The boyfriend and I were watching a Mythbusters we saved from earlier, and they were trying to use powerful magnets to climb ductwork. Some discussion on magnets followed, and I asked the BF, “Where do magnets come from?” and he said “The magnet factory?” This was unsatisfactory.
I mean, I know there’s such a thing as lodestones that are just naturally magnetic. Do they mine some magnets? Don’t they, uh, stick to the front loaders and stuff?
How do they manufacture magnets? I assume through electricity, right? I know the strong magnets in hard drives and such are hard to get off of things if you accidentally stick them together or something - do they have equipment to keep them seperate and to take them apart once they’re together? Isn’t it pretty dangerous to work around a bunch of really strong magnets? (If you’re holding that one, and I let go of this one, and they’re extremely strong, your hand could definately get crushed, right?) What’s the difference in manufacture between a bar magnet we played with in third grade science and the strong magnets in computers? What makes a magnet strong? (It stays longer in the magnet machine?) Does size have anything to do with magnet strength?
Magnets are manufactured. As a kid, I made magnets by stroking a needle with a powerful magnet, or by wrapping wires around a large bolt and hooking it up to a battery (making an electromagnet), or even by aligning a bar with the eaerth’s magnetic poles and striking it.
I don’t know how they currently manufacture commercial magnets, especially the flexible refrigerator magnets and ceramic oxide magnets, but I’ll bet they do it using large electromagnets.
Back in the old days, when people knew little about this, natural Lodestones that exhibited magnetic properties were highly esteemed, and were often “packaged” with jackets and mounts for holding them. You can’t count on finding enough lodestones to meet your needs, though. ASnd they aren’t consuiastent enough or, in general, powerful enough for anything you want to do with them.
I am not expert but I would guess your are on the right track.
I suppose that iron or other magnetic metal is heated to increase atomic motion. Most likely the metal is cooled in the presence of a magnetic field created by an electromagnet to allow the atoms to align in their proper orientation. End result = magnet.
Magnetic fields can be quite dangerous; in the case of MRI medical scanners, the magnetic field (which is generated by electromagnets, not permanent ones) is strong enough to turn nearby loose ferrous metal items into dangerous missiles.
And yes, permanent magnets can easily be powerful enough to cause injury; I have given myself blood blisters on my fingers from getting the skin pinched between the powerful rare earth magnets I stripped out of hard drives. I have a pair of these magnets on my desk right now that are so powerful, I cannot get them apart, even with tools - if I try really hard, I can barely slide them across one another by a couple of millimetres - I think I will have to find a resilient plastic wedge or something that I can drive between them to get them apart.
Yes indeed. You can severely damage fingers and stuff with the magnets from magnetron mirowave vacuum tubes. When not installed in a tube the magnets are fitted with a keeper which is a metal cylinder that closes the air gap. The keeper on the magnet from a high powered magnetron has to be installed with caution if you don’t want a smashed finger.
I agree with Cal Meacham. Magnetic materials have two characteristics that count here. One is called “coercive force” which is the magnetic field strength that is required to saturated the material. That means that if you increase the applied electromagnetic field the field strength within the material increases for a while and then no longer increases as it has reached its limit. The other quality is “retentivity” which means the field strength remaining within the material after the external, applied field is removed. Permanent magnets are made from material with a high retentivity. They are placed within a field, usually generated by an electromagnet, that saturates the material and the external field is then switched off.
Let’s back up and get it right. Coercive force is the magnetic field required to completely demagnetize a magnet. Otherwise my statement is correct. Sufficient magnetic field is applied to saturate the magnetic material and then the field is switched off leaving the material magnetized.
And by the way, Wiki says that solkoe is correct as far as Alnico magnets are concerned. The Alnico material has to be heated while the field is applied in order to get maximum field strength in the resulting magnet. The material is heated above a certain critical temperature in the presence of a magnetic field and then cooled with the field still applied.
Also, don’t let toddlers play with small rare-earth magnets. If more than one is ingested, they will stick to each other through the intestinal walls, possibly causing an obstruction in the short term and eventually causing ulceration/perforation in the long term.
Though I’m quite sure no one cares, I just wanted to point out that this term is named after Pierre Curie, who did lots of research on electricity and magnetism.
Pierre’s wife, Marie, is better known for her discovery of radium (and polonium)
and research on the subject of radioactivity. She has a unit of measure and an element named after her, as well as being the first woman to win the Nobel Prize (1903, jointly with Pierre), the first female professor at the Sorbonne (she took over Pierre’s position after his death), and the first person of either gender to win a second Nobel Prize (1911).
Are you sure about that? I know the Curie Temperature is the temperature above which ferromagnetic materials become paramagnetic.
I guess maybe a patamagnetic material could be magnetized slightly, µ just barely greater than 1, by an applied field and then become highly magnetized upon the switch back to ferromagnetic when cooled. But somehow it just doesn’t sound right.
So, I guess these answers have been not so much over my head as very abstract, in a way. What does a magnet assembly line look like? What happens to material that’s going to become a 3rd grade science magnet? A hard drive magnet? An MRI magnet? The understanding I’m getting from previous posts is that the difference is in the material of the magnet, that you could prepare one of those bar magnets like the hard drive magnet and it still wouldn’t be any stronger of a magnet, is that right?
In other words, I dropped physics in high school and the last thing I remember about magnets is 8th grade earth science.
If I understand you, yes, the whole difference in the strength of a magnet is in the material from which is is made. Each material has a characteristic magnetization curve which is a graph with the magnetizing force plotted on the horizontal axis and the resulting magnetic flux in the material plotted on the vertical axis…
I guess I should add that this is for magnets of the same size. Since a given magnetizing force results in a certain flux density, the bigger the magnet the more total flux and the more force that is available.
Electron Energy Corporation has put together a lovely ~12min video describing their modern magnet design and manufacturing facilities, and the many uses to which EEC magnets are put.
If you can ignore any suspicion that Troy McClure did the narration, you’ll find some decent shots of alloy production and magnetic materials manufacture.
Speaking of the danger of working with magnets, I was discussing this with a friend recently. I was telling about problems with the original design of an amusement park ride that used Linear Induction Motors (LIMs). It seems that the 1/2" bolts holding them down weren’t beefy enough as the motors were pulling the heads off the bolts after a few runs of the cars.
He then told me about some LIM magnets that they had around their shop because they were considering a purchase of a LIM driven assembly line. Apparently, it was necessary to keep these magnets separated by a distance of a number of feet to prevent them from slamming into each other. Some plant manager or other came into their shop, and while talking, picked up one of the LIM magnets to ask what it was. Before anyone could tell him about it, the other LIM magnet JUMPED off the table and slammed into it’s mate. IIRC, he had 4 broken fingers, but the doctors managed to save all of them.
