Читать книгу Fundamentals of Heat Engines - Jamil Ghojel - Страница 61

If two systems are in thermal equilibrium with a third system, then they are in thermal equilibrium with each other and the three systems are said to be at the same temperature.

This law was added to the laws of thermodynamics early in the twentieth century because it was realised that the concept of equal‐in‐temperature is a prerequisite to a logical development of those laws. And to be logical, it was named the zeroth law of thermodynamics.