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Magnetic constant query

  1. Jul 21, 2010 #1
    1. The problem statement, all variables and given/known data
    Hi. I don't have any physics book at the moment. This has something to do with magnets&magnetic poles:

    What is the force between two magnet poles of strengths 40amp-m and 50amp-m at a distance of 10cm in the air?

    This sounds easy, but my problem is I don't know the magnetic constant to use. Our professor said the constant is 10^7N/Amp^2. But, I don't think its correct since he wasnt sure about it too. I tried to look for it in the net, but I can find nothing with that value...

    Thanks


    2. Relevant equations

    Also, our professor told us that the formula is: F = (constant(q1)(q2))/(distance^2)



    3. The attempt at a solution

    so using the constant he gave us

    F = (10^7N/A^2)(40amp-m)(50amp-m)/(0.10m)^2
    F= 10^7(40)(50)N

    Which seems correct, but i'm not sure about the value of the constant...

    thanks :D
    1. The problem statement, all variables and given/known data



    2. Relevant equations



    3. The attempt at a solution
     
  2. jcsd
  3. Jul 21, 2010 #2
    The constant he gave you is the http://en.wikipedia.org/wiki/Permeability_%28electromagnetism%29" [Broken].
    Basically a measure of how "easily" a material (in this case vacuum) can support a magnetic field.

    However it should be used in place of the Permittivity of free space you find in Coulomb's Law for electrostatics.

    There appears to be a second (computational) mistake in your calculation as well.
     
    Last edited by a moderator: May 4, 2017
  4. Jul 21, 2010 #3
    thanks...a lot... i think i forgot the 0.01 :D thanks :D
     
    Last edited by a moderator: May 4, 2017
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