Skip to main content
Select Source:

perpetual-motion machine

perpetual-motion machine, device that would be able to operate continuously and supply useful work, in violation of the laws of thermodynamics. A machine that would produce more energy in the form of work than is supplied to it in the form of heat would violate the first law of thermodynamics, which is a special case of the law of conservation of energy (see conservation laws, in physics), and is known as a perpetual-motion machine of the first kind. A machine that would completely convert heat from a warm body into work, without letting any heat flow into a cooler body, would violate the second law of thermodynamics, which is concerned with entropy changes, and is known as a perpetual-motion machine of the second kind. There were a number of early attempts to design and construct various types of perpetual-motion machines; however, since the 19th cent., when the laws of thermodynamics became understood, most such attempts have been abandoned.

Cite this article
Pick a style below, and copy the text for your bibliography.

  • MLA
  • Chicago
  • APA

"perpetual-motion machine." The Columbia Encyclopedia, 6th ed.. . Encyclopedia.com. 16 Aug. 2018 <http://www.encyclopedia.com>.

"perpetual-motion machine." The Columbia Encyclopedia, 6th ed.. . Encyclopedia.com. (August 16, 2018). http://www.encyclopedia.com/reference/encyclopedias-almanacs-transcripts-and-maps/perpetual-motion-machine

"perpetual-motion machine." The Columbia Encyclopedia, 6th ed.. . Retrieved August 16, 2018 from Encyclopedia.com: http://www.encyclopedia.com/reference/encyclopedias-almanacs-transcripts-and-maps/perpetual-motion-machine

Learn more about citation styles

Citation styles

Encyclopedia.com gives you the ability to cite reference entries and articles according to common styles from the Modern Language Association (MLA), The Chicago Manual of Style, and the American Psychological Association (APA).

Within the “Cite this article” tool, pick a style to see how all available information looks when formatted according to that style. Then, copy and paste the text into your bibliography or works cited list.

Because each style has its own formatting nuances that evolve over time and not all information is available for every reference entry or article, Encyclopedia.com cannot guarantee each citation it generates. Therefore, it’s best to use Encyclopedia.com citations as a starting point before checking the style against your school or publication’s requirements and the most-recent information available at these sites:

Modern Language Association

http://www.mla.org/style

The Chicago Manual of Style

http://www.chicagomanualofstyle.org/tools_citationguide.html

American Psychological Association

http://apastyle.apa.org/

Notes:
  • Most online reference entries and articles do not have page numbers. Therefore, that information is unavailable for most Encyclopedia.com content. However, the date of retrieval is often important. Refer to each style’s convention regarding the best way to format page numbers and retrieval dates.
  • In addition to the MLA, Chicago, and APA styles, your school, university, publication, or institution may have its own requirements for citations. Therefore, be sure to refer to those guidelines when editing your bibliography or works cited list.

perpetual motion

per·pet·u·al mo·tion • n. a state in which movement or action is or appears to be continuous and unceasing. ∎  the motion of a hypothetical machine that, once activated, would run forever unless subject to an external force or to wear.

Cite this article
Pick a style below, and copy the text for your bibliography.

  • MLA
  • Chicago
  • APA

"perpetual motion." The Oxford Pocket Dictionary of Current English. . Encyclopedia.com. 16 Aug. 2018 <http://www.encyclopedia.com>.

"perpetual motion." The Oxford Pocket Dictionary of Current English. . Encyclopedia.com. (August 16, 2018). http://www.encyclopedia.com/humanities/dictionaries-thesauruses-pictures-and-press-releases/perpetual-motion-0

"perpetual motion." The Oxford Pocket Dictionary of Current English. . Retrieved August 16, 2018 from Encyclopedia.com: http://www.encyclopedia.com/humanities/dictionaries-thesauruses-pictures-and-press-releases/perpetual-motion-0

Learn more about citation styles

Citation styles

Encyclopedia.com gives you the ability to cite reference entries and articles according to common styles from the Modern Language Association (MLA), The Chicago Manual of Style, and the American Psychological Association (APA).

Within the “Cite this article” tool, pick a style to see how all available information looks when formatted according to that style. Then, copy and paste the text into your bibliography or works cited list.

Because each style has its own formatting nuances that evolve over time and not all information is available for every reference entry or article, Encyclopedia.com cannot guarantee each citation it generates. Therefore, it’s best to use Encyclopedia.com citations as a starting point before checking the style against your school or publication’s requirements and the most-recent information available at these sites:

Modern Language Association

http://www.mla.org/style

The Chicago Manual of Style

http://www.chicagomanualofstyle.org/tools_citationguide.html

American Psychological Association

http://apastyle.apa.org/

Notes:
  • Most online reference entries and articles do not have page numbers. Therefore, that information is unavailable for most Encyclopedia.com content. However, the date of retrieval is often important. Refer to each style’s convention regarding the best way to format page numbers and retrieval dates.
  • In addition to the MLA, Chicago, and APA styles, your school, university, publication, or institution may have its own requirements for citations. Therefore, be sure to refer to those guidelines when editing your bibliography or works cited list.