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A '''Perpetuum Motion''' (lat: eternal movement) device is a hypothetical machine that can produce work indefinitely without energy source or produce more energy than they consume.

A '''Perpetuum Motion''' (lat: eternal movement) device is a hypothetical machine that can produce work indefinitely without energy source or produce more energy than they consume.

A great number of inventors claim that they have build a perpetual motion machine, but none of them could prove it. Often these claims were made by fraudsters and scammers. Since such a device would violate the laws of thermodynamics, it is also scientific consensus that it is impossible.

A great number of inventors claim that they have build a perpetual motion machine, but none of them could prove it. Often these claims were made by fraudsters and scammers. Since such a device would violate the laws of thermodynamics, it is also scientific consensus that it is impossible. Despite that fact, the pursuit of perpetual motion remains popular.

 

==Classes of Perpetuum Motion devices==

==Classes of Perpetuum Motion devices==

[[image:pmleonardodavinci.jpg|PM nach Leonardo da Vinci|left|thumb]]

[[image:pmleonardodavinci.jpg|PM nach Leonardo da Vinci|left|thumb]]

[[image:BesslerRad.jpg|PM Bessler Rad|200px|thumb]]

[[image:BesslerRad.jpg|PM Bessler Rad|200px|thumb]]

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 would 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. This kind is also called "overunity" by its fans.

*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 any work. The idea is that if friction is completely removed such a machine might run forever. And while it is impossible to reach that goal, it is possible to come pretty close. It has actually useful appliances e.g in the construction of flywheels.

==Examples==

==Examples==

*http://en.wikipedia.org/w/index.php?title=History of perpetual motion machines

*http://en.wikipedia.org/w/index.php?title=History of perpetual motion machines

*[http://www.lhup.edu/~dsimanek/museum/unwork.htm The Museum of Unworkable Devices]

*[http://www.lhup.edu/~dsimanek/museum/unwork.htm The Museum of Unworkable Devices]

 

==Versions of this article in other languages==

==Versions of this article in other languages==

*deutsch: [http://www.psiram.com/ge/index.php?title=Perpetuum_Mobile Perpetuum Mobile]

*deutsch: [http://www.psiram.com/ge/index.php?title=Perpetuum_Mobile Perpetuum Mobile]

[[category:Abbreviation/Definition]]

[[category:Abbreviation/Definition]]