What is Peltier effect?

Hint: The Peltier effect is a phenomenon related to the dissimilarity in temperatures at the junction of a circuit wire made of two different materials. It is a type of thermoelectric effect along with the Thomson and Seebeck effects.

Complete step by step answer:
The Peltier effect was first observed by and named after the French physicist Jean Charles Athanase Peltier who discovered this effect in 1834.
According to this effect, when electric current passes through a part of a circuit consisting of dissimilar conductors, there is a temperature difference at the junction of the two conductors.
For example, if a circuit wire is made by joining a small piece of Bismuth wire in between the copper circuit wire, the temperature rises in the junction where the current goes from copper to bismuth and a temperature drop is observed at the junction where electric current passes from bismuth to copper.
This happens because heat is absorbed in the first junction and released in the latter junction.
The heat generated per unit time is dependent upon the current passing through and the difference in the peltier constants of the two materials of conductors.

Additional information:
The Peltier effect is used in various devices like the thermoelectric Peltier pump where various dissimilar conductors are joined together and a current is passed through. Heat is generated at some junctions and lost from the others. The generated heat is tapped into.

Notes: Students should have a brief idea of the three thermoelectric effects that is the Peltier effect, Thomson effect and the Seebeck effect. These are especially important since they relate electrical energy to thermal energy and all of them have various real world practical applications. Students must also know that the Peltier effect and the Seebeck effect are almost like the opposites of each other and hence knowing the difference between the two is important.