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| {{Use dmy dates|date=July 2013}}
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| A '''conventional electrical unit''' (or '''conventional unit''' where there is no risk of ambiguity) is a [[unit of measurement]] in the field of [[electricity]] which is based on the so-called "conventional values" of the [[Josephson constant]] and the [[von Klitzing constant]] agreed by the [[International Committee for Weights and Measures]] (CIPM) in 1988. These units are very similar in scale to their corresponding [[SI unit]]s, but are not identical because of their different definition. They are distinguished from the corresponding SI units by setting the symbol in italic typeface and adding a subscript "90" – e.g., the conventional volt has the symbol ''V''{{sub|90}} – as they came into international use on 1 January 1990.
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| This system was developed to increase the precision of measurements: The Josephson and von Klitzing constants can be realized with great precision, repeatability and ease. The conventional electrical units have achieved acceptance as an international standard and are commonly used outside of the physics community in both engineering and industry.
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| The conventional electrical units are "quasi-[[natural units|natural]]" in the sense that they are completely and exactly defined in terms of [[dimensionless physical constant|fundamental physical constant]]s. They are the first set of measurement units to be defined in this way, and as such, represent a significant step towards using "natural" fundamental physics for practical measurement purposes. However, the conventional electrical units are unlike other systems natural units in that some physical constants are not set to unity but rather set to fixed numerical values that are very close (but not precisely the same) to those in the common [[SI]] system of units.
| | e - Shop Word - Press is a excellent cart for your on the web shopping organization. Affilo - Theme is the guaranteed mixing of wordpress theme that Mark Ling use for his internet marketing career. Change the site's theme and you have essentially changed the site's personality. Dead links are listed out simply because it will negatively have an influence on the website's search engine rating. To find out more info on [http://shortener.us/wordpress_backup_plugin_84475 wordpress backup plugin] look into our own webpage. It is found that most of the visitors only look for the results that are displayed on the first page of the search engines and so if you get the service from professional service providers then they strive for the first page ranking of your site and improve the online visibility. <br><br>Most Word - Press web developers can provide quality CMS website solutions and they price their services at reasonable rates. WPTouch is among the more well known Word - Press smartphone plugins which is currently in use by thousands of users. Well Managed Administration The Word - Press can easily absorb the high numbers of traffic by controlling the server load to make sure that the site works properly. E-commerce websites are meant to be buzzed with fresh contents, graphical enhancements, and functionalities. By using Word - Press, you can develop very rich, user-friendly and full-functional website. <br><br>But before choosing any one of these, let's compare between the two. s cutthroat competition prevailing in the online space won. For a much deeper understanding of simple wordpress themes", check out Upon browsing such, you'll be able to know valuable facts. Every single Theme might be unique, providing several alternatives for webpage owners to reap the benefits of in an effort to instantaneously adjust their web page appear. Customization of web layout is easy due to the availability of huge selection of templates. <br><br>There has been a huge increase in the number of developers releasing free premium Word - Press themes over the years. Cameras with a pentaprism (as in comparison to pentamirror) ensure that little mild is lost before it strikes your eye, however these often increase the cost of the digital camera considerably. One of the great features of Wordpress is its ability to integrate SEO into your site. It's now become a great place to sell it thanks to Woo - Commerce. Fortunately, Word - Press Customization Service is available these days, right from custom theme design, to plugin customization and modifying your website, you can take any bespoke service for your Word - Press development project. <br><br>Under Settings —> Reading, determine if posts or a static page will be your home page, and if your home page is a static page, what page will contain blog posts. In fact portfolio Word - Press themes is a smooth and attractive but considerably flawed Word - Press theme in creating simpler to the photographers or designers to develop a specific internet site showcasing their most current perform since it appear modern-day and has fantastic typography and large photographs which would develop an attractive wanting portfolio internet site. While deciding couple should consider the expertise of the doctor,clinics success rate,the costs of fertility treatment,including fertility tests and IVF costs and overall ones own financial budget. And, it is better that you leave it on for the duration you are writing plugin code. However, if you're just starting out your blog site or business site, you can still search for an ideal theme for it without breaking your bank account. |
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| Four significant steps were taken in the last half century to increase the precision and utility of measurement units. In 1967 the Thirteenth [[General Conference on Weights and Measures]] (CGPM) defined the [[second]] of atomic time in the International System of Units as the duration of 9,192,631,770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the cesium-133 atom. In 1983, the seventeenth CGPM redefined the [[metre]] in terms of the second and the speed of light, thus fixing the speed of light at exactly 299,792,458 m/s. And in 1990, the eighteenth CGPM adopted conventional values for the Josephson constant and the von Klitzing constant, fixing the conventional Josephson constant at exactly 483,597.9 {{e|9}} Hz/''"V"'', and the conventional von Klitzing constant at exactly 25 812.807 ''"Ω"'' (again, these volts and ohms are not precisely the same as the SI definitions but very nearly equivalent).
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| ==Definition==
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| Conventional electrical units are based on defined values of the [[Josephson constant]] and the [[von Klitzing constant]], which allow practical measurements of [[electromotive force]] and [[electrical resistance]] respectively.
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| {| class="wikitable"
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| |-
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| ! Constant
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| ! Conventional (defined) value<br/>(CIPM, 1988)
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| ! Empirical value (in SI units)<br/>(CODATA, 2010{{CODATA2010}})
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| |-
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| | Josephson constant
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| | ''K''{{sub|J–90}} = 483 597.9 GHz/V
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| | ''K''{{sub|J}} = 483 597.870(11) GHz/V
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| |-
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| | von Klitzing constant
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| | ''R''{{sub|K–90}} = 25 812.807 Ω
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| | ''R''{{sub|K}} = 25 812.807 4434(84) Ω
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| |-
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| |}
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| *The conventional [[volt]], ''V''{{sub|90}}, is the electromotive force (or electric potential difference) measured against a [[Josephson effect]] standard using the defined value of the Josephson constant, ''K''{{sub|J–90}}.
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| *The conventional [[ohm]], ''Ω''{{sub|90}}, is the electrical resistance measured against a [[quantum Hall effect]] standard using the defined value of the von Klitzing constant, ''R''{{sub|K–90}}.
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| *Other conventional electrical units are defined by the normal physical relationships, as in the conversion table below.
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| ==Conversion to SI units==
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| {| class="wikitable"
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| |-
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| ! Unit
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| ! Definition
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| ! SI equivalent (CODATA 2006){{Update after|2012|04|01}}
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| |-
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| | conventional [[volt]]
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| | ''see above''
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| | ''V''{{sub|90}} = (''K''{{sub|J–90}}/''K''{{sub|J}}) V = [1 + 1.9(2.5){{e|−8}}] V
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| |-
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| | conventional [[ohm]]
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| | ''see above''
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| | ''Ω''{{sub|90}} = (''R''{{sub|K}}/''R''{{sub|K–90}}) Ω = [1 + 2.159(68){{e|−8}}] Ω
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| |-
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| | conventional [[ampere]]
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| | ''A''{{sub|90}} = ''V''{{sub|90}}/''Ω''{{sub|90}}
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| | ''A''{{sub|90}} = [1 − 0.3(2.5){{e|−8}}] A
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| |-
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| | conventional [[coulomb]]
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| | ''C''{{sub|90}} = ''A''{{sub|90}} [[second|s]] = [[second|s]] ''V''{{sub|90}}/''Ω''{{sub|90}}
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| | ''C''{{sub|90}} = [1 − 0.3(2.5){{e|−8}}] C
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| |-
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| | conventional [[watt]]
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| | ''W''{{sub|90}} = ''A''{{sub|90}}''V''{{sub|90}} = ''V''{{sub|90}}<sup>2</sup>/''Ω''{{sub|90}}
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| | ''W''{{sub|90}} = [1 + 1.6(5.0){{e|−8}}] W
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| |-
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| | conventional [[farad]]
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| | ''F''{{sub|90}} = ''C''{{sub|90}}/''V''{{sub|90}} = [[second|s]]/''Ω''{{sub|90}}
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| | ''F''{{sub|90}} = [1 − 2.159(68){{e|−8}}] F
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| |-
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| | conventional [[henry (unit)|henry]]
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| | ''H''{{sub|90}} = ''Ω''{{sub|90}} [[second|s]]
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| | ''H''{{sub|90}} = [1 + 2.159(68){{e|−8}}] H
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| |-
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| |}
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| ==Comparison with natural units==
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| {{See also|Natural units}}
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| Conventional electrical units can be thought of as a scaled version of a system of [[natural units]] defined as
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| :<math> c = e = \hbar = 1 \ </math>
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| having consequence:
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| :<math> \frac{1}{4 \pi \epsilon_0} = \frac{\mu_0}{4 \pi} = \alpha \ </math> .
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| This is a more general (or less specific) version of either the particle physics "[[natural units]]" or the [[Natural units|quantum chromodynamical system of units]] but that no unit mass is fixed. Like n.u. or QCD units, with conventional electrical units any observed variation over space or time in the value of the fine-structure constant, α, is attributed to variation in the Coulomb constant or [[vacuum permittivity]] or, since the speed of light, ''c'', is fixed, as a variation in the [[vacuum permeability]].
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| The following table provides a comparison of conventional electrical units with other natural unit systems:
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| {| class="wikitable" style="margin: 1em auto 1em auto; background-color: #ffffff"
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| ! Quantity / Symbol
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| ! Planck
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| ! Stoney
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| ! Schrödinger
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| ! Atomic
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| ! Electronic
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| ! Conventional Electrical Units
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| |-
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| |[[speed of light in vacuum]] <br> <math>c \,</math>
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| |<math>1 \,</math>
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| |<math>1 \,</math>
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| |<math>\frac{1}{\alpha} \ </math>
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| |<math>\frac{1}{\alpha} \ </math>
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| |<math>1 \,</math>
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| |<math>299 792 458 \ </math>
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| |-
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| |[[Planck's constant]] <br> <math>h \,</math>
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| |<math>2\pi \,</math>
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| |<math>\frac{2\pi}{\alpha} \ </math>
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| |<math>2\pi \,</math>
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| |<math>2\pi \,</math>
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| |<math>\frac{2\pi}{\alpha} \ </math>
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| |<math>\frac{4 \times 10^{-18}}{(25812.807) (483597.9)^2} \ </math>
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| |-
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| |reduced [[Planck's constant]] <br> <math>\hbar=\frac{h}{2 \pi}</math>
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| |<math>1 \,</math>
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| |<math>\frac{1}{\alpha} \ </math>
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| |<math>1 \,</math>
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| |<math>1 \,</math>
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| |<math>\frac{1}{\alpha} \ </math>
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| |<math>\frac{2 \times 10^{-18}}{\pi (25812.807) (483597.9)^2} \ </math>
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| |-
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| |[[elementary charge]] <br> <math>e \,</math>
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| |<math>\sqrt{\alpha} \,</math>
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| |<math>1 \,</math>
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| |<math>1 \,</math>
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| |<math>1 \,</math>
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| |<math>1 \,</math>
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| |<math>\frac{2 \times 10^{-9}}{(25812.807) (483597.9)} \ </math>
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| |-
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| |[[Josephson constant]] <br> <math>K_J =\frac{2e}{h} \,</math>
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| |<math>\frac{\sqrt{\alpha}}{\pi} \,</math>
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| |<math>\frac{\alpha}{\pi} \,</math>
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| |<math>\frac{1}{\pi} \,</math>
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| |<math>\frac{1}{\pi} \,</math>
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| |<math>\frac{\alpha}{\pi} \,</math>
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| |<math>483597.9 \times 10^9 \,</math>
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| |-
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| |[[von Klitzing constant]] <br> <math>R_K =\frac{h}{e^2} \,</math>
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| |<math>\frac{2\pi}{\alpha} \,</math>
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| |<math>\frac{2\pi}{\alpha} \,</math>
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| |<math>2\pi \,</math>
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| |<math>2\pi \,</math>
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| |<math>\frac{2\pi}{\alpha} \,</math>
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| |<math>25812.807 \,</math>
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| |-
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| |[[characteristic impedance of vacuum]] <br> <math>Z_0 = 2 \alpha R_K \,</math>
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| |<math>4 \pi \,</math>
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| |<math>4 \pi \,</math>
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| |<math>4 \pi \alpha \,</math>
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| |<math>4 \pi \alpha \,</math>
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| |<math>4 \pi \,</math>
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| |<math>2 \alpha (25812.807) \,</math>
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| |-
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| |[[electric constant]] (vacuum permittivity) <br> <math> \varepsilon_0 = \frac{1}{Z_0 c} \,</math>
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| |<math>\frac{1}{4 \pi} \,</math>
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| |<math>\frac{1}{4 \pi} \,</math>
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| |<math>\frac{1}{4 \pi} \,</math>
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| |<math>\frac{1}{4 \pi} \,</math>
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| |<math>\frac{1}{4 \pi} \,</math>
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| |<math>\frac{1}{2 \alpha (25812.807) (299792458)} \ </math>
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| |-
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| |[[magnetic constant]] (vacuum permeability) <br> <math> \mu_0 = \frac{Z_0}{c} \,</math>
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| |<math>4 \pi \,</math>
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| |<math>4 \pi \,</math>
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| |<math>4 \pi \alpha^2 \,</math>
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| |<math>4 \pi \alpha^2 \,</math>
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| |<math>4 \pi \,</math>
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| |<math>\frac{2 \alpha (25812.807)}{299792458} \ </math>
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| |-
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| |[[gravitational constant|Newtonian constant of gravitation]] <br> <math>G \,</math>
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| |<math>1 \,</math>
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| |<math>1 \,</math>
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| |<math>1 \,</math>
| |
| |<math>- \,</math>
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| |<math>- \,</math>
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| |<math>- \,</math>
| |
| |-
| |
| |[[electron|electron mass]] <br> <math>m_e \,</math>
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| |<math>- \,</math>
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| |<math>- \,</math>
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| |<math>- \,</math>
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| |<math>1 \,</math>
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| |<math>1 \,</math>
| |
| |<math>- \,</math>
| |
| |-
| |
| |[[Hartree energy]] <br> <math> E_h = \alpha^2 m_e c^2 \,</math>
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| |<math>- \,</math>
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| |<math>- \,</math>
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| |<math>- \,</math>
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| |<math>1 \,</math>
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| |<math>\alpha^2 \,</math>
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| |<math>- \,</math>
| |
| |-
| |
| |[[Rydberg constant]] <br> <math> R_\infty = \frac{E_h}{2 h c} \,</math>
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| |<math>- \,</math>
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| |<math>- \,</math>
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| |<math>- \,</math>
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| |<math>\frac{\alpha}{4 \pi} \,</math>
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| |<math>\frac{\alpha^3}{4 \pi} \,</math>
| |
| |<math>- \,</math>
| |
| |-
| |
| |[[caesium]] [[ground state]] [[Hyperfine structure|hyperfine]] <br/> [[Second|transition frequency]]
| |
| |<math>- \,</math>
| |
| |<math>- \,</math>
| |
| |<math>- \,</math>
| |
| |<math>- \,</math>
| |
| |<math>- \,</math>
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| |<math>9\ 192\ 631\ 770 \,</math>
| |
| |}
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| ==See also==
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| *[[Centimetre–gram–second system of units]]
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| ==External links==
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| * [http://seaus.free.fr/spip.php?article964 History of the electrical units.]
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| ==References==
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| *{{CODATA2006}}
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| {{Reflist}}
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| {{systems of measurement}}
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| {{DEFAULTSORT:Conventional Electrical Unit}}
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| [[Category:Electromagnetism]]
| |
| [[Category:Metrology]]
| |
| [[Category:Systems of units]]
| |
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