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Power, root-power, and field quantities

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This is an old revision of this page, as edited by BD2412 (talk | contribs) at 23:50, 10 August 2015 (Disambiguated: Complex modulus, Level (2), Sound level). The present address (URL) is a permanent link to this revision, which may differ significantly from the current revision.

A field quantity is a quantity such as voltage, current, pressure, electric field strength, speed, or charge density, the square of which in linear systems is proportional to power.[1]

A power quantity is a power or a quantity directly proportional to power, e.g., energy density, acoustic intensity, and luminous intensity.[citation needed]

Finally, a root-power quantity is a term introduced in the ISO 80000-1#Annex C, defined as the square root of a power quantity; it replaces and deprecates the term field quantity.

If a field quantity is a complex value (e.g., a phasor), then its magnitude is implied in the logarithm calculations involved.[citation needed] The phrase "root-power quantity" avoids this ambiguity by definition, as power is always positive, and its square root is always real-valued.

The distinctions here described have implications for the definition of decibel, which depends on whether the measured property is a power quantity or a field quantity. So does the level of a root-power quantity or of a power quantity.

See also

References

  1. ^ Brian C.J. Moore (1995). Hearing. Academic Press. p. 11. ISBN 9780080533865.