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Electromagnetic Induction and Magnetism Questions

  1. Aug 9, 2008 #1
    Ok, I have two questions:
    First of all, are there any instances in which a magnet (not an electromagnet) will remain magnetized forever? I know that some magnets do lost their magnetivity

    Secondly, if the above is true then consider the following theoretical scenario:

    Imagine a large Iron sphere in space that is magnetized, it is large enough to allow multiple small satellites to orbit it. Now, all of these little satellites are in the same orbit path and are connected to each other with a large wire. Since the the satellites would be orbiting around the sphere, wouldn't this create energy through electromagnetic induction? Moreover, wouldn't this system continue to produce energy unless it was destroyed? I'm not doubting the law of conservation of energy, just a bit confused


    P.S. I have a poor knowledge of physics so if what I say is just completely idiotic or I left something out forgive me.
  2. jcsd
  3. Aug 9, 2008 #2
    hi krfkieth,

    They would perfrom electromagnetic induction in the same way a faraday or homopolar generator would.

    however, it wouldn't defy the laws of conservation of energy because the magnetic field of the sphere would create drag on the satalites as they orbit so they would eventially slow down and plumit tot he surface of the sphere.

    Perhaps you have seen this experiment? You need an alluminium pipe and a reasonably strong magnet.

    first drop the magnet at shoulder height and note how long it takes for the magnet to hit the ground.

    then drop the magnet through the alluminium tubes. You will notice it falls ALOT slower.

    This is because fo the drag from the induction on the alluminium tube by Lenz law. The same drag can be found in any dynamo or electromagnetic generator. (and god help you if you break Lenz law because then you have a generator with no drag! You would have a so called "free energy device").
  4. Aug 16, 2008 #3
    Thank you! I had not heard of the Lenz law!
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