ઢાંચો:Physical constants/doc માટે સ્રોત જુઓ

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{{template shortcut|physconst}}
This template provides easy inclusion of the latest [[CODATA]] recommended values of [[physical constant]]s in articles. It gives the most recent values published, and will be updated when newer values become available, which is typically every four years.

The values have been updated to the CODATA 2018 values.  This includes the [[2019 redefinition of SI base units]], which made the values of several constants exact (e.g. [[Elementary charge|''e'']]), whereas some previously exactly defined constants acquired an uncertainty (e.g. [[Vacuum permeability|''μ''<sub>0</sub>]]).

=== Usage ===
==== Arguments ====
;<code>symbol</code>: If set to <code>yes</code>, the value is preceded by the symbol of the constant, followed by {{xt|≈}} or {{xt|&#61;}} depending on whether or not <code>round</code> is set.
;<code>round</code>: If omitted, the value is shown along with its standard uncertainty. If set to an integer ''n'', the value is rounded to the first ''n'' digits after the decimal point (retaining trailing zeros).
;<code>unit</code>: If set to <code>no</code>, the unit of measurement is not shown.
;<code>ref</code>: If set to <code>no</code>, no reference is given. If set to <code>only</code>, only the reference is given.
;<code>after</code>: Text (e.g. punctuation) to be shown after the constant before the reference.
;<code>runc</code>:If set to <code>yes</code>, this will provide ''only'' the relative standard uncertainty of the value and its reference.

====Available constants====
{| class="wikitable"
|-
! Code !! Constant !! Value !! Relative standard uncertainty
|-
| <code>a0</code>
| [[Bohr radius]]
| {{/data/disp|a0}}
|-
| <code>alpha</code>
| [[fine-structure constant]]
| {{/data/disp|alpha}}
|-
| <code>A90</code>
| [[Conventional electrical unit|conventional ampere]]
| {{/data/disp|A90}}
|-
| <code>atm</code>
| [[Atmosphere (unit)|standard atmosphere]]
| {{/data/disp|atm}}
|-
| <code>bwien</code>
| [[Wien's displacement law|Wien wavelength displacement law constant]]
| {{/data/disp|bwien}}
|-
| <code>bwien'</code>
| [[Wien's displacement law|Wien frequency displacement law constant]]
| {{/data/disp|bwien'}}
|-
| <code>c</code>
| [[speed of light]]
| {{/data/disp|c}}
|-
| <code>c1</code>
| first radiation constant
| {{/data/disp|c1}}
|-
| <code>c1L</code>
| first radiation constant for spectral radiance 
| {{/data/disp|c1L}}
|-
| <code>c2</code>
| second radiation constant  
| {{/data/disp|c2}}
|-
| <code>C90</code>
| [[Conventional electrical unit|conventional coulomb]]
| {{/data/disp|C90}}
|-
| <code>DnuCs</code>
| [[Hyperfine structure#Use in defining the SI second and meter|hyperfine structure transition frequency of caesium-133]]
| {{/data/disp|DnuCs}}
|-
| <code>e</code>
| [[elementary charge]]
| {{/data/disp|e}}
|-
| <code>Eh</code>
| [[Hartree energy]]
| {{/data/disp|Eh}}
|-
| <code>EheV</code>
| [[Hartree energy]] in eV
| {{/data/disp|EheV}}
|-
| <code>eps0</code>
| [[vacuum electric permittivity]]
| {{/data/disp|eps0}}
|-
| <code>eV</code>
| [[electronvolt]]
| {{/data/disp|eV}}
|-
| <code>F</code>
| [[Faraday constant]]
| {{/data/disp|F}}
|-
| <code>F90</code>
| [[Conventional electrical unit|conventional farad]]
| {{/data/disp|F90}}
|-
| <code>G</code>
| [[gravitational constant]]
| {{/data/disp|G}}
|-
| <code>G0</code>
| [[conductance quantum]]
| {{/data/disp|G0}}
|-
| <code>g0</code>
| [[Standard gravity|standard acceleration of gravity]]
| {{/data/disp|g0}}
|-
| <code>ge</code>
| electron [[g-factor (physics)|''g''-factor]]
| {{/data/disp|ge}}
|-
| <code>GF/hbarc3</code>
| [[Fermi coupling constant]]
| {{/data/disp|GF/hbarc3}}
|-
| <code>gmu</code>
| muon [[g-factor (physics)|''g''-factor]]
| {{/data/disp|gmu}}
|-
| <code>gp</code>
| proton [[g-factor (physics)|''g''-factor]]
| {{/data/disp|gp}}
|-
| <code>h</code>
| [[Planck constant]]
| {{/data/disp|h}}
|-
| <code>H90</code>
| [[Conventional electrical unit|conventional henry]]
| {{/data/disp|H90}}
|-
| <code>hbar</code>
| [[reduced Planck constant]]
| {{/data/disp|hbar}}
|-
| <code>h/2me</code>
| quantum of circulation
| {{/data/disp|h/2me}}
|-
| <code>invalpha</code>
| inverse [[fine-structure constant]]
| {{/data/disp|invalpha}}
|-
| <code>invG0</code>
| inverse [[conductance quantum]]
| {{/data/disp|invG0}}
|-
| <code>k</code>
| [[Boltzmann constant]]
| {{/data/disp|k}}
|-
| <code>KJ</code>
| [[Josephson constant]]
| {{/data/disp|KJ}}
|-
| <code>KJ90</code>
| [[Conventional electrical unit|conventional value]] of [[Josephson constant]]
| {{/data/disp|KJ90}}
|-
| <code>lP</code>
| [[Planck length]]
| {{/data/disp|lP}}
|-
| <code>MC12</code>
| molar mass of [[carbon-12]]
| {{/data/disp|MC12}}
|-
| <code>me</code>
| [[electron]] mass
| {{/data/disp|me}}
|-
| <code>meDa</code>
| [[electron]] mass in [[Dalton (unit)|dalton]]s
| {{/data/disp|meDa}}
|-
| <code>mmu</code>
| [[muon]] mass
| {{/data/disp|mmu}}
|-
| <code>mn</code>
| [[neutron]] mass
| {{/data/disp|mn}}
|-
| <code>mnDa</code>
| [[neutron]] mass in [[Dalton (unit)|dalton]]s
| {{/data/disp|mnDa}}
|-
| <code>mP</code>
| [[Planck mass]]
| {{/data/disp|mP}}
|-
| <code>mp</code>
| [[proton]] mass
| {{/data/disp|mp}}
|-
| <code>mpome</code>
| [[proton-to-electron mass ratio]]
| {{/data/disp|mpome}}
|-
| <code>mtau</code>
| [[tau]] mass
| {{/data/disp|mtau}}
|-
| <code>Mu</code>
| [[molar mass constant]]
| {{/data/disp|Mu}}
|-
| <code>mu</code>
| [[atomic mass constant]]
| {{/data/disp|mu}}
|-
| <code>muc2</code>
| [[atomic mass constant]] energy equivalent
| {{/data/disp|muc2}}
|-
| <code>mueV</code>
| [[atomic mass constant]] energy equivalent in MeV
| {{/data/disp|mueV}}
|-
| <code>mu0</code>
| [[vacuum magnetic permeability]]
| {{/data/disp|mu0}}
|-
| <code>muB</code>
| [[Bohr magneton]]
| {{/data/disp|muB}}
|-
| <code>muN</code>
| [[nuclear magneton]]
| {{/data/disp|muN}}
|-
| <code>mW/mZ</code>
| [[Weinberg angle|W-to-Z mass ratio]]
| {{/data/disp|mW/mZ}}
|-
| <code>NA</code>
| [[Avogadro constant]]
| {{/data/disp|NA}}
|-
| <code>NAh</code>
| molar Planck constant
| {{/data/disp|NAh}}
|-
| <code>ohm90</code>
| [[Conventional electrical unit|conventional ohm]]
| {{/data/disp|ohm90}}
|-
| <code>Phi0</code>
| [[magnetic flux quantum]]
| {{/data/disp|Phi0}}
|-
| <code>R</code>
| [[molar gas constant]]
| {{/data/disp|R}}
|-
| <code>re</code>
| [[classical electron radius]]
| {{/data/disp|re}}
|-
| <code>Rinf</code>
| [[Rydberg constant]]
| {{/data/disp|Rinf}}
|-
| <code>RK</code>
| [[von Klitzing constant]]
| {{/data/disp|RK}}
|-
| <code>RK90</code>
| [[Conventional electrical unit|conventional value]] of [[von Klitzing constant]]
| {{/data/disp|RK90}}
|-
| <code>sigma</code>
| [[Stefan–Boltzmann constant]]
| {{/data/disp|sigma}}
|-
| <code>sigmae</code>
| Thomson [[Cross section (physics)|cross section]]
| {{/data/disp|sigmae}}
|-
| <code>TP</code>
| [[Planck temperature]]
| {{/data/disp|TP}}
|-
| <code>tP</code>
| [[Planck time]]
| {{/data/disp|tP}}
|-
| <code>V90</code>
| [[Conventional electrical unit|conventional volt]]
| {{/data/disp|V90}}
|-
| <code>VmSi</code>
| [[Molar volume#Molar volume of silicon|molar volume of silicon]]
| {{/data/disp|VmSi}}
|-
| <code>W90</code>
| [[Conventional electrical unit|conventional watt]]
| {{/data/disp|W90}}
|-
| <code>Z0</code>
| [[Impedance of free space|characteristic impedance of vacuum]]
| {{/data/disp|Z0}}
|-
|}

====Examples====
<code><nowiki>{{Physical constants|c|unit=no|after=&amp;nbsp;[[metre per second|metres per second]].}}</nowiki></code>
:{{Physical constants|c|unit=no|after=&nbsp;[[metre per second|metres per second]].}}
<code><nowiki>{{Physical constants|mu0|symbol=yes}}</nowiki></code>
:{{Physical constants|mu0|symbol=yes}}
<code><nowiki>{{Physical constants|G|symbol=yes}}</nowiki></code>
:{{Physical constants|G|symbol=yes}}
<code><nowiki>{{Physical constants|hbar|round=2|symbol=yes}}</nowiki></code>
:{{Physical constants|hbar|round=2|symbol=yes}}
<code><nowiki>The relative standard uncertainty of ''m''<sub>u</sub> is {{Physical constants|mu|runc=yes|after=.}}</nowiki></code>
:The relative standard uncertainty of ''m''<sub>u</sub> is {{Physical constants|mu|runc=yes|after=.}}
<code><nowiki>For the electron mass, {{Physical constants|me|runc=yes|symbol=yes|ref=no}}.</nowiki></code>
:For the electron mass, {{Physical constants|me|runc=yes|symbol=yes|ref=no}}.
<code><nowiki>NIST publishes the CODATA value of the [[elementary charge]].{{Physical constants|e|ref=only}}</nowiki></code>
:NIST publishes the CODATA value of the [[elementary charge]].{{Physical constants|e|ref=only}}

=== See also ===
*[[/data]], the subtemplate that holds all of the data
*{{tl|CODATA2010}}, the older version of this template used for the 2010 values

=== References ===
{{reflist}}
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