The Zeroth Law Of Thermodynamics
Logically, this is an inductive conclusion depend on inspection or experiments with systems in thermal equilibrium. When the idea of temperature equality is exerted to an experiment including three systems, S1, S2, & S3, and experimental law concerning temperature can be determined.
Assume the systems S1 and S3 be equivalent in temperature, as proved by the absence of any change in the physical properties of either system whenever they are brought into (i.e., thermal) contact. Likewise, let S2 and S3 be equivalent in temperature and hence no change takes place whenever they are brought into contact. When now S1 and S2 are brought into contact, it is an empirical surveillance that no change takes place in their physical properties; leading to the conclusion that S1 and S2 are equivalent in temperature.
This lead to the formulation of the Zeroth law of thermodynamics as follows:
“The two systems that are equivalent in temperature to a third system are equivalent in temperature to each other.”
This law gives the foundation for temperature measurement. It turns the thermometer into a helpful instrument, by removing the requirement for bringing into physical contact each pair of systems whose temperatures we desire to compare.
To some extent, the Zeroth law might emerge to be as apparent as to be trivial, though, as will be shown now, it is not so. Let consider three analogies:
• An amber rod A which has been rubbed with fur will attract a pith ball C. Therefore will another amber rod B, though the two amber rods will not attract each other.
• The north pole of a magnet A will attract the south pole of magnet B; therefore will the north poles of another magnet C. Though the north poles of the magnets A & C will not attract each other.
• Now for an illustration from exterior science: when Ashley loves Bob, and Charlie also loves Bob, it does not mean that Ashley and Charlie love each other, just the reverse!
Therefore the Zeroth law is not a mathematical proposition, though symbolizes the essence of empirical information concerning temperature and thermal equilibrium.
Why it is termed as the Zeroth law? Since although this statement logically precede the first and the second laws, it was not explicitly formulated until afterward. The British astrophysicist R. H. Fowler is accredited with having specified this name. It is fascinating that an Indian physicist figures in this account. Whereas analyzing the book titled “Heat and Thermodynamics” by Meghnad Saha for a scientific journal in England, Fowler referred to this statement made in the book as the Zeroth law, and the name fixed.