Question

Two bodies A, B and bodies B, C are in thermal equilibrium with each other. If the temperature of A and B is ${45}^{\circ }\text{C}$, then the temperature of C is ${45}^{\circ }\text{C}$. Explain.

Answer 1

According to zeroth law of thermodynamics, if two thermodynamic systems are in thermal equilbrium with a third one individually, then they are in thermal equilibrium with each other.
Accordingly, thermal equilibrium between systems is transitive relation. So, If A, B and B, C are in thermal equilbrium & temperature of A is given as ${45}^{\circ }\text{C}$, then C must be at ${45}^{\circ }\text{C}$ temperature as well.