Revised 24 May 2019

The First Law of Thermodynamics is also known as the Law of Conservation of Energy and can be stated as: 

Energy may be transformed from one form into another, but energy is neither created nor destroyed. 

The First Law of Thermodynamics rules out any pos­sibility of a perpetual motion machine of the first kind ─ a machine that will put out more energy in the form of work than is absorbed in the form of heat. Many attempts have been made to construct a perpetual motion machine and have failed.