Electromagnetism Question

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If I have an electromagnet and I want to boost the flux density and its magnetic strength, do I increase the voltage or current through the conductor(s)?

Also ... which makes a more efficient and just overall better electromagnet? AC or DC?


Hmmm, what do you need a powerful electromagnet for? Nosy sods who enjoyed their physics lessons would love to know. Digging out old textbooks as we speak btw

Keep in mind I am not an expert, just a lay person.

I am not sure about flux density. I think a higher voltage will push the fields out further, but that is just a guess. Maybe rewind the coil to a different shape? Also keep in mind that magnetic strength is equal to distance squared.(twice the distance has only a fourth the magnetic field)

Your limiting factors for current through the conductor will be IR^2 losses(twice the current means four times the losses). Too much current and you will over heat your magnet. For voltage your limiting factor will be insulation(I am guessing enamel?) breaking down due to high voltage combined with high heat, and electric arcing.

As for AC vs DC efficiency. I think DC is slightly more efficient for wattage through a given wire size and type. By that I mean more power can flow through a thinner wire, not that you will loose less power to heat. If the frequency is high, such as 60Hz or more, and you have three or more phases than it does not really matter, as both AC and DC will carry about the same energy.  If you meant energy losses that depends on current, components that you use, and the quality of your electromagnet.

Another thing to keep in mind is that AC is much more gentle on electronics because it slowly builds voltage and repeatedly crosses the zero potential mark. Many switches and breakers can handle a lot more AC power than DC because DC will try to arc weld the contacts when they open. AC does not have that much of a problem because when the voltage reaches zero the electric arc shuts down and will not try to jump back across when it builds back up.

As for flux and electromagnets. I think depending on what you are trying to do there may be a big difference between an AC magnet and a DC magnet. The AC electromagnet will have it's fields constantly growing and collapsing with whatever frequency (Hz) it is running at. That can make things more complex than a DC magnet with fixed magnetic fields.

I hope something I said was useful. I will try to attach a freeware magnetic flux program that I have. Edit: I Found it and uploaded it to my site. http://www.dustin.o-f.com/storage/femm34bin.exe

Try www.otherpower.com There are many experts there that can help you, or search their archive. Also www.eng-tips.com can help you.

Bill, it's funny how you assume this needs to be a powerful magnet. I never stated it needed to be powerful, however, your assumption this time is correct. I want to produce piece by piece and tinker with a miniature rail gun from which to launch light grain projectiles. BTW: My conception on launch differs and strays somewhat from current physics.

Fair point lol, I never said I was smart did I? Assumptions are a bad habit of mine.

On the other hand mini rail guns could make a fun project. Combined with a REALLY big carbon arc beam weapon, hmm.


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