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{{wiktionary}}
 
== Production and uses ==
=== Generation ===
{{main|Electricity generation}}
[[किपा:Parque eólico La Muela.jpg|thumb|left|Wind power is of increasing importance in many countries]]
Thales' experiments with amber rods were the first studies into the production of electrical energy. While this method, now known as the [[triboelectric effect]], is capable of lifting light objects and even generating sparks, it is extremely inefficient.<ref name=batteries>
{{citation
| first = Ronald | last = Dell
| first2 = David | last2 = Rand
| title = Understanding Batteries
| pages = 2–4
| year = 2001
| publisher = Royal Society of Chemistry
| isbn = 0854046054}}
</ref> It was not until the invention of the voltaic pile in the eighteenth century that a viable source of electricity became available. The voltaic pile, and its modern descendant, the [[Battery (electricity)|electrical battery]], store energy chemically and make it available on demand in the form of electrical energy.<ref name=batteries/> The battery is a versatile and very common power source which is ideally suited to many applications, but its energy storage is finite, and once discharged it must be disposed of or recharged. For large electrical demands electrical energy must be generated and transmitted in bulk.
 
Electrical energy is usually generated by electro-mechanical [[electrical generator|generators]] driven by [[steam]] produced from [[fossil fuel]] combustion, or the heat released from [[nuclear energy|nuclear reactions]]; or from other sources such as [[kinetic energy]] extracted from wind or flowing water. Such generators bear no resemblance to Faraday's homopolar disc generator of 1831, but they still rely on his electromagnetic principle that a conductor linking a changing magnetic field induces a potential difference across its ends.<ref>
{{citation
| first = Peter G. | last = McLaren
| title = Elementary Electric Power and Machines
| pages = 182–183
| year = 1984
| publisher = Ellis Horwood
| isbn = 0-85312-269-5}}
</ref> The invention in the late nineteenth century of the [[transformer]] meant that electricity could be generated at centralised [[power station]]s, benefiting from [[economies of scale]], and be [[Electric power transmission|transmitted]] across countries with increasing efficiency.<ref name=Patterson_p44-48>
{{citation
| first = Walter C. | last = Patterson
| title = Transforming Electricity: The Coming Generation of Change
| pages = 44–48
| year = 1999
| publisher = Earthscan
| isbn = 185383341X}}
</ref><ref>
{{citation
| last = Edison Electric Institute
| title = History of the Electric Power Industry
| url=http://www.eei.org/industry_issues/industry_overview_and_statistics/history
| accessdate = 2007-12-08}}
</ref> Since electrical energy cannot easily be stored in quantities large enough to meet demands on a national scale, at all times exactly as much must be produced as is required.<ref name=Patterson_p44-48/> This requires [[Electric utility|electricity utilities]] to make careful predictions of their electrical loads, and maintain constant co-ordination with their power stations. A certain amount of generation must always be held in [[Operating reserve|reserve]] to cushion an electrical grid against inevitable disturbances and losses.
 
Demand for electricity grows with great rapidity as a nation modernises and its economy develops. The United States showed a 12% increase in demand during each year of the first three decades of the twentieth century,<ref>
{{Citation
| last = Edison Electric Institute
| title = History of the U.S. Electric Power Industry, 1882-1991
| url=http://www.eia.doe.gov/cneaf/electricity/chg_stru_update/appa.html
| accessdate = 2007-12-08}}
</ref> a rate of growth that is now being experienced by emerging economies such as those of India or China.<ref>
{{Citation
| last = Carbon Sequestration Leadership Forum
| title = An Energy Summary of India
| url=http://www.cslforum.org/india.htm
| accessdate = 2007-12-08}}
</ref><ref>
{{Citation
| last = IndexMundi
| title = China Electricity - consumption
| url=http://www.indexmundi.com/china/electricity_consumption.html
| accessdate = 2007-12-08}}
</ref> Historically, the growth rate for electricity demand has outstripped that for other forms of energy, such as [[coal]].<ref>
{{Citation
| last= National Research Council
| authorlink = United States National Research Council
| title = Electricity in Economic Growth
| publisher = National Academies Press
| year = 1986
| page = 16
| isbn = 0309036771}}
</ref>
 
[[Environmental concerns with electricity generation]] have led to an increased focus on generation from [[Renewable energy|renewable sources]], in particular from [[wind power|wind-]] and [[hydropower]]. While debate can be expected to continue over the environmental impact of different means of electricity production, its final form is relatively clean.<ref>
{{Citation
| last= National Research Council
| authorlink = United States National Research Council
| title = Electricity in Economic Growth
| publisher = National Academies Press
| year = 1986
| page = 89
| isbn = 0309036771}}
</ref>
 
=== Uses ===
[[किपा:Gluehlampe 01 KMJ.png|right|thumb|upright|The [[incandescent light bulb|light bulb]], an early application of electricity, operates by [[Joule heating]]: the passage of [[current (electricity)|current]] through [[Electrical resistance|resistance]] generating heat]]
Electricity is an extremely flexible form of energy, and has been adapted to a huge, and growing, number of uses.<ref>
{{Citation
| first = Matthew | last = Wald
| title = Growing Use of Electricity Raises Questions on Supply
| newspaper = New York Times
| url= http://query.nytimes.com/gst/fullpage.html?res=9C0CE6DD1F3AF932A15750C0A966958260
| date = [[21 March]] [[1990]]
| accessdate = 2007-12-09}}</ref> The invention of a practical [[incandescent light bulb]] in the 1870s led to [[lighting]] becoming one of the first publicly available applications of electrical power. Although electrification brought with it its own dangers, replacing the naked flames of gas lighting greatly reduced fire hazards within homes and factories.<ref>
{{Citation
| first = Peter | last = d'Alroy Jones
| title = The Consumer Society: A History of American Capitalism
| page = 211
| publisher = Penguin Books}}
</ref> Public utilities were set up in many cities targeting the burgeoning market for electrical lighting.
 
The [[Joule heating]] effect employed in the light bulb also sees more direct use in [[electric heating]]. While this is versatile and controllable, it can be seen as wasteful, since most electrical generation has already required the production of heat at a power station.<ref>
{{Citation
| first = Charles and Penelope | last = ReVelle
| title = The Global Environment: Securing a Sustainable Future
| publisher = Jones & Bartlett
| page = 298
| year = 1992
| isbn = 0867203218}}
</ref> A number of countries, such as Denmark, have issued legislation restricting or banning the use of electric heating in new buildings.<ref>
{{Citation
| last = Danish Ministry of Environment and Energy
| work = Denmark´s Second National Communication on Climate Change
| title = F.2 The Heat Supply Act
| url= http://glwww.mst.dk/udgiv/Publications/1997/87-7810-983-3/html/annexf.htm
| accessdate = 2007-12-09}}
</ref> Electricity is however a highly practical energy source for [[refrigeration]],<ref>
{{Citation
| first = Charles E. | last = Brown
| title = Power resources
| publisher = Springer
| year = 2002
| isbn = 3540426345}}
</ref> with [[air conditioning]] representing a growing sector for electricity demand, the effects of which electricity utilities are increasingly obliged to accommodate.<ref>
{{Citation
| first = B. | last = Hojjati
| first2 = S. | last2 = Battles
| title = The Growth in Electricity Demand in U.S. Households, 1981-2001: Implications for Carbon Emissions
| url= http://www.eia.doe.gov/emeu/efficiency/2005_USAEE.pdf
| accessdate = 2007-12-09}}
</ref>
 
Electricity is used within [[telecommunication]]s, and indeed the [[electrical telegraph]], demonstrated commercially in 1837 by [[William Fothergill Cooke|Cooke]] and [[Charles Wheatstone|Wheatstone]], was one of its earliest applications. With the construction of first [[First Transcontinental Telegraph|intercontinental]], and then [[Transatlantic telegraph cable|transatlantic]], telegraph systems in the 1860s, electricity had enabled communications in minutes across the globe. [[Optical fibre]] and [[Communications satellite|satellite communication]] technology have taken a share of the market for communications systems, but electricity can be expected to remain an essential part of the process.
 
The effects of electromagnetism are most visibly employed in the [[electric motor]], which provides a clean and efficient means of motive power. A stationary motor such as a [[winch]] is easily provided with a supply of power, but a motor that moves with its application, such as an [[electric vehicle]], is obliged to either carry along a power source such as a battery, or by collecting current from a sliding contact such as a [[Pantograph (rail)|pantograph]], placing restrictions on its range or performance.
 
Electronic devices make use of the [[transistor]], perhaps one of the most important inventions of the twentieth century,<ref>
{{Citation
| first = Dennis F. | last = Herrick
| title = Media Management in the Age of Giants: Business Dynamics of Journalism
| publisher = Blackwell Publishing
| year = 2003
| isbn = 0813816998}}
</ref> and a fundamental building block of all modern circuitry. A modern [[integrated circuit]] may contain several billion miniaturised transistors in a region only a few centimetres square.<ref>
{{Citation
| first = Saswato R.| last = Das
| title = The tiny, mighty transistor
| newspaper = Los Angeles Times
| date = [[2007-12-15]]
| url = http://www.latimes.com/news/opinion/la-oe-das15dec15,0,4782957.story?coll=la-opinion-rightrail}}
</ref>
 
== Electricity and the natural world ==