I was playing around with two magnets when I realized that I don’t have a clue where the repelling and attracting energy comes from. When you place two magnets close to each other they’ll repel (if they’re placed south-to-south or north-to-north) or attract (if they’re placed north-to-south) each other. What energy causes the magnets to move as they slide across the table towards each other? What energy causes the magnets to resist my attempts to push them together?
More importantly, where is this energy stored? It cannot come from nowhere and there cannot be an infinite amount of it, so sooner or later every magnet must run dry, right? Why haven’t I ever heard of or encountered an “empty” magnet?
I feel silly even having to ask this, but I honestly don’t know.
Basically, it seems as if the atomic structure of magnetic element emulates an electromagnet. In other words, each iron atom is a tiny little electromagnet. When all the little tiny electromagnets’ poles line up, the whole chunk of iron turns into a magnet. Electromagnetism is one of the four basic forces.
So, to answer your questions, the energy is “stored” in the movement of the electrons in the individual atoms, and thus, as long as the electrons keep doing whatever it is they do, the magnet won’t “run dry.”
(That last part referring to the magnetism of an individual atom. The magnetism of a chunk of a particular metal can be made to go away by making some of the groups of atoms “point” one way, and some the other, thus “cancelling out” the magnetism of the entire chunk. You can do this by heating the metal, pounding it with a hammer, or stroking it randomly with another magnet.)
To understand it deeper, I think you’d have to get into Quantum Mechanics and Maxwell’s equations.
I know how magnets work. I just don’t get where they get their power from.
But the electrons can’t keep doing whatever it is they do forever. If there’s no energy input, they must be doing it slower and slower all the time until they don’t do it at all.
They get their power from the electrons whizzing around. Where the electrons get their power from, I don’t know. That, I’d imagine, is where the quantum mechanics comes in.
And I guess maybe they can’t do it FOREVER, but they’ve been doing it since the beginning of the Universe and aren’t likely to stop anytime soon. I suppose they might be slowing down. I wonder how we’d detect that.
which would be operation of the second law of thermodynamics (I think it’s the second) acting out, but it would take longer than you cloud notice with the magnets.
Meanwhile, consider the embarrassing accelerating expansion of the universe.
If you want to worry about kookie perpetual motion schemes that can’t possibly work, I urge you to solve that one
So magnets will become progressively weaker and eventually, one day, run dry? It’s just that it’s going to take a really, really, really, REALLY long time? And also, once that happens, magnets not working will be the least of our problems.
Which will eventually stop accelerating, right? Same way a bullet still accelerates after leaving the gun barrel but stops doing so after a while.
It all has to do with atomic alignment. Each atom is essentially a tiny magnet with a North and a South pole. When all the atoms are aligned, all those South poles face one way and the North poles face the other way. The magnetic force of each atom is combined and the material has magnetic properties.
If the atoms point at random directions, then the magnetic forces cancel each other out and the material has no magnetic properties.
If you touch a magnet on a piece of iron and remove the magnet, the piece of iron will behave as a magnet for a little while. That is because the atoms in that piece of iron were aligned with those of the magnet. As time passes, atoms lose their alignment and assume random positions again. Hardened iron (steel) doesn’t lose alignment that easily. I don’t know about natural magnets (FeO4 if I’m not mistaken), I think they never lose their alignment.
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Sure. I’ve seen “dead” magnets lots of times. Haven’t you ever had one that keeps on falling of your fridge for no reason? You can’t get around the Law of Conservation of Energy - each time a magnet exerts force, it loses a bit of its charge. Home magnets just don’t do much work so the charge can last for a very long time.
I imagine those magnets had lost thier charge NOT because the individual atoms had lost their charge, but because the atoms, for one of the reasons I listed above, weren’t lined up properly. It probably could have been fixed by stroking another magnet across it several times in the same direction.
Magnets do lose their power, and it happens every day. Dog80 has already expleined it in easy terms.
But if I find a way to destablise the magnet, it’ll lose it’s power.
When you heat a magnet up it loses some of it’s power. as it cools down it regains it. but if I heat it up beyond a temperature known as the Curie temperature (Curie Temp of iron = 1043K), then the magent will lose all of it’s power, even when it cools down to room temp.
Another way is to apply an opposite magnetic field.
If I have 2 magnets, one much more powerful than the other, and I push them together so that they repel each other, the weaker magnet will become demagnetized much faster than it normally would.
I think we are getting confused with force and energy. A compressed spring can exert a force forever until the universe ends. No energy is expended or taken in until the spring expands or contracts. Where did the energy stored in the spring comes from? From the person who pushed it in. Where is it stored? Well ultimately if one goes deep enough, in the strained electric fields of the atoms making up the spring.
Two magnets can in theory exert a force on each other forever. Where did the stored energy come from? From the guy who pushed them together (NN alignment) or pulled them apart (NS alignment). Where is the energy stored? In the electron spin repulsion of the atoms.
Note that permanent magnets can lose strength just like a spring can, in the former case from magnetic domains losing alignment. This is a separate effect from above and varies from material to material.