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B Conductive ring levitated by electromagnet

  1. Nov 18, 2015 #1
    I am an eleventh grade student currently in AP Physics C. My teacher did a demonstration with an electromagnet where he drew AC current from the wall to shoot a conductive ring. I was wondering where i could find the blueprint for such a device, or perhaps receive some guidance on how many coils i need/how much current i need to shoot a ring to a certain height.
    ( )

    out of curiosity, is it possible to do the same with dc current. for example, maybe i could use some D cell batteries connected in series, a capacitor, and the device i talked about above for just a magnetic pulse rather than oscillating magnetic flux.
    what about just batteries connected in series?
    (i've already tried that but with not nearly enough coils. since i didnt have any resistors and the wires were relatively thick, I only connected the circuit for a fraction of a second, because i didn't want the circuit to short out)

    And some questions that weren't answered in my lessons:
    how does the difference between thick and thin wires affect the device? (i do know that usually as cross sectional area increases resistance decreases)
    i cant think of any more questions atm

    If i seem like I'm completely loss or my logic is all muddled up, please don't just point it out, but also try to correct me so that i may learn something.

    Cheers from the high school student that feels like he doesn't know enough physics.

    reposted from classical physics because after looking at the difference between classical physics and general phyics i thought it might belong here more.
  2. jcsd
  3. Nov 18, 2015 #2


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    This requires quite a lot of power, and is not something you should be doing at home
    Please ONLY do this with teachers/lecturer supervision

  4. Nov 18, 2015 #3

    Naturally, I wouldn't make one the same size as my teacher's. I just want to make one powerful enough to make the ring jump a little and float just above the coil.
  5. Nov 18, 2015 #4


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    been a long time since I have done one, 20VAC or so at several amps into ... cant remember how many turns of wire I used ... probably 20++

    Yes it must be AC
  6. Nov 18, 2015 #5
    i found a link outlining a project for this device, thanks for the input guys.
    << Link deleted by Mentor >>
  7. Nov 18, 2015 #6


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    That link uses AC Mains voltage as the power source. As already pointed out, this is extremely dangerous, and you should not do that.

    Instead, find a "wall wart" or "brick" power supply that has a good current AC output (like 24VAC at a couple amps). Use that instead and you will be MUCH safer.
  8. Nov 19, 2015 #7
    I found a wall wart to buy, but I'm still using the page as a guide on what sort of materials to buy and # of coils and whatnot. As such, i have a few questions about the materials.

    1) Is the rod for real 9 inch diameter? I'm pretty sure he meant to type 3/4 inch, because nine inches is ridiculous(ly expensive?), plus it doesn't seem to look like 9 inches in the image.
    2) I understand the safety aspect of a fuse, but if i were to use 200 feet of #18 magnet wire, how much current would 120V and 24V (the wall wart) generate respectively? (i could use R=pl/A and then ohms law, but i"m a little lazy, and also lost because i'm starting to realize how skewed theoretical knowledge becomes in real life.) I am asking this because the page says specifically to use a fuse with a 7A rating, and i was wondering where he got the number from, experimentation?
    3) The worst part is, I don't think the author really knows that much physics. the reason a steel/iron core is needed is obviously because an electromagnet must have a ferromagnetic core, yet he filled an iron tube with an aluminum core. My third question is this: would a hollow ferromagnetic tube work for this experiment? why or why not?

    those are the questions i have so far. I understand most of the theoretical aspect of what's going on, such as eddy currents, magnetic fields and whatnot. I'm just struggling to apply my precious knowledge to real life. (quite harder than just acing physics tests tbh)

    sorry if my posts get annoying
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