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Thread: dynamo propelled by Earth's magnetic field?

  1. #1 dynamo propelled by Earth's magnetic field? 
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    I've dreamed up this device, but I'm not sure if it would be possible and I hardly have the math/physics skills to figure it out so I need some help.

    what if?

    would it be possible to make a dynamo built small enough so it would be propelled by the Earths magnetic field? Imagine for instance a small Gyro polarised to be opposite to the earths manetic field, creating a rotation from the repulsive force resulting and drawing energy from that motion?
    I imagine it would be necesary to switch the polarisation to keep the gyro from attaining equilibrium, but if this is possible with less energy than a revolution yields...?

    anybody any input?


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  3. #2  
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    Well I think all dynamo are powered by the earths magnetic field...no field, no magnets...

    I doubt it is possible, since the magnetic field isn't very strong that it would move a giant gyro...


    Maybe if it on the north pole exaclty since Im pretty sure its strongest there and then you might disrupt the flow and cause us to die of cancer...


    :wink:


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  4. #3  
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    I don't think it would work. If you have an incredibly strong magnet, it doesn't pull you to the nearest magnetic pole, so the field clearly isn't strong enough to cause any significant movement.

    When the magnet is floating in equilibrium, it still only just manages to orientate to the magnetic field, slowly. The Earth's magnetic field simply doesn't have the strength.
    "The major difference between a thing that might go wrong and a thing that cannot possibly go wrong is that when a thing that cannot possibly go wrong goes wrong it usually turns out to be impossible to get at or repair." ~ Douglas Adams
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  5. #4  
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    The problem is that a magnet (such as the needle of the compass) aligns itself with the Earth's magnetic field, but removing this alignment requires as much energy as you can get out (plus a little extra due to friction). So yes, you can get some energy from such a dynamo (enough to turn the needle of a compass), but it would only make one half revolution, so not very useful.

    A real dynamo needs a changing magnetic field. This is typically done by revolving a coil in a static magnetic field, which results in a changing field from the point of view of the coil.

    I think, however, that the Earth's magnetic field varies a very tiny little bit, so hypothetically, you might be able to use this change to generate electricity, but I doubt it would be much, and you would probably need huge coils.
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  6. #5  
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    And to add to all the pessimistic responses you have here - the dynamo (gyroscopically stabilised or not) will have to be 'still' relative to the earth's rotation, but all that means, thanks to relativity, is that you have to impart it a counter-rotation equal and opposit to that of the earth. Ergo, you would be generating the electricity by spinning this device against the earth's rotation and producing only as much power as you generate (if perfectly efficient, but likely, thanks to the Second Law of Thermodynamics, to be less).

    This, of course, unless I've misunderstood your notion altogether.
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  7. #6  
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    well thanks for all your feedback. I would like to amend my statement somewhat though.

    I do realize the Earth's magnetic field is relatively weak, so I was thinking in terms of very very small dynamo's. Rather than having one very large coil, I was thinking in terms of many (ridiculously tiny) coils. Small enough to be effected by the earths field individually and together generating enough to be valuable, but I would imagine as long as they work on an individual scale that wouldn't be a problem.

    Also the gyro would not stabilise a coil, but be the moving part itself.

    finally, again I'm not sure if this is possible scientificly, the gyro would have to be magnetically polarized, and has to be able to shift it's polarisation (perhaps by alternating current?) so the Earth's field is always "pushing" - somewhat similar to magnetic monorail trains are propelled. After all they can reach absurd speeds using the same principle right?

    sunshinewarrior; I'm not sure how 2nd law influences this, there really shouldn't be any friction involved, how else would you account for an energy loss?
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  8. #7  
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    Quote Originally Posted by keen
    well thanks for all your feedback. I would like to amend my statement somewhat though.

    I do realize the Earth's magnetic field is relatively weak, so I was thinking in terms of very very small dynamo's. Rather than having one very large coil, I was thinking in terms of many (ridiculously tiny) coils. Small enough to be effected by the earths field individually and together generating enough to be valuable, but I would imagine as long as they work on an individual scale that wouldn't be a problem.
    There is not much difference between a lot of small coils or one big coil, it's the amount of magnetic flux (and more specifically, the change of it) you catch that's important. The electrical resistance in the small coils is also likely to be much higher, increasing losses.
    Quote Originally Posted by keen
    finally, again I'm not sure if this is possible scientificly, the gyro would have to be magnetically polarized, and has to be able to shift it's polarisation (perhaps by alternating current?) so the Earth's field is always "pushing" - somewhat similar to magnetic monorail trains are propelled. After all they can reach absurd speeds using the same principle right?
    Not really, a magnetic monorail is not propelled by a stationary field. Even if it was, the monorail would go to one end, and then be stuck there.
    Quote Originally Posted by keen
    sunshinewarrior; I'm not sure how 2nd law influences this, there really shouldn't be any friction involved, how else would you account for an energy loss?
    1st law: You can only get as much energy out of a static magnetic system as you put in.
    2nd law: you can never get as much energy out of a static magnetic system as you put in, because there is always friction (and other kinds of energy loss, such as Joule losses in the case of electric current)
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  9. #8  
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    Propulsion coils on the guideway are used to exert a force on the magnets in the train and make the train move forward. The propulsion coils that exert a force on the train are effectively a linear motor: An alternating current flowing through the coils generates a continuously varying magnetic field that moves forward along the track. The frequency of the alternating current is synchronized to match the speed of the train. The offset between the field exerted by magnets on the train and the applied field creates a force moving the train forward.
    http://en.wikipedia.org/wiki/Maglev_(transport)

    this is the mechanism I was referring to.

    with the modification that it is the gyro's magnetic quality that is modified, as opposed to the rails in this example. And its the earth's magnetic field counter reacting to it. Instead of trying to move forward along a track the timing would be set to the proper alignment of the gyro, relative to the earth's magnetic field, to create rotation.
    I imagine even with the train it wouldn't matter if the trains magnetic field was modified, because in the end the governing principle is that two opposing magnetic fields repel each other..

    First law of thermodynamics, about the conservation of energy:
    The change in the internal energy of a closed thermodynamic system is equal to the sum of the amount of heat energy supplied to the system and the work done on the system.
    Second law of thermodynamics, about entropy:
    The total entropy of any isolated thermodynamic system tends to increase over time, approaching a maximum value.
    http://en.wikipedia.org/wiki/Thermodynamics

    I don't really see how the second law applies here, as it is practically not a closed(or static if you will) system, since the earth should be continiously excerting force on the moving part of the system.

    however I agree, to make it work with virtually no friction would be quite a challenge, maybe if one could somehow suspend the gyro in an magnetic field this could be surpassed. Obvious problem would be the interference of the two fields..

    As far as current loss in the wires etc.. I really don't have a clue, perhaps use of superconducters, or otherwise resistance free materials? well basically once you succeed in speeding up the gyro to a sufficient velocity, you can compensate for this loss? In the end don't conventional powerplants have to overcome the same efficiency problems, they just generate enough current to cover the loss.
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  10. #9  
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    Quote Originally Posted by keen
    Propulsion coils on the guideway are used to exert a force on the magnets in the train and make the train move forward. The propulsion coils that exert a force on the train are effectively a linear motor: An alternating current flowing through the coils generates a continuously varying magnetic field that moves forward along the track. The frequency of the alternating current is synchronized to match the speed of the train. The offset between the field exerted by magnets on the train and the applied field creates a force moving the train forward.
    http://en.wikipedia.org/wiki/Maglev_(transport)

    this is the mechanism I was referring to.

    with the modification that it is the gyro's magnetic quality that is modified, as opposed to the rails in this example. And its the earth's magnetic field counter reacting to it. Instead of trying to move forward along a track the timing would be set to the proper alignment of the gyro, relative to the earth's magnetic field, to create rotation.
    I imagine even with the train it wouldn't matter if the trains magnetic field was modified, because in the end the governing principle is that two opposing magnetic fields repel each other..
    I'm familiar with the mechanism of magnetic levitation. Describing the governing principle as a repulsion between two magnets is only part of the story. What's really happening is that you have a system with high potential magnetic energy and every system strives for minimal potential energy. This change in potential energy can be converted in kinetic energy, but you'll end up with less potential energy. It's like a ball rolling downhill. The only way to keep it rolling is adding energy to raise the level of the potential energy again. In a train this is done by continuously changing the polarity of the fields, to always stay ahead of the train.

    I'm not entirely sure how you want to make your system, but continuously changing the magnetic field of your gyro doesn't work, because changing that field requires at least as much energy as you'd get out of it (you have to roll the ball uphill before it can roll downhill again).
    Quote Originally Posted by keen
    First law of thermodynamics, about the conservation of energy:
    The change in the internal energy of a closed thermodynamic system is equal to the sum of the amount of heat energy supplied to the system and the work done on the system.
    Second law of thermodynamics, about entropy:
    The total entropy of any isolated thermodynamic system tends to increase over time, approaching a maximum value.
    http://en.wikipedia.org/wiki/Thermodynamics

    I don't really see how the second law applies here, as it is practically not a closed(or static if you will) system, since the earth should be continiously excerting force on the moving part of the system.
    Are you perhaps mixing up force and energy? (Also, a closed system isn't necessarily static and vice versa.) A continuous force does not equal a continuous source of energy.
    If I understand your system correctly, you can see the earth as one giant magnet. The system consists then of a big and a small magnet. You start out with only potential energy. The small magnet turns, converting some of the potential energy into kinetic. If you suppose no losses and no extraction of energy, the rotating magnet has just enough energy to reach it original position, but it will again stand still at that position.
    If both fields are stationary, no energy enters the system. If you change one of the fields, the energy has to come from somewhere.
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  11. #10  
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    You imagined the idea. Only you can prove if it will work or not.

    Just gather all the terms of physcis needed, angular momentum, Maxwells equations, etc. Just don't forget that the Earth's magnetic field isn't constant all over the world. There are fluctuations here and everywhere. I suppose you must put that in a equation to make your device operate.

    So you are going to need Maxwells tensors, Newtons motion laws, maybe even Einsteins. Consider that the moving magnets is going to cause electricity, that will interact with the weak nuclear force also. My limited physics knowledge can't answer your question. But if you use your common sense and note all contributing factors to this device working, seen and unseen you should be able to make it work.

    I trust you can put all the into equations and work it all out...

    PS. The Earths magnetic field is weak. It probably won't move anything, the mass of the dynamo must be tiny for it to move at all. Perhaps you need to channel the energy from the Earths magnetic field become channeled to your dynamo so that it will have more effect on your dynamo.

    In theory, relativity has a big (Einsteins special relativity) can have a big effect on your device, it may be possible if you use some relative concepts to channel the energy that you need to make it work as you dream.

    There could be any number new concepts you need to come up with to make your device work as efficient as you imagined. Just take your time and you'll do fine.
    "If you wish to make an apple pie from scratch, you must first invent the universe". - Carl Sagan
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  12. #11 The Earth as a dynamo 
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    Alas, it seems the other posters are correct that a small dynamo on earth cannot produce energy from the rotation of the earth, because, like a compass, it would simply line up with the magnetic poles and stay there until someone put energy in to budge it from the spot.

    There is however hope for generating energy from the rotation of the earth.
    If one were to make a dynamo of The Earth itself.
    This rather large and impractical setup would involve winding conductive wires around the entire circumference of the earth.

    Simply wind a coil of wire from north to south pole, all the way around, many times.
    As the earth spins in the magnetic field of The Sun, it would indeed produce current!

    The Earth itself would become a conductive rotor in a magnetic field (The Suns'), and in accordance with Maxwells equations, produce power from the rotation of the earth and ever so slightly slow the earths spin in producing this electrical power.

    (This is the same principle used in regenerative braking in electric and Hybrid cars, where the wheels are slowed as electrical energy is drained from them by a coil moving in a magnetic field.)

    So the worlds energy crisis would be over and the days would grow ever longer. Maybe not such a bad thing, I could do with a few more hours in the day
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    There is that which is known.That which is known to be Unknown. The unknown that is unknown to be unknown... and that which is thought to be known, but is actually unknown.
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  13. #12  
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    There's an easier way of harnessing the Earth's magnetic field. Read more about it here.
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  14. #13  
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    mmm, I feel there is some more work possible on the whole concept.

    thanks for your feedback and opinions.
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  15. #14  
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    The Tether deal is great, if you are NASA , somewhat impractale for us average scientists
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  16. #15  
    Forum Radioactive Isotope MagiMaster's Avatar
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    Well, it's somewhat more practical than winding the earth pole-to-pole.
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