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I How does a magnetizer/demagnetizer work?

  1. Aug 13, 2016 #1
    Hi.
    These things can be used to magnetize/demagnetize tools, e.g. screwdrivers:
    Magnetizer.jpg

    How do they work? I'm particularly interested in the demagnetizer part. How do the field lines look like?
    And why is there this stair-like structure in the upper hole?
     
  2. jcsd
  3. Aug 13, 2016 #2

    berkeman

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    Staff: Mentor

    I know how powered magnetizers and powered demagnitizers work, but I haven't seen effective unpowered versions. Can you provide a link to that product's datasheet or other info?

    BTW, the search term for a powered demagnitizer is "DeGauss Coil". I'm assuming you know how a powered magnetizing coil works. :smile:
     
  4. Aug 15, 2016 #3

    Tom.G

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    Science Advisor

    By sequentially using steps in the de-magnetize window, the device supplies progressively less magnetizing force when the tool is passed thru.
    See this link for details:
    https://www.quora.com/How-does-a-tool-demagnetizer-work
     
  5. Aug 15, 2016 #4

    berkeman

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    Staff: Mentor

    I wasn't able to watch the video, but does it show the tool being turned or in some other way being exposed to a decreasing alternating magnetic field?
     
  6. Aug 15, 2016 #5

    davenn

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    yup, same problem as berkeman, video doesn't exist
     
  7. Aug 15, 2016 #6

    Tom.G

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    This video does not exist

    Hmm, so it doesn't. I didn't even try to watch it.
    Here is one that exists, at least at the moment.
     
  8. Aug 16, 2016 #7

    davenn

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    Gold Member

    interesting

    would love to know how the demag part works
     
  9. Aug 16, 2016 #8

    OmCheeto

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    Gold Member
    2016 Award

    After watching numerous videos of how the demagnetizer apparently doesn't work, I decided to build one last night.
    tool.mag.demag.test.setup.2016.08.16.png
    Interesting project, and results.
    What everyone missed, was that the paperclip/screw/metal thingy became magnetized when touched with a magnetized tool.
    So even if they did successfully demagnetize their screwdriver, their metal test object would still be attracted to it.

    Without actually having one, I had to guess as to how they work.
    Here is my theory:

    oms.theory.png
    The explanation for example A is self apparent to me.
    Example B displays over-demagnetization.
    Example C kind of explains the stair-step structure of the demagnetizer: Just the correct reduced magnitude of a reversed field strength will theoretically demagnetize the screwdriver.

    ps. I would wordsmith my explanation, but I'm late for an appointment with the coast. Ciao!
     
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