Q.State Zeroth Law of Thermodynamics.

The Zeroth Law of Thermodynamics states that if two systems, A and B, are each separately found to be in thermal equilibrium with a third system, C, then A and B must also be in thermal equilibrium with each other. Two systems are in thermal equilibrium when, placed in contact through a thermally conducting boundary, no net heat flows between them.

Despite being numbered zero, this law was formally recognized as a necessary, independent postulate only after the First and Second Laws had already been established and named — the "zero" label reflects that it logically had to precede them, even though it was identified later. Without it, the entire concept of "temperature" as a single, well-defined property shared by any two objects in thermal equilibrium would have no rigorous logical basis. …