The Seebeck effect, discovered by Thomas Seebeck in 1821, involves the generation of a voltage difference between two dissimilar conductors or semiconductors when a temperature gradient is applied. This phenomenon results in the flow of electrons from the hot conductor to the cooler conductor, producing a direct current in the connected circuit. The Seebeck effect is the basis for thermocouples, which are widely used for temperature measurement in various applications.
The Seebeck coefficient, which determines the efficiency of thermoelectric generators and coolers, can be positive or negative depending on the material’s charge carriers. Measuring the absolute Seebeck coefficient directly can be challenging, as the voltage output of a thermoelectric circuit depends on the differences in Seebeck coefficients between materials. However, utilizing superconductors in thermocouples can allow for direct measurement of the absolute Seebeck coefficient of other materials.
The Peltier effect, discovered by Jean Peltier in 1834, and the Thomson effect, predicted by Lord Kelvin in 1851, are additional thermoelectric phenomena related to the Seebeck effect. Thermocouples, consisting of two dissimilar metals connected in a loop, are widely used for temperature measurement applications. Challenges in thermocouple usage include accurately determining the reference junction temperature and understanding the behavior of thermopiles, which consist of multiple thermocouples connected in series or parallel for power generation from heat sources.