Will 2 magnets lose energy while repelling each other?

[IATF]

It is now a one month completed for my research on magnets all way around on internet. During this session, I got to know that domains don't lose their energy until they are completely destroyed. So I am very much keen on the question that can magnets produce force without losing any energy?

 

[russ_watters]

A month? Really?

Force isn't energy, so there is no reason exerting a force should require expense of energy.

 

[Drakkith]

So I am very much keen on the question that can magnets produce force without losing any energy?

The fundamental forces (of which magnetism is part of one of them) do not require that energy be expended in order to exert themselves in static situations like this. A book on a table is repelled by the atoms in the table, but it loses no energy over time.

 

[Charles Link]

The literature on this question=standard textbook material and/or laboratory experiments appears to be something that is not easily found on-line. One thing that would seem to be the case is if two like poles are brought in close proximity that the magnetization would be reduced somewhat by the strong field in the opposite direction being superimposed on the strong magnetic field and strong magnetization inside the other magnet. When the magnet is removed, does the permanent magnet(s) completely recover all of its magnetization? I would think different types of magnets might give different results, but I have yet to find a good book on magnetism that answers these types of questions in a simple manner that can be readily understood.

 

[jerromyjon]

One thing that would seem to be the case is if two like poles are brought in close proximity that the magnetization would be reduced somewhat by the strong field in the opposite direction being superimposed on the strong magnetic field and strong magnetization inside the other magnet.

Isn't that the reason magnets are supposed to be stored in a certain arrangement, to avoid "weakening" them?

It does help to understand that every magnetic atom has some relative position, when they are randomly opposed equally there is no net magnetic field generated... it's not like the individual atoms lose energy, ever.

 

[Charles Link]

Isn't that the reason magnets are supposed to be stored in a certain arrangement, to avoid "weakening" them?

It does help to understand that every magnetic atom has some relative position, when they are randomly opposed equally there is no net magnetic field generated... it's not like the individual atoms lose energy, ever.

Mostly for the OP: The energy equations involved in these processes is also something that doesn't seem to be spelled out in simple form in any elementary literature that I have seen=perhaps because the complete energetic gets somewhat complicated. In more advanced E&M coursework, they teach what the energy density is for a magnetic field. In the case of the permanent magnet it gets more complex though, and if I'm not mistaken, the permanent magnet is actually in a state of lower energy than the unmagnetized state. The magnetized material (magnetic moments) in its own magnetic field, basically generated from bound magnetic surface currents from the magnetization, results in a lower energy state than the unmagnetized state. Because it is a lower energy state, the permanent magnet state can be extremely stable in many cases, but bringing magnets together with like poles facing each other could potentially disrupt the permanent magnetized states. $\\$ Instinctively, one would conclude, correctly so, that there must be some energy of some kind associated with the magnetic field. The complete dynamics of that in the case of the permanent magnet can get somewhat complex. What further complicates the matter is even in the less than fully magnetized state, there are microscopic domains that individually can be completely magnetized, but they can point in somewhat random directions in non fully magnetized material. I don't want to get "pinned" for a personal theory which is not allowed according to Physics Forums rules, but I believe it is some complicated energetics of this kind that makes the difference in whether a magnetic material becomes a permanent magnet, as opposed to materials like soft iron that make very good electromagnets, but become unmagnetized once the external magnetic field is removed.

 

[IATF]

How much complex is Quantum Mechanics! If my friend and me try to push one another, we are going to lose all of our relish within five minutes; but that's not the case with magnets. Don't you think we can use this never-ending force in generating energy?

 

[Drakkith]

How much complex is Quantum Mechanics!

It requires about 3-4 years of intense study at a university before you can even begin to study QM in a way to gain a good understanding. You need to learn many different mathematical topics and you need to learn classical physics first, which takes several years.

If my friend and me try to push one another, we are going to lose all of our relish within a minute; but that's not the case with magnets.

I hope you don't lose all of your relish, that would be messy.

Anyways, the human body is an imperfect machine and exerting a force with your muscle causes the tissue fibers to alternately contract and relax. This stretches them out, using energy which is eventually lost as heat. So while work is being performed on your muscles at the cellular level, no work is being performed on your bodies as a whole since neither of you are moving. Magnets do not use muscles and require no energy to exert their force on one another. Similarly, two electrically charged particles require no energy to exert a force on each other, nor does a rock sitting on the ground require energy to exert a force on the Earth.

Don't you think we can use this never-ending force in generating energy.

No. Energy is the potential to do work, and work is the application of a force over a distance. Since your magnets aren't moving, no energy is being generated or expended. And once you allow the magnets to move relative to each other, the force is no longer "neverending". You can generate energy by allowing the magnets to separate, which reduces the force as the magnets move apart, or you can use energy to push the magnets closer together, in which case the force increases.

I really have a brilliant idea for its progress, but that is beyond the scope of this website.

Yes it is, as we do not allow personal theories. Moreover, we don't allow them for the exact reason shown here. You don't know anything about physics beyond some very basic concepts yet you think you've discovered some amazing new idea. Trust me. You haven't. It sucks to hear this, but it's true. I've had several ideas get demolished when I learned some new fact that I hadn't learned before (including one that I had to let go of just the other day).

 

[IATF]

Sir Drakkith, Brillant discoveries are only a result of working on impossible, and I'm doing so.

 

[IATF]

Will a magnet still retain its energy if it is used to magnetize another piece of metal with its magnetic field?

 

[Drakkith]

Sir Drakkith, Brillant discoveries are only a result of working on impossible, and I'm doing so.

Nonsense. Brilliant discoveries are a result of working at the forefront of physics, which means you need to know a good portion of the existing physics before you can push past them to new theories beyond. No brilliant discovery ever came from working in ignorance or by ignoring existing theories. When Einstein developed his theory of Special Relativity he did so by knowing exactly where the weaknesses in existing physics lay and developing a theory formulated to address and explain those weaknesses. He did not ignore anything in physics at the time.

 

[CWatters]

So I am very much keen on the question that can magnets produce force without losing any energy?

In general yes. The force a magnet produces does not "use up" energy stored in the magnet. Magnets are not a source of energy and cannot be used to make a permanent magnet motor (despite what many youtube videos claim).

Excess heat, vibration and stray electromagnetic fields can wear out a magnet. Ferrite magnets are quite robust but the stronger rare Earth magnets are more sensitive to heat. This reference claim that...

http://www.sciencefocus.com/qa/do-magnets-wear-out

a modern samarium-cobalt magnet takes around 700 years to lose half its strength.

 

[tech99]

Magnets are not a source of energy

I do notice, however, that an electromagnet stores energy in its magnetic field, and we can easily extract it by switching off the current.

 

[my2cts]

Sir Drakkith, Brillant discoveries are only a result of working on impossible, and I'm doing so.

Working on the impossible seems impossible to me. Do you perhaps mean :
“The only way of discovering the limits of the possible is to venture a little way past them into the impossible.”
― Arthur C. Clarke

 

[my2cts]

Will a magnet still retain its energy if it is used to magnetize another piece of metal with its magnetic field?

An analysis of exactly how "a magnet ... is used to magnetize another piece of metal" will reveal the answer to you.
Energy is required to magnetize a material, that much is certain.

 

[CWatters]

I do notice, however, that an electromagnet stores energy in its magnetic field, and we can easily extract it by switching off the current.

Yes I should have been clear ideas referring to permanent magnets.

 

[darth boozer]

Magnets do not produce energy by themselves. When repelling, they act more like springs. Push on a spring to compress it and you supply the energy. Release the spring and the energy stored in the spring is returned as kinetic energy, minus the energy lost as heat.

 

[Merlin3189]

Will a magnet still retain its energy if it is used to magnetize another piece of metal with its magnetic field?

You can use a magnet to magnetise another piece of metal as often as you like and your original magnet will be as strong as if you had not done so.*

Any energy needed to magnetise the metal comes from you or other outside agency. Your magnet is not supplying any energy to the metal, so it is not losing any itself.
Magnetism is not like a material substance nor like heat (a form of energy). The original magnet does not have a quantity of magnetism which it gives to the pieces of metal, so it does not lose any of its own magnetism in the process.*

Contrary to some earlier comments, I would say magnets can be used to generate energy - provided by generate we mean convert energy from one form to another. I have three generators built with permanent magnets, one on my bike and two on torches. They all work the same way: when i put energy in by turning them, the magnets inside move and generate an electric voltage in a coil. This can then make a bulb or LED light up. The magnets will work indefinitely* in these machines and do not use up any energy of their own: they take the energy I supply as movement and pass it on to electrons to give the electric current.

* As others have said, permanent magnets can gradually lose their magnetic strength over time, even if you don't use them. Using them may sometimes (not always) increase this loss, because you may incidentally increase the amount of thermal agitation which allows magnets to lose their permanent magnetism.

If you ask clear questions using words that you understand, you will find out more than by asking vague questions or using words you do not understand (I'm thinking about energy, force and domain.).

 

[Drakkith]

Contrary to some earlier comments, I would say magnets can be used to generate energy - provided by generate we mean convert energy from one form to another. I have three generators built with permanent magnets, one on my bike and two on torches. They all work the same way: when i put energy in by turning them, the magnets inside move and generate an electric voltage in a coil. This can then make a bulb or LED light up. The magnets will work indefinitely* in these machines and do not use up any energy of their own: they take the energy I supply as movement and pass it on to electrons to give the electric current.

No one is saying that permanent magnets aren't used to generate/convert energy. We are saying that permanent magnets, by themselves with no external sources to move them, are not a continual source of energy. You can get energy out of them once, when you let them come together or fly apart, but that's it.

 

[Nugatory]

It requires about 3-4 years of intense study at a university before you can even begin to study QM in a way to gain a good understanding.

It's not quite that dire. If you've studied single-variable differential and integral calculus before you start college (not at all unusual) it is quite reasonable to start in on QM in the second semester of the second year.

What is challenging is that QM will be the first time that you have to rely on the mathematical formalism instead of your intuition about the world works.

 

[my2cts]

How much complex is Quantum Mechanics! If my friend and me try to push one another, we are going to lose all of our relish within five minutes; but that's not the case with magnets. Don't you think we can use this never-ending force in generating energy?

The magnetic field is by definition the part of the force that does not perform work.
When work is involved you need to consider the electric field because your magnet is moving.

 

[Garfunkel]

A month? Really?

Force isn't energy, so there is no reason exerting a force should require expense of energy.

But force can do work, and energy is the ability to do work isn't it? Doesn't force come from energy?

 

[russ_watters]

But force can do work...

Yes. "Can". But they don't have to.

and energy is the ability to do work isn't it?

Yes.

Doesn't force come from energy?

No.