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Building an electromagnet

  1. Oct 23, 2013 #1
    Hi, I decided to do a little weekend project and build an electromagnet. I read online to use copper wire and wrap it around an iron core. I was wondering If I could use anything other than iron, also, I hope you guys can tell me where I can commonly find the parts necessary for this project? Thanks, I hope you guys can help.

    P.S. I know how to make an electromagnet, just wondering what materials to use and where I can find them commonly. I have a small model but it's extremely weak due to the thick insulation on the wire.
  2. jcsd
  3. Oct 23, 2013 #2
    As for a core - it does not need to be pure iron, a bolt or large nail is the common item ( as long as it is magnetic - i.e. a magnet will be drawn to it- Stainless / aluminum will not work). If you can find a thin sleeve material,that the core fits into nicely - you can wind on that and also use as a solenoid type assembly.

    Look for / use magnet wire, it is coated with a thin enamel and allows the windings to be closer together.
  4. Oct 23, 2013 #3


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    rexdez, Welcome to Physics Forums!

    Since you say you "know how to make an electromagnet", but wonder about what materials to use for the core, I suggest that you do some "homework" or studying of the physics involved. Wikipedia is one place you might begin. Don't overlook the references at the bottom.

    "In electromagnetism, permeability is the measure of the ability of a material to support the formation of a magnetic field within itself. In other words, it is the degree of magnetization that a material obtains in response to an applied magnetic field."
    http://en.wikipedia.org/wiki/Permeability_(electromagnetism [Broken])

    Do let us know how your project/experiment progresses.
    Last edited by a moderator: May 6, 2017
  5. Oct 24, 2013 #4
    I have started to scrap small motors and such for wires, one wire I keep finding is this copper wire coated with a red substance. Does anyone have any idea what it is? I suspect it may be a chemical insulation but I have no assumptions based on fact. Also, I was wondering where I could find larger amounts of wire. I may go look around this weekend for my parts.
    Last edited: Oct 24, 2013
  6. Oct 24, 2013 #5


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    that's the enamel coating that windact spoke of in post #2

    red and brown colours are common for enamel

  7. Oct 24, 2013 #6
    I have a small collection of wires and two small scale electromagnets that don't seem to work, can you tell me what I may have done wrong? Also, I heard speakers have an abundance of good wires in them, is this true, and is it worth it?

    Attached Files:

  8. Oct 24, 2013 #7
    At the ends of the wire you need to remove the enamel e.g. with sandpaper, before you connect it to the battery. Also, do you have a multimeter to measure the resistance of the wire? It could help with making the magnet as strong as possible.
  9. Oct 25, 2013 #8
    I am going to sand down the wires later today, but I do not have a multimeter. Does Radioshack/Best Buy carry those?
  10. Oct 25, 2013 #9
    Nevermind, I found some, but I don't really know how to use one and how the resistance correlates with the strength of the magnet. I am doing to this project to learn more about this topic and to pass time.
  11. Oct 25, 2013 #10
    It is a good way to tinker with the subject. Yes Radio Shack will have a basic meter, digital multi meter (DMM) - look out for the VERY cheap ones, they may take a wierd battery, but you do not need much for these types of experiments.

    What are you using for power, a battery?

    If you are able measure the resistance (with the DMM) the expected current that will flow will be the Voltage (of the battery(s) ) divided by the resistance. I (current) = V / R.

    Another way to get the enamel off is carefully scrape off with a razor knife.

    Lastly - a very sensitive indicator - so see if the electromagnet is working is a compass - useful for when you are just starting out.

    good luck.
  12. Oct 25, 2013 #11
  13. Oct 25, 2013 #12
    The cost of the wire depends mostly on the amount of copper.
    For example those two products cost nearly the same because they both have about 1/2 pound of copper in them even though the length is very different.

    If you know the voltage and current you want to use and the volume of the copper coil, you can calculate what wire size you need to get a coil with the right resistance.
  14. Oct 26, 2013 #13
    I just bought the 315 ft thing of cord and a spdt switch. I also just found a vacuum and now it's a pile of plastic with no motor :). I was wondering if I can use it for any projects or just scrap it for wire?
  15. Oct 27, 2013 #14


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    Wire is cheap. Don't scrap the motor without good reason. 15 years from now you may be glad you kept it when you use it to crack some walnuts.
  16. Oct 27, 2013 #15


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    Looking at your kit, you have 3 wire sizes.
    22ga copper, 0.161 ohms /10ft
    26ga 0.408 ohms/10ft
    30ga 1.032 ohms per 10 ft
    (from http://www.cirris.com/testing/resistance/wire.html)

    So, 1.5V D cell and 30 ft of #30 would be about 0.5amps (calculate it). #30 will heat to 80C at 2 amps. (look it up). You can do different calculations. An ohm meter will allow you to measure resistance directly, and an ammeter will tell you the current through the coil. (multimeters have both modes)

    As for the electromagnet strength, you can calculate it based on current and number of turns. http://www.daycounter.com/Calculators/Magnets/Solenoid-Force-Calculator.phtml
  17. Oct 28, 2013 #16
    Well, I sawed the motor open to reveal a ton of wire. Although, it's held together by a very tight nut, and it just spins when I try to use a ratchet on it. I was wondering if anyone had any techniques on how to remove this because I can't seem to find any links anywhere.
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