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Help with my large scale electromagnet

  1. May 9, 2008 #1
    I am working on a project to make a large scale electromagnet and try as I might I just cant get past one part. Getting it to magnetize.

    I have built the unit primarily out of a 5 ft rod of threaded steel (I will be replacing it with iron I just happened to have the rod already) wrapped in a copper wire that covers 3.5 ft of the rod.

    My problem is that no matter what i hook up for a power source I simply cannot get it to magnetize I started from a design that indicated a few 9 volt batteries up to a battery out of a semi that weighs 80 lbs and even a few DC adapters all that came with the same result.

    I ran as many tests as I could think of to find the solution I used a multimeter to measure the volts with and without the wire connected i powered some LEDs through the wire and even hooked up a semi battery witch resulted in the plastic on the wire to actually boil but still not even enough force to pick up a paper clip.

    I just don't know what else to try or where else to look any help would be greatly appreciated.

    I assumed this is large scale as all the pages i have found primarily talked about using nails for the core this is even just a prototype for a much larger project for moving scrap metal.
  2. jcsd
  3. May 9, 2008 #2


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    Welcome to PF, Yomega.
    How many layers of how many turns do you have?
    Also, plastic-insulated wire isn't often used for this purpose. Switching to enamel-insulated magnet wire might help. I'm not sure whether or not the threads on the rod make a difference, but it might be worth looking into.
    Last edited: May 9, 2008
  4. May 9, 2008 #3
    It currently only has one layer with probably 100 turns maybe more.
    I have some rubber coated wire all tho i doubt that would work any better.
    As for the treads I did some research on it and it wont interfere with the field but it does very well to guide the wire in a smooth spiral.
  5. May 9, 2008 #4


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    If you have just wrapped one length of wire around the thread then the turns/length is too low unless you are putting a huge current through the wire.
    You would typically wrap a few hundred turns around the lengh of a nail to even be able to pick up paperclips with just a batterey.
  6. May 9, 2008 #5
    What kind of steel is the rod made of? You may just have a low permeability material.
  7. May 9, 2008 #6
    I just guessed at the turns I know it is 30 ft of wire around a 3/4in thread and I placed a magnet to the rod and it gets a pretty good connection
  8. May 9, 2008 #7


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    For the length of the bolt that you want to wrap, you're probably looking at close to 1,000 feet of wire to get any significant lifting attraction out of it.
  9. May 10, 2008 #8
    Oh, I just got the picture of what you're doing. Wind all the turns in about a three inch section right at the very end of the rod. Then try that end as an electromagnet. It still won't be great, but you should see some effect. Why five feet?
  10. May 11, 2008 #9
    Thanks for the suggestion I will try that and the rod is five feet simply because it was something i had on hand the final product is likely going to be very different than my prototype
  11. May 11, 2008 #10
    OK. In an electromagnet, extra core length hurts rather than helps; when you make the real one, keep the core as short as possible and try to keep it in the general area where the field lines would be anyway.
  12. Jul 1, 2008 #11
    I managed to source some high quality magnet wire and I was wondering if having a hole in the center of the core would really affect the magnet i was having problems with the wire slipping as i was making the extra layers so if the wire could return to the bottom through a hole it may help. If this is a bad idea please let me know or possibly suggest a better way to wind the core thanks in advance
  13. Jul 1, 2008 #12
    I'm not sure what you're doing with the return, so I can't really say. The hole wouldn't hurt the core much. But, what you need is some very thin Teflon tape to secure each layer as you make it.
  14. Jul 1, 2008 #13
    I was planning for the hole to be used only for coiling the wire on extra layers but i will try the Teflon tape i tried electric tape but it just slipped off
  15. Jul 1, 2008 #14
    I still don't have a good picture of your problem. Are you using any kind of form for the coil? If not, do you have tension? What sort of aspect ratio?
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