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Earth magnets vs Electromagnets ? Answered


If I have an earth magnet in my pocket but I want a more powerful magnet would an electromagnet be more stronger?? Thanks. AL.

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kelseymhBest Answer (author)2011-07-08

That depends. A rare-earth magnet (note the name) has a fixed strength determined by the materials and manufacturing. An electromagnet's strength depends on how much power (current) you put through it, which is determined by a combination of it's manufacturing (specifically, the resistance of the coil) and the applied voltage.

So if you need a more powerful magnet than what you have now, you can either buy a larger (or differently made) permanent magnet, or a buy or make an electromagnet with a big, beefy power supply.

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alsports2000 (author)kelseymh2011-07-08

Thank you very much for taking the time to respond and your answer is very much appreciated. Thanks. AL.

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lemonie (author)alsports20002011-07-09


Click a blue "Select as best answer" button.

L

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steveastrouk (author)kelseymh2011-07-08

It also depends on the saturation flux density of the core material.

Steve

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kelseymh (author)steveastrouk2011-07-08

Yes, indeed. Different core materials can produce substantially different field strengths for the same coil current. I felt that the fundamental difference for the OP, was the "tunability" of electro- vs. permanent magnets. The rest is engineering details (so spake the physicist :-).

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Jack A Lopez (author)kelseymh2011-07-08

Hey, uh, if y'all want some magnet porn, this link is good one: http://www.magnet.fsu.edu/mediacenter/features/meetthemagnets/index.html

I especially like their 36 T resistive (copper) magnet. No fancy-schmansy superconductors. No ferromagnetic core, because there is no ?known? ferromagnetic material that doesn't saturate well before about 2 tesla.

It just uses copper, and very large amounts of electric current, and also large amounts of fast moving cooling water.  According to this page,
http://www.magnet.fsu.edu/education/tutorials/magnetminute/bitterplate-transcript.html
the current through the helical winding is about 40 KA, and on this page
http://www.magnet.fsu.edu/mediacenter/features/meetthemagnets/35tesla.html
they say  the total power consumption is about 20 MW, and solving for R in P=I2*R, suggests the total resistance of the copper helix is only about 12.5 milliohm.

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alsports2000 (author)2011-07-17


Also, the advantage of an earth magnet is that you don't have to deal with over heating. Thanks. AL.

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steveastrouk (author)2011-07-08

Technically, yes, you CAN get stronger fields with an electromagnet.

The remanence of a rare earth magnet is failry high, at around 1.4 T, but an electromagnet can offer field strengths up to 1.6 T with a conventional magnetic material, 2 with some exotics.

State of the art, using fancy magnetic systems, which are completely unaffordable, is 30 T.

But you won't fit them, and their power supply in your pocket.

Steve

PS. State of the art is 1000T. But you have to blow the magnet up with explosives !

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Arano (author)steveastrouk2011-07-08

a few days ago i read that the world record is about 91 Tesla http://www.hzdr.de/db/Cms?pOid=33768&pNid=473 (in the upper right corner should be a button to change language if the page is displayed in german)

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steveastrouk (author)Arano2011-07-09

I can believe that, for a static magnet. Exploding coil magnets go an order of magnitude higher.

Steve

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Arano (author)steveastrouk2011-07-09

well its at least the strongest magnetic field where the coil does not destruct itself on usage...

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