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

Unusual movement of square fridge magnets

  1. Jun 5, 2014 #1
    At home I have a series of small square fridge magnets (about 25mm by 25mm and about 1mm thick).

    If I select two of these fridge magnets and place them together then, as you would expect, they attract one another. However the interesting observation is that sometimes the fridge magnets are only loosely bound and can be slid over one another without any sudden jolting of attraction. If I then rotate either of the fridge magnets 90 degrees (clockwise or anticlockwise) the magnets have greater attraction but only in certain positions (unlike all positions as was the case previously) - in this setup they attract each other most strongly when the two bases of the magnets don't cover each other up completely.

    This effect occurs with any and all of the magnets I select off the fridge.

    I am yet to study magnetism in detail however I am interested to know how this phenomenon can be explained in terms of magnetic fields.

    Thanks.
     
  2. jcsd
  3. Jun 5, 2014 #2

    mfb

    User Avatar
    2016 Award

    Staff: Mentor

    I guess those magnets have several areas with a different orientation of the magnetic field - the forces and the stable positions/regions then depend on those areas.
     
  4. Jun 5, 2014 #3
    fridge magnets are shaped in such a way that both north and south end of the magnets are on the same side of the magnet (the side that sticks to the fridge). Try sticking the magnet to the fridge with the wrong side down and you will see that it wont stick at all. If you could see the north and south ends of the magnets a fridge magnet would look like that

    NNNNNNNNNNNN
    SSSSSSSSSSSSSS
    NNNNNNNNNNNN
    SSSSSSSSSSSSSSS
    NNNNNNNNNNNN
    SSSSSSSSSSSSSS
    NNNNNNNNNNNN

    now, if you put two magnets back to back, either the stripes align to each other in which case the SSSSSSS sticks strongly to the NNNNNNNNNN and when you try to displace the magnets the different ridges will ride over each other creating the bumpy feeling you described, or if you turn one of them 90° the stripes don't align no matter how you try so you get only a rather weak attraction which feels much smoother than the other configuration.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Unusual movement of square fridge magnets
Loading...