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Steel top + magnet

  1. Jul 16, 2011 #1
    a steel top which remains upright when not spinning has an electromagnet pulling on it from the side. Q=does it make any diff how much the emagnet moves the top sideways if the top is spinning or not? Please dirregard the friction factor at the bottom point of the top. thanx
  2. jcsd
  3. Jul 16, 2011 #2
    At first, I thought No; but then,

    I started to wonder what is really happening, I mean, for as long as there is motion, there might be some currents being induced in the top as it spins but I have not put much thought into what the boundary conditions are, whether they are symmetric or not and what the currents might be...the relative motion of the steel is in one direction between the magnet and the center of the top and in the other direction after the center of the top

    needless to say, these induced current should tend to stop the rotation of the top (no perpetual motion machine here) but that is beside the point, the point is that without rotation the attraction is what it is, with motion you now have the extra interaction between the two magnetic field, the magnet' s and the one from the induced currents, whether the effect of the induced current's magnetic field from both sides of the top simply cancel each other out and does not affect the attraction ...that, I wouldn't know at this time.

    ...just thinking aloud
  4. Jul 17, 2011 #3
    i didnt consider rotational slowing as possible energy loss. Was just wondering if the 2 tops would move differently due to spin factor.....keep thinking aloud
  5. Jul 17, 2011 #4
    By definition, I would have to say that the attraction is going a bit different with the spinning top...I mean, they are not even the same system...one of them has an additional energy input...the attraction will have to be disturbed one way or another due to the currents induced in the spinning top and the interaction between the magnet's field and the induced current's field.

    If you put a magnet and the non-spinning top in front of it...the magnet will attract the top until they are in contact. No doubt about that.

    Or, if the top cannot be moved, the magnet will drag itself until it is in contact with the non-spinning top (bear with me).

    No, let's say that instead of sending the spinning top off on its own, let's say that we actually connect a shaft to it, so that we can keep spinning it all the time (inputting mechanical energy all the time)...would the magnet drag itself all the way until it touches the top? I think it would come close and then stop without touching, since the spinning top will have a magnetic field of its own! ...assuming a nice uniform magnetic field going up and the top spinning clockwise, I think the magnetic field of the top would be going to the right thru the top and coming back around through the outside of the top.

    Maybe this can be easily tested by taking two magnets and placing one perpendicular to the north pole of the other one...do they get together without hesitation? or not? Try that...I don't have magnet handy here.
  6. Jul 17, 2011 #5
    yes, put the top on a motor & let the magnet do the moving..............lemme know what happens,lol, +VVV
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