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== განმარტება ==
ვოლტი განიმარტება როგორც ძაბვა, რომელიც მოდებულია [[გამტარზე|გამტარი]] როდესაც 1 [[ამპერი]] [[ელექტრული დენი]]ს გავლისას მასში გამოიყოფა 1 [[ვატი]] [[სიმძლავრე]].<ref>[http://www.bipm.org/utils/common/pdf/si_brochure_8_en.pdf BIPM SI Brochure: Appendix 1, p. 144]</ref> [[SI სისტემა|SI სისტემის]] სხვა ერთეულებში ვოლტი შემდეგნაირად გამოისახება:
The volt is defined as the value of the [[voltage]] across a [[conductor]] when a [[Electric current|current]] of one [[ampere]] dissipates one [[watt]] of [[power (physics)|power]] in the conductor. <ref>[http://www.bipm.org/utils/common/pdf/si_brochure_8_en.pdf BIPM SI Brochure: Appendix 1, p. 144]</ref> It can be written in terms of SI base units as: [[metre|m]]<sup>2</sup> · [[kilogram|kg]] · [[second|s]]<sup>−3</sup> · [[ampere|A]]<sup>−1</sup>. It is also equal to one [[joule]] of [[energy]] per [[coulomb]] of charge, J/C.
:<math>\mbox{V} = \dfrac{\mbox{W}}{\mbox{A}} = \dfrac{\mbox{J}}{\mbox{A} \cdot \mbox{s}} = \dfrac{\mbox{N} \cdot \mbox{m} }{\mbox{A} \cdot \mbox{s}} = \dfrac{\mbox{kg} \cdot \mbox{m}^2}{\mbox{A} \cdot \mbox{s}^{3}} = \dfrac{\mbox{kg} \cdot \mbox{m}^2}{\mbox{C} \cdot \mbox{s}^2} = \dfrac{\mbox{N} \cdot \mbox{m}} {\mbox{C}} = \dfrac{\mbox{J}}{\mbox{C}}</math>
== ძაბვის ტიპიური მნიშვნელობები==
=== Josephson junction definition ===
[[სურათი:Electronic multi meter.jpg|thumb|250px| [[მალტიმეტრი]] არის ხელსაწყო, რომლის მეშვეობითაც შეიძლება ძაბვის გაზომვა ორ წერტილს შორის.]]
Since 1990 the volt has been 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:
[[სურათი:BateriaR14.jpg|150px|thumb|1.5 ვ ძაბვის ბატარეები]]
:''K''<sub>{J-90}</sub> = 0.4835979 GHz/µV.
== Water flow analogy ==
In the ''[[hydraulic analogy|water flow analogy]]'' sometimes used to explain electric circuits by comparing them to water-filled pipes, [[voltage]] difference is likened to water [[pressure]] difference – the difference determines how quickly 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 per unit time ([[volumetric flow rate]]). The flow rate is determined by the width of the pipe (analogous to [[electrical conductivity]]), and the pressure difference between the front end of the pipe and the exit (analogous to [[voltage]]). The analogy extends to power dissipation: the power given up by the water flow is equal to flow rate 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 ==
[[File:Electronic multi meter.jpg|thumb|250px| A [[multimeter]] can be used to measure the voltage between two positions.]]
[[File:BateriaR14.jpg|150px|thumb|1.5 V C-cell batteries]]
Nominal voltages of familiar sources:
* [[Nerve cell]] [[resting potential]]: around −75 mV<ref>Bullock, Orkand, and Grinnell, pp. 150–151; Junge, pp. 89–90; Schmidt-Nielsen, p. 484</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 iron phosphate battery|LiFePO4]] rechargeable battery: 3.3 V
* [[Lithium polymer]] rechargeable battery: 3.75 V (see [[Rechargeable battery#Table of rechargeable battery technologies]])
* [[Transistor-transistor logic]]/[[CMOS]] (TTL) power supply: 5 V
* [[PP3 battery]]: 9 V
* [[Automobile]] electrical system: nominal 12 V, about 11.8 V discharged, 12.8 V charged, and 13.8–14.4 V while charging (vehicle running).
* Household [[mains electricity]]: 230 V [[Root mean square|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]])
* Commercial and Military Jet aircraft: 400 V AC, 28 V DC {{Citation needed|date=February 2010}}
* [[Truck]]s/[[lorries]]: 24 V DC
* [[Rapid transit]] [[third rail]]: 600–750 V (see [[List of current systems for electric rail traction]])
* High speed train overhead power lines: [[25 kV AC|25 kV RMS at 50 Hz]], but see the [[list of current systems for electric rail traction]] and [[25 kV AC#60 Hz|25 kV at 60 Hz]] for exceptions.
* High voltage [[electric power transmission]] lines: 110 kV RMS and up (1.15 MV RMS was the record as of 2005{{Citation needed|date=November 2009}})
* [[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 as the unit for electromotive force. At that time, the volt was defined as the potential difference [i.e., what is nowadays called the "voltage (difference)"] across a conductor when a current of one [[ampere]] dissipates one [[watt]] of power.
The international volt was defined in 1893 as 1/1.434 of the [[Electromotive force|emf]] of a [[Clark cell]]. This definition was abandoned in 1908 in favor of a definition based on the international [[ohm]] and international ampere until the entire set of "reproducible units" was abandoned in 1948.
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 cells]]'''. The United States used a design called the [[Weston cell]] from 1905 to 1972.
ძაბვის ტიპიური მნიშვნელობები:
▲* [[ Nerveნერვული cell]] [[resting potentialუჯრედი]]: around −7575 mVმიკროვ<ref>Bullock, Orkand, and Grinnell, pp. 150–151; Junge, pp. 89–90; Schmidt-Nielsen, p. 484</ref>
* ქიმიური [[ბატარეა]]: 1-5 ვ
* მაღალი ძაბვის გადამცემი ხაზები: 110 კვ
* [[ელვა]]: ცვალებადია, მაგრამ ხშირად 100 მეგავ აღწევს.
[[კატეგორია:ფიზიკა]]
[[კატეგორია:ფიზიკური ერთეულები]]
[[კატეგორია:SI სისტემის ერთეულები]]
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