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I could come up with electrical motors and generators. Before that I saw them for controlling the arm of spinning hard drives, and those aren't used that much anymore. What else is there?

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> spinning hard drives, and those aren't used that much anymore

Hey! Are you basing this statement on your own experience of your personal/business hardware? Because spinning rust has never been more heavily used, for bulk on/near-line storage.

Judging by the list of alumni from Prof. Wang's group, HDD manufacturers have a strong demand for advanced applications of magnets, plus a tiny fraction from biomedical techs.

[0]: http://www.nanospin.umn.edu/people-0

You were right, I did not consider bulk storage outside my personal use. Thanks.

Hard drives are one of those big technologies that are more widely used and more important after they are obsolete[0].

[0] for some definition of obsolete.

> and those aren't used that much anymore

There's still a lot of active research going into magnetic tape storage, I find it very difficult to believe research into hard drive storage is going to slow any time soon.

> spinning hard drives, and those aren't used that much anymore.

Not sure if serious or not. Just because SSD's are popular, does not mean HDD's are unused.

Here are some more items I can think of: speakers, earphones, magnetic switches (eg. laptops), relays, sensors, CD/DVD ROM, maglev.

AFAIK they all use electromagnets rather than permanent magnets.

Last time I checked speakers and headphones still had a single permanent magnet + an electromagnet. However, for speakers, the "old" iron permanent magnets generally work just fine - they just have to be bigger.

"Just have to be bigger"?

I want lighter guitar amps that don't cost an arm and a leg, dammit! :)

Then go solid-state.

Inverter-based power supplies are sufficiently light that a guitar amp should only be the weight of the wood and the speakers.

And, the speakers have to be a certain size to move the correct amount of air--so the copper coil is probably the limiting weight. It's remarkable how much air you have to actually move to get decent sound volume.

Hm...sounds plausible from a physics POV, but maybe there's something else? Since, in practice (at least as far as I can speak from experience), old-school ferrit 15" speakers are ~7-8kgs, while you can get similarly specced neodymium speakers that weigh about half (3-4kgs).

Maybe ferrite, but you can also get ceramic magnets:

Ceramic 4.4lbs 50W http://celestion.com/product/20/rocket_50/

Neodymium 3.7lbs 60W http://celestion.com/product/14/g12_century_vintage/

And, yes, you will find that the values are all over the map in terms of weight. There are some much less powerful speakers that are quite a bit heavier.

At least earphones and speakers use permanent magnets[1], though according to Wikipedia[2] the early ones actually used electromagnets. I agree though that relays and maglev use electromagnets. I'm not sure about the rest.

[1]http://www.physics.org/article-questions.asp?id=54 [2]https://en.wikipedia.org/wiki/Loudspeaker#History

Some types of Maglev use permanent magnets: https://en.wikipedia.org/wiki/Inductrack

Oh, interesting. I didn't know about any project like this; thank you for the link.

Most commercial drones have 4 motors w about 12 magnets each.

Some others: electric bikes, electric skateboards, power tools, blow dryers, iPad cases.

If I recall correctly, one of the earlier iPhones was basically held together w rare earth magnets, with the screen module magnetically stuck into the case. Can't find info to verify this though, so take it w a grain of salt.

Wasn't this the iMac?

Why is this being downvoted? Prev post said you don't realize how many magnets are around you, so the parent is asking. I wanna know too. I additionally came up with speakers/headphones, connectors, reed switches.

Low-field MRI could probably benefit from a 2x improvement in the state of the art.

High temperature superconductors are what MRI needs.

"MRI" covers a very wide variety of imaging and analysis techniques under the general category NMR (Nuclear Magnetic Resonance). Some forms of NMR analysis actually use the Earth's magnetic field (https://en.wikipedia.org/wiki/Earth%27s_field_NMR).

Basically, the stronger the fixed magnetic field, the more you can see and do.

Exactly. Super conductors are the ones I use and high temperature superconduction will likely make maintaining a super conductor much cheaper (after you spent lots on a whole new system).

Wigglers and undulators.

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