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Homework Help: Energy Density

  1. Feb 10, 2008 #1
    1. The problem statement, all variables and given/known data
    I found on Wikipedia the formula for energy density of an electric field in a vacuum to be

    [tex]U = \frac{1}{2}\epsilon_0 E^2.[/tex]

    I was wondering if someone could point me in the right direction to figure out how this was derived.

    2. Relevant equations

    3. The attempt at a solution
    I was thinking maybe using Gauss's law?
  2. jcsd
  3. Feb 11, 2008 #2

    Shooting Star

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    Homework Helper

    It starts with total energy = 1/2[Integral over volume(rho*phi*dV)], where rho is the volume charge density, phi the potential.

    Then this has to be written as e0/2[Integral over volume(div E*phi*dV)]. After that you can break up the integrand into two parts.

    You can try to do it from here, but it'd best if you look up a book.
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