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Does a magnet radiate a line force or piont force

  1. Mar 9, 2009 #1
    I am working on a project, using magnets, and I am having trouble figuring out how to orient that magnets. I plan on lining a rotor and an armature with magnets. The magnets should repel off of each other and begin spinning, and before I hear this again, not that I don't appreciate you skepticism; this will not be perpetual motion. It will run for so long, the magnets will decay (at an accelerated rate), and then it will stop. So I plan on "burning" the magnets like a fuel. I have seen this working on YouTube (several times), However I don't know how to orient the magnets. I was thinking something like this.

    S----N S----N
    or
    S N----S
    !
    !
    N

    If the magnets act like a point charge force then the first one would be the way to go. however the lines of force make me think that the second one would work.

    Any comments would be appreciated

    Thanks
     
  2. jcsd
  3. Mar 10, 2009 #2
    Won't work. The magnets will attract as well as repel, so there is no net acceleration. Sorry.
    You should work with currents or an electromagnet as a stator. First, remember that the basic force is based on the Lorentz equation, where the force between a magnetic field B and a current in a wire I is equal to F = I x B, where the latter is a vector cross product (the force is perpendicular to both I and B). I am now looking at a small motor I built, where B (neodymium iron boron, on the rotor) is along the axis of rotation, and the stationary currents I are radial, giving a force along theta. I use a Hall effect sensor to switch the current. The total power is about 18 miiliamps at 250 millivolts. I have no iron in the stator (for demonstration purposes).
     
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