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Magnetic Generators

  1. Jun 6, 2004 #1
    Why couldn't permanent magnets be used to create electricity?
    If permanent magnets never lose or change their magnetic properties, then would a generator using permanent magnetics be essentially free energy?
    Isn't this some sort of contradiction to the conservation of energy?
     
  2. jcsd
  3. Jun 6, 2004 #2

    turin

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    They can be, but you still have to turn the stator.




    It would be "free" in roughly the same sense that solar energy is "free," or, if you like dramatic analogies, in roughly the same sense that your inheritance is free. Sure, you can find objects that are already magnetized, and maybe even ones with just the right properties of magnetism for your generator, but there are two points about this scenario: 1) Something, at some time, had to magnetize them, so, in a sense, you are only taking advantage of the fruits of some other "labor." 2) Magnets do not last for ever at temperatures higher than 0 K. In other words, a permanent magnet will eventally "die."




    No. The conservation of energy does not say that every single individual must pay money for their energy. There are basically two accepted fundamental sources of energy available to the inhabitants of Earth: solar energy that travels through space from the Sun and radioactivation energy that travels up through the magma from the core. The solar energy is believed to be, by far, the primary source of energy for the surface dwellers of our planet. It is believed that natural magnetization happens to be one of those rare jewels of surface dwelling natural phenomena that our own Earth has done for us on its own. Both the solar energy and the radioactivation energy will run out, eventually. Don't forget, though, that there is, to varying degrees of efficiency, a provision in the first law (conservation of energy) to store energy for later use (called internal energy).
     
  4. Jun 6, 2004 #3

    krab

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    A common pitfall is to conclude from the fact of a continuing force, that there is free energy to be had. The same happens regarding gravity. A force is always present, so why can the force not continuously produce energy? Like the device of wooden weights on a sloped chain, the topside weights in air, and the bottomside ones in water so they float up. This seems like a win-win: the top ones fall and the bottom ones float upwards, both top and bottom pushing the chain in the same direction.

    Anyway, none of these devices work. Energy is conserved, so you cannot get any for free. The fields are conservative, meaning that a cycling machine must be given at least as much energy to put it back to the initial state, as it produced getting out of the initial state.
     
  5. Jun 7, 2004 #4
    Actually, this isn't a very good analogy to the permanent magnet. Permanent magnets are used in direct current motors all the time. They would always be used in motors except that more often than not it is advantageous to be able to change the polarity of the field, especially with AC. Motors with permanent magnets don't take half the energy to run. No stored energy is being harvested from the magnets.
    Strictly speaking it doesn't take much energy to magnetize a magnet, and you are not tapping into a storage of energy when you use a magnet to do work. The magnetic field is static, just like gravity. If you generate electricity by pushing a bar magnet into a coil of wire, you are doing all the work. The magnet is not "depleted" by this. The magnetic field is coming from the electric field of a certain small percentage of electrons in the atoms of the elements in the magnet. Those electrons and their electric fields are never "worn out" or "used up"
    What happens is that the little domains of magnetic influence will eventually slip out of alignment with each other. The magnets will seem "weaker", but this is more akin to an engine whose timing is off, than to a car that has run out of gas. Stick the magnets between two electromagnets and zap them for a brief instant from a bank of capacitors, and the magnet will be good as new for decades. No energy has been added. The domains have been forced back into alignment, that's all. Newer magnets are better because there is vastly more friction between the domains and it takes much longer for them to slip out of alignment.

    Permanent magnets can be used both in motors and generators. The main reason they aren't is that we usually use, or want to generate, AC which is easier to achieve with all electromagnetic elements in the motor or generator. Once an AC generator is in motion the magnetic fields are self sustaining. They don't have to be fed all the time. The electric power coming out is converted from the mechanical power being fed in. It isn't being harvested from the magnetic fields.
     
  6. Jun 7, 2004 #5

    turin

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    What the hell was I talking about. It wasn't even late at night when I posted that garbage. I agree with almost everything you said, zooby.

    If no energy is added when you "zap" a magnet to magnetize it, then why do you have to "zap" it? The magnetic field has an energy density, and this density is supported by magnetization. When a magnet wears out, the energy density dissipates. In order to magnetize a magnet, you have to supply a magnetic field, and thus a magnetic energy density ~ B2. (Not that any of this has anything to do with the original issue, though.)
     
  7. Jun 7, 2004 #6
    You don't have to. Better set ups are more quiet and don't have the cool "zapping" noise.

    It takes an expenditure of energy to realign the domains. The energy you expend isn't added to the field, though, like it would be if you were compressing a spring. It's like Krab pointed out: there's no energy in a magnet that constitutes something like a fuel. It can't be added to or subtracted from. It is a static force. What is useful about it is that it can be used like a tool to knock the electrons in a conductor into motion to create electricity. You aren't depleteing the magnet any more than you are depleting the copper in the coil in which you generate the electricity.
     
  8. Jun 7, 2004 #7
    zoobyshoe, could one make the following analogy:

    You can "make" a strong gravitational field by collecting a lot of mass together in one place. It may take work to move the smaller particles together, but no energy is actually being placed into the gravitational field by our work. The gravitational field just grows stronger by the superposition of what smaller fields already existed. Is this similar to aligning the magnetic domains in a ferromagnetic material?

    Additionally, we harness the work of gravity all day long in hydroelectric dams, but the Earth's gravitational field isn't "sapped" by the energy we extract from it. The gravitational force is just a useful way to get back the potential energy that the sun put into the water.
     
  9. Jun 7, 2004 #8
    Yes, this is similar: you are not creating the gravity, just putting it where you want it.

    I can see you understand exactly what I'm saying, but I'm leary of bringing hydroelectric dams, and gravitational potential energy into it, because those are situations where gravity is used essentially as a spring with a certain amount of force stored in it. Better, maybe, to merely point out that we use gravity all day long to keep us stuck to the earth without using the gravity up, or weakening it in any way.
     
  10. Jul 25, 2006 #9
    There has got to be a way to exploit the energy of a magnetic field of a magnet. The only thing I don't know is if the magnetic field is a moving (flowing) force. If the field is a flowing force, there must be a way to generate electricity in the wake of this field. A magnet stays on my refrigerator door for years without falling off even though the Earth's gravity is acting on it. To me this seems like energy at work, keeping the magnet secure to the door.

    Also there are no scientific facts, what we know today may be disproved tomorrow, as this has happened before. One should keep an open mind in looking for answers.

    I am not a scientist, just an average Joe with a huge fascination on the topic of Free Energy Generators. I hate running out of power, Imagine if one day we can take electricity for granted, and have cell phone chargers a thing of the past.
     
  11. Jul 26, 2006 #10
    hmmm magnets do lose their magnetic properties.
    this question of reminded me of something i read in this forum site, somone asked for a way to demagnetize some metal rod, and it was replied that ac magnetic field can do the trick.

    so besides the heat in the generaton, the generator create ac magnetic field in it, which also demagnetizes the magnet.

    though i do not know what is the effectiveness of each on a magnet.

    if magnets were permanent, it would be gre8, we wouldnt lose any energy on the coil's resistance of the electromagnet...
     
    Last edited: Jul 26, 2006
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