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The A Field?

  1. Nov 1, 2006 #1
    The "A" Field?

    Hello All,

    A while ago, I had a chance to read this research paper that was trying to explain how the "Marinov Motor" works. In the paper, they explain that it does not use regular induction through magnetic B fields, but instead makes use of the "A" field. I don't remember reading anything about this field in my physics book and was wondering if anyone could point me in the right direction to some good introductory info about it. I heard it has to do with magnetic potential or something. In case you are interested, I also attached the file I was looking over.

    Jason O

    Attached Files:

  2. jcsd
  3. Nov 1, 2006 #2


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    It is the magnetic vector potential. (One form of one of) Hemlhotz's theorem says that any divergenceless vector field [itex]\vec{B}[/itex] can be written as the curl of of a vector field:

    [tex]\vec{B}=\nabla \times \vec{A}[/tex]

    Note that just as the electric potential or the potential energy function in mechanics, the potential vector [itex]\vec{A}[/itex] is not unique but rather for any [itex]\vec{A}[/itex] such that
    [itex]\vec{B}=\nabla \times \vec{A}[/itex], [itex]\vec{A}+\nabla\lambda[/itex] where [itex]\lambda[/itex] is any (properly bahaved) scalar function is another vector potential for [itex]\vec{B}[/itex].

    Additionally (though this information might be superfluous at this point, it is very important), according to (another version of another) Helmhotz theorem, any vector field can be written as a function of its curl and its divergence only. Since we only need that the curl of A be B, we can litrally choose any value we want for the divergence of A.
    Last edited: Nov 1, 2006
  4. Nov 1, 2006 #3
    This paper doesn't seem to refer to what google calls the the "Marinov Motor". The latter does not really depend on fields; a current selectively heats and deforms ball bearings so that they (through frictional forces) apply an acceleration. :smile:
  5. Nov 2, 2006 #4
    That is not the Marinov motor I am looking into. Here is another document referencing it:



    Thanks for the info. What physical significance does the A field have? What physical entities does it react with? Or is it just some sort of mathematical abstraction?

    Jason O
  6. Nov 2, 2006 #5


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    I quote Feynman:

    From lecture 15 chapter 5 of volume 2.
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