Carnot’s theorem also known as Carnot’s rule was developed by Nicolas Léonard Sadi Carnot in the year 1824, with the principle that there are limits on maximum efficiency for any given heat engine. It depends mainly on hot and cold reservoir temperatures.

Carnot’s theorem states that:

• Heat engines that are working between two heat reservoirs are less efficient than the Carnot heat engine that are operating between same reservoirs.
• Irrespective of the operation details, every Carnot engine is efficient between two heat reservoirs.
• Maximum efficiency is given as: