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Question about magnets.

  1. Mar 26, 2008 #1
    If you combine many small magnets together in a cube or spherical shape (say those 1.5 tesla rare earth magnets), is the resulting magnetic field able to affect even heavier objects, or is there no difference in the range/energy of the field?
     
    Last edited: Mar 26, 2008
  2. jcsd
  3. Mar 26, 2008 #2
    Well I know that the magnetic field definitely does get stronger when you make a big cube out of many small magnetised cubes because I've tried it.

    Makes sense really, the domain theory says that a magnet that you can hold in your hand is just a collection of very tiny microscopic (weak) magnets all side by side, and end to end. Put them all together and you can pick up comparatively gigantic objects(compared to the size and strength of the domains) .

    So yes, the more you have the stronger the field.
     
  4. Mar 28, 2008 #3

    clem

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    If you build a cube out of rectangular magnets, The lifting force will be increase as the contact area of a face of the cube and the face of the object to be picked up.
    In gaussian units, F=2pi M^2 A for the lifting force of a magnet of magnetization M on a high mu object, with A the contact area.
     
  5. Mar 31, 2008 #4
    So this would mean that for 2 magnets with the same volume, the one with the biggest surface-area would have the strongest field. Is that correct?
     
  6. Apr 2, 2008 #5

    clem

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    Not quite. The B field just outside the magnet does not depend on the area.
    The lifting force ~B times the area of contact between the magnet and the flat surface of an iron object.
    One other thing. The formula I gave is only if the magnet is large enough that effect of the distant face can be neglected. If the magnet is too thin, the the effects of the close face and the distant face tend to cancel.
     
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