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URL: https://en.wikipedia.org/wiki/ISO_31-5

โ‡ฑ ISO 31-5 - Wikipedia


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Part of international standard ISO 31
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ISO 31-5 is the part of international standard ISO 31 that defines names and symbols for quantities and units related to electricity and magnetism. It is superseded by ISO 80000-6.[1]

Some of its definitions are below, with values taken from NIST values of the constants:[2]

Name Symbol Definition Value
Speed of light in vacuum 0 299 792 458 m sโˆ’1 299 792 458 m sโˆ’1
Magnetic constant 0 4ฯ€ ร— 10โˆ’7 N Aโˆ’2 12.566 370 614... x 10โˆ’7 N Aโˆ’2
Electric constant 0 ๐Ÿ‘ {\displaystyle {\begin{matrix}{\frac {1}{\mu _{0}{c_{0}}^{2}}}\end{matrix}}}
8.854 187 817... x 10โˆ’12 F mโˆ’1
Characteristic impedance of vacuum 0 0 0 376.730 313 461...ฮฉ

References

[edit]
  1. ^ "ISO 31-5:1992 Quantities and units". International Organization for Standardization. November 1992. Retrieved 14 June 2025.
  2. ^ "Fundamental Physical Constants from NIST". physics.nist.gov. Retrieved 14 June 2025.