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Oscillating Current Loops

  1. Jun 13, 2004 #1

    - Two current loops oscillating at ~ 9GHz Square Wave

    - Stack the two loops one on top of the other at ~ 1cm seperation.

    What I See:
    - At that distance and frequency of oscillation it appears as if you could get a force with an equal reaction. From the time delay of speed of light propagation. If both loops start with a clockwise current, but then one flips to counter-clockwise just as the propagating magnetic fields reach the opposite loop. One loop would be attracted, while the other pushed away.

    - This isn't my webpage, but the author has the same idea as mine and has some pretty graphics for a better explanation.

    http://dsp7.ee.uct.ac.za/~mdevill/emthrust.html [Broken]

    - What am I doing wrong? Where is the equal and opposite reaction and how is it created?

    edit begins:

    Because of integral's misunderstanding, I'm going to clarify a few things here:

    - I know this won't work, and I know it violates several laws.
    - What I'm asking for is an explanation of why as I can't figure it out.
    - The webpage I linked to is NOT mine, it was only meant so you could see the configuration of the system, not study the author's physics.

    edit ends:
    Last edited by a moderator: May 1, 2017
  2. jcsd
  3. Jun 13, 2004 #2
    Thrust in space comes from the reaction between the ship and whatever you're throwing overboard, not between what you're throwing overboard, and what it might hit.

    You wouldn't be able to create something like a helicopter ground effect by throwing a magnetic field off the ship, and then hitting it with a second magnetic field: the second would never catch up with the first to build up any back-pressure.

    Two magnetic waves traveling in opposite directions don't experience anything that could convert into back pressure either. They meet, add together briefly, then separate and continue on their way in their original directions.

    I'm pretty sure this is correct. If not, at least it will get a discussion started.
  4. Jun 13, 2004 #3


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    You do not provide any information about the properties of your loops. Number of turns, area and DC resistance are critical properties. What are they?

    9GHz is in the range of frequencies which require very carefully circuit design and high end test equipment to even begin to know what you are actually getting on your coils. my guess would be that you don't have what you think you do.
    This is not what you see, this is what you think you might see. What DO YOU SEE. I would be amazed if you had test equipment sensitive enough to measure anything having to do with this circuit.
    Your link to a pseudo science site gets this moved to Theory Development.
    Last edited by a moderator: May 1, 2017
  5. Jun 13, 2004 #4
    Right, two EM waves don't do crap to each other. But two current loops with the same current attract each other, while opposite currents repel. So if you've got one loop at 1A, the magnetic field created by it propagates through space at c..right?

    If you've got two loops, always at 1A, they'll be attracted to each other. But if you flip the current of one of the loops just before the field gets there, the first will be attracted to the second one while the second will be repelled by the first. Because the first loop sees the second loop having the same current and thus attracts. But only until the changed field gets there (it was flipped). The second loop sees the first loop having opposite current and is repelled because the second loops current was flipped. Keep the process going and you've got this system that can't exist.

    So no, one EM wave doesn't create a force on another. But an EM wave does create a force on a current loop...right?

    The reason I added the website was to show more clearly the orientation of the two loops, and why the separation of the loops and the current oscillation depend on c.
  6. Jun 13, 2004 #5

    Jesus Christ; I linked there because there were pictures. I frickin' know this is impossible. I can't figure out why!!!! I don't know what's wrong with my physics understanding of EM and I want to know what IS wrong.

    I don't care about the high frequencies or what's actually happening in this circuit because it doesn't matter as it's impossible to make anyways. I want people to explain what is wrong with my physics and where to look to correct it because I can't figure it out.

    You probably think I've actually built this thing, nope. I just thought up the idea and couldn't figure out how to disprove it so I came here.
  7. Jun 13, 2004 #6

    What you're talking about with the loops being affected is much like what happens in an induction motor, where one firld changes polarity before the other has a chance to catch up. They end up out of phase and a torque is created. In that situation, though, the magnetic fields are still attached to the coils and core generating them.

    In your set up you said the magnetic fields have detached themselves from the source. It is clear that they have in those pictures. Being detached, they have lost their influence on the generating coils.
  8. Jun 13, 2004 #7
    I'm going to go back a bit further.

    1) When a dipole changes directions from up to down. As when the current in a loop reverses direction. What happens with the magnetic and electric field. Does it detach, and if it does what does detach mean.

    2) How does a static magnetic field propagate. I'm assuming it just spreads out at the speed of light.

    3) zoobyshoe: When you said detached fields don't have an influence on the generating coils. Don't EM waves have an influence on antennae and aren't they detached from their source? Or am I misunderstanding "detached"?
  9. Jun 13, 2004 #8
    I am really just following the logic of the site you linked to. That person has little drawings of the field detaching from the antenna and traveling as independent entities from it. Stipulating, therefore, that this can happen, his logic about being able to create a thrust from it breaks down as I described in an above post.
  10. Jun 13, 2004 #9
    Ah, that site has caused a heck of a lot of problems I didn't intend for. I'm wondering what would happen if one of the loops would switch it's current direction right before a static magnetic field got to it.
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