Editing Machine (section)

== Power sources ==
{{More citations needed|section|date=November 2021}}
[[File:Model Engine Luc Viatour.jpg|thumb|Diesel engine, friction clutch and gear transmission of an automobile]]
[[File:Generator-20071117.jpg|thumb|Early [[Ganz]] Electric Generator in [[Zwevegem]], [[West Flanders]], [[Belgium]]]]
Human and animal effort were the original power sources for early machines.{{citation needed|date=November 2021}}

'''Waterwheel:''' [[Waterwheel]]s appeared around the world around 300 BC to use flowing water to generate rotary motion, which was applied to [[watermill|milling grain, and powering lumber, machining and textile operations]]. Modern [[water turbine]]s use water flowing through a [[dam]] to drive an [[electric generator]].

'''Windmill:''' Early [[wind mill|windmills]] captured wind power to generate rotary motion for milling operations. Modern [[wind turbine]]s also drives a generator. This electricity in turn is used to drive [[Electric motor|motors]] forming the actuators of mechanical systems.

'''Engine:''' The word engine derives from "ingenuity" and originally referred to contrivances that may or may not be physical devices.<ref>[http://www.merriam-webster.com/dictionary/engine Merriam-Webster's definition of engine]</ref> A [[steam engine]] uses heat to boil water contained in a pressure vessel; the expanding steam drives a piston or a turbine. This principle can be seen in the [[aeolipile]] of Hero of Alexandria. This is called an [[external combustion engine]].

An [[automobile]] engine is called an [[internal combustion engine]] because it burns fuel (an [[exothermic]] chemical reaction) inside a cylinder and uses the expanding gases to drive a [[piston]]. A [[jet engine]] uses a turbine to compress air which is burned with fuel so that it expands through a nozzle to provide thrust to an [[aircraft]], and so is also an "internal combustion engine."  <ref>"Internal combustion engine", ''Concise Encyclopedia of Science and Technology'', Third Edition, Sybil P. Parker, ed. McGraw-Hill, Inc., 1994, p. 998 .</ref>

'''Power plant:''' The heat from coal and natural gas combustion in a [[boiler]] generates steam that drives a [[steam turbine]] to rotate an [[electric generator]]. A [[nuclear power plant]] uses heat from a [[nuclear reactor]] to generate steam and [[electric power]]. This power is distributed through a [[electrical grid|network of transmission lines]] for industrial and individual use.

'''Motors:''' [[Electric motor]]s use either [[alternating current|AC]] or [[direct current|DC]] electric current to generate rotational movement. Electric [[servomechanism|servomotors]] are the actuators for mechanical systems ranging from [[robotics|robotic systems]] to [[fly-by-wire|modern aircraft]].

'''Fluid Power:''' [[hydraulic cylinder|Hydraulic]] and [[pneumatic cylinder|pneumatic]] systems use electrically driven [[pump]]s to drive water or air respectively into cylinders to power [[linear actuator|linear movement]].

'''Electrochemical:''' Chemicals and materials can also be sources of power.<ref>{{Cite book|last1=Brett|first1=Christopher M. A|url=https://www.worldcat.org/oclc/26398887|title=Electrochemistry: principles, methods, and applications|last2=Brett|first2=Ana Maria Oliveira|date=1993|publisher=Oxford University Press|isbn=978-0-19-855389-2|location=Oxford; New York|language=English|oclc=26398887}}</ref> They may chemically deplete or need re-charging, as is the case with [[Electric battery|batteries]],<ref name=":0">{{Cite book|last=Crompton|first=T. R.|url=https://books.google.com/books?id=QmVR7qiB5AUC&q=battery+one+or+more+cells&pg=PA11|title=Battery Reference Book|date=2000-03-20|publisher=Elsevier|isbn=978-0-08-049995-6|language=en}}</ref> or they may produce power without changing their state, which is the case for [[solar cell]]s and [[thermoelectric generator]]s.<ref name=":1">{{Cite web|title=Solar Cells -- Performance And Use|url=http://solarbotics.net/starting/200202_solar_cells/200202_solar_cell_use.html|access-date=|website=}}</ref><ref name=":2">{{Cite journal|last1=Fernández-Yáñez|first1=P.|last2=Romero|first2=V.|last3=Armas|first3=O.|last4=Cerretti|first4=G.|date=2021-09-01|title=Thermal management of thermoelectric generators for waste energy recovery|journal=Applied Thermal Engineering|language=en|volume=196|pages=117291|doi=10.1016/j.applthermaleng.2021.117291|issn=1359-4311|doi-access=free|bibcode=2021AppTE.19617291F }}</ref> All of these, however, still require their energy to come from elsewhere. With batteries, it is the already existing [[Chemical energy|chemical potential energy]] inside.<ref name=":0" /> In solar cells and thermoelectrics, the energy source is light and heat respectively.<ref name=":1" /><ref name=":2" />