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Revision as of 05:44, 14 July 2003 by Reddi (talk | contribs) (presentation)(diff) ← Previous revision | Latest revision (diff) | Newer revision → (diff)Perpetual motion machines are a class of hypothetical machines which produce energy "from nowhere." The existence of a perpetual motion machine is impossible according to current known laws of physics. Perpetual motion machines are divided into two subcategories, referred to as perpetual motion of the first kind and perpetual motion of the second kind.
Criteria
Perpetual motion machines violate one or both of the following two laws of physics: the first law of thermodynamics and the second law of thermodynamics. True Perpetual motion machines would need to produce energy from a unseen potential or force. True perpetual motion machine would have to not violate the laws of physics, the first law of thermodynamicsm, and the second law of thermodynamics. All other laws of physics and thermodynamics would be not in voilation either by a true perpetual motion machine. The first law of thermodynamics is essentially a statement of conservation of energy. The second law has several statements, perhaps the most well known is that entropy, or disorder, always increases. Another statement is that no engine can be more efficient than a Carnot heat engine. See the respective articles, and thermodynamics, for more information.
Kinds of Violations
First Kind
A perpetual motion machine of the first kind is one which produces power without energy uptake. Such a machine would, once started, operate indefinitely. This is forbidden by the law of conservation of energy.
Note that this explicitly prohibits the existence of devices which produce more energy than their input energy, as they can trivially be converted to a perpetual motion machine of the first kind by diverting part of their output energy back to their input.
Note that heat engines with an 'efficiency' greater than one do not violate this rule: the 'efficiency' in this case is defined as the ratio of heat output to work input -- the total energy input (heat + work) is still equal to the total energy output (heat).
Second Kind
A perpetual motion machine of the second kind is one which converts heat completely into other forms of energy. Such a device would violate the second law of thermodynamics (see also entropy) and would be viewed with great skepticism.
Inventions and Patents
The invention of perpetual motion machines is a favourite pastime of many crackpots, who often come up with elaborate Rube Goldberg machine designs which may appear to work on paper at first glance, but which have various flaws or obfuscated external power sources that render them useless in practice. This sort of invention has become common enough that the United States Patent and Trademark Office (USPTO) has made an official policy of refusing to grant patents for perpetual motion machines without a working model.
Proponents of perpetual motion machines use a number of other terms to describe their inventions, including "free energy" and "over unity" machines.
The USPTO granted at least two patents for motors that are claimed to run without net energy input. These patents were issued because it was not obvious from the patent that a perpetual motion machine was being claimed. These are:
- 4,151,431 on April 24, 1979 ("Permanent Magnet Motor")
- 4,074,153 on February 14, 1978 ("Magnetic propulsion device")