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A physics experiment with magnets and a vote pole

  1. The spinning magnet will repel

    1 vote(s)
  2. The spinning magnet will attract

    0 vote(s)
  3. The spinning magnet will do virtually nothing

    3 vote(s)
  1. Apr 20, 2003 #1
    A physics experiment with magnets and a vote pole-results

    This is an experiment with magnets in motion.

    The question is that if one magnet is spinning along a circular plane such that
    the north end arrives at a point on the circle just as often as the south end, then what will happen if another magnet is brought close to the spinning one and held with the south end facing and parrellel to the plane? Will the spinning magnet attract to the stationary one or repel or do nothing?
    What if the north end of the stationary one is brought close to the spinning magnet?
    What would you guess will happen?

    Safety glasses!(magnets chip easily and anything moving at high speed is dangerous, except watermellons),
    one small electric motor and a battery,
    2 magnets or several magnets clustered together, a length of fishing string and some tape.
    approximate cost $8 at radioshack

    Putting it together:
    Using the tape to anchor the electric motor to a desk, and taping up a cluster of magnets to lessen chipping in case they contact, attach one end of the
    fishing string to the magnet at the middle so that as it spins the charged ends are moving around not rotating up and down, and attach the other end to the shaft of the motor( one may need to file a tiny grove around the shaft to get keep the string from slipping off or super glue it on).
    Also a 1.5V battery and a thumb sized motor is plenty to get the magnet up to a high rate of spin.
    Last edited by a moderator: Apr 24, 2003
  2. jcsd
  3. Apr 21, 2003 #2
    I voted nothing, but that is only if you can get the magnet spinning fast enough, most likely in a fast spinning magnet, you would simply see a wobble on the other magnet.
  4. Apr 21, 2003 #3
    I voted for nothing because oscillation or spining were not options.
    Let me tell you what I did this spring with 6 little disk Neodymium magnets. Rather than spinning a bar with dipolar axis in the plane perpendicular to the axis of rotation and teasing with a fixed pole of another bar magnet in also the same plane. I devised a wooden disc, 1/8"thick, with six 3/8" dia sockets in a ring of dia about 7/8". I seated and glued each 1/8" thick magnet in each hole against a narrow flange of wood at the hole bottom. To the center of the disk I attached a Dremel mandril the axis of which was necessarily perpendicular to the wooden disk - the dipole axis of each magnet was parallel to the mandril but the poles were alternated which meant that each magnet was attractive to both its neighbors and its diametrically opposite neighbor. I mounted my little "armature" in my drill press and rotated it at modest speed with the plane of the magnets about an inch above the cast iron press table and brought a simple magnetic compass up to the edge with the needle in the plane of the armature and noted its rapid vibration. When I dropped the compass below but near the face of the disk with the needle parallel to the disk and moved it hear and there the needle continued to vibrate but about center position that rotated (without any obvious pattern) and without my video cam looking to see which end ,N or S of the needle was pointing toward the spindle direction. I further noticed that when the center of the needle was directly under the circular center line of the magnets the needle spun freely. Its my guess that when the needle center is inside the magnet circle one pole of the vibrating needle prevails toward the spindle while, when the needle center is outside the circle the other pole of the needle points toward the spindle. When I did the sampling on the Chuck side of the armature I again got spinning directly over the circle of centers. I dropped the cast iron table down a couple more inches and I found that the movements of the compass below the armature was not as active as it was with the table close-by. The iron "core" effect may be what caused what I was seeing. The point is proven here that a successful experiment really leads to a logarithmic demand for more. Voila Jim
  5. Apr 21, 2003 #4
    I had to read that a few times to get it, I wish I knew how to draw pictures here too.
    A disk of half up half down spinning
    magnets- that's interesting, normally a spinning magnet should form new polarity fields perpendicular to the spin, but if I'm getting this right what you did is to reverse half the spinning magnetics and create an oscillating polarity field above and below the spinning disk, causing the needle to vibrate and sometimes switch needle poles, or is it forming a polarity inside the circle and the other polarity outside the circle? Either way magnets do some strange things when they move
    and I agree it only makes one more curious.
  6. Apr 21, 2003 #5
    The magnets don't spin

    Hi, The magnets rotate. When my eye thinks it sees a needle woggling back and forth within a few degrees it may really be swinging very rapidly through 350 degrees and only a fast camera and or a slower rotational speed could reveal such a sublimnal behavior. Incidentally, the beauty of alternating polarities tends to counter the tremendous centrifugal force that high rotary speed would present. Cheers, Jim.
  7. Apr 23, 2003 #6
    Consider this:
    If two magnets were aligned side by side a small distance so that they would very slowly slide free of friction in space if you let them go, and one of the magnets had a magical property that caused it to flip or reverse polarity from + to - very fast at say 20 flips per second and at exactly the same ratio of - to positive, would the two magnets come together repel or do nothing?
  8. Apr 23, 2003 #7
    there would be a hum!

    Hi again,
    however, the hum at 20 cycles might be inaudible. You undoubtedly have witnessed the 60 cycle hum set up in the laminated iron plates of a power transformer. That's just a surmise! Cheers, Jim
  9. Apr 24, 2003 #8
    The results of this experiment is always a noticeable attractive movement of the spinning magnet to the stationary one regardless of which stationary magnet pole approaches the spinning magnet. Common sense would say this shouldn't happen, there should be no movement,
    that's what I guessed anyway before doing the experiment. Also the attractive force seems to decrease as the speed increases, and perhaps be virtually non-existant at near the speed of light.
    Can someone please explain what is going on here using known physics? Why should the spinning magnet only be attracted to the stationary one regardless of which pole approches it?
  10. Apr 27, 2003 #9
    Can someone please give me any explanation or guess or whatever comment as to why the spinning magnet always attracts. Is the explanation of the experiment not clear?

    The spinning magnet forms poles at the top and bottom so if you approach the spin with a stationary magnet to the top half the time it'll attract half the time it won't. So that roughly 2/3 of the spinning magnet is attractive and 1/3 repulsive regarless of stationary magnet orientation. This doesn't seem to balance out and follow nature's laws, there's an overall attraction resulting here.
  11. May 17, 2003 #10
    I want to push the topic to the 1st page one last time in hopes someone can explain this.
  12. May 17, 2003 #11
    Why only spinning? Any free to move magnnets attract - spinning or non-spinning.
    Last edited by a moderator: May 18, 2003
  13. May 17, 2003 #12
    You should have specified. See, if it's spinning very fast, it's basically like having both ends of the magnet at the same spot.

    Thus the charges cancel eachother out. Thus the second magnet acts as if no magnet is there.

    Not sure why there's a poll, such an easy question.
  14. May 18, 2003 #13
    I agree, if the magnet were to spin at say 1/3 the speed of light there would be such a small attractive force(but would have to remain attractive) as to seem irrelevant and so "do virtually nothing" is appropriate. And yet if the magnet were spinning due to the force of heat and there were little to no heat present they would spin very very slowly and that force of attraction be very strong, so it's somewhat dependent on heat, kind of like the relationship between gravity and the massive light stopping(reduced to 30mph) properties of a Bose-Einstein condensate near absolute zero temperature.
    In this experiment the magnet is spinning at approximately 18 revolutions per second + or - 5 revolutions, and there is an observable attractive movement once the stationary magnet approaches within 2cm or less of the spinning one, this distance increase as the rate of spin decreases.
    The two ends of the charges can't occupy the same location at the same time so if they are spinning very slowly or very fast there should remain an attractive force that diminishes with the distance and heat- I mean rate of spin.
    So given that they do attract, how would you deduce this is so?
    I want to hear what conclusions others might draw from this.
    I was thinking the same thing Alexander, if two magnets were placed in space spinning or not they should eventually come together, in this expirement I was hoping to simulate a 50/50 attractive versus repulsive relationship between 2 charged bodies to see if the effect would cancel.
  15. May 19, 2003 #14
    If the "observer" magnet (or pair of charges) is fixed and one ("source") is rotating, then average force between magnets is zeo. But if the "observer" is free to rotate or to move in some direction(or both), then it'll indeed MOVE (oscillate) in such way that minimises their mutual potential energy (PE), so the average PE (of free system) will be LESS than average PE with fixed magnet (or fixed charge pair), thus results in overall ATTRACTION between them.

    Same with neutral atoms - because charges in them (electrons) are free to move, then wnen atoms come close they interact dynamically (constantly "polarising" each other so to speak), which results in the average in more attraction than repulsion. We call that "interatomic forces", or "formation of solid state", etc
  16. May 20, 2003 #15
    I don't think I completely understand what you mean by the mutual PE of free systems....I'll study that.
    Why hasn't anyone voted that they in fact do attract? If no one believes me then you'll have to do the experiment.
    With 2 magnets spinning polarity fields are formed on the tops and bottoms so depending on which way it's set up will either always attract or always repel 50/50, but this is a static polarity and isn't really the type of oscillating field I was looking for.
  17. Oct 1, 2003 #16
    still looking for the answer...

    ... would it help if I made an mpeg recording of the experiment and posted on a web site?
    Last edited by a moderator: Oct 11, 2003
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