energy density

Energy density is a term used for the amount of energy stored in a given system or region of space per unit volume. Often only the useful or extractable energy is quantified, which is to say that chemically inaccessible energy such as rest mass energy is ignored. Quantified energy is energy that has some sort of, as the name suggests, quantified magnitude with related units.

For fuels, the energy per unit volume is sometimes a useful parameter. Comparing, for example, the effectiveness of hydrogen fuel to gasoline?, hydrogen has a higher specific energy? than gasoline? does, but, even in liquid form, a much lower energy density.

Energy per unit volume has the same physical units as pressure, and in many circumstances is an exact synonym?: for example, the energy density of the magnetic field may be expressed as (and behaves as) a physical pressure, and the energy required to compress a compressed gas a little more may be determined by multiplying the difference between the gas pressure and the pressure outside by the change in volume. In short, pressure is a measure of volumetric enthalpy of a system. A pressure gradient has a potential to perform work on the surroundings by converting enthalpy until equilibrium is reached. Wikipedia, Energy Density (external link)

See Also

cosmological constant
cosmological equation of state
dark energy
Scalar Potential
Universal Energy Unit

Page last modified on Sunday 23 of October, 2011 03:27:14 MDT

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