The cooling of one junction and the heating of the other when electric current is maintained in a circuit of material consisting of two dissimilar conductors. Peltier effect was discovered in 1834 by the French physicist Jean-Charles Athanase Peltier. The Peltier effect is the reverse phenomenon of the Seebeck effect. Seebeck effect is the conversion of temperature differences directly into electricity. This effect is named after German Physicist Thomas Johann Seebeck. In 1821, Johann Seebeck discovered that a compass needle would be deflected by a closed loop formed by two metals joined in two places, with a temperature difference between the junctions. This was because the metals responded differently to the temperature difference creating a current loop and a magnetic field. In 1834, Peltier found that an electrical current would produce a temperature gradient at the junction of two dissimilar metals when the current direction was reversed, the cold junction would get hot while the hot would get cold. Applying a current (e- carriers) transports heat from the warmer junction to the cooler junction.The Peltier effect can be used to create a refrigerator that is compact and has no circulating fluid or moving parts. Such refrigerators are useful in applications where their advantages outweigh the disadvantage of their very low efficiency. The Peltier effect is also used by many thermal cyclers, laboratory devices used to amplify DNA by the polymerase chain reaction (PCR). PCR requires the cyclic heating and cooling of samples to specified temperatures. The inclusion of many thermocouples in a small space enables many samples to be amplified in parallel.
