Power, root-power, and field quantities
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.