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Magnetic field of a Toroid

  1. Jun 22, 2015 #1
    Layman speaking here..

    I have for a while been interested in a small desk toy. It is a magnetic levitating globe.

    There is a doughnut shaped electromagnet at the base which according to the internet is a toroid. Within the globe sits a disc shaped neodymium magnet.

    The globe hovers barely a cm above the base.

    What i am interested in is how high could you actually get the magnet to hover?
    If you increase the voltage would it increase the magnetic field and raise the hight of the magnet?

    Any assistance in explaining this would be appreciated,
    i promise i will use this knowledge only for good.

    Thanks
     
  2. jcsd
  3. Jun 22, 2015 #2
    No, you need to increase the current not the voltage.
     
  4. Jun 22, 2015 #3

    mfb

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    Maybe, but it could also make the system unstable. Also, the system needs active stabilization which could fail. In addition, a higher current could overheat the coil.

    If it would be easy to make the globe levitate higher, the manufacturer would have done that.
     
  5. Jun 22, 2015 #4
    I dont own one of these magnetic globes btw. Its just a toy so i dont really think the manufacturer really wants to run a lot of electricity through it. It only needs to hover a centimeter or so. Its just a low powerd toy.

    But i was imagining a home built version something like 10 inches in diameter. I was just curious if anyone knew how high you could possibly levitate the magnet if you if you increased the current?

    The globe toy, from what i have read on the internet senses the height of the magnet somehow and adjusts the current accordingly.

    Im assuming here that we wont overheat the coil.
    But say i did build one and made a nice magnetic field and balanced my magnet on there but wanted to go further? higher?
    But i couldn't increase the current because i would overheat the copper coil.

    What could i do? instead of building a bigger coil would there be any other materials that i could use instead of copper that i could use?

    Im assuming that increasing the current will give me as larger magnetic field here. I honestly am learning as i go.

    Thanks
     
  6. Jun 23, 2015 #5

    Hesch

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    I'm curious how this thing works:

    How will a magnetic field escape a toroid?
    Is ac-current used as for the toroid?
    Is the "magnet" in the globe a magnet or just a piece of metal wherein eddy-currents are induced?
    If the "magnet" in the globe is repelled by the toroid, why will the hovering globe not turn upside down? ( magnet too heavy? )
     
    Last edited: Jun 23, 2015
  7. Jun 23, 2015 #6

    mfb

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    Copper is the best reasonable conductor - I guess you don't want to make a coil out of silver or cool it with liquid nitrogen. The stabilization system is tricky and significantly harder than just getting something to not fall down.
    In general, height will scale with the size of the base - getting a height larger than the width of the base would be really tricky.
     
  8. Jun 23, 2015 #7

    NascentOxygen

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    Perhaps the electromagnet is not toroidal?
     
  9. Jun 23, 2015 #8

    Hesch

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    Are you saying that it is not a toroid, but a solenoid?

    And then:
     
  10. Jun 23, 2015 #9

    NascentOxygen

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    Until a photo is posted, we can't say whether the solenoid core is toroidal or not.
     
  11. Jun 23, 2015 #10
    Here is a link anyhow of the type of levitating toy i described:



    I will, after this post search the web for a teardown but please have a look at this for now.

    In response to Herch i honestly dont know the answers to your questions im afraid. It is described as a magnet in some videos but it may not be i will try and find out.

    At first i just called the magnet at the base a "doughnut electromagnet" and after some goggling i came across a "toroid" which appeared, at least to me to be what i was looking for.

    In response to mfb i would consider silver if it was significantly better. I in all likelihood wont but here im just seeing how high i could really go.
     
  12. Jun 23, 2015 #11
  13. Jun 24, 2015 #12

    mfb

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    No. Its resistance is about 5% lower, but its price is higher by a factor of 100. Copper is the best conductor for all practical purposes, unless superconductors become interesting (for things like large particle accelerators, or multi-megawatt applications elsewhere).

    The globe probably uses multiple magnets in some unknown arrangement.
     
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