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Device That may defy the law of conservation

  1. Jul 3, 2010 #1
    I have what is likely a very stupid question, but here go's.
    I was sitting around and got thinking how I might make a better generator. One that doesn't develop opposing torque on the armature when it is under load.

    How would the laws of conservation come into play if I were to build a generator that had a stator consisting of a ring of strong permanent magnets and a rotor consisting of a series of soft iron plates that are spaced apart the same width as the width of the magnets. The rotor would have a small space between the magnets and the soft iron plates.

    So what I would have is the soft iron plate’s temporarily blocking the magnetic field from the magnets as the plates pass by. On the opposite side of the rotor would be a series of coils sitting stationary directly across from the magnets the coils would only have magnetic flux breaking across when the iron plates passed by and there is the space between the plates.

    My question is would such a generator not develop any opposing torque. And would this device not possibly produce more energy then what it would take to run it.

    I have not built such a device yet, but it sure has me wondering.
     
  2. jcsd
  3. Jul 3, 2010 #2
    Yes it would "develop any opposing torque". I mildly sketchy on what you meant by: "blocking the magnetic field from the magnets".

    No matter what configuration or magnetic shielding you use, to generate power the coils MUST cut through the magnetic field. That is what sets the electrons in motion to generate power. This alone induces drag, and even if everything else has perfect efficiency you will still only get as much power as drag induced.

    The way the question is stated is suspect under the rules here.

    The master tech at a company I once worked for thought a he could take power from a thermocouple in a perfectly insulated heated box indefinitely. I never did get him to understand that even if the box would stay hot forever, it would start cooling off as soon as he started drawing power from the thermocouple.

    Same applies to magnets. To get power the coil must pass through the magnetic field. To pass it through the magnetic field induces drag, even if everything, bearing and all, has perfect efficiency.
     
  4. Jul 3, 2010 #3

    Integral

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    Since it is the current you are trying to produce that generates the back EMF, if your device works perfectly and eliminates all back EMF, you will have zero current out. Is that your goal?
     
  5. Jul 3, 2010 #4
    The device would no eliminate any of the back emf and would not the back emf only be created when the magnetic field collapses? And wouldn't it be 180 degrees out of phase with the original emf?
     
  6. Jul 4, 2010 #5
    No matter how complicated a 'device' you build, of any nature, nothing you can do is going to violate conservation of momentum.
    If you start from there rather than any other position, you can save yourself a lot of trouble.

    The reverse torque on a generator shaft is the direct result of doing work on the load. At best what you have is a complicated lever to help you do it.

    All of the theoretical mathematics involving magnetic fields, back emf's, phase and current are just descriptions of the lever mechanism.
     
  7. Jul 4, 2010 #6

    Dale

    Staff: Mentor

  8. Jul 4, 2010 #7
    Uh, that's not possible.

    One can not design a 100 megawatt generator that is driven by the wind force of a butterfly.
     
    Last edited: Jul 4, 2010
  9. Jul 4, 2010 #8
    That may be but nobody seems to be able to explain to me in terms that I can understand as to how any opposing torque is generated in the shaft turning the iron plates.
     
  10. Jul 4, 2010 #9

    Dale

    Staff: Mentor

    We don't have to. The reason that I posted http://farside.ph.utexas.edu/teaching/em/lectures/node89.html" [Broken] is that it explains in general how energy is conserved in all situations. The details of your specific design are 100% completely irrelevant. All generators work based on Maxwell's equations and Maxwell's equations always conserve energy in general and without reference to the details.
     
    Last edited by a moderator: May 4, 2017
  11. Jul 4, 2010 #10
    I never meant to imply that anyone had to tell me anything, In fact I Have nothing but respect and gratitude that all the people that responded to this thread. I realize my question must seem foolish to those individuals that have a firm understanding of physics are able to understand the mathematical equations that clearly explain the principles as to why a device like I purpose could not work. The only reason I venture to even defie the laws of conservation, is because If anyone were to explain with mathematical equations as to weather a bumble bee can fly or not the the math would say he can't. But the bumble doesn't know that.
     
    Last edited by a moderator: May 4, 2017
  12. Jul 4, 2010 #11

    Dale

    Staff: Mentor

    :rolleyes: Then you best not ask such questions nor study the link for fear that you might accidentally learn something and then your device would suddenly stop working. Never fear however, even if it does not violate the conservation of energy, an ignorance-powered device should have quite an abundant supply of fuel.
     
  13. Jul 4, 2010 #12

    Integral

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    At this point all we can say to you is build it, come back and taunt us when you are raking in the $$$.

    Until then... Thread closed.
     
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