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Red Hot Magnetics

  1. Dec 16, 2003 #1
    Hypothetical experiment:

    I have a single 2-inch by 2-inch by 1-inch thick Neodymium magnet affixed on the outer rim of a 1-foot diameter circular hard plastic disk(1/8th-inch). The disk and magnet are held stationary by whatever means.
    The underside of the plastic disk has a coating, an insulating coating, sufficient to withstand, let's say, 2000 degrees F with a coating thickness of 1/2 inch.
    Now, underneath this assembly I have another disk(same 1-foot diameter dimension), separated from the first disk by a nominal air-space. This second disk is allowed to rotate freely and in fact motor driven, unlike the first, which is held static.
    The properties of this second disk is this: This disk is composed of iron(or other suitable ferromagnetic material) On the outside perimeter of this "iron" disk 2-inch diameter holes are drilled. With 2-inches between drillings, this provides for 6 holes on the outer rim of the 1-foot "iron" disk.
    If I rotate this "iron" disk underneath the NIB magnet, a choppy "drag" will occur, due to the fact the iron disks' rotation will self-impede motion because of the magnet, yet the hole spaces provide relief, then drag. Choppy.
    Now, let's heat the "iron" disk, very hot.
    The "iron" disk, now super-heated and in rotation is not drag-affected by the magnet, but will spin freely.
    Energy is used to heat the disk, so conservation is maintained.
    However, the holes in the disk allows the magnetic field to pass during rotation of this heated disk, albeit in a pulsed manner.
    Not getting something for nothing, but the question is this: Will this operate as I described?
  2. jcsd
  3. Dec 16, 2003 #2


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    I really can't tell what this is supposed to do.

    - Warren
  4. Dec 17, 2003 #3
    Warren. What I am trying to understand is the interaction of a magnetic field with a red hot piece of iron.
    A magnet will not attract red hot iron, does not repel it and does not go through it(if solid).
    So what happens to the field if it doesn't do any of the above?
  5. Dec 17, 2003 #4
    The curie temperature of Fe is around 1000C. When Fe is above it's curie temp. its thermal energy is large enough to cause random flips in the spin of electrons. Above the curie temperature Ferromagnets turn into a paramagnet. and you apply a magnetic field to a paramagent, the spins of the electrons try to align with the magnetic field.

  6. Dec 17, 2003 #5
    What happens is, before the curie temperature is reached, you smash your hand between the two plates like a crepe
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