-ELECTRIC EFFECT By, Prajwal Keranahalli
WHAT IS IT?The thermoelectric effect is the direct conversion of temperature differences to electric voltage or vice-versa.The direction of heat flow can be controlled by changing polarity of the voltage source
HISTORYIn the 1820’s Thomas Seebeck (Germany) discovered that if two metals at different temperatures were touching you could create an electric currentJean Peltier discovered that the opposite was also true. By sending a current through two metals you could create differences in temperature
WHY DOES THIS EFFECT OCCUR?Charge Carrier Diffusion and Phonon Drag Seebeck Effect Peltier Effect
THE ZEROTH LAW OFTHERMODYNAMICSPairs of P and N type conductors are both it contact with a copper plate.There will thermo power until the system is at equilibrium. (All three materials are at the same temperature)
SEMICONDUCTORS Semiconductors have an electrical conductivity between materials like copper and glassThey possess and interesting property where its conductivity increases with added temperatureP and N type (thermocouples) semiconductors are created by doping.
APPLICATIONSThermoelectric generatorCooling ComputersDrink CoolersRecharging DevicesSpace ProbesSolar PowerClothingUseful, Quiet, no Moving PartsIt is less efficient (10%) and more expensive
TEST FOR UNDERSTANDINGThe USB Coffee cup warmer is an example of the Seebeck Effect or the Peltier Effect?Before the P and N type Semiconductors what material were used instead as thermal couples for thermoelectric modules?What are the advantages of using thermoelectric generators over, for example heat engines?
REFERENCESRockwood, Alan L. (1984). "Relationship of thermoelectricityto electronic entropy". Phys. Rev. A 30 (5): 2843–4. Bibcode1984PhRvA..30.2843R. doi:10.1103/PhysRevA.30.2843G. Jeffrey Snyder and Eric S. Toberer "ComplexThermoelectric Materials" Nature Materials 7, 105-114(2008).CRC Handbook of Thermoelectrics, Introduction, Edited byD.M. Rowe, CRC Press, 1995.G. Jeffrey Snyder, Tristan Ursell. "Thermoelectric efficiencyand compatibility" Physical Review Letters, Vol 91 p. 148301(2003)