Changes

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

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

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

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

From a theoretical point of view, these machines are classified into three categories based on which law of thermodynamics they  violate:

From a theoretical point of view, these machines are classified into three categories based on which principle of thermodynamics they  violate:

*Perpetual motion device of the first category: This machine would show an efficiency of more than 100% (PM supporters will also call it 'overunity'). Such a device will be in violation of the first law of thermodynamics, the law of energy conservation, as it would produce energy from nothing.  

*Perpetual motion device of the first kind: This machine would show an efficiency of more than 100% (PM supporters will also call it 'overunity'). Such a device will be in violation of the first principle of thermodynamics, that of energy conservation, as it would produce energy from nothing.  

*Perpetuum Motion device of the second category: This machine will work cyclically and and will take the energy necessary from a heating bath. Such a device will be in violation of the second law of thermodynamics, since the total conversion of work into heat happens to be irreversible. Heat pumps therefore  may not be seen as a second category PM.

*Perpetual Motion device of the second kind: This machine will work cyclically and and will take the energy necessary from a heat reservoir. Such a device will be in violation of the second principle of thermodynamics, since the total conversion of work into heat happens to be irreversible. Heat pumps therefore  may not be seen as a second category PM.

*Perpetuum Motion device of the third kind: A machine that runs 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 achieve, it is however possible to come pretty close. Such devices have actually useful appliances e.g in the construction of flywheels.

*Perpetual Motion device of the third kind: A machine that runs 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 achieve, it is however possible to come pretty close. Such devices have actually useful appliances e.g in the construction of flywheels.

==Examples==

==Examples==