@JohnRennie hello sir...yes...cooking an egg is endothermic and increases its entropy...I got the reason but why sir...?Shouldn't entropy be decreased like if we consider the case of a piston system?
@JohnRennie also when we pull a rubber band, its entropy is decreased....but the rubber band will heat up a little...so shouldn't it increase?
So what happens is that the band heats up and that raises the entropy again. The entropy increase due to temperature rise exactly balances the entropy decrease due the shape of the molecules so the total entropy change is zero.
Note that no heat is being added or removed. What happens is that the internal energy of the rubber is redistributed.
I'll have to think about that. As I recall the argument is that if that were possible you could hook the heat engine up to a heat pump and get a free energy i.e. create energy from nothing.
Carnot's theorem, developed in 1824 by Nicolas Léonard Sadi Carnot, also called Carnot's rule, is a principle that specifies limits on the maximum efficiency any heat engine can obtain. The efficiency of a Carnot engine depends solely on the temperatures of the hot and cold reservoirs.
Carnot's theorem states that all heat engines between two heat reservoirs are less efficient than a Carnot heat engine operating between the same reservoirs. Every Carnot heat engine between a pair of heat reservoirs is equally efficient, regardless of the working substance employed or the operation details.
The...