APSC Legal Metrology: Paper 2 MCQ on Seebeck effect

A thermocouple can be used for temperature measurement. This is based on
(A) Seebeck effect
(B) Peltier effect
(C) Thomson effect
(D) Joule’s law

The correct answer is:
(A) Seebeck effect

Explanation:

A thermocouple measures temperature based on the Seebeck effect, which is the generation of an electromotive force (EMF) when there is a temperature difference between the junctions of two dissimilar metals.

• Seebeck effect: Voltage is produced due to a temperature gradient across different conductors (basis of thermocouples).
• Peltier effect: Heat is absorbed or released when electric current passes through the junction of two different materials (used in thermoelectric cooling).
• Thomson effect: Heat is absorbed or evolved when current flows in a conductor with a temperature gradient.
• Joule’s law: Describes the heating effect of electric current (not related to thermocouples directly).

So, thermocouples operate on the Seebeck effect.