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Electromagnet? Answered

Hello smart People of Instructables.
I want to build a very powerful Magnet, i planned on using a microwave transformer.
Heres my question: Can i plug the Transformer into my house electric?
Im in Europe so we got 230V AC.
And will the Magnet get stronger or weaker if i wrap really thick wire around it?
Thanks for you Answers


Jack A Lopez

Best Answer 3 years ago

Yikes! Watch out where you're dropping those capital letters. Somebody could trip over one of those!

So you are asking asking about magnets: how do they work?

It is a question people ask the Answers forum from time to time. I think Shaggy 2Dope, of ICP fame, posted a question about magnets here one time, but I don't know if he liked the answer he got.

Probably the best answers posted to your question so far
are those pointing you towards Wikipedia, like maybe this one,


I don't want to spoil the ending, but the magnitude of the magnetic field produced, tends to be proportional to N, the number of turns, and I, the current (in amperes) through each turn.

Including a core of some kind of "magnetically soft" material, can give stronger magnetic field, but only up to a point, because of magnetic saturation.


Other spoilers: Electric currents produce heat via Ohm's law, I^2*R. For large currents you may have problems keeping the wires from melting, or buring up their insulation.

If the current you use for your electromagnet is alternating current (AC), then the field produced will be an alternating field. and this alternating field can induce eddy currents in concutors near the magnet, or even in the core itself, via Faraday's Law,


I dunno. It seems like I'm kind of having to explain everything about everything, and, uh, you know, that could take a while...

You mentioned a microwave oven transformer (MOT), and I have no idea what role that's supposed to play. Maybe you were planning to cut the top off from it, and let that be your electromagnet? Or maybe cut out the high voltage winding, for to put a one or two turn secondary, similar to these homemade welder projects?

Whatever you're doing, the MOT would probably be safer with its high voltage winding removed. I don't know if anybody every told you that high voltage circuits are dangerous. Usually there is at least one warning-danger-electrocution-death label, sometimes two or three of these warnings, printed on the back of the microwave oven itself, or in the printed manual. What can I say about this, except to tell you the rumors are true. You definitely don't want to be near any of that stuff when it's turned on. When turned off, it's not totally safe either, due to charge stored on big capacitor. So, yeah. You, don't want to touch it. Come to think of it, the same is true of "ordinary" 230 VAC mains power. Don't want to touch that either.

Regarding the question of attaching low-impedance (looks like short-circuit) things to mains power, the usual result is the circuit breaker trips off, like it's supposed to, because it is preventing the wires in your house from melting due to overcurrent. For example, I would expect a MOT with its top cut off to do this; i.e. have much less impedance than a whole, stock, MOT with its magnetic circuit intact.

So it would be desireable if you had some easy way to limit the current from the mains. One trick is to put the suspect shorty-load in series with an old-fashioned incandescent light bulb. Somewhere on the web, you can find a complete explaination of the in-series-incandescent-light-bulb trick, but here I just mention it without explaination.

Another sort of general purpose strategy for limiting power is to use a lamp-dimmer. I am thinking of the the inexpensive, triac based, kind that chop up the AC waveform. Although for something like a cut-open transformer, I think the in-series-incandescent-light-bulb trick would work better. Using both lamp dimmer and in-series-incandescent-light-bulb would work also, I imagine.

Remember: DO NOT to touch any of these things while the power is turned on. That's very important. If you have to poke, prod, manipulate some part of your setup while it is turned on, do this using a length of insulating plastic pipe, also called a "chicken stick". Hmmm... I guess Wikipedia calls this device a "hot stick"


No matter what it's called, the concept is the same. It's all about not electrocuting yourself.


3 years ago

The video below (guess it didn't want to embed....) is this awesome guy who make CRAZY stuff, and indeed did use a MOT transformer to make epic magnet shoes, just like the "Magneboots" from Ratchet & Clank!


3 years ago


Jack A Lopez

3 years ago

Hey, I just tried searching the Instructables website for something resembling an electromagnet made by cutting open a microwave oven transformer (MOT).

I found one I had not seen before,


which is mostly just a stub linking to this Youtube video,

Anyway, I am guessing this is what you meant by "using microwave transformer" to "build a very powerful magnet".

I don't know if you've seen already seen this one or not. There might be some details worth reading in the comments sections that both those places.

Also, I thank you for choosing that other answer I wrote as a "Best Answer"


3 years ago

Slow down.

If your current level of knowledge is as suggested by your question your a long way away from being able to safely build anything such as you suggest.

You can buy large powerful neodymium magnets at very reasonably prices, easily powerful enough to cut off your fingers if your not careful.

Your electrical knowledge is apparently extremely sketchy - i would suggest you do much more electrical and electromagnetic research and come back when you have a much more specific question relevant to your project.

Start small and build knowledge, then at some point you will know enough to complete your project without having to ask.

PS if you want a really really strong electromagnet start saving because it is going to cost you more than you earn.


3 years ago

Maybe you should get the plans straight first.
What tranformer? You wanted a magnet not a transformer...
Look up electromagnets on Wikipaedia to get started.