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Magnet problems

  1. May 21, 2014 #1
    Can you explain me this:
    Ferromagnet has permanent magnetic force and can't lose it in the constant conditions, so if i put magnet and piece of the metal it will be pulled away from the magnet creating some kinetic energy. As energy can't be created, just transfered, so I don't understand who lost energy in this situation?
    Thank you in advance
  2. jcsd
  3. May 21, 2014 #2


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    The person pulling the metal plate supplies the energy.
  4. May 21, 2014 #3
    You didint get it. If you put metal piece next to the magnet, magnetic force will push it away and kinetic energy will be created, no human interfering
  5. May 21, 2014 #4


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    How do you put it?

    (1)It will not push the metal, it will attract it.
    (2)As you said before,it is not created, the potential energy of the magnet is transferred to kinetic energy. It gains potential energy while you(Or anything) puts it near the magnet.
  6. May 21, 2014 #5

    Meir Achuz

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    "You" are an interfering human.
  7. May 21, 2014 #6
    You put on the table magnet and next to it piece of the metal. It doesn't matter if it attract or push, the point is that the metal will move.
    Magnet doesn't generate or produce any kind of energy it is a force field. And if you are using this field to create energy, something has to loose the same amount of energy, So my question is who is loosing energ????
  8. May 21, 2014 #7


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    According to the law of conservation of energy, energy in a closed system will stay constant. It can only change from one form to another.
    What happens here is that the potential energy of the metal is being changed to kinetic energy. So it moves.

    Or are asking from where this potential energy comes from?
  9. May 21, 2014 #8
    I understood your point adjacent, in that case the same example but from different point.
    Lets say we have a nail nailed in the tree. If i want to take it out i need certain amount of energy but instead of using my own energy, i just can put next to it powerful enough magnet and pull out the nail. In the first scenario i would use much more energy to pull it out than in the second. How can it be?
  10. May 21, 2014 #9


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    Newton's third law. As much as the magnet will be pulling on the nail, you'll feel the pull towards the tree. You'll have to expand energy to keep the magnet in place and have the nail come to you.
  11. May 21, 2014 #10
    Metal is loosing energy. It lost potential energy it had on account of kinetic energy. Basically as long as thre is some magnet, all the metals in the universe have some potential energy due to it.
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