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Electromagnets?

Discussion in 'General Electronics Discussion' started by Moha99, May 17, 2012.

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  1. Moha99

    Moha99

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    Nov 18, 2011
    Hallo everyone!

    Im interested in building an electromagnet! Now I'm still learning about it a few things came to mind:

    1) Electromagnet's fileds can be strengthened by increase the current or decreasing the radius, how can I decrease the radius?

    2) Are electromagnets constantly changing their magnetic poles(N>S>N>S)?


    Thanks!
     
  2. BobK

    BobK

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    Jan 5, 2010
    1. Wind the coil on a 1 inch core instead of a 3 inch core. (BTW increasing the number of windings also increases the field)

    2. Only if the applied power is AC. On DC the poles remain contant.

    Bob
     
  3. Moha99

    Moha99

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    Nov 18, 2011

    I want to build a simple electromagnet with 1 inch core and a lot of windings!

    The thing is how can I measure the magnetic pull?

    I'll use a double AA battery 1st then move on using other source(I'll build a simple bridge rectifier to solve the problem ;) )
     
  4. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Jan 21, 2010
    I wrote a whole lot of stuff, but this explains it better.

    Google is your friend.
     
  5. Moha99

    Moha99

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    Nov 18, 2011
    Alright, Thanks Steve!
     
  6. timothy48342

    timothy48342

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    Nov 28, 2011
    Also to decrease the radius, you can use thinner wire. You can fit more turns of wire in a smaller space if the wire itself takes up less space.

    And also using wire that has thinner insulation. If you were planning to use speaker wire, household wiring, bell wire or anything with a thick insulating layer, then switching to magnet wire would be a huge improvement.

    Now in both these cases your going to make a trade-off between size and how much current and voltage it can handle before it arcs or melts. (arcs meaning the insulation breaks down and melts means the wire itself melts.)

    So you definately want to be using magnet wire, (perhaps you already are), but whether you want 18 gauge or 22 gauge or something else, I can't say.

    One other issue with thinner wire is that it increases the resistance. There are probably some other considerations, too, that I haven't thought of.

    If you have some success in this, I'd like to hear about it. I must admit at this point that I made a lot of electromagnets as a kid and they were mostly all pretty weak. (Fail!)

    You might want to check out the wiki on Magnet Wire There are some links in there for further research about temperature and breakdon voltage.
    --tim
     
  7. Moha99

    Moha99

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    Nov 18, 2011
    Much appreciated!
     
  8. Raven Luni

    Raven Luni

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    Oct 15, 2011
    I take it you must really need alot of turns. Here's one I knocked up a while ago - basically a bit of ferrite and some enameled wire wound between 2 layers of heat shrink (so no accidental shorting). I powered it from a couple of D cells and the strength wasnt even worth mentioning. I didnt count the number of turns but they are in a single layer and as close as possible. I probably needed a few layers right?

    magnet.jpg
     
  9. Moha99

    Moha99

    261
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    Nov 18, 2011

    My knowledge about this is weak... I want to start on this project and learn about it very soon. 1 question though... Isn't you're electromagnet strong enough? Or is it weak?

    Personally I'll build an electromagnet based on a smaller core, more turns, thinner wires.
     
  10. BobK

    BobK

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    Jan 5, 2010
    Ferrite is the wrong thing for an electromaget, you want iron.

    I played with them when I was about 12. I would get basically really weak things, until I wrapped about 50 turns of house wiring (probably 14ga) around a piece of rebar and powered it by 2 D cells. It was quite powerful. The difference between this and everything else I had tried was the current (the D cells didn't last long.)

    Bob
     
  11. CocaCola

    CocaCola

    3,635
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    Apr 7, 2012
    Not really that simple, ferrite is a pretty generic term and could be used to describe iron or several other ferromagnetic alloys that can be used for electromagnets or other uses...
     
  12. Raven Luni

    Raven Luni

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    Oct 15, 2011
    Interesting, I'll keep that in mind if I try it again, thanks. One question though: wouldn't an iron core become permanently magnetised?
     
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