Energy flux

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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. Rate of energy transfer per unit area.[1] (SI units: 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 second definition.
    • Radiative flux, heat flux, and sound energy flux are specific cases of energy flux density.
  2. Total rate of energy transfer.[2] (SI units: W = J·s−1)

See also[edit]


  1. ^ "Energy flux". Retrieved 2008-12-24. 
  2. ^ "Solar Physics Glossary". Nasa. Retrieved 2008-12-24.