Energy flux is the rate of transfer of
energy
In physics, energy (from Ancient Greek: ἐνέργεια, ''enérgeia'', “activity”) is the quantitative property that is transferred to a body or to a physical system, recognizable in the performance of work and in the form of heat a ...
through a surface. The quantity is defined in two different ways, depending on the context:
# Total rate of energy transfer (not per unit area);
SI units: W = J⋅s
−1.
#
Specific
Specific may refer to:
* Specificity (disambiguation)
* Specific, a cure or therapy for a specific illness
Law
* Specific deterrence, focussed on an individual
* Specific finding, intermediate verdict used by a jury in determining the fina ...
rate of energy transfer (total normalized per unit
area
Area is the quantity that expresses the extent of a region on the plane or on a curved surface. The area of a plane region or ''plane area'' refers to the area of a shape
A shape or figure is a graphics, graphical representation of an obje ...
);
SI unit
The International System of Units, known by the international abbreviation SI in all languages and sometimes pleonastically as the SI system, is the modern form of the metric system and the world's most widely used system of measurement. E ...
s: W⋅m
−2 = J⋅m
−2⋅s
−1:
#* This is a vector quantity, its components being determined in terms of the normal (perpendicular) direction to the surface of measurement.
#* This is sometimes called ''energy
flux density
Flux describes any effect that appears to pass or travel (whether it actually moves or not) through a surface or substance. Flux is a concept in applied mathematics and vector calculus which has many applications to physics. For transport ph ...
'', to distinguish it from the first definition.
#*
Radiative flux
Radiative flux, also known as radiative flux density or radiation flux (or sometimes power flux density), is the amount of Power (physics), power radiated through a given area, in the form of photons or other elementary particles, typically measure ...
,
heat flux
Heat flux or thermal flux, sometimes also referred to as ''heat flux density'', heat-flow density or ''heat flow rate intensity'' is a flow of energy per unit area per unit time. In SI its units are watts per square metre (W/m2). It has both a ...
, and
sound energy flux
Sound power or acoustic power is the rate at which sound energy is emitted, reflected, transmitted or received, per unit time. It is defined as "through a surface, the product of the sound pressure, and the component of the particle velocity, at ...
are specific cases of this meaning.
See also
*
Energy flow (ecology)
Energy flow is the flow of energy through living things within an ecosystem. All living organisms can be organized into producers and consumers, and those producers and consumers can further be organized into a food chain. Each of the levels wi ...
*
Flux
Flux describes any effect that appears to pass or travel (whether it actually moves or not) through a surface or substance. Flux is a concept in applied mathematics and vector calculus which has many applications to physics. For transport ph ...
*
Irradiance In radiometry, irradiance is the radiant flux ''received'' by a ''surface'' per unit area. The SI unit of irradiance is the watt per square metre (W⋅m−2). The CGS unit erg per square centimetre per second (erg⋅cm−2⋅s−1) is often used ...
*
Poynting vector
In physics, the Poynting vector (or Umov–Poynting vector) represents the directional energy flux (the energy transfer per unit area per unit time) or '' power flow'' of an electromagnetic field. The SI unit of the Poynting vector is the watt ...
*
Stress–energy tensor
The stress–energy tensor, sometimes called the stress–energy–momentum tensor or the energy–momentum tensor, is a tensor physical quantity that describes the density and flux of energy and momentum in spacetime, generalizing the stress ...
*
Energy current Energy current is a flow of energy defined by the Poynting vector (), as opposed to normal current (flow of charge). It was originally postulated by Oliver Heaviside. It is also an informal name for Energy flux.
Explanation
"Energy current" is ...
References
{{reflist
Physical quantities
Vector calculus