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Hollow magnetic sphere?

  1. Jan 13, 2008 #1
    Hello, I am new to this forum and have a couple of questions. One person has already asked it but with no answers I thought I would give it ago.

    The topic is about magnetism and magnetic fields (I’m a newbie to the subject, so please forgive me if I make no sense but I got to learn somewhere).

    Question 1: If I have a near perfect HOLLOW soft iron core sphere (made up of 2 hemispheres to allow me access to the centre if I need to open it) and wrap insulated copper wire around the outside of it from bottom to top (so that it covers the entire sphere) and pass a large current through the wire would this create an electromagnet?

    Question 2: Would there be a magnetic force exerted on the inside? If so would it hold another metal sphere in the centre? Or would the wire need to be on the inside?

    Question 3: Does anyone know what the magnet fields would look like (I mean a picture or diagram even a sketch)? This would be useful.

    Question 4: If this is impossible why? And is there any way to make it work?

    For anyone interested the reason behind the questions, it is because I’m simply curious and want to learn more about the things I do not understand. And any reading materials are greatly appreciated.

    Thanks in advance... Transfixed
  2. jcsd
  3. Jan 13, 2008 #2
  4. Jan 14, 2008 #3
    So (I think) it would be possible.....

    Thanks for the reply, below I have tried to answer my own questions. But again any input on the topic is great.

    Yes, this would produce an electromagnet and in turn radiate a magnetic field outwards/inwards from the poles on the soft iron core. The soft iron core amplifies the magnetic field in the copper wire that is caused the electrons; it is also paramagnetic so no magnetic field is present without live current.

    There would be a magnetic force exerted on the inside as magnetic fields are vector fields and occupy every point of space within the fields range.

    This means that when the inner sphere is placed in the centre of the symmetrical "external" magnetic field produced by the outer hollow sphere, it will be subject to a torque tending to orient the magnetic moment parallel to the field meaning it would float, in the exact centre of the field of the outer sphere. The inner sphere would not have to be a magnet itself; instead it would just need to be a metal that could be magnetized, due to an applied external magnetic field the inner sphere’s (metal) electron magnetic moments will be lined up. Then the metal can produce a net total magnetic field, which can potentially be quite strong and repel against the edges on the outer sphere.

    The magnetic field would look like the magnetic field of earth.
    To get the strongest magnetic field I would need to take into account the Curie point, and the gauge of the wire in use. The point at which the temperature of the wire exceeds the Curie point is where the magnetism is destroyed. In general lower temperatures stronger fields.

    I think by this that the construction would be possible (see 1st post)....... what do you think?

    Thanks again for your help, and yes any knowledge on the subject please share :smile:
  5. Jan 14, 2008 #4
    I request you to kindly go through this also. Better if you get answer yourself by reading it.
    http://www.practicalphysics.org/go/Collection_42.html;jsessionid=alZLdQlAHb1?topic_id=7&collection_id=42 [Broken]

    http://www.practicalphysics.org/go/Topic_7.html;jsessionid=alZLdQlAHb1?topic_id=7 [Broken]

    Last edited by a moderator: May 3, 2017
  6. Jan 18, 2008 #5
    Thanks for the help,

    got the details down and modified the design. The original construction was all about equal magnetic compression on a central core, after reading up (thanks to the materials you supplied) I scrub the original idea and started to incorporate the theta pinch coil system and found a way to exert pressure on a levitating spheres 3 dimensional axis.

    Thanks again ... Transfixed
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