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ISO 31-5

From Wikipedia, the free encyclopedia

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 It is superseded by ISO 80000-6.[1]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 c0 299 792 458 m s−1 299 792 458 m s−1
Magnetic constant μ0 4π × 10−7 N A−2 12.566 370 614... x 10−7 N A−2
Electric constant ε0 8.854 187 817... x 10−12 F m−1
Characteristic impedance of vacuum Z0 μ0 c0 376.730 313 461...Ω

References

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  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.