Question

A reversible process changes the state of a system in such a way that the net change in the combined entropy of the system and its surroundings is :

• A. Zero
• B. Unity
• C. Not equal
• D. More than zero

Answer 1

Answer: (A)

Zero

A reversible process changes the state of a system in such a way that the net change in the combined entropy of the system and its surroundings is zero. Reversible processes define the boundaries of how efficient heat engines can be in thermodynamics and engineering: a reversible process is one where no heat is lost from the system as "waste", and the machine is thus as efficient as it can possibly be (see Carnot cycle).