Question

The law that forms the basis of measurement of temperature is 
1. 0^th law of Thermodynamics 
2. 1^st law of thermodynamics
3. 2^nd law of thermodynamics 
4. Kirchhoff’s law 

Answer 1

Correct Answer - Option 1 : 0^th law of Thermodynamics 

Explanation:

The zeroth law of thermodynamics states that if two thermodynamic systems are in thermal equilibrium with a third system, then they are in thermal equilibrium with each other.

A thermometer works on the principle of Zeroth's law of Thermodynamics.

A thermometer is based on the principle of finding the temperature by measuring the thermometric property.

Points to remember

• The first law of thermodynamics states that energy can neither be created nor destroyed in an isolated system. The first law measures internal energy.
• The second law of thermodynamics states that the entropy of an isolated system always increases. the second law measures entropy.
• According to the Third law of thermodynamics, when the temperature of a perfect crystal is equal to absolute 0 (0 K), the entropy of the crystal is 0.

Kirchhoff's law:

It states that the emissivity (ϵ) of the surface of a body is equal to its absorptivity (α) when the body is in thermal equilibrium with its surroundings.

ϵ = α.