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How to build a Large electromagnet?

  1. Jun 1, 2005 #1
    I need to build an electromagnet. I have 2500 feet of 19 gauge magnet wire, and an iron core available. I'm not sure how to get a power supply that would supply enough amps to make the magnet strong enough... Anyone have any suggestions?

  2. jcsd
  3. Jun 1, 2005 #2


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    Considering that you can buy an electromagnet that lifts 500 pounds and runs on 2 'D' cells, I don't really think that it's a problem. Just make sure that your windings are tight and uniform. I don't know if number of layers vs total turns makes any difference. ie: Is short and fat better than, worse than, or equal to long and skinny?
  4. Jun 1, 2005 #3
    Well, my main reason for building the electromagnet is because I need it of a certain shape. The primary problem that I've encountered is that this: I bought a regulated power supply. It has two adjustable knobs, one for voltage, and another for current. The strange thing however, is that I can't adjust the current once the thing is hooked up... I was just wondering if there were any alternatives to using a power supply out there that people knew of...
  5. Jun 1, 2005 #4


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    Pretty much the only alternatives are batteries, solar panels, or a generator. If it's amps you want, hooking it up to a car battery could probably suck the iron out of your blood. (If you choose to use one, be very careful. They can kill you, and one that isn't totally sealed can spill acid on you and releases hydrogen.)
  6. Jun 1, 2005 #5
    you really need a material of which the remanent magnetization is as big as possible...start studying some hysteresis curves, that is my suggestion to you
    Will you be needing a hard or a soft magnet ?

  7. Jun 1, 2005 #6
    I making it out of iron, so I believe it should be a hard magnet. I've looked up materials with high saturation levels, but unfortunately, they are two expensive for my budget. It turns out that right now, I have all of the equipment I need, but I think I'm doing something wrong with my power supply. The following links provide a few pictures of it:


    When I hook the electromagnet up to it, I get no reading for current. If I hook two heavy gauge wires to each of the terminals and flip it on, I can change the amperage to whatever I want... I'm not sure what's going on. The dials say it's capable of 25 amp output and 10 volt output DC. Anyway, If anyone has any suggestions as to why it would work with just the two heavy gauage wire connected together, and not with the solenoid hooked up, I would really appreciate it.
  8. Jun 1, 2005 #7


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    You have a lot of options. The main thing you need to do is to get a better handle on your current requirements, then you can pick or design a suitable power supply. Without knowing what current range you need, it is difficult to recommend any specific power supply design or source.

    If your existing power supply has the capability of supplying the current, you can probably just put a series current limiting resistor in with the circuit, then you will probably be able to adjust the current - the problem is that you apparently can't adjust the current into a dead short, if you put some series resistance in the circuit, you'll probably be able to adjust the current.
  9. Jun 1, 2005 #8
    To get 25 amps out of a dc supply of 10 volts the resistance of your coil must not be higher then 0.4 ohm.
    I don't know which wire is used but a copper wire of gauge 34 (= diameter of 0.1601 mm) has 0.833 ohm for every meter. So even half a meter of this product is already too long.

    You will have to reduce the number of windings and use a higher diameter wire for this power supply. Product I*N will probably remain the same but the resistance will be much reduced.
    I hope this will help, best of luck,
  10. Jun 10, 2010 #9
    Am doing something similar to that. I have decided to get about 300 feet of copper wire and wrap 12 oval shaped coils around a car wheel that I will then attach to the hitch on the back of a truck. The power source will be an alternator, which will take place of the secondary air in on the drive belt. If I idle the truck, a small amount of energy will be made, but the energy will pass through the copper wire around the wheel and create a very large amount of energy. It will be magnetized enough to pick up a small car.
  11. Jun 10, 2010 #10
    The iron in your blood is not arranged in a form that is ferromagnetic. It's actually very slightly diamagnetic, but not enough to matter. The superconductive magnets in an MRI don't have any affect on tissue at all, and some of the strongest special-purpose magnets in the world have been used to levitate living frogs and other samples, with no ill effects.

    Any magnet you make won't hurt you, except by throwing other objects at you.

  12. Jun 10, 2010 #11
    Wire tables show the maximum current in 19 Ga. wire to be about 1.8 amps, and the resistance about 8.2 ohms per 1000 feet. The best magnet design is a "C" magnet or an "H" magnet, either with two coils. The coils (in series) would each be ~ 1000 ft long and I2R = 27 watts. For a tightly packed coil, the power should probably be closer to about 10 watts (or 1.1 amps), and 18 volts total. What insulation do you have on the wire, and what is its maximum temperature rating?

    Very roughly, the magnetic field in the gap is about

    B = μ0NI/g Tesla

    where μ0 = 4 π x 10-7 Henrys per meter, N = total # of turns in both coils, I = current (amps), and g = gap (meters).

    What are dimensions of your magnet, and what magnetic field do you want?

    Bob S
    Last edited: Jun 10, 2010
  13. Mar 23, 2011 #12
    I am 14 years old, and limited in rescources, so if anyone has any ideas how i could make an extremely powerful electromagnet (90 pounds of lift) that would be really great and I would thank you very much.
  14. Jul 17, 2011 #13
    Okay I read in one of the lines that you can buy an electron magnet that will lift 500 lbs I want to build an magnetic bed and I need help with the magnet part if anyone can help me with this part that would be outstanding. you can email me at pearisjm@yahoo.com I am hoping to turn this into a great science project at the school that I work at also. Thank you for the help all
  15. Jul 17, 2011 #14
    hey where can I buy this magnet that you are talking about because I am hoping to get two to life a bed in my room to sleep in do you have any ideas pearisjm@yahoo.com
  16. Sep 23, 2011 #15
    I am new here and hope somebody can help me. I am wanting to build an electromagnet attachement to go on my skidloader for picking up scrap. The ones I have seen built for this purpose are approx. 16-20k. I am not willing to spend that much and believe I can make my own much cheaper. I would like to use an old 3500 watt generator head that is on a cheap generator I bought at a Walmart type place. My plan is to take a truck wheel and wrap the wire around it and use a hydraulic motor to power the generator head. I would like to be able to have at least one outlet on this magnet that could be used for 110v applications if needed. The high priced ones I have looked at are that way.

    I'll get to the point now. I don't know how to figure out what size of hydraulic motor I need, how many wraps of wire and so on. Is there anybody on here that could possibly help me out.

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