A thermometric refrigerator works on:
A) Joule effect.
B) Seebeck effect.
C) Peltier effect.
D) Thermometric emission.

Hint:A thermometer is a device which is used for temperature measurement. Temperature is known as the degree of hotness and coldness and the heat is expressed in the form of Joules. The temperature can be measured in the form of Celsius $\left( {^\circ C} \right)$, Kelvin (K) and Fahrenheit $\left( {^\circ F} \right)$.

Complete step by step solution:
It is asked in the problem about the working principle of the thermometric refrigerator.

Seebeck effect:
If two dissimilar metals are connected to two ends of the circuit and one of the metal is cooled and the other is heated then there will be passing of current through the circuit and the reverse of this is used in the thermometric refrigerator.

Peltier effect:
When a circuit is connected to two dissimilar metals at the two ends of the circuit and a current is passed through the circuit then one metal starts cooling and other metal starts heating and this is what is known as peltier effect. The peltier effect is the reverse of the Seebeck effect.

When a metal from one end is heated and the metal on the other side is cooled therefore the electrons rush from one side to the other side of the metal and hence the flow of current takes place.

The thermometric refrigerator works on the principle of Peltier effect.

The correct option for this problem is option C.

Note:A thermocouple is a device having two dissimilar materials connected to its two ends and by the end of the circuit and the formation of the circuit has a temperature dependent voltage due to thermoelectric effect and by the help of this voltage any temperature can be measured.