3 Questions around this concept.
The Zeroth Law of Thermodynamics-
If two systems are in thermal equilibrium with a third system, they must be in thermal equilibrium with each other.
If system B is in thermal equilibrium with system A and system C is also in thermal equilibrium with system A, system B, and system C are in thermal equilibrium with each other.

A hot body has a higher temperature than a cold body. The temperature of two bodies decides the direction of heat flow when the two bodies are put in contact. The heat flows from the hot body to the cold body till the bodies are at the same temperature it is known as thermal equilibrium.
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