15.7 Entropy

A quantity called Entropy can be derived from the study of the Carnot Cycle. This quantity can then be used to formulate mathematically The Second Law of Thermodynamics.

When heat Q is exchanged at temperature T then the entropy changes by amount

Now, in Carnot Cycle

Thus in a reversible thermodynamic process the change in entropy of the system is zero, i.e. the entropy remains constant whereas in an irreversible process we find that change in entropy is always greater than zero.

Hence, the second Law of Thermodynamics states that entropy of the universe never decreases.

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Index

15.1 The Zeroth Law
15.2 The First Law
15.3 Work done and Some applications of First Law
15.4 Thermodynamic Processes
15.5 Carnot Cycle
15.6 The Second Law
15.7 Entropy

  Chapter 16