Where does the energy go - magnetism question.

Discussion in 'Physics & Math' started by Ickyrus, Nov 15, 2011.

  1. Ickyrus Registered Senior Member

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    I have some neodynimum magnets I am observing. I put a couple on a bathroom tile and they seem to align themselves with earths magnetic pole. If I spin them they slow down very quickly and align back to the N/S pole. If I were to do the same experiment with non-magnetic pieces of metal they would spin for longer before friction and air resistance would bring it to a halt.

    Where does the the energy go when a force is applied to spin a magnet in a magnetic field? :shrug: As energy can neither be gained or lost in a closed system.
     
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  3. prometheus viva voce! Registered Senior Member

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    Ask yourself what is comprising your closed system in these examples.
     
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  5. Robittybob1 Banned Banned

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    I don't know but here is an attempt.

    A moving magnetic field would affect electrons within that field. In the process of shifting electrons there is a resistance and resistance creates heat. So the answer is the energy is lost as heat.
     
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  7. OnlyMe Valued Senior Member

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    The magnetic fields of the magnets and the earth are interacting. This interaction slows down the spinning magnet and in the end it aligns itself with the earth's magnetic filed. The mechanical energy of the spinning magnet is being transferred from the magnet to the earth, through the interaction of the two magnetic fields. The difference in mass makes the effect on the earth insignificant, while for the magnet the change is easily observed.
     
  8. Robittybob1 Banned Banned

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    That is not an explanation for you don't explain where the energy goes. The term "Interaction" on it's own is insufficient.
     
  9. billvon Valued Senior Member

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    Depends. If it's in an ideal H-field and you spin an ideal frictionless magnet, there's no loss of energy - it spins forever, although it speeds up and slows down at different parts in its spin.

    If, however, there is metal nearby, the moving magnetic field generates eddy currents within the metal. (How a generator works.) These drain energy from the motion of the magnet. If the field source within the magnet is not ideal (i.e. it's ferromagnetic, which means it will realign its spins to conform to new magnetic fields) then the energy required to flip those spins back and forth will dissipate energy as well.
     
  10. Dywyddyr Penguinaciously duckalicious. Valued Senior Member

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    Learnt to read yet?
     
  11. prometheus viva voce! Registered Senior Member

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    Saying energy is lost as heat is a bit like saying "every time I insert a screwdriver into my eye I feel a sharp stabbing sensation." It comes well and truly from the department of stating the obvious.
     
  12. Dywyddyr Penguinaciously duckalicious. Valued Senior Member

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    That happens to me too!
     
  13. Robittybob1 Banned Banned

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    Of couse I read that . You can say it is transferred but how is it transferred?
     
  14. Robittybob1 Banned Banned

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    It might be numbed with local and you feel nothing.
     
  15. Dywyddyr Penguinaciously duckalicious. Valued Senior Member

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    How does a speedometer work?
    "Magnetic interaction".
     
  16. Robittybob1 Banned Banned

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    So! So what!
     
  17. Dywyddyr Penguinaciously duckalicious. Valued Senior Member

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    The invisible pixies get caught in the magnetic field and start to push the Earth because the magnetism annoys them.

    Please Register or Log in to view the hidden image!

     
    Last edited: Nov 16, 2011
  18. Ickyrus Registered Senior Member

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    The earth’s magnetic field must be subject to many local interruptions from other magnetic material. We have a large quantity of cars with magnets in them all affecting the earth’s magnetic field. Is the gradual shifting of the pole increased by this mass of magnets?

    This would be difficult to say because we know that from geological studies that the N/S pole position has reversed in the past.

    If the electron is a small magnet how much influence does the Earths magnetic field have on it and chemical processes. Non-magnetic material also has electrons so it may be concluded that something else is influencing them beyond any magnetic strength that can be applied to such material.

    These answers posted above may be correct but I just can't avoid feeling that something is missing.
     
    Last edited: Nov 16, 2011
  19. OnlyMe Valued Senior Member

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    To the first question about how much all the magnets and motors on earth might affect the Earth's magnetic field.... This is another issue of scale. Put all those motors together with all the magnets you can find and they are insignificant next to the magnetic field and mass of the earth. So yes they theoretically have some affe t but is would be insignificant.

    The questions about electron's and molecules, I best leave for someone else. While I have a fair understanding even at that scale, I am not likely to provide a good answer.
     
  20. Robittybob1 Banned Banned

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    +This answer sounds about right. Thanks Dywyddyr, go to the top of the tree.

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  21. Dywyddyr Penguinaciously duckalicious. Valued Senior Member

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    I forgot to mention that the invisible pixies also made the Sun get smaller and that they started life on Mercury.
     
  22. Robittybob1 Banned Banned

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    Just because I promoted you to the top of the tree, didn't mean you get free reign to be foolish.

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  23. Dywyddyr Penguinaciously duckalicious. Valued Senior Member

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    Yeah sorry. That's your province.
     

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