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Finding Magnetic Field from a Box

  1. Apr 9, 2015 #1
    1. The problem statement, all variables and given/known data
    A uniform magnetic field exists in a cubic volume of space with a
    50-mm side length.
    If the magnetic energy stored in this volume is
    19J , what is the magnetic field magnitude?
    (This is all the information I got. Been a bad week for since it just seem information for my homework is missing)

    2. Relevant equations
    This is where things are a little shaky. 0Al


    3. The attempt at a solution
    Taking the length I used it to find the area of the cube. Which is what I take A to be, which I find weird considering I needed l as well.
    Setting it up I got

    (19*2*4piE-17)/(0.015)(5E-4) = B^2

    B = 2.51E-5 T
  2. jcsd
  3. Apr 9, 2015 #2
    I believe the equation you started with is the energy density, not just the Energy (check the units)

    [itex]\frac{U}{Volume of cube} = \frac{1}{2} \frac{B^2}{\mu}[/itex]
  4. Apr 9, 2015 #3
    actually, it looks like you did divide by the volume in your calculation, but the volume of the cube should just be (side length)^3.
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