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Iron rod - will flux link with disk above it

  1. Jun 6, 2012 #1
    If an aluminium disk is placed above a COMPLETELY vertical current carrying iron rod will any flux link with the aluminium disk...


    Firstly, does it matter if the current is AC or DC. I presumed not as the only difference is that the magnetic field will vary in one case and stay constant in the other. The type of current would only be important if we were considering induced EMF.

    Secondly, here is what I thought (but was not sure it was correct):
    The rod is completely vertical so, as per the cork-screw rule the magnetic field should be circular around the rod. This would imply NO flux links with the aluminium disk.
    However, on watching the following clip (first 40 seconds):

    it seems I may have been mistaken. The only way I can see that the metallic disk is repelled is if flux DOES link with it. Perhaps also I am not comparing like with like.
     
    Last edited by a moderator: Sep 25, 2014
  2. jcsd
  3. Jun 7, 2012 #2
    perhaps this image will help
    attachment.php?attachmentid=154620&d=1339056751.png
     
  4. Jun 7, 2012 #3

    Doc Al

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    Staff: Mentor

    In your example, you have a vertical wire. In the video is a solenoid, made up of horizontal coils of wire. Different situations.
     
  5. Jun 7, 2012 #4
    I realised that after...in my situation, however, would the disk be repelled....I presumed not as the magnetic field does not link with the disk...is this correct?

    also would I be correct in thinking that the solenoid behaves like a bar magnet?
     
    Last edited: Jun 7, 2012
  6. Jun 7, 2012 #5

    Doc Al

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    That's what I would say.
    Yes, close enough.
     
  7. Jun 7, 2012 #6
    thanks alot :)
     
  8. Jun 7, 2012 #7
    Is it irrelevant whether it is AC/DC
    again I presumed it would be irrelevant?
     
  9. Jun 7, 2012 #8

    Doc Al

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    Staff: Mentor

    I don't see how that would be relevant.
     
  10. Jun 7, 2012 #9
    ok thanks a lot :)
     
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