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Calculate Magnetic Field of Electromagnet with Hollow-Iron Core

  1. May 11, 2005 #1
    Hey everyone,

    I'm doing a physics project, and I need to construct an electromagnet with a hollow iron core. I have searched everywhere on google, and checked my physics textbook as well, but have unfortunately found nothing. I basically just need the formula of how to calculate the magnetic field of an electromagnet, which has an iron-cylinder core.

  2. jcsd
  3. Apr 3, 2009 #2
    I am dying to know that too.......!!!!!:cry:

    please help me if you have already got the solution..

    I have the same configuration ...i.e. a coil wound round a iron tube .I want to know the field inside the tube.Having a core complicates the matter........
  4. Apr 3, 2009 #3
    For a hollow iron tube without windings inside the tube, what tangential component of the magnetic field is continuous across the air-iron boundary? Why?
  5. Apr 3, 2009 #4
    Sorry,Bob S I did'nt exactly understand your question...

    There are no coils inside the tube.The coil is outside the tube.It is made by winding a magnet wire on a soft iron tube...simple.

    Actually what I have found so far is that there are standard formulas for air core electromagnetic coils.So we get a more or less uniform field within the coil.there is small radial variation and axiially i.e. along the height of the coil the field at the middle is maximum and at the two ands (top and bottom)half of the maximum.

    Now, as I add a hollow cylindrical soft iron core (a soft iron tube)almost all the flux lines go through the iron tube thus in effect screening the inside and so the inside of the tube is starved of magnetic flux.The field will be very high at the top of the tube wall as it is now turned into a magnet due its magnetization and north pole and south pole will be formed at the two ends(it also formed for a air core solenoid but the strength would be weak)just at the top of the tube wall.Hope I didn't mess up the explanation........

    This is all fine and validated.I want exact field values at arbitrary points in 3d space both inside the tube and out side the tube i.e the 3d field distribution of B and H.

    I know couple of solvers (simulators)which can be of some help but I need someone to accompany me by sharing their results of the simulation of the configuration in prder to validate my understanding.
    1.FEMM....excellent....so far the best and lightweight field solver I have ever encountered.Its open source software so ..FREE DOWNLOAD!!
    this is the homepage:
    2.Maxwell SV:
    complicated....dont know much about
    3.VIZIMAG small software ,lacks in flexibility to model complex geometries.

    Or one can try and solve MAXWELL equations in the 3d (or 2d)space to get the field distribution....

    Please share your thoughts...
    Thanks to all.
  6. Apr 3, 2009 #5
    We agree. There are no coils inside the tube. So Curl H = 0. Solve it at the boundary. So what tangential component of the magnetic field is continuous across the boundary on the inside of the iron tube? What tangential component of the field is NOT continuous?
  7. Jun 4, 2010 #6
    I want to know that too :) created a post too just to find this 1 out.

    I am trying to find the solution to that exact construction.
  8. Apr 20, 2012 #7
    Hi Souviktor, I read your reply to Bob S. In that you said that there are standard formulas for air core electromagnetic coils. Im now searching for that equation for my project. It will be helpful to me if you provide me that equation.

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