Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Electrical Applying current only to temporatrily demagnetize a magnet

  1. Feb 13, 2019 at 1:48 PM #1
    Ladies & Gents,

    Instead of applying current to a non-magnet to induce magnetism, is it possible to apply current only to temporarily de-magnetize a magnet (natural or man-made)?

    This would seem to use up less electricity, especially since the default mode for a desktop application I'm working on is to keep a device magnetized.

  2. jcsd
  3. Feb 13, 2019 at 2:23 PM #2
    Yes. It is as simple as it sounds.
    Just like you can permanently (sort of) magnetize some materials with applied fields (like a steel screwdriver, for example), some magnets can be permanently demagnetized. This depends on the materials, some are resistant to this, others aren't.
    In the power supply design world some companies marketed pre-magnetized transformer cores for single ended operation so that more dynamic energy could be stored (stored and removed at 100KHz, or so). These never really caught on because of their cost. However, it is an application of exactly what you described.
    BTW, this is an easy experiment to do with a DC power supply and lots of coils of wire.
  4. Feb 13, 2019 at 4:11 PM #3
    DaveE, thanks so much. I figured it was as easy as it sounds but didn't have those materials in front of me just yet. I'll do some research on the materials to see which are the more and less resistant types. Thanks again!
  5. Feb 14, 2019 at 2:11 PM #4


    User Avatar

    Staff: Mentor

    How are you going to re-magnetize it? And don't you think that will also take an energy investment?
    Not sure I agree with this. Degaussing magnetized materials takes a special waveform, and again. leaves it unmagnetized.

    @J8675309 -- can you say more about the application? It may be that just temporarily rotating the permanent magnet will reduce the field in your application.
  6. Feb 15, 2019 at 11:10 AM #5
    IIRC, you can get door-hold magnets that 'fail secure'. They have a coil over the magnet, DC run in opposition to magnet to release.

    There are issues such as the magnet type must tolerate such treatment, not lose its residual magnetism during working life...
    'Very High Coercivity' ??
  7. Feb 15, 2019 at 11:24 AM #6


    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    Presumably you don't want to demagnetise the magnet itself, just reduce the field near one of its poles to zero temporarily?
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook

Have something to add?