Why do magnets not wear out?

Concave wrote:

The best super-simplified explanation for magnets that I've heard is to imagine them as springs. A typical car with spring suspension is compressing the springs, but the springs aren't expending any energy to hold the car up.

Or something.

but they are exerting a force, just try holding a compressed spring down.you will have to work I it. And if gravity were to suddenly fail the car would suddenly get higher.

Nosferatu wrote:
Concave wrote:

The best super-simplified explanation for magnets that I've heard is to imagine them as springs. A typical car with spring suspension is compressing the springs, but the springs aren't expending any energy to hold the car up.

Or something.

but they are exerting a force, just try holding a compressed spring down.you will have to work I it. And if gravity were to suddenly fail the car would suddenly get higher.

I think people associate exertion of force with consumption of energy because that's how the human body works, our muscles require energy to contract. The force you're exerting does not necessarily do work though.

That's not true. Most molecules on the Earth's surface are atoms being combined and recombined in various forms and states continuously, most obviously by the process we refer to as "life."

Okay, to be more precise, non-radioactive atoms don't wear out. Molecules can break apart and be made into new molecules, but their component parts keep working for the next closest thing to forever. I think there's some phenomenon where atoms disappear over unimaginably huge periods of time, but the Universe will long since have reached steady state (aka, total death) long before that happens.

I don't think you have the science to support such a statement, and I'd welcome the opportunity to discuss that with you in a dedicated thread.

Note: when I say work, I mean the physics unit, not a colloquial definition.

LeapingGnome wrote:

Why do magnets not wear out?

They can. It takes a while. In a nonmagnetic environment, ferromagnets, (stable magnets based on iron) will wear out if you do a bunch of stuff to them. This may or may not happen outside the lab, ie real world conditions, depending on what're you doing, how intensely you're doing it compared to how intensely the Earth's magnetic field is doing its stuff, and so forth.

LeapingGnome wrote:

It would seem if an object can exert force on another object perpetually wouldn't that violate the law of conservation of energy? I mean a magnet will hold an iron bar to it basically forever, where does it get the energy from to do this and how come the energy does not run out?

Work = Energy = Force * Distance for constant force. Example: Your iron bar is in proximity to a magnet. It isn't moving. The magnetic force is 1 gauss. Force = 1G, Distance= 0m, Work = 1*0= 0. No work is being done, so neglecting everything else the magnet will never wear out.

Note: The magnet will induce a magnetic dipole in the iron bar, effectively turning it into a magnet too, which is how the two interact. This means all the iron atoms will get shifted around from loosely chaotic to more ordered. (Think a random crowd adjusting to stand in rows, facing the same direction.) This takes work.

Now, let's suppose you take that iron bar, and you start wiggling it. The energy you put into the iron bar wiggling it will cover some of the energy costs of the movement as the iron polarizes and depolarizes. The earth's magnetic field may also be inducing polarization, as may nearby electrical currents, stray voltages, etc. All of these things may be doing work.

An important note is that some kinds of stuff like ferromagnets will naturally form magnets in an external field. Just because of the way they bond, how the electron clouds are shaped, how all that interacts with the ambient fields, etc, results in a somewhat ordered state being being the ground state. This presumes the ambient field is doing work. In this case, the induced magnet (the original ferromagnet we were talking about) will remain indefinitely polarized provided A) we don't disturb it too much(We're not melting it, beating it with a jackhammer, inducing high currents, etc.) and B) the external field (the Earth with smaller contributions from the Sun) keeps working to put things back in place. The Earth and the Sun may be doing all the work to restore the magnet, and in general, they're keeping it from wearing out. This is the most direct answer to the OPs question but is a vast oversimplification.

Miashara wrote:

B) the external field (the Earth with smaller contributions from the Sun) keeps working to put things back in place. The Earth and the Sun may be doing all the work to restore the magnet, and in general, they're keeping it from wearing out. This is the most direct answer to the OPs question but is a vast oversimplification.

I don't think this is true in general. Most of the time the earth's magnetic field won't be aligned with a magnet's own field, so the earth's field won't be restoring or increasing the magnetization in the original direction.

LarryC wrote:

I don't think you have the science to support such a statement, and I'd welcome the opportunity to discuss that with you in a dedicated thread.

As requested.

Hypatian wrote:

Heh. Feynman wins, of course. And to build on that: fundamental forces can't be explained because we cannot break them down into simpler things--that's why we consider them fundamental. If we discover some deeper insight (for example, when we learned that electrical and magnetic forces were very much the same, or when we learned that they also unify with the weak nuclear force), then it becomes possible to go just a little bit deeper. But then, we've simply moved the understanding one level further down.

So if I'm reading this right you're saying that Insane Clown Posse has a point? :p

Yeah, I think they always did. I don't know why people scorn them so much. We really don't understand how magnets work, they just do.

Like with gravity, we can describe what's going on down to a gnat's eyebrow, but we don't actually understand the root cause.

Malor wrote:

Yeah, I think they always did. I don't know why people scorn them so much. We really don't understand how magnets work, they just do.

Like with gravity, we can describe what's going on down to a gnat's eyebrow, but we don't actually understand the root cause.

Some context on who you are supporting.

The question 'How do magnets work?' is actually pretty simple. It induces magnetic dipoles in other materials, causing them to be magnets too. Then magnetic interactions take place.

The question 'Why do magnets work?' is nearly impossible to answer unless you allow a handwave of 'what is charge?' Magnetism itself has been fairly clearly linked to relativistic effects on electrical potentials.

The OCP asked the first question, and admittedly subtle difference between them should not be ignored.

Kyrieee: that doesn't seem to make much of a difference. I'll get all my ducks in a row and go into it.

Then magnetic interactions take place.

How?

Malor wrote:
Then magnetic interactions take place.

How?

Short version:
F= q(E+VxB)

That's a description of the effect. How does the effect actually happen? What carries the force? How does it get from object A to object B?

Malor wrote:

That's a description of the effect. How does the effect actually happen? What carries the force? How does it get from object A to object B?

Short version:
F=cking(Miracle)

Miashara wrote:
Malor wrote:
Then magnetic interactions take place.

How?

Short version:
F= q(E+VxB)

Longer version:
Eff equals lowercase kyoo times leftbracket uppercase ee plus uppercase vee times uppercase bee rightbracket.

Hope that clears it up.

Spoiler:

I'm sorry.

Gravey wrote:
Malor wrote:

That's a description of the effect. How does the effect actually happen? What carries the force? How does it get from object A to object B?

Short version:
F=cking(Miracle)

Or:
A wizard did it.

So... would now be a good time for me to say "I put on my robe and wizard hat"?

Post-meme, it is never a good time to put on your robe and wizard hat. Even if you're a wizard.

If you're looking for a succinct recap of Freshman E&M, Amazon has the Feynman lectures hardcover for $100, and you can get them a lot cheaper than that by looking. It's one of the clearest, most succinct summations of introductory physics available and is written very conversationally. Little math is required.

I'm not going to recap it here.

Aries wrote:

Longer version:
Eff equals lowercase kyoo times leftbracket uppercase ee plus uppercase vee times uppercase bee rightbracket.

Hope that clears it up.

Pedantic: Actually, that's a cross product. So ...uppercase vee cross uppercase bee... Sorry. /pedantic

Miashara wrote:
Aries wrote:

Longer version:
Eff equals lowercase kyoo times leftbracket uppercase ee plus uppercase vee times uppercase bee rightbracket.

Hope that clears it up.

Pedantic: Actually, that's a cross product. So ...uppercase vee cross uppercase bee... Sorry. /pedantic

Hat-tip to you, good sir!

Malor wrote:

That's a description of the effect. How does the effect actually happen? What carries the force? How does it get from object A to object B?

Virtual photons, in the case of electromagnetism.
Still, that's also just a description, albeit a more fundamental one. But that's what physics is though, it's finding theories that accurately predict repeated experiments. If you ask "why?" enough times you eventually get philosophy. You can't explain something with nothing, you always need a starting point, some axiom, in order to conduct a logical or mathematical argument.

Photon goes in. Photon goes out. Never a miscommunication.

You can't explain that.

Even that page says that virtual photons are an approximation that doesn't actually work a lot of the time.

Why did it take so long to invent this!?

Magnetic Soap!

Where are the cats, again?

Why does gravity not wear out?

Why does Certis' patience not wear out?

Quintin_Stone wrote:

Why does gravity not wear out?

The problem with gravity, like all things, is that it is demonstrably a fad.....and like all fads it just keeps coming back and back and back again!

But, if it keeps coming back, doesn't that mean it's not a fad, by definition?