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From a theoretical point of view these machine are classified by the law they violate:

From a theoretical point of view these machine are classified by the law they violate:

*Perpetuum Motion device of the first kind: This machine produces energy without input or more that it consumes and violates the first law of thermodynamics.

*Perpetuum Motion device of the first kind: This machine produces energy without input or more that it consumes and violates the first law of thermodynamics. This kind is also called "overunity" by its fans.

*Perpetuum Motion device of the second kind: This machine converts heat to mechanical energy. Since this cools the environment, it cannot go on forever and violates the second law of thermodynamics.

*Perpetuum Motion device of the second kind: This machine converts heat to mechanical energy. Since this cools the environment, it cannot go on forever and violates the second law of thermodynamics.

*Perpetuum Motion device of the third kind: A machine that can run indefinitely without doing work. Since friction and other interactions with the environment cannot be avoided, such a machine cannot be build (but one can come very close)

*Perpetuum Motion device of the third kind: A machine that can run indefinitely without doing work. Since friction and other interactions with the environment cannot be avoided, such a machine cannot be build (but one can come very close)