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Magnetic field due to a solenoid.

  1. Nov 1, 2013 #1

    PhysicoRaj

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    Hi.
    I have a solenoid, of length l, radius r, which has n turns of copper wire wound on it, carries a current of I amperes, and has a ferromagnetic core of relative permeability μr. How do I determine the magnetic field at a point in free space, x meters from the center of the solenoid?
    Also, how to calculate the force of attraction experienced by a ferromagnetic substance(whose magnetic properties are known) due to the same solenoid, placed at that point?
    Thanks for any reply.
     
    Last edited: Nov 1, 2013
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  3. Nov 1, 2013 #2

    Simon Bridge

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  4. Nov 1, 2013 #3

    PhysicoRaj

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    Thanks.
    The problem I came upon was that the field inside the solenoid will be influenced by the permeability of the core whereas the point I wish to measure the field is in a medium of different permeability.
    I used B=μnI/l which gives the field inside the solenoid. For the field outside it, what expression should I use so as to switch over to the permeability of free space?

    Can I use the below equation(total field by integrating the equation for a current loop) by just replacing μ° by μ°μr?
    B=(μ°/4∏)[nIr2/2(r2+x2)3/2]
    Wouldn't this mean the point is also in the same medium as the core?
     
    Last edited: Nov 1, 2013
  5. Nov 1, 2013 #4

    Simon Bridge

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    That's pretty much it yeah - remembering how the feld changes at the boundary ... you basically have materials with different refractive indexes.
     
  6. Nov 1, 2013 #5

    PhysicoRaj

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    Thanks a lot!
     
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