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Magnetic sphere , magnet properties

  1. Aug 27, 2014 #1
    Hello , firs of all I know that every magnet has two poles ad the field lines exit one pole and enter into the other , now if we take a bunch of magnets , for simplicity assume an infinitely long line of magnets each seperated by a distance , all of the magnets facing N-S N-S N-S , now do the field lines of the previous magnet exit and enter the poles of the same magnet or can the field lines say exit from the previous magnet's N pole and enter into the next magnets S pole? In other words if a magnets one pole is already attracted to a different magnet can the other pole field lines of the same magnet then go on to yet another magnet and so forth as long as each next magnet meets a new one for the field lines to go to ?

    Now my second question is what happens in a magnet sphere ? Now I know that the E field inside a conducting sphere with a surface charge is zero and I ahve heard that also f a sphere would be made out of magnetic material the B field inside would also be zero , but what would happen if I had half a sphere in other words a permanent magnet sphere jsut cut in half , so that each side has a N and a S pole , assuming the inner sides are the N or S poles , I then put these half sides together but leave a tiny gap so that they dont touch physically , what would happen ? the two sides would be repelled constantly right? Say I hold them together with screws (non conducting ones) what happens , do I have a B field inside ? and is the line of the tiny seperation a cusp ?
    Last edited: Aug 27, 2014
  2. jcsd
  3. Aug 27, 2014 #2


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    This is true for isolated bar magnets only.

    Yes they can (and do).

    What is a magnet sphere?

    It does not have to be zero.

    If you split a regular magnet in half and separate the two parts by a tiny distance, you'll see a strong attraction between them.
  4. Aug 27, 2014 #3


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    See Figure 6.8 on page 10 of this file, which shows the magnetic field produced by a uniformly magnetized sphere (is that the sort of thing you meant?):

    Last edited: Aug 27, 2014
  5. Aug 31, 2014 #4
    imagine the half sphere is a permanent magnet , could it be formed so that it's one pole is in the inside while the other is on the outside and what would happen if I placed two such half sphere close together in a way that would normally resemble a sphere only with a slight gap between them ? Would there be a monopole like magnetic field inside the volume enclosed by the half spheres ? Would the field lines come out through that small gap between them to form loops and if I would close the gap by putting these two magnetized half spheres the field would vanish right ?Because there would be no loops anymore

    now imagine the same situation with the two magnetized or permanent magnet half spheres only this time the gap between them would be closed with a bismuth circle , in other words the two half spheres physically put together with a bismuth connection , what would happen then ? Bismuth is the best natural diamagnetic as I read , aka it expels b field lines so if I have two same polarity poles facing inwards but not touching each other magnetically or physically what would ahppen in such a situation ? Yes Jtbell I guess im thinking about something similar to the paper you sourced

    Attached Files:

    Last edited: Aug 31, 2014
  6. Aug 31, 2014 #5


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    The fields would cancel nearly completely (and completely if you close the gap).


    The reaction of all conventional diamagnetic materials to magnetic fields is quite weak.
    You can use superconductors, they are perfect diamagnetic materials. Then you'll see a higher field strength close to the borders of those superconductors.
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