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Thread: Perpetual Motion

  1. #1 Perpetual Motion 
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    Firstly I want to apologize, I know without searching the forums that this topic will have been hammered, relentlessly. I completely understand that full perpetual motion is not possible. I might be missing something STILL, but is it not possible for a magnetic motor to achieve 98%-100% efficiency (ex if I manually spin the gear by hand, it should at least maintain that speed and produce energy FOR A LIMITED TIME before eventually slowing due to friction?).


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  3. #2  
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    If you apply energy to a motor via your hand, then yes, it will spin and produce energy until friction stops it. The energy produced will never be greater than the energy you put in because you cannot create energy, merely transfer it. Several factors prohibit you from transferring energy with 100% efficiency outside a friction-less vacuum.


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    Ok, but since the magnets help maintain the initial speed, if I were to input X watts of energy to start up a "magnetic motor", by the time it stops spinning and producing electricity because of friction, should the resulting energy not be greater than X?
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    or am I wrong in thinking that a magnetic motor provides ANY assistance
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    The magnet is not a source of energy. You can store energy in the magnetic field, but it's no different than storing energy in any other way as far as conservation of energy is concerned.
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    Quote Originally Posted by k. wolfe View Post
    or am I wrong in thinking that a magnetic motor provides ANY assistance
    A common misconception is that spinning a generator will give you "free" energy for as long a time as friction allows. But even if you had perfect lubrication, perfect bearings, zero air drag and superconducting windings, a generator will still never give you more output than input. As soon as you connect a load to the generator, turning it gets harder. If you let go, it will slow down and eventually stop, just as if you had friction, even if it were mechanically perfect and electrically lossless. If you add up all the energy delivered to the load, you will always find that it is no bigger than the mechanical energy you spent to spin up the shaft in the first place.

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    but what if you make both the motor and the generator on the same axel. then suspend the that axel with magnetic feilds to eliminate friction at the bearings. doing this your only drag would be air drag and gravity which i would thearize you could over come with a very small low voltage motor. If this is true the output generated by the finetic energy of the magnets should be larger then the input used to turn the low voltage motor. if this theary is wrong please explain to my why because i am very interested in the subject.
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    Quote Originally Posted by vintox View Post
    but what if you make both the motor and the generator on the same axel. then suspend the that axel with magnetic feilds to eliminate friction at the bearings. doing this your only drag would be air drag and gravity which i would thearize you could over come with a very small low voltage motor. If this is true the output generated by the finetic energy of the magnets should be larger then the input used to turn the low voltage motor. if this theary is wrong please explain to my why because i am very interested in the subject.
    Because the rotational energy out of the motor is less than the input. And the electrical energy out of the generator is less than the input. The rest goes as heat due to resistance, etc.

    (And no, you can't solve that by making everything superconducting. There will be losses due to eddy currents induced in the motor and generator and other losses.)
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    Quote Originally Posted by vintox View Post
    but what if you make both the motor and the generator on the same axel. then suspend the that axel with magnetic feilds to eliminate friction at the bearings.
    And just to add another problem: magnetic fields are not 'free'; it takes energy to make them.
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  11. #10  
    Brassica oleracea Strange's Avatar
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    And, even if you could make it 99.999% efficient it would eventually stop. And as soon as your tried to draw any power from it, it would grind to a halt.
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    Quote Originally Posted by k. wolfe View Post
    Ok, but since the magnets help maintain the initial speed, if I were to input X watts of energy to start up a "magnetic motor", by the time it stops spinning and producing electricity because of friction, should the resulting energy not be greater than X?
    Perhaps it would be useful if you could explain what you mean by a "magnetic motor".

    To me, "motor" implies something that does more than freewheel, i.e. it produces power from some energy input. An ordinary electric motor works by magnetic force between the rotor and stator, so that is a "magnetic motor" of one sort, at least. But of course that uses a flow of electric current to power it.

    There is, among some people, a misconception that permanent magnets emit energy in some way. They don't. They do exert a force (on another magnet or magnetic material) and that force, if applied through a distance, can do work, i.e. be a source of power, just as the force of gravity can. But the Earth does not emit energy due its gravitational pull: an object has to move through a distance under the influence of that force for any work to be done.
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    In power generation, isn't there some degree of efficiency lose due to magnetism as well? Thinking there are magnetic materials used to seperate the conductors.
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    Quote Originally Posted by vintox View Post
    but what if you make both the motor and the generator on the same axel. then suspend the that axel with magnetic feilds to eliminate friction at the bearings. doing this your only drag would be air drag and gravity which i would thearize you could over come with a very small low voltage motor. If this is true the output generated by the finetic energy of the magnets should be larger then the input used to turn the low voltage motor. if this theary is wrong please explain to my why because i am very interested in the subject.
    Here's the thing you need to realize:

    The more energy your generator is asked to provide, the harder it is to turn. So, for example, if I am turning a generator that is hooked up to a 100 watt light, it will take a given amount of effort on my part to turn the generator. If I now hook up another 100 watt light, and then try and turn the generator so that both bulbs light up as much as the first did, I will find it twice as hard to turn the generator.

    Also, the more work you make a motor do, the more energy it requires. If you hook the output of a generator up to a motor, and then make the motor work under various loads, you will find that as you increase the load the motor does, you will increase the work you have to do to turn the generator.

    If you then try to drive the generator by the same motor that it gets its power, you will find that the work the motor has to do to turn the generator at any speed will always require more energy from the generator then the generator can provide turning at that speed. Even if you could get rid of all losses, the most you could get in something that just freely spins on its own. If you were now to try and use this device to to useful work, you would increase the work load of the motor, which in turn would need more energy from the generator, which would further increase the work load of the motor, etc. Basically the system would not be able to provide the new work demand and it would slow to a stop as the external work load drains it. And the most energy the external load could get would be the energy it too to get the system up and spinning in the first place.
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  15. #14  
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    Quote Originally Posted by vintox View Post
    but what if you make both the motor and the generator on the same axel. then suspend the that axel with magnetic feilds to eliminate friction at the bearings. doing this your only drag would be air drag and gravity which i would thearize you could over come with a very small low voltage motor. If this is true the output generated by the finetic energy of the magnets should be larger then the input used to turn the low voltage motor. if this theary is wrong please explain to my why because i am very interested in the subject.
    See post 6, right above yours, and Janus's fuller explanation above this post.

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  16. #15  
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    Quote Originally Posted by keeseguy View Post
    In power generation, isn't there some degree of efficiency lose due to magnetism as well? Thinking there are magnetic materials used to seperate the conductors.
    There are many sources of loss. Conduction loss in the windings, eddy current losses in the metal frame (and wires, again), hysteresis losses in magnetic materials, friction in bearings...it goes on and on. Nature does not want you to win.
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