Question

Define the Peltier coefficient.

Answer 1

Hint: We will first learn about the Peltier Effect, and then we will try to understand this coefficient. It is also essential to understand what is the importance of this coefficient and how it is calculated. The Peltier Effect is seen in a thermocouple.

Complete solution:
A thermocouple is an electric device that has two dissimilar wires that together form an electrical junction. As a consequence of the thermoelectric effect, the thermocouple junction experiences a temperature change, producing a voltage change. This change in voltage is interpreted to find out the temperature change.
When current is passed through it, heat is evolved at one junction and absorbed at another junction inside a thermocouple. This phenomenon is called the Peltier Effect, named after French physicist Jean Charles Athanase Peltier, who discovered this in $1834$.
The amount of heat generated or absorbed in a thermocouple is directly proportional to the current amount and total time the current is passed. Therefore we write-
$H \propto I \times t$
$ \Rightarrow H = \pi \times I \times t$
Where $\pi $ is a proportionality constant. This proportionality constant is termed as Peltier coefficient. The amount of heat energy evolved or absorbed in a thermocouple while passing $1$ ampere current for $1$ second is called the Peltier coefficient.

The Peltier coefficient is also denoted by $\pi $.

Note: In S.I., the unit of the Peltier coefficient is volt. A thermocouple is used to measure the temperature of various systems such as diesel engines, gas turbine exhaust, and other industrial purposes. It is also used for fire safety purposes, such as in thermostatic machines and flame sensors.