Power, root-power, and field quantities: Difference between revisions
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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. |
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. |
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If a field quantity is [[complex-valued]] (e.g., a [[phasor]]), then its [[complex modulus|magnitude]] is implied;{{citation needed|date= |
If a field quantity is [[complex-valued]] (e.g., a [[phasor]]), then its [[complex modulus|magnitude]] is implied;{{citation needed|date=May 2015}} root-power quantities avoid this ambiguity by definition, as power is always positive, and its root is always [[real-valued]]. |
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The distinctions here described have implications for the [[Decibel#Definition|definition of decibel]], which depends on whether the measured property is a [[Decibel#Power quantities|power quantity]] or a [[Decibel#Field quantities|field quantity]]. So does the [[Level (logarithmic quantity)|level]] of a [[Level#Root-power quantities|root-power quantity]] or of a [[Level#Power quantities|power quantity]]. |
The distinctions here described have implications for the [[Decibel#Definition|definition of decibel]], which depends on whether the measured property is a [[Decibel#Power quantities|power quantity]] or a [[Decibel#Field quantities|field quantity]]. So does the [[Level (logarithmic quantity)|level]] of a [[Level#Root-power quantities|root-power quantity]] or of a [[Level#Power quantities|power quantity]]. |
Revision as of 03:47, 16 May 2015
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 complex-valued (e.g., a phasor), then its magnitude is implied;[citation needed] root-power quantities avoid this ambiguity by definition, as power is always positive, and its 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
- Fresnel reflection field and power equations
- Sound level, defined in different ways for the pressure or power of sound
References
- ^ Brian C.J. Moore (1995). Hearing. Academic Press. p. 11. ISBN 9780080533865.