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Thread: question about energy in a magnetic field

  1. #1 question about energy in a magnetic field 
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    Energy is stored in a magnetic field. This energy came from work that was done on the ferromagnetic material that made it into a permanent magnet. Does this energy get used then when lets say we use the magnet to pick up stuff or repel another magnetised object(holding the like ends towards each other). Is this energy coming from the original energy when the magnet was produced. Does the magnetic field then have a slightly weaker field after some it does some work?


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  3. #2  
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    That sound's about right to me, I do know that magnets will lose their strength over time. Not sure on the specifics, but I know Rocket will be able to enlighten us soon.


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  4. #3  
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    I suppose what i'm trying to figure out is the energy transfer in a dynamo. lets pick a wind turbine. is the wind doing work which releases energy that was stored in the permanent magnet?
    in which case does the electricity come from what was stored in the magnet since it was made in the factory.
    after a long amount of time will the magnet be "depleted?" or does the whole process keep storing energy in the magnet which in turn keeps turning into electricity. which would mean the electricity at the start was just originally from the factory and eventually the electricity coming from the wind?

    or does the magnet provide the force and the wind provide the energy and moving the magnet just sweeps all the electrons along somewhat like me using a stick to move something along.
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  5. #4  
    Forum Bachelors Degree Apopohis Reject's Avatar
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    Quote Originally Posted by haventaclue
    I suppose what i'm trying to figure out is the energy transfer in a dynamo. lets pick a wind turbine. is the wind doing work which releases energy that was stored in the permanent magnet?
    in which case does the electricity come from what was stored in the magnet since it was made in the factory.
    after a long amount of time will the magnet be "depleted?" or does the whole process keep storing energy in the magnet which in turn keeps turning into electricity. which would mean the electricity at the start was just originally from the factory and eventually the electricity coming from the wind?

    or does the magnet provide the force and the wind provide the energy and moving the magnet just sweeps all the electrons along somewhat like me using a stick to move something along.
    Interesting questions indeed, and here is another to add to the list;

    As I understand it, the earth is a huge magnet, which is continually spinning. We know that vast amounts of energy are being continually absorbed by this spinning magnet - with it's atmospheric envelope, so the question is; what happens to all this energy that has been forever assimilated?

    I mean, by now the planet perhaps should have heated up to the point where life of any variety can no longer be sustained, yet we seemingly continue to enjoy the same perfect range of conditions as ever.
    sunshinewarrior: If two people are using the same word, but applying different meanings to it, then they're not communicating.
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  6. #5  
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    Quote Originally Posted by haventaclue
    I suppose what i'm trying to figure out is the energy transfer in a dynamo. lets pick a wind turbine. is the wind doing work which releases energy that was stored in the permanent magnet?
    in which case does the electricity come from what was stored in the magnet since it was made in the factory.
    after a long amount of time will the magnet be "depleted?" or does the whole process keep storing energy in the magnet which in turn keeps turning into electricity. which would mean the electricity at the start was just originally from the factory and eventually the electricity coming from the wind?

    or does the magnet provide the force and the wind provide the energy and moving the magnet just sweeps all the electrons along somewhat like me using a stick to move something along.
    The energy produced by a dynamo comes from the prime mover, in your case the windmill.

    The magnetic field serves to create an electromotive force (i.e. voltage) in the coils which in turns creates a current flow to the load. That current flow creates an opposing magnetic field and the interaction between the magnetic field of the rotor and the stator creates the resistance against which the torque from the windmill does work.

    Neglecting friction and various other losses, if there were no electrical load on the generator there would be no torque required to turn the generator and no work done by the windmill.

    The energy generated by the dynamo has nothing to do with the energy used to create the magnet. The magnet is not "depleted" in the process. Some generators do not even use a permanent magnet.
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  7. #6 Re: question about energy in a magnetic field 
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    magnet works on polarization. their is no energy gain or loss.
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