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I Movement of a iron ring inside a toroidal solenoid

  1. Apr 16, 2016 #1


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    What happens when you apply power to a toroidal solenoid with a iron ring inside?
    Does the ring move? Does the speed of movement depend on the amount of power?

    Sorry if this is too easy, I have no education in physic.

  2. jcsd
  3. Apr 16, 2016 #2
    I don't really get why it SHOULD move at all...
    First of all the magnetisation of the iron seems irrelevant here.
    If you powered a straight coil of wire with an conductive (iron) core inside, the increasing magnetic field would induce a current
    in the core.(An "eddy current" to be exact)
    However, the Lorentz-force acting on that current would (under the approximation that the Magnetic field inside the coil is perfectly straight) be either inwards or outawards.So there would be no net force on the core and it wouldn't move.
    You can check that by using the left hand rule.
    I don't see any reason why it would be different for a toroidal solenoid.

    But there IS a phenomenon where inductive currents do make conductors move.
    If there is a divergence or convergence in the part of the magnetic field where the conductor is,(like the ends of the coil) and you increase the magnetic
    Field, then it will be shot away from the source of the magnetic field.
    Here is a video of it
    Sadly they dont actually talk about WHY the ring flies away at all.And i wont either since that wasn't your question.
    But i am confident that if you are interested in it you will find it out with Lenz's Law and the left hand rule.(maybe a diagram will help ;) )
  4. Apr 17, 2016 #3
    They say in the video that the ring creates it's own magnetic field because of the current induced by the devices magnetic field and t7hat both magnetic fields repel each other.

    Thanks for the educational video.
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