Energy flux

 ( Physical Quantities ) 

Energy flux is the rate of transfer of energy through a surface. The quantity is defined in two different ways, depending on the context:

1. Total rate of energy transfer (not per unit area); SI units: W = J⋅s⁻¹.
2. Specific rate of energy transfer (total normalized per unit area); : 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, to distinguish it from the first definition.
• Radiative flux, heat flux, and /ref> (also /ref> are specific cases of this meaning.

• Energy flow (ecology)
• Flux
• Irradiance
• Poynting vector
• Stress–energy tensor
• Energy current