Questions people actually ask about magnets

#1How do magnets actually work?

Before I try to answer, let's acknowledge that every answer not in terms of graduate-level physics is going to involve a certain amount of hand-waving. There's a very entertaining video of the legendary Richard Feynman explaining that he can't explain it to you in terms of what you already know, and I am not under the illusion of having exceeded Dr. Feynman in my explanatory prowess. So, at some level, I will always disappoint the Juggalos out there. But here's my go at it:

Every electron is a tiny magnet, partly because it moves around its atom (moving charge makes a magnetic field) and mostly because of a property called spin, which, despite the name, isn't anything actually spinning. In most atoms, the electrons pair off and their magnetism cancels out. In iron, a quirk of quantum mechanics makes it cheaper for neighboring atoms to keep their electrons pointing the same way, so every tiny region of iron is already fully magnetized. Ordinary iron just arranges those regions so they cancel each other out. Apply a magnetic field and the regions line up, making a magnet. A permanent magnet is a material built so that, once you get the regions lined up, they stay that way.

I have absolutely glossed over a bunch of fascinating concepts like Maxwell's Equations, Schrödinger's Wave Equation, and the Pauli exclusion principle because it's outside the scope of a FAQ, but that's as honest an answer as I can give without "cheating you," as Dr. Feynman described it.

If you want the version that doesn't hand-wave, the same man wrote it down: Volume II, Chapter 36 of the Feynman Lectures is on ferromagnetism and is free to read. The piece I glossed over hardest — why neighboring atoms agree to point the same way at all — has a name and a whole literature behind it, the exchange interaction. Or, if you want it one “but why?” at a time, with the pictures moving, until we hit the floor of physics, I wrote that too: F***ing magnets, how do they work?

Short version: Magnets are weird, but also useful. Like me.

#2Where does a magnet get its energy? Doesn't holding something up forever violate conservation of energy?

Magnets don't do work — YOU do work.

It takes no energy to hold something still. A magnet holding a wrench to a wall is doing the same job as a hook, and nobody has ever asked where the hook gets its energy. Force without motion isn't work. Neither one runs down.

Energy only changes hands when something moves, and it's your energy. When you bring the wrench close, that's like dropping it on the floor. When you pull it away from the magnet, that's like picking it up. The magnetic field is like the gravity field — it's just the thing you do work against.

Which disposes of the magnet motor, and I'll put this as respectfully as I can, because people have spent real years of their lives on it. A permanent magnet's field is fixed in space. Move anything around a closed loop in a fixed field and the net work is exactly zero — whatever the field hands you on the way in, it takes back on the way out. This is not an engineering problem waiting on a cleverer geometry. Magnets are superb at converting energy, which is precisely what a motor does. They are not a source of it.

Feynman works the "magnetic forces do no work" argument properly in Volume II, Chapter 13 if you want it done with the mathematics attached. And if you're about to write to me about a design that gets around this, read the history of perpetual motion first — not because you're a crank, but because it is genuinely worth knowing how many very clever people have already been here.

#3Do magnets lose strength over time? How long does a magnet last?

Mostly no, but also yes. For all intents and purposes, permanent magnets are indeed permanent until you do something to them. That something can be heating up, applying a demagnetizing field, or chemically breaking it down.

Left alone on a shelf at room temperature, a sintered neodymium magnet gives up a small fraction of a percent in its first weeks as the least stable domains relax, and then essentially stops. Ferrite and samarium-cobalt are steadier still. Nobody's refrigerator magnet has ever fallen off from old age.

The three real killers, in roughly the order you're likely to meet them. Heat above the grade's rated working temperature, which costs you performance temporarily at first and then permanently — that's its own question below. A strong opposing field, meaning another magnet forced pole-to-pole or stray flux from an electromagnet, which is why alnico used to ship with steel keepers across the poles and why any motor designer worth hiring checks the demagnetization curve before committing to a geometry. And corrosion, which matters more than people expect: a neodymium magnet is mostly iron, and once the plating is scratched a rusted magnet has simply lost volume. It isn't weaker material. There's just less of it.

Here's the part that surprises people. A magnet knocked down by heat or by an opposing field can usually be brought all the way back in a pulse magnetizer, provided the material itself is still intact. Magnets don't run out. They get knocked down, and they can be stood back up. The property that decides how hard they are to knock down in the first place is coercivity, which turns up in nearly every answer on this page.

#4Why are only iron, nickel and cobalt magnetic? Why does a magnet stick to some stainless steel and not other stainless steel?

This is another question that takes a deep dive into graduate school-level science to answer properly. However it has to do with the way atoms bond, and what's unique about those elements, being the first d-row elements on the chart, is that they have relatively few ways they can bond. As you get down in the chart, electron structures get more complicated, which offers more ways to avoid magnetism (which is the preferred state in nature). That said, the more complex electron structures can also be very USEFUL, which is how rare earths joined the party — more on that here.

Aluminum, copper and silver are the everyday examples of that avoidance. Their electrons are either paired off or free to roam, and no hand magnet will stick to any of them. It isn't quite nothing — it's just far too small to feel. Gadolinium is genuinely ferromagnetic, but only if you keep it below about room temperature, which is a lovely piece of trivia and of no practical use to anybody.

Stainless steel is the one that starts arguments, because "stainless" is a family and not a material. The austenitic grades — 304 and 316, which is your sink, your countertop and most of your cookware — carry enough nickel to lock the iron into a crystal structure that isn't ferromagnetic, and a magnet slides straight off. The ferritic and martensitic grades — 430, and the hardened steels in a good knife — keep iron's ordinary structure, and a magnet grabs hard. Then there's the case that makes people think they're losing their minds: cold-work a 304 part by bending or stamping it and some of that structure converts on the spot, which is why a magnet will sometimes catch the pressed corners of a sink that is resolutely non-magnetic everywhere else.

#5What happens if I cut a magnet in half? Can I have a magnet with just a north pole?

You get two complete magnets, each with its own north and south. Cut those and you get four. Keep going and you arrive at a single atom, which is still a dipole.

The reason is that poles are not objects stuck on the ends. They're the two faces of one circulation. A magnetic field is a closed loop — out at north, around, back in at south — and there is no way to cut a loop so that only one end of it survives. People have hunted for a genuine magnetic monopole with real money and real careers behind the search, and nobody has found one. There is exactly one famous candidate event, recorded by a single detector at Stanford on the night of 14 February 1982, and it has never been reproduced. Every magnet ever made has two poles, which is why every magnet supplier on earth keeps a polite form letter for the customer who wants one with only a north.

The practical consequence is that the halves come out weaker than you'd expect. Not because magnetism leaked out of the cut, but because each half is now a shorter magnet, and a shorter magnet works harder against its own field.

#6Why can't I make a magnet float? How do maglev trains do it?

Ironically, in my day job now, we do exactly this. The trick to it is "why can't I make a magnet that isn't moving float?"

Set one magnet above another, repelling, and it will slide off sideways or flip over every single time. That is not a lack of patience on your part. Earnshaw proved in 1842 that no fixed arrangement of magnets can hold another magnet stably in mid-air — there is always at least one direction in which a small nudge grows instead of correcting itself. It's a theorem, not a materials problem, and no grade of neodymium is going to get you around it.

So every levitation you've ever seen cheats, and it's worth knowing which cheat is which. The floating globe on an office desk is an electromagnet with a sensor, correcting thousands of times a second. The spinning-top toy works only while it spins. A magnet hovering over a chilled superconductor is doing something different again — that's the Meissner effect, and there's more on that here. Pyrolytic graphite floats because diamagnets are the one loophole Earnshaw left open, which is further down as well. Commercial maglev is the desk globe, scaled up and moving considerably faster.

And if all you want is the look of the thing, one point of contact is permitted. That's the entire secret of the levitating-pen desk toy, and it isn't cheating so much as reading the rules carefully.

#7Can anything block a magnetic field? How far does a magnet's pull reach?

Nothing blocks a magnetic field the way a wall blocks light. It goes through wood, plastic, glass, aluminum, water and your hand without noticing any of them. What you can do is offer it an easier road. Steel and the nickel-iron alloys carry flux far more willingly than air does, so the field lines crowd into the metal and travel around whatever is sitting behind it. That's shielding: redirection, not blockage. It's why a steel case protects a compass, and why an MRI magnet lives in a room lined with the stuff.

One significant exception are superconductors, which are considered perfect diamagnets and reject all magnetic fields. This is a side effect of the extremely high charge carrier mobility in the material — surface currents spring up instantly to cancel anything trying to get in, and the field is expelled from the body of the material entirely. That expulsion has a name, the Meissner effect, and it is the closest thing to a true magnetic wall that exists. It's also the reason a magnet hovers above a cold superconductor rather than sitting on it, which is the levitation trick referred to earlier — the superconductor isn't repelling the magnet the way another magnet would, it's refusing to let the field inside at all.

As for reach, there's no edge, but the falloff is brutal. For a small magnet the field drops with roughly the cube of the distance, so twice as far away is about an eighth as much. In practice a magnet does useful work out to something like its own dimension and is negligible a few times past that. The one-inch disc that will snatch a wrench out of your hand on contact will barely twitch a compass from across the room. This is the thing people most often get backwards when they ask whether a magnet is safe to have around: the answer is almost always about distance, not about strength.

#8Do magnets work underwater? In space?

Yes to both, and for the same reason. Water is very nearly transparent to a static field and vacuum is perfectly so. A magnet is exactly as strong at the bottom of a lake or in orbit as it is sitting on your desk.

Underwater your problem isn't magnetism, it's rust. A neodymium magnet is mostly iron, and once the plating is nicked, salt water will have it inside of weeks. Marine work uses heavier plating, full encapsulation, or steps away from neodymium altogether to ferrite or samarium-cobalt, neither of which corrodes.

Space adds a wrinkle at the cold end. Some sintered neodymium grades weaken sharply once you take them well below −100 °C, which is a real constraint for satellite designers. Praseodymium iron boron magnets don't suffer this effect, and are still used in some specialty applications for this reason. At ordinary temperatures the trend runs the other way — cold makes a permanent magnet slightly stronger, not weaker, which is two questions down.

#9Can you magnetize wood, plastic, or other non-metals?

Not in the sense you mean. To hold a magnetization you need unpaired electrons willing to line up with their neighbors, and the atoms in wood, plastic and glass have theirs fully paired and accounted for. Those materials are in fact very slightly repelled by a magnet — diamagnetism — but you need several tesla before it becomes visible.

At which point it becomes very visible indeed. The canonical demonstration is a live frog floating in a 16-tesla bore at Nijmegen, written up by Berry and Geim in Of flying frogs and levitrons, which is one of the most enjoyable physics papers ever published and won Geim an Ig Nobel a decade before he won the real one for graphene. The frog was unharmed. Strawberries, water droplets and grasshoppers work too.

What you can do at ordinary field strengths is put magnet inside something that isn't one. The flexible sheet on your refrigerator is exactly this: ferrite powder in a rubber binder. Bonded neodymium is the same idea with much better powder in nylon or epoxy, and it turns up in small motors and sensors where getting a complicated shape straight out of a mold matters more than getting the last ten percent of performance. So magnetic plastic is real and you can buy it today. It just isn't magnetized plastic — it's plastic full of magnet.

#10Why are neodymium magnets so strong when neodymium itself isn't magnetic?

True — and very nearly the same is true of iron. A lump of pure iron isn't a useful magnet either. Iron is trivially easy to magnetize and just as trivially easy to demagnetize, which is why the nail you just picked up doesn't stay a magnet after you take it off.

A neodymium magnet is a compound, Nd₂Fe₁₄B, and the two metals have completely different jobs. Iron supplies nearly all of the magnetism; there are fourteen iron atoms in that formula for every two of neodymium. Neodymium supplies the discipline. Think back to those complicated rare-earth electron structures — think of neodymium as an exceptionally good field marshal that has tight control of his troops, his troops in this case being the iron atoms. Its inner electrons couple hard to the crystal around them and make the whole structure refuse to turn: magnetize it along its preferred axis and it takes an enormous opposing field to flip it back. That stubbornness is called coercivity. What the Nd does really well is keep iron from demagnetizing. It doesn't make it MORE magnetic.

The property doing the work has a proper name — magnetocrystalline anisotropy, the crystal's preference for magnetizing along one particular axis — and if you only learn one term of art from this page, that's the one that explains why rare earths are in magnets at all.

That distinction is the entire reason this material took over the world. Iron gives you strength you cannot keep. Neodymium and boron let you keep it, in a piece small enough and thin enough to sit on a rotor — and that, rather than raw field, is why nearly every high-performance motor built today is full of the stuff.

#11What is the strongest magnet? What's the strongest magnet I can buy?

Among permanent magnets, sintered neodymium iron boron, and within that family the top of the energy-product ladder. N52 is the strongest grade you can buy without having a conversation first; N55 exists from a handful of producers, and every year somebody announces something higher.

Be careful with the word "strongest," though, because buyers almost always mean pull force, and pull force is far more a question of size than of grade — more on that here. Going from N42 to N52 buys you something like twenty percent. Doubling the volume buys you a great deal more. A two-inch N52 cube will hold several hundred pounds against a steel plate and is genuinely dangerous — not "be careful" dangerous, but "this will take a fingertip off and you will not be strong enough to stop it" dangerous.

Past permanent magnets the numbers get silly, and the people who hold the records publish them. A clinical MRI sits at 1.5 or 3 tesla. The strongest superconducting magnet runs at 32 tesla and the strongest continuous-field magnet at 45. A pulsed magnet at the same lab has hit 100.75 tesla, for about a tenth of a second. And the record holders in the universe are magnetars — neutron stars running somewhere around a billion tesla — which is the honest answer to "could a magnet pull the iron out of my blood." Yes. At that scale. Which is not a scale at which you still have blood.

#12What does heat do to a magnet? What if I melt one? And if iron loses magnetism at 770 °C, how is the Earth's core magnetic?

Heat is a permanent magnet's natural enemy, and it attacks in two stages.

Warm a magnet and you shake the atoms hard enough to loosen their agreement about which way to point, so the field drops. Let it cool and a neodymium magnet hands most of that back. Push it further and some domains flip for good — now it comes back weaker and wants a trip through a magnetizer.

Every grade carries a published maximum working temperature. Call it 80 °C for plain neodymium, out to roughly 230 °C for the specialty grades, and considerably higher for samarium-cobalt, ferrite and alnico. Read those as practical limits, not physical ones. They are the temperature at which the magnet stops doing its job in MOST applications, which is a statement about the magnet, its shape, and whatever is pushing back on it, all at once. Two magnets of the same grade in two different motors will not fail at the same temperature. That is precisely why a datasheet gives you a family of curves instead of a number.

The Curie temperature is a different thing, and it is always the higher of the two. That's the point where the material stops being ferromagnetic at all — 770 °C for iron, and a few hundred degrees above the working limit for a neodymium magnet. The gap between those two numbers is where the H, SH and UH grades live. They don't move the Curie point much. They just hold their domains in line much closer to it.

Melt a magnet and there's nothing left to discuss. A liquid has no crystal for domains to live in. Freeze it back and you have an unmagnetized lump until somebody puts it in a coil.

Which brings up the question people actually want to ask. If iron quits at 770 °C, how is the Earth's core magnetic at several thousand? Because the core isn't a permanent magnet at all. It's an electromagnet. The outer core is molten iron, it conducts, and it circulates; a moving conductor in an existing field drives a current, and that current sustains the field. That loop is the geodynamo, and it is the cleanest illustration I know of why "permanent magnet" and "electromagnet" are genuinely different animals. One of them survives being frozen but not melted. The other runs hotter than a furnace indefinitely.

#13Why do magnets get stronger when they're cold?

Same mechanism as heat, run backwards. The field is the sum of an enormous number of atomic magnets that mostly agree on a direction, and thermal jitter is what stops them agreeing perfectly. Take the jitter away and the alignment tightens up. For neodymium it's roughly a tenth of a percent per degree. Ferrite gains more.

There are limits, and one of them catches people out. Some neodymium grades pass through a spin reorientation down around −135 °C and start losing ground again — the reason praseodymium grades exist for cryogenic work. And ferrite, which gains remanence as it cools, becomes EASIER to demagnetize at the same time, so a ferrite motor magnet on a cold morning is more vulnerable than it was the day before, not less. For anything you'll meet outside a laboratory, though, cold is a modest free upgrade.

#14What do N35, N42 and N52 mean? What's gauss? What's "pull force," and will a 20-pound magnet lift 20 pounds?

The number is a rough estimate of the energy product of a magnet in Megagauss-Oersted. For a one-number metric of how strong a magnet is, it's as good as any, and it's useful for explaining how strong a magnet is. The letters after the number help to add some color to it by explaining HOW the magnet develops that energy product.

In practice: a plain N grade gets its number from maximum flux and modest coercivity and is good to 80 °C, while M, H, SH, UH, EH and AH trade away a little flux for a great deal more coercivity and climb to somewhere around 230 °C. If you want to see what that trade actually looks like, it's drawn out on Reading a B-H curve.

Gauss is a unit of flux density, and 10,000 of them make one tesla. The important thing to know is that a magnet does not have "a" gauss value, however often you see one advertised. The datasheet figure is remanence, which is the flux density inside the material — call it 14,500 gauss for N52. The number your hand-held gaussmeter reads at the surface is much lower and depends entirely on the shape of the part. And neither of those is what you'll measure an inch away. Anyone selling you a magnet on a single gauss number is either being loose with the term or counting on you not to ask which one it is.

Pull force is the force required to pull a magnet straight off a thick, flat, clean plate of mild steel, under laboratory conditions, with nothing in between. As a way of comparing two magnets to each other it's perfectly fine. As a prediction of what the thing will hold on your actual job it is optimistic to the point of fiction. Thin sheet instead of a thick plate, a coat of paint, a few thousandths of air gap, or a load hanging in shear rather than in straight tension will each take a serious bite out of it — figure roughly a third of rated pull once you're loading it sideways. And no, one pole is not stronger than the other. They're identical, and they always have been.

If you want a real number for a real part, K&J's pull force calculator is built on measured test data rather than theory, and it is the best free tool of its kind on the public internet. I don't work for them and I'm not going to pretend there's a better one just because it isn't mine.

#15Does stacking magnets make them stronger?

Yes, up to a point, and then emphatically no. Two identical discs stacked north-to-south behave like a single magnet of twice the thickness, and a thicker magnet reaches further and pulls harder at its face. But the returns fall off a cliff. Once the stack runs a few times longer than it is wide, the far end is simply too far away to contribute anything at the near end, and you are now buying magnets to hold up other magnets. If what you want is more pull at a surface, go wider, not taller.

Stacking side by side with the poles alternating does something entirely different, and it's the more interesting trick: it concentrates the field tight against the surface and makes it die off fast. That's why a refrigerator magnet strip holds well and still can't reach through the door. Do it deliberately, with the right geometry, and you have a Halbach array — which is how the magnetic charger on a phone manages a firm grip on the back of the case while putting almost nothing into the electronics an inch behind it. It's also, in cruder form, how a box of magnets gets onto an aeroplane.

#16Will magnets damage my phone, laptop, hard drive or credit cards?

I got my start in magnetics figuring out how to erase floppy disks and hard drives, so this is one I know super-well.

The warning used to be excellent advice, and it was about three things specifically. Cathode-ray tubes, where a magnet bends the electron beam and can permanently magnetize the steel shadow mask behind the glass. Floppy disks and tape, which store data as magnetic patterns that a decent field will happily rearrange for you. And the older, low-coercivity stripes on credit cards. Look around your desk: none of those three is still there.

A modern phone keeps its data in flash, which is electrical rather than magnetic and completely indifferent to a static field. The screen is LCD or OLED. The processor doesn't care. The one part that notices is the magnetometer — the compass — which will read nonsense while a magnet is near it and be perfectly fine the instant you take it away. That's why the magnets in phone cases and chargers are arranged to keep their field close to home, as above. Card stripes and hotel keys are mostly high-coercivity now and will shrug off a refrigerator magnet, though a large neodymium block pressed directly against one can still do real damage, and a magnetic wallet clasp riding against an older stripe all day is asking for it.

Spinning hard drives are tougher than their reputation, and there's a distinction here that almost nobody makes: stopping a drive from working and erasing what's on it are very different achievements. A strong magnet against the case can upset the head positioning or interfere with the drive's own motor magnets and make it misbehave, which certainly feels like destruction. Actually scrambling the bits on the platters takes a much stronger field, much closer to the media than the case will let you get. That's why degaussers are purpose-built machines with a real price tag — and why the data on a drive somebody "killed with a magnet" is very often still sitting there, waiting for anyone who cares enough to go and get it.

Rule of thumb, and I want to be clear that this is a rule of thumb and not a law of physics: keep anything large a hand's width from a spinning disc, a compass, or a magnetic stripe. Everything else in modern consumer electronics is fine.

#17Is it dangerous to be near strong magnets? Will a magnet pull on the iron in my blood?

I sure hope not, because I have been around a lot of the world's very strongest magnets!

A static magnetic field, at any strength you can buy, has no established effect on the human body. The iron in your blood is not the iron in a nail: it sits one atom at a time inside a hemoglobin molecule, with no neighbors to line up with, so blood simply isn't ferromagnetic. You can prove this to yourself by holding a powerful neo magnet in your hand. You will notice it DOESN'T leave a red patch where it pulled blood in. Or said differently, it didn't make you blush.

Your nerves run on ions moving through solution, not electrons moving through wire, and a steady field doesn't push those around either. This is why an MRI — which parks you inside a field twenty thousand times the Earth's for half an hour — is considered safe enough to repeat as often as your doctor likes. The odd sensations people report around the really big research magnets, the dizziness and the metallic taste, come from MOVING through the field, and they stop when you hold still. The exposure limits are set internationally and are public reading: 0.4 tesla for the general public and 2 tesla occupationally for head and torso. You will not approach either outside a laboratory or an MRI suite.

The real dangers of strong magnets are mechanical, and they are not theoretical. Two neodymium magnets closing on each other will crush whatever is in between, including a finger, and the material is brittle enough to shatter and throw sharp pieces while it does. Wear eye protection with anything over an inch, and I mean that. Swallowed magnets are a genuine surgical emergency, because two of them will find each other through a loop of bowel and pinch the wall between them — the CPSC has a standard and a body count behind this one, and small powerful magnets and small children do not belong in the same house. If you have a pacemaker or an implanted defibrillator, keep strong magnets away from your chest entirely: the device makers cite fields as low as 5 to 10 gauss at the implant as enough to put the device into a magnet mode, and a small neodymium disc clears that from several inches away. And metal implants in an MRI are a question for the radiologist, who asks precisely because some are fine and some absolutely are not.

Sleeping next to a magnet will do nothing to you. Sleeping next to a large one and rolling onto it is another matter.

#18Do magnetic bracelets or "magnet therapy" actually do anything?

No.

If you'd like that with a citation rather than a syllable: the meta-analysis of randomized trials in CMAJ pooled the evidence and found no effect on pain distinguishable from placebo.

#19Why is there a limit on shipping magnets by air?

Because aircraft still carry a magnetic compass as a backup instrument, and a pallet of strong magnets in the hold will swing it. The air freight rules define "magnetized material" as anything producing more than 0.00525 gauss at 15 feet — a wonderfully specific number that traces straight back to the distance from the cargo hold to the flight deck. Above that you're shipping declared dangerous goods, and above a higher threshold it doesn't fly at all.

How shippers get under the limit is worth knowing, because it's the same trick as the refrigerator magnet strip a few questions up: pack the magnets in alternating orientation so their fields largely cancel each other, then line the carton with steel to catch whatever's left. That's why a small box of neodymium arrives startlingly heavy. None of this applies to trucks and trains, which is why ground freight is cheaper and easier for anything substantial.

#20How are magnets made? And how was the very first magnet made, before there were magnets?

This one deserves more than a paragraph, so it has a page of its own: How magnets are made walks the whole route from ore to the final magnetizing pulse.

The short version for the impatient: a modern magnet is made as a powder, aligned in a field, pressed, sintered solid, machined, coated, and magnetized dead last. Until that final pulse it's a heavy gray block that does nothing at all.

As for the first magnet — nature made that one. Lodestone is magnetite that got magnetized somewhere along the way, most likely by a lightning strike, and somebody in antiquity noticed it pulling on iron. Stroke an iron needle with it and you have a compass. From Ørsted in 1820 onward we've used electricity for the job, and every magnet in your house was born that way.

#21What is a "rare earth" magnet? Are rare earths actually rare?

The rare earths are the fifteen lanthanides plus scandium and yttrium — a row of chemically similar metals near the bottom of the table. Two of them make magnets. Neodymium goes into neodymium iron boron, samarium into samarium cobalt. Two more, dysprosium and terbium, go in at small percentages to help neodymium magnets survive heat. Praseodymium rides along with neodymium in most commercial magnets, because separating the two completely is both difficult and pointless. A "regular" magnet, by contrast, is ferrite or alnico and has no rare earth in it whatsoever.

They aren't rare in the sense of not being anywhere in the world. Cerium is more abundant in the crust than copper, neodymium more abundant than lead, and there are deposits on every continent — the supply chain atlas shows where. The name dates to the eighteenth century, when the oxides were hard to find and much harder to tell apart. They are rare in the sense of being deposited in a concentration that makes them economical to go and get.

And even a good deposit is only the beginning. These elements occur together and behave almost identically in chemistry, which is the whole problem: pulling one out at magnet purity takes hundreds of stages of solvent extraction, running continuously, in a plant that costs real money and takes years to tune. The scarcity was never in the rock. It's in the concentration and the separation — and today that capability sits in a very small number of places.

If you want the actual numbers rather than my summary of them, the USGS publishes reserves and production by country every year, free, and it is the document most of the journalism on this subject is quietly rewriting.

#22Where are magnets made? Does the US make them?

Overwhelmingly in China — roughly nine in ten sintered neodymium magnets, and a comparable share of the refined rare-earth metal that feeds them. Japan is the other established producer and holds much of the original patent lineage. Germany has one serious maker. Everyone else — the United States, the rest of Europe, Korea, India, Vietnam — sits somewhere on the spectrum between restarting and starting. The supply chain atlas maps who actually does what, stage by stage, from ore to finished magnet — because "magnet company" covers everything from a genuine mine-to-magnet operation to a shop that buys blocks and grinds them to print. That distinction is the single most useful thing to hold onto when you read a press release.

The American history here is worth knowing, because it explains the present. The neodymium magnet was co-invented in the United States, and the first plants were built here in the 1980s. Over the next two decades essentially all of that production went away — not because the technology was lost, but because it could not compete on price. Rebuilding began in earnest after 2020 on the back of defense and EV demand, and there is now sintered neodymium coming out of Texas — MP Materials at Independence in Fort Worth, and Noveon Magnetics in San Marcos — with more capacity under construction. Domestic output is still a small fraction of what American motor builders consume and will be for some years yet. But the answer to "does the US make them" is, for the first time in a long while, yes.

You might expect ferrite and alnico to be the exception, since neither depends on rare earths at all. They aren't. Both are now overwhelmingly Chinese as well, for a duller reason than the rare-earth story: they're cheap, heavy, energy-intensive, and sold almost entirely on price, which is precisely the competition that hollowed out everything else. There is still some Western production. But if you're reaching for a rare-earth-free magnet specifically as a way around a Chinese supply chain, check where the part was actually pressed before you count on it.

#23How do magnets make electricity? Why is there a magnet in every speaker and every motor?

Electricity and magnetism are two faces of the same thing, and once you have that, the rest is arrangement. A current in a wire makes a field around it. A field that CHANGES near a wire drives a current through it — that second one is Faraday's law, and it is arguably the most economically important sentence in physics. Everything from a power station to an earbud is one of those two statements, built cleverly.

A generator is the second one. Spin a magnet past coils, or coils past a magnet, and current flows. Every turbine on the grid — steam, gas, wind, hydro — ends in one of these, which means the entire business of generating electricity is really the business of finding something to turn a shaft.

A motor is the first one, run in reverse. Push current through a coil sitting in a magnet's field and the coil gets shoved sideways by the Lorentz force. Arrange the shoving to go round in a circle and you have rotation. There are a great many ways to arrange it, and they're drawn out on how electric motors work.

A speaker is a motor that doesn't rotate. The coil is glued to the cone and hangs in the gap of a ring magnet, the music is a current that wiggles the coil back and forth, and the cone wiggles the air. Complicated sound is just a complicated wiggle — there's nothing more to it, which is why a speaker built in 1925 and one built last week work in exactly the same way.

The permanent magnet's job in all of these is to supply the field for nothing. You can do it with a second coil instead, and early motors did, but then you are paying for that field in current, heat and copper for as long as the machine runs. A magnet gives you the same field and never asks for anything again. That's the whole reason nearly every small motor and every loudspeaker on earth has one in it.

#24Recycling plants use magnets to sort aluminum. How, if aluminum isn't magnetic?

With a magnet that MOVES. I love eddy currents, and if you've never watched an eddy-current separator throwing cans off the end of a conveyor, go and watch that before you read the rest of this.

A stationary magnet does nothing to aluminum. But a rapidly changing field induces currents in any conductor — eddy currents — and those currents raise a field of their own, which pushes back against the field that created them. So: the waste stream rides a belt over a drum with a magnet rotor spinning inside it a few thousand times a minute. The steel has already been lifted out upstream by an ordinary magnet, so what arrives at the drum is aluminum mixed in with glass, paper and plastic. The aluminum sees a violently changing field, generates currents, gets shoved, and flies forward off the end of the belt. Everything non-conducting simply drops where gravity says it should. Two streams, no sorting, and nothing with moving parts ever touches the material. The machine that does it is called an eddy current separator, and there are thousands of them working right now.

The same effect heats the pan on an induction cooktop, stops a roller coaster without touching it, and lets a metal detector find a ring in the sand. It's one of the more useful pieces of physics ever put to work, and it's the answer any time somebody tells you a magnet is doing something to a material that "isn't magnetic."

#25How do I separate two magnets stuck together? Can I cut, drill or glue a neodymium magnet?

Slide, don't pull. Two magnets face to face are at their strongest in exactly the direction you're trying to pull and much weaker sideways, so push one across the other until it overhangs the edge, then lever it off. For anything bigger than a coin, do this at the edge of a bench with the lower magnet held down, and think about where both of them are going to go when they finally let go, because they'll go there fast. Store them with a spacer between them or a steel keeper across the poles, and never tip a bag of them out onto a workbench unless you enjoy that sort of thing. And if there are children in the house, read the swallowing hazard before you read anything else on this page.

Don't cut or drill them. Sintered neodymium is as brittle as a ceramic and harder than most steels: the bit skates, the magnet chips, and the heat you generate demagnetizes the material right where you're working. The more serious problem is the swarf. Fine neodymium-iron powder is reactive enough to heat up and light itself, and a metal fire in a home shop is not something you want to meet. The factory does all of this BEFORE the magnet is magnetized, with diamond tooling under flood coolant — which is why buying the shape you need is always cheaper than making it, and why the process page puts machining where it does.

The topic of bonding has been the focus of many, many years of my career in the industry and I could write multiple books about it. The single most important thing in gluing magnets is surface prep — get a clean, rough surface and it works. Scuff the nickel, get the oils off it, and use a two-part epoxy or a gel cyanoacrylate. For anything structural, buy magnets with a countersunk hole and put a screw through them. And know where the joint will actually fail: glue holds a magnet to wood or plastic beautifully. It's the magnet-to-steel and magnet-to-magnet joints that let go, because the magnet is pulling itself off a thin glue line toward that steel every second of its life.