State seeback effect. Describe the working of thermocouple.
Seebeck effect: Seebeck effect states that whenever two dissimilar metals are connected together to form two junctions out of which, one junction is subjected to high temperature and another is subjected to low temperature then, an e.m.f is induced proportional to the temperature difference between the two junctions.
thermocouple has two connected to form two junctions. One junction is kept at a constant temperature (cold junction) and the other in the medium whose temperature is to be measured (hot junction). When a temperature difference exist between both the junctions a very low emf is produced which causes a current in the circuit.