The law of conservation of energy in physics

In physics, the conservation of energy states that the total amount of energy in an isolated system remains constant, although it may change forms, e.g. friction turns kinetic energy into thermal energy.

In thermodynamics, the first law of thermodynamics is a statement of the conservation of energy for thermodynamic systems, and is the more encompassing version of the conservation of energy. In short, the law of conservation of energy stated that energy can not be created or destroyed, it can only be changed from one form to another, such as when electrical energy is changed into heat energy. From a mathematical point of view, the energy conservation law is a consequence of the shift symmetry of time; energy conservation is implied by the empirical fact that nothing depends on time itself.