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About: Magnetic force

  1. Oct 24, 2012 #1
    Hi, I am trying to play around with magnets on my free time, I ordered some neodyum magnets and I've been thinking of making my own electromagnets, I had some of questions and I was hoping someone here mmight help me:



    1. About magnetic force:
    AFAIK magnetic force is perpendicula to the surface it is emitted from right? but my question is, if I cut an angle in a magnetic rod (say at 45 deg), will I be able to exert a force at 45 degrees?


    How does magnetic polarization work with unevenly shaped magnets:

    if I cut a magnetic rod and make it pointy on one side (but not the other), it would loose its symmetry, where would the "mid-point" be? (where the polarity changes) or will it loose its magnetism just for being uneven?
    I would assume it would be in the center of mass (thats just my assumption, but I would like to get this confirmed)

    Here's the project I have in mind (its a really simple sketch but I hope it gets the idea across):

    http://imageshack.us/a/img22/493/weirdexperiment.png [Broken]



    ======== not so important question ============

    2. Where can I get some "custom sized" soft-iron rods?, TBH I've searched the internet and they only come in like super small sizes
    2.a. are they only sold in small sizes because bigger sizes are not "magnetically efficient" ?
     
    Last edited by a moderator: May 6, 2017
  2. jcsd
  3. Oct 24, 2012 #2
    In a nutshell. No.

    A magnet is actually not a single thing, it is a collection of magnetic particles all roughly lined up with each other. The general result of that is a magnetic field that appears to come from a point somewhere inside the magnet near one end (the north pole) and circles round to vanish back inside to a point near the other (the south pole)

    Whatever shape the surface is has pretty well nothing to do with it.
     
  4. Oct 24, 2012 #3
    1) The shape of the end has little effect on the direction of the magnetic field. Consider the relative size of the space around the end and the tip size itelf.

    2) There is no such point as a neutral point in a magnet. If you break a magnet at any point each part has a N pole at one end and an S pole at the other.

    3) You need to reorder the numbering of your questions.

    4) I suggest you look in a toolshop for screwdriver magnetiser/demagnetisers. They are very cheap and can perform their stuff on screwdriver shafts or other ferrous metal object.
     
  5. Oct 24, 2012 #4
    Thank you for the replies



    2) I know there is no such point as a neutral, but if you see a diagram of the magnetic field
    Magnet0873.png
    you can clearly see there is a "mid point" (mid not neutral)


    but again, take that same idea (as this picture), how would the magnetic force lines be affected by that shaped I drew?
    as you can see all the magnetic force lines are somewhat perpendicular to the surface they are coming from, thats where my question arises from
     
  6. Oct 25, 2012 #5
    Sorry, I don't see that.
     
  7. Oct 25, 2012 #6
    Nor do I. The metal surface just happens to be perpendicular to the field lines in a few places.

    It IS possible to 'shape' a magnetic field by design of the shape of pole pieces. In electric motors for example, the pole pieces and armature are curved to create a radial field.
    But you can't just alter the shape of a bar magnet and expect to 'shoot' magnetic field in some direction.
     
  8. Oct 26, 2012 #7
    AJ Bentley, would you be so kind as to point me where to get information on "shaping" magnetic fields
     
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