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Power supply for electromagnet

  1. May 24, 2012 #1
    i am wanting to make an electromagnet as a project and i have ordered 916 meters of 0.125mm ENAMELLED COPPER MAGNET WIRE.
    i am a electronics hobbyist but i have not played with bench top power supply's before and i dont know where to start what is the best/ safest or how to use them safely for powering the electromagnet.

    many thanks for any help and advice anyone might offer
  2. jcsd
  3. May 24, 2012 #2
    Re: power supply

    ps i know an iron core is good but what about cast iron?
  4. May 25, 2012 #3


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    Staff: Mentor

    When your reel of enamelled wire arrives, measure off a length of, say, 5 metres and use a multimeter to measure the resistance of that length of wire. Tell us what it reads.

    First, use fine sandpaper or a single-edged razor blade to carefully scrape away some of the enamel from a few centimeters at each end of your 5 meters of wire before you connect the wire to the multimeter.

    If you don't have a multimeter, can you buy one?

    You could experiment with a cast iron core if you have some of suitable shape. Some materials will retain more magnetism than others, and in an electromagnet, being able to completely switch off the magnetism (and have no residual magnetism) is sometimes desirable.

    What is the voltage and current range of your bench DC supply? Does it have its own voltmeter and current meter?
  5. May 26, 2012 #4
    You gave the diameter of the wire, you must know the gauge of the wire. Look up what is the specification.

    What are you trying to do? When you wind the coil, power up with the DC supply set to 0V first and slowly increase the voltage while monitoring the current.

    One thing I learn working with guitar pickup. You don't have to scrape the wire to get rid of the coating. Have a solder iron, melt some solder and touch the end of the wire. Move back and fore a little, you can burn the coating away easily and leave a tinted surface.
  6. May 26, 2012 #5
    i don't have a power supply yet (that was partly why i started this thread cos i don't know the first thing abt them so i don't know what to look 4 when getting one) but the wire is marked as SWG - 39.5 / AWG - 36 (i think this is the gage?)as soon as i get the wire i will measure the resistance.

    many thanks
  7. May 27, 2012 #6


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    Staff: Mentor

    So you do have a multimeter, wolfspirit? Something that will measure ohms, amperes, and volts?
  8. May 27, 2012 #7
    yes i do have a multimeter an it will measure omes voltage and current
  9. May 27, 2012 #8
    You should describe what you are trying to do so people can have an idea what to lookout and make suggestion what supply you need......and that will govern what you have to look out.
  10. May 27, 2012 #9
    yes sorry I was not very clear; I want to experiment (for the sake of learning) with electromagnets (I have built a few b4 but it was with batterers which drain easily and it is hard to get custom current or voltage) so I want to use a bench power supply but I don't know the first thing about them. I don't have one yet and I don't know what to buy.
  11. Jun 1, 2012 #10


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    Science Advisor
    Gold Member

    Hi wolfspirit. Please use proper English here as text-speak is not permitted.

    You can look up the resistance of AWG 36 wire on the web. This is very tiny wire, about the diameter of a human hair. It's so thin that it's hard to handle, and it will carry very little current . Look up the "fusing current" to see the current at which it melts in air. When wound in a coil, heat builds up inside so back off from the fusing current by a factor of something like 10. To get an appreciable field with such low current, you'll need to use hundreds or thousands of turns.

    Cast iron is a lousy magnetic core because it's a hard, brittle material that "freezes in" a lot of stress. Ordinary mild steel, like what ordinary nails and wood screws are made of, is a better way to go.
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