The Second Law of Thermodynamics
Most natural processes are not reversible.
The Second Law of Thermodynamics, which can be stated in different ways, describes this irreversibility of Nature.
One statement of the Second Law of Thermodynamics is that
Heat does not spontaneously flow from a low-temperature region
to a high-temperature region.
(c) 2005, Doug Davis; all rights reserved
First Law Ideal Heat Engines Return to ToC, Thermodynamics