The principle of increase in Entropy
Principle of increase of entropy Figure: Temperature VS Entropy Let a system change from state 1 to state 2 by a reversible process A and return to state 1 by another reversible process B. Then 1A2B1 is a reversible cycle. Therefore, the Clausius inequality gives: If the system is restored to the initial state from 1 to state 2 by an irreversible process C, then 1A2C1 is an irreversible cycle. Then the Clausius inequality gives: Subtracting the above equation from the first one, Since the process 2B1 is reversible, Where the equality sign holds good for a reversible process and the inequality sign holds good for an irreversible process. Now let us apply the above result to evaluate the entropy change of the universe when a system interacts with its surroundings and exchanges energy as heat with the surroundings. Let Tsur and Tsys be the temperatures of the surroundings and the system such that Tsur >Tsys. Let ...