I’ve read somewhere that magnets dont do work so they dont use energy, but then how come they can move metallic objects? where is that coming from?
In: Physics
Whoever said magnets do not do work is wrong. Magnets can totally do work. Usually, you need to couple this with other kinds of motion to make it useful (a magnet just sitting there isn’t going to be moving mountains!), but it is totally possible for magnets to do work.
That’s one of the ways magnets can wear out, actually. By doing work against an opposing magnetic field, some of the atoms inside the magnet (which are what give the magnet its magnetic field!) get pushed, so they no longer nicely line up with all of their neighbors. This effect is very small in most cases, so it takes a lot of wear to wear out a magnet–but no so-called “permanent” magnet actually stays permanently magnetic forever.
ELI5: Replace magnets with a rubber band…. You have to pull it back first, then it snaps back together.
magnets and rubber bands at rest dont have energy, separate them and its potential energy waiting to snap.
This might be the first question I can answer, so here goes:
You have a magnet and an iron ball, we’ll call it a marble. You secure your magnet to one end of a frictionless table, while placing the marble at the other end. The marble, will slowly start rolling towards the magnet, slowly accelerating, until it finally smashes into the magnet and they are now joined. How did this happen? Well as soon as you placed the marble down on the table you started a process of turning all the potential energy stored in the marble into kinect energy. The energy to move the marble was always there, just in a form you couldn’t directly observe until you released the ball. This same principle of turning potential into kinect energy can be observed by throwing a ball in the air, where instead of magnetism, it is gravity that causes the ball to eventually return to earth. (This process is actually kinect to potential to kinect, but same principles)
It’s kind of weird. I don’t think there’s a way to fully explain it because Physics only knows so far.
Magnets work because they have a “charge”. Atoms like to have a certain number of electrons. Magnets are made of a material that either has too many or not enough of those electrons. When something is “charged” like that, it will attract other atoms to try and form combinations of atoms that have the “right” number of electrons. Actually a TON of chemistry is about just learning the “rules” atoms tend to follow so you can predict what happens when you mix different ones together.
So the reasons magnets “pull” or “push” things has to do with atoms REALLY wanting to have the “right” number of electrons.
This is the part that’s weird: this doesn’t “use” energy. It’s just how the universe works. We might have to spend energy to “charge” the magnet by changing how many electrons its atoms have. The pushing and pulling may do work by changing the kinetic or potential energy that other things have. But we don’t really have to do things to the magnet to make it do that. There’s no “battery” or other way to “power” it. It just is, and this concept of atoms with charges pushing or pulling each other is just a thing Physics says happens with no explanation.
COULD there be some reasoning? Sure, we’re always trying to understand it. If we could figure out WHY this “just is”, maybe we could figure out ways to make it happen with other materials. In theory that could help us have free energy or maybe some other crazy things. But so far we haven’t had much success figuring out the WHY.
And it’s not much use for free energy on its own. Yes, I can use a magnet in my hand to push things. But those things push against the magnet, which pushes against my hand, which causes forces through my body to push against the ground through my feet. In other words, the magnet doesn’t do any work, my body does work. We know ways to use magnets to do interesting things, but we usually have to use energy for something to MOVE the magnet to make that happen.
(Also: yes, I can lift heavy objects with magnets on the ground. But remember, atoms REALLY like having the “right” number of electrons. To make a VERY strong magnet, I need atoms with a VERY wrong number of electrons. The universe hates this so much you can’t just make a piece of metal be this “wrong”. The only way to make SUPER strong magnets is… electromagnets. Those do work to constantly MOVE electrons through a material to generate a field. It’s kind of like I’m constantly spending energy to make the atom “wrong”, then the universe is “fixing” it, then I spend more energy making it “wrong” again. These super strong magnets can’t stay super strong because the universe very quickly balances things back out by redistributing electrons UNLESS I’m spending energy to unbalance it again. (In fact, it’s not really changing between “right” and “wrong”, it’s more like I’m “pushing” or “pulling” electrons into the atoms, and the universe is “pulling” or “pushing” back, and I have to work harder than the universe to keep the magnetic field active.))
They do. Magnetic fields produced by finite loops of current don’t do work. Intrinsecal magnetic fields (electron spin) do. The saying “magnetic fields do no work” comes from the fact classical electrodynamics doesn’t contemplate spin.
For a long rant about the same thing, check [this video](https://youtu.be/fHG7qVNvR7w)
doesn’t physics say that everything is made of energy ??
Do magnets “run out” of magnetism?
What people don’t realize about fixed magnetics (and why they can’t produce perpetual motion) is that they actually lose their magnetism over time.
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