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

Magnetic "shielding"

  1. Jan 12, 2015 #1
    Hi, I'm working on a project, interested in your opinion
    Need a material for magnetic "shielding"
    image.jpg

    There must be no repulsion or attraction between M1 and S since non of them is stationary and it would affect the motion. There will be a ferromagnetic material behind S that cannot be affected by the magnet until S opens.
    S should be 0.5mm thick with an opening of 1 mm

    I don't think I could use diamagnetic materials since the distance between M1 and S should be 0.1 to 0.2 mm and there might be some repulsion effect.

    It needs to be like in picture 2 with no repulsion/attraction between M and S
    The magnetic flux must reach the recuperator (ferromagnetic so it will attract it, while S open)
    Do not propose electromagnets - can't use electricity on this one
     
  2. jcsd
  3. Jan 12, 2015 #2

    mfb

    User Avatar
    2016 Award

    Staff: Mentor

    I don't think this is possible. To act as shielding, S has to be influenced by the magnetic field, and this will always lead to forces.
    Mu-metal is a common material for shielding, but then the geometry should be different.
    Superconductors are (up to some field strength) ideal diamagnets and therefore great shields, but then you get a force between shield and magnet as well.
     
  4. Jan 12, 2015 #3
    Thank you for your reply, I greatly appreciate your advice
    So, in my device I need to control the magnetic flux of a permanent magnet using the kinetic force of the device, the permanent magnet will be in motion but it's flux can only access the recuperator once it's at 1mm of it, so my solution was to put something between them that would open once the magnet is close enough and close once it distances it again.
    One of the conditions was not to use electricity. Otherwise it would be too easy
    I'll figure out something
     
  5. Jan 12, 2015 #4

    mfb

    User Avatar
    2016 Award

    Staff: Mentor

    What do you want to achieve with that setup? There could be alternative options with a different design.
     
  6. Jan 12, 2015 #5
    I could use an electromagnet and the problem would be resolved but one of the conditions is not to use electricity, so I'm stuck with a permanent magnet
    I just need to control it's flux, when the rec. will receive it and when not. So I only have some kinetic force to achieve this.
    Shielding was the first thing to come to my mind but I just started working on it and it seemed a little problematic so I started this post.
    If you have any ideas I welcome them
     
  7. Jan 12, 2015 #6

    Low-Q

    User Avatar
    Gold Member

    Magnetism is not possible to shield as you want it to. You must apply energy to do so. A coil around a permanent magnet could make an opposite magnetic field. If it WAS possible to do it the way you want it to, everyone could make themself a motor that is "powered" by controlling the force between permanent magnets without energy supply.

    And as you sure know, energy cannot be created from nothing. Only transfer from one form to another.

    Vidar
     
  8. Jan 12, 2015 #7

    berkeman

    User Avatar

    Staff: Mentor

    Thread closed for Moderation...

    (Looks like we Mentors are piling on in this thread...) :-)

    Thread re-opened for now. If we find out you are trying to get help with a PMM or over-unity device, this thread will be closed for good.
     
  9. Jan 12, 2015 #8

    mfb

    User Avatar
    2016 Award

    Staff: Mentor

    @MXM13: See X-Y-question. What is the problem you want to solve with that concept?

    By the way:
    And we still do.

    Edit: Sorry berkeman, didn't see your post.
     
  10. Jan 12, 2015 #9

    Baluncore

    User Avatar
    Science Advisor

    This is an example where the concept of a magnetic circuit is useful. Rather than having a hole in a shield you could short circuit the permanent magnet's field by using a magnetic shunt fixed either side of the proposed aperture.
     
  11. Jan 13, 2015 #10
    Google permanent magnetic chuck. The magnetic force is "turned on and off" by mechanically moving permanent magnets in relation to each other internally while the face of the "magnet" stays fixed in place. No electricity is used, just a lever.
     
  12. Jan 13, 2015 #11
    Thank you very much, I greatly appreciate your reply
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook