Fontem paginae Volta (unitas) inspicere

[[Fasciculus:Electronic multi meter.jpg|thumb|{{Creanda|en|Multimeter|Multimetrum}} ad voltium metiendam inter duo punctos adhibetur.]]
[[Fasciculus:BateriaR14.jpg|150px|thumb|[[Accumulatrum|Accumulatra]] "C-cell" 1.5 V.]]
'''Volta'''<ref name="dael-volta">{{DAEL|voltio|1124}}.</ref> ({{pns|ae|f}}), sive '''voltium''' ({{pns|ii|n}}),<ref>John C. Traupman, ''The New College Latin and English Dictionary,'' ed. tertia (Novi Eboraci: Bantam Books, 2007), 697, s.v. ''volt.''</ref><ref>Scil ''electronis.'' Petrus Lucusaltianus Latinophilus, ''Lexicon Latinum Hodiernum vel Vocabularium Latinitatis Huius Aetatis,'' ed. 23 electronica (Lentiae ad Danuvium: Dicasterium ad Relatinizandum Orbem Terrarum, 2023), 95, s.v. ''Elektronvolt.''</ref><ref name="dael-volta">{{DAEL|voltio|1124}}.</ref> [[abbreviatio|siglis]] '''V''' scriptum, in [[SI|Systemate Internationali]] est [[unitas physica|unitas]] [[tensio electrica|tensionis electricae]], potius {{Creanda|en|Potential difference|differentiae potentialis}} vel {{Creanda|en|Electromotive force|virium electromotivarum}}.<ref name="BIPM Definition">{{cite web| url = http://www.bipm.org/en/si/si_brochure/chapter2/2-2/table3.html| title = SI Brochure, Table 3 (Section 2.2.2)| accessdate = 2007-07-29|date= [[2006]]| publisher = BIPM}}</ref><ref>Rudolf F. Graf, "Volt", Dictionary of Electronics; Radio Shack, 1974-75. Fort Worth, Texas. ISBN B000AMFOZY</ref> Ex [[Alexander Volta|Alexandro Volta]] [[physicus|physico]] [[Italia|Italo]] (1745–1827) appellatur, qui {{Creanda|en|Voltaic pile|cumulum voltaicum}}, primum {{Creanda|en|Battery (electricity)|accumulatrum}} chemicum hodiernum, [[inventio|excogitavit]].

Una volta valet 1 [[m]]<sup>2</sup> · [[kg]] · [[secundum|s]]<sup>-3</sup> · [[amperium (unitas)|A]]<sup>-1</sup>, vel 1 [[Joulium|iulium]] [[energia]]e per [[coulomb (unitas)|culombium]], J/C. 

In [[lingua]] [[mathematica]]:
:<math>\mbox{V} = \dfrac{\mbox{W}}{\mbox{A}} = \dfrac{\mbox{W} \cdot \mbox{s}}{\mbox{A} \cdot \mbox{s}} = \dfrac{\mbox{J}}{\mbox{C}} = \dfrac{\mbox{N} \cdot \mbox{m} }{\mbox{A} \cdot \mbox{s}} = \dfrac{\mbox{kg} \cdot \mbox{m}^2}{\mbox{A} \cdot \mbox{s}^{3}}</math>

Secundum [[lex Ohmica|legem Ohmicam]], in filo conductore cuius [[resistentia electrica]] est unius ohmii, tensio electrica unius volti fluxionem electricam unius amperii provocat, ut possimus scribere unam voltam uno amperio per unum ohmium multiplicato aequalem esse.
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== Definition ==
The volt is defined as the [[potential difference]] across a conductor when a [[Electric current|current]] of one [[ampere]] dissipates one [[watt]] of [[power (physics)|power]].<ref>[http://www.bipm.org/utils/common/pdf/si_brochure_8_en.pdf BIPM SI Brochure: Appendix 1, p. 144]</ref> 

=== Josephson junction definition ===
Since 1990 the volt is maintained internationally for practical measurement using the [[Josephson effect]], where a conventional value is used for the [[Josephson constant]], fixed by the 18th [[General Conference on Weights and Measures]] as 

:'''K<sub>{J-90}</sub>''' = 0.4835979 GHz/µV.

== Hydraulic analogy ==
In the ''[[hydraulic analogy]]'' sometimes used to explain electric circuits by comparing them to water-filled pipes, [[voltage]] is likened to water pressure – it determines how fast the electrons will travel through the circuit.  Current (in amperes), in the same analogy, is a measure of the volume of water that flows past a given point.  This volume is determined by the width of the pipe and the water pressure on the front end of the pipe compared with the exit. The analogy extends to power dissipation:  the power given off by the water flow is equal to current times pressure, just as the power dissipated in a resistor is equal to current times the voltage drop across the resistor (amperes x volts = watts).

The relationship between voltage and current (in ohmic devices) is defined by [[Ohm's Law]].

== Common voltages ==

Nominal voltages of familiar sources:
* [[Nerve cell]] [[action potential]]: around 75 mV<ref>The dual effect of membrane potential on sodium conductance in the giant axon of Loligo. ''J Physiol'' 1952 Apr;116(4):497-506.  PMID 14946715</ref>
* Single-cell, rechargeable [[Nickel metal hydride battery|NiMH]] or [[Nickel-cadmium battery|NiCd]] battery: 1.2 V
* [[Mercury battery]]: 1.355 V
* Single-cell, non-rechargeable [[alkaline battery]] (e.g. [[Battery (electricity)#Common battery sizes|AAA, AA, C and D cells]]): 1.5 V
* [[Lithium polymer]] rechargeable battery: 3.75 V
* [[Transistor-transistor logic]]/[[CMOS]] (TTL) power supply: 5 V
* [[PP3 battery]]: 9 V
* [[Automobile]] electrical system: "12 V", about 11.8 V discharged, 12.8 V charged, and 13.8-14.4 V while charging (vehicle running).
* Household [[mains electricity]]: 240 V RMS in Australia, 230 V RMS in Europe, Asia and Africa, 120 V RMS in North America, 100 V RMS in Japan (see [[List of countries with mains power plugs, voltages and frequencies]])
* [[Rapid transit]] [[third rail]]: 600 to 750 V (see [[List of current systems for electric rail traction]])
* High speed train overhead power lines: 25 kV RMS at 50 Hz, but see the [[list of current systems for electric rail traction]] for exceptions.
* High voltage [[electric power transmission]] lines: 110 kV RMS and up (1150 kV RMS was the record as of 2005)
* [[Lightning]]: Varies greatly, often around 100 MV.

Note: Where 'RMS' ([[root mean square]]) is stated above, the peak voltage is <math>\sqrt{2}</math> times greater than the RMS voltage for a [[sinusoidal]] signal centered around zero voltage.

== History of the volt ==
In 1800, as the result of a professional disagreement over the galvanic response advocated by [[Luigi Galvani]], Alessandro Volta developed the so-called [[Voltaic pile]], a forerunner of the [[Battery (electricity)|battery]], which produced a steady electric [[current (electricity)|current]]. Volta had determined that the most effective pair of dissimilar metals to produce electricity was [[zinc]] and [[silver]]. In the 1880s, the International Electrical Congress, now the [[International Electrotechnical Commission]] (IEC), approved the volt for electromotive force. At that time, the volt was defined as the potential difference across a conductor when a current of one [[ampere]] dissipates one [[watt]] of power.

Prior to the development of the Josephson junction voltage standard, the volt was maintained in national laboratories using specially constructed batteries called '''[[Weston cell|standard cell]]s'''. The United States used a design called the [[Weston cell]] from 1905 to 1972.-->

== Notae ==
<references />

{{NexInt}}
{{Wiktionary}}
* [[Amperium (unitas)|Amperium]]
* [[Electronvoltium]] (eV)
* [[SI]] for unit prefixes
* [[SI electromagnetism units]]
* [[Vattium]]
* [[Voltage]]
* [[Voltmeter]]

== Nexus externi ==
* Muller, Richard A. [https://web.archive.org/web/20110520022521/http://video.google.com/videoplay?docid=5645396659673218353&q=Physics+for+Future+Presidents+Electricity&total=5&start=0&num=10&so=0&type=search&plindex=0#0h20m30s Acroasis de electricitate et voltio.]
* [http://www.aqdi.com/rms.htm "What is RMS?"]

{{Unitates SI}}
[[Categoria:Unitates physicae]]
{{Myrias|Physica}}