Why is a magnetic field of a permanent magnet not considered energy?

[Victheromanian]

1 law cant create energy. ok but you can give energy to a ferromagnetic and magnetize it. then magnetize as many ferromagnetic material as you want, and not diminish the magnetic field of the 1st one you had. I don't understand how no loss and how that is not considered braking the 1st rule

[swansont]

How are you magnetizing the other magnets? Somewhere, work will be involved, or some other energy transfer.

The magnetic field does contain energy, and would diminish if no energy is added to the system.

[Charles 3781]

1 hour ago, swansont said:

How are you magnetizing the other magnets? Somewhere, work will be involved, or some other energy transfer.

The magnetic field does contain energy, and would diminish if no energy is added to the system.

When you  say  "How are you magnetising the other magnets",  I think you have in mind rubbing a magnet against a bit of non-magnetised iron..  Thereby turning the second bit of iron into a magnet.  This can be plausibly explained, by a transfer of kinetic energy from the "rubbing" between the two bits of iron.

 

 

[Victheromanian]

i have a vise and i stick both of my big 2700 Gauss each on either side and then put a small 500 Gauss in the middle and close the vise . did this for 200 times and the magnetic reading didn't change. how can that be i asked k&j and they said that this is normal how can that not brake the 1 law?

[Charles 3781]

10 minutes ago, Victheromanian said:

i have a vise and i stick both of my big 2700 Gauss each on either side and then put a small 500 Gauss in the middle and close the vise . did this for 200 times and the magnetic reading didn't change. how can that be i asked k&j and they said that this is normal how can that not brake the 1 law?

Vic,  when you changed the spatial position between the magnets and your visa, you  had to expend kinetic energy -  by employing physical movement -  and this movement was converted into electromagnetic energy, which restored the steady state of the magnetism.

[Victheromanian]

i put energy to get them far apart but the magnets pull them-self together by they own. i think it almost equals out. but that is what you think?  the pulling away of the magnets or them pulling each other together converts into electromagnetic energy ? 

[Charles 3781]

11 minutes ago, Victheromanian said:

i put energy to get them far apart but the magnets pull them-self together by they own. i think it almost equals out. but that is what you think?  the pulling away of the magnets or them pulling each other together converts into electromagnetic energy ? 

Yes it might be.  To pull the magnets apart, you have to use physical force, and this force is equalised when the magnets come together again, so the overall expenditure of force is balanced.

[iNow]

53 minutes ago, Charles 3781 said:

Yes it might be.  To pull the magnets apart, you have to use physical force, and this force is equalised when the magnets come together again, so the overall expenditure of force is balanced.

Bullshit

[J.C.MacSwell]

8 minutes ago, iNow said:

Bullshit

?

[Charles 3781]

29 minutes ago, iNow said:

Bullshit

So how do magnets retain their pulling force, without any input of kinetic energy?  I mean suppose you said: 

 "I've invented a new fuel-less car.  It's got magnets  which will pull it towards your destination.  Then when  you want to go home,  you turn the car round, and the reversed polarity of the magnets will repel it back to your starting point."

Without the car using any petrol during your travels.  Is that credible?

Edited October 11, 2020 by Charles 3781

[joigus]

Magnets do have energy density proportional to the field squared. Maybe the bell that's ringing in your head is that a magnetic field doesn't do work on a moving charged particle.

If that's the case, it's true that a magnetic field doesn't do work on a charged particle with velocity v, because the force is perpendicular to the displacement.

Magnets acting on each other also have energy.

[swansont]

1 hour ago, J.C.MacSwell said:

?

Force is not a conserved quantity. If he had said energy, then ideally, that would be true.

2 hours ago, Victheromanian said:

i have a vise and i stick both of my big 2700 Gauss each on either side and then put a small 500 Gauss in the middle and close the vise . did this for 200 times and the magnetic reading didn't change. how can that be i asked k&j and they said that this is normal how can that not brake the 1 law?

You’re going to have to do a better job of describing what you’re doing. Earlier you described magnetizing something, and now you’re putting magnets next to each other.

When you put a magnet near a ferromagnetic material, work is done. You don’t appear to be acknowledging this. Energy doesn’t have to come from the magnet if you’re doing work.

[Charles 3781]

1 hour ago, joigus said:

Magnets do have energy density proportional to the field squared. Maybe the bell that's ringing in your head is that a magnetic field doesn't do work on a moving charged particle.

If that's the case, it's true that a magnetic field doesn't do work on a charged particle with velocity v, because the force is perpendicular to the displacement.

Magnets acting on each other also have energy.

Thanks joigus,  I know magnets have energy, as you say, because if you take two magnets, and try to push them together against their opposite poles, they won't come together no matter how hard you try to force them.  The question is this:

How can two lumps of inert metal create such resistive force out of nothing?

[iNow]

26 minutes ago, Charles 3781 said:

How can two lumps of inert metal create such resistive force out of nothing?

By definition, magnets aren’t inert

[Charles 3781]

26 minutes ago, iNow said:

By definition, magnets aren’t inert

iNow,  Magnets seem inert if left to themselves.   Do you mean, they contain potential energy?   Couldn't the same be said for other substances, such as petrol. Or "gas" , as you Americans  ambiguously, but beguilingly,  call it. 

The difference is this:  If you put the "gas" into your "automobile",  it supplies energy for a while.  But then the energy gets used up, by your driving around. Whereas magnets keep their  energy forever.  Because the electrons inside the magnet never lose their charge.  Why don't they?

Edited October 12, 2020 by Charles 3781

[iNow]

You should start your own thread if you wish to explore such off-topic topics

[J.C.MacSwell]

3 hours ago, swansont said:

Force is not a conserved quantity. If he had said energy, then ideally, that would be true.

 

Thank you. I didn't know what an "overall expenditure of force" was, but I thought it deserved more of a reply than "bullshit".

[swansont]

8 hours ago, Charles 3781 said:

iNow,  Magnets seem inert if left to themselves. 

Well, yeah. Something that’s inert doesn’t interact with other things. If you take away other things, a lot of things will seem inert. Acid is inert if it’s left to itself.

[joigus]

9 hours ago, Charles 3781 said:

Thanks joigus,  I know magnets have energy, as you say, because if you take two magnets, and try to push them together against their opposite poles, they won't come together no matter how hard you try to force them.  The question is this:

How can two lumps of inert metal create such resistive force out of nothing?

You can picture magnets as pieces of metal that package circulating currents inside. In the case of ferromagnetism, it's somewhat more involved, because you need quantum mechanics for ferromagnetism to be possible. But you can start by seeing from Maxwell's equations that small magnetic dipoles exert forces on each other, because they have an energy depending on their relative position. Then you should go on to picture the chunck of metal as having many of these little magnetic dipoles aligned with each other.

I don't know if that helps. Trying to understand these things with vague concepts like "inert" is perhaps not the best way.

As iNow says, magnets are not "inert." Something is "moving" inside so as to keep the fields in place.

An as Swanson says too, the magnet, left to itself, looks quiet, but there is some "tension" inside, if you will. The acid example is a very good one. You look at sulfuric acid in a vessel and it looks pretty much inert. But there's a lot of potential energy in it that can cause quite some damage.

Edited October 12, 2020 by joigus

[studiot]

26 minutes ago, joigus said:

The acid example is a very good one. You look at sulfuric acid in a vessel and it looks pretty much inert. But there's a lot of potential energy in it that can cause quite some damage.

Not sure about this as an example.

 

The main thing is that a magnet is a source of force not energy.

Force and energy are different things with different properties.

In particular you can use up all the energy from a source of energy, but you can't use up all the force from a source of force.

Note I said a magnet is not a source of energy.
This does not mean a magnet has no energy,  just that to use a magnet to obtain energy you require another party to actually do the work that becomes the energy you obtain.
So if you hold a mgent in your hand and drag some nails etc along the table you are doing work (ie sufflying energy) not the magnet.
The magnet is an intermediary that supplies the force instead of moving the nails direct with your hand (when you are still doing the work).

But acid may contain considerable energy, but this will become exhausted with use, unlike the magnetic force exerted by a magnet.

Edited October 12, 2020 by studiot

[joigus]

I agree that there are important differences. I said that in the spirit of an analogy, which was --I think-- Swansont's original intention. Many physical systems look inert, but they have certain "tension" stored in them. A rubber band, a compressed spring, chemical energy --free energy is the useful concept in the acid's case, rather than potential energy,* as you know very well. In an analogous way, magnets have this tension stored in them. Whether this tension is released to produce work (where there's work, there's force), depends on the presence of other magnets. Once you put a magnetic dipole in front of a magnet, there is a potential energy of interaction that depends both on the distance and the relative orientation of both. The most elementary version of this potential energy is that between a magnetic dipole and a magnetic field:

https://en.wikipedia.org/wiki/Potential_energy#Magnetic_potential_energy

The OP, and then Charles, seemed to be confused with how something "inert" can produce work.

* Although they can be related from a fundamental POV

[swansont]

6 hours ago, studiot said:

Not sure about this as an example.

 

The main thing is that a magnet is a source of force not energy.

Don’t see why that matters. Inert in this context means it doesn’t interact, but interaction requires something to interact with, so saying if left to itself/themselves is kinda pointless. That was the main issue.

Magnets exert forces and torques. They will induce currents. They interact, so they are not inert. That’s the other issue.

IOW, Charles was doubly wrong. I don’t see the benefit of splitting hairs at this point, seeing as this is not the question before us.

 

 

[Charles 3781]

On 10/12/2020 at 2:14 PM, swansont said:

Don’t see why that matters. Inert in this context means it doesn’t interact, but interaction requires something to interact with, so saying if left to itself/themselves is kinda pointless. That was the main issue.

Magnets exert forces and torques. They will induce currents. They interact, so they are not inert. That’s the other issue.

IOW, Charles was doubly wrong. I don’t see the benefit of splitting hairs at this point, seeing as this is not the question before us.

 

 

 Swansont rightly draws our attention back to the original question posed by Victheromanian.

 This question was:  Why aren't the fields generated by inert permanent magnets considered as energy.  Isn't the answer this :  that  our modern science cannot admit the possibility of energy  coming from nothing.  Always, we think, energy has be the result of some physical change in the state of matter.  

The matter may change its state by travelling,  thus gaining kinetic energy.  Or by undergoing physical changes to its internal  atomic structure - by nuclear fission or fusion. Thus releasing "atomic" energy.  In the form of nuclear reactors or bombs. 

In both cases,  the matter must underdo some change of state, in order to produce energy.  So, the concept of a permanent magnet producing energy without moving, or undergoing fission or fusion, is deeply hostile to modern science.  And is therefore resisted.

Such resistance is not new in the history of Science.  You'll recall that in the 17th Century,  Newton's theory of Gravitational attraction was strongly attacked, especially by French philosophers, as it didn't seem reasonable.  It didn't seem reasonable to Einstein either,  which is why he devised Relativity Theory to replace it.

 

[swansont]

4 hours ago, Charles 3781 said:

 Swansont rightly draws our attention back to the original question posed by Victheromanian.

 This question was:  Why aren't the fields generated by inert permanent magnets considered as energy.  Isn't the answer this :  that  our modern science cannot admit the possibility of energy  coming from nothing.  Always, we think, energy has be the result of some physical change in the state of matter.  

They aren’t inert, and the fields possess energy.

Photons, for example, have energy, and are not matter.

 

Quote

The matter may change its state by travelling,  thus gaining kinetic energy.  Or by undergoing physical changes to its internal  atomic structure - by nuclear fission or fusion. Thus releasing "atomic" energy.  In the form of nuclear reactors or bombs. 

In both cases,  the matter must underdo some change of state, in order to produce energy.  So, the concept of a permanent magnet producing energy without moving, or undergoing fission or fusion, is deeply hostile to modern science.  And is therefore resisted.

The fields have a constant energy, so they do not “produce” energy. It does not take a source of energy to sustain the field of a permanent magnet, because the energy in the field doesn’t “go” anywhere.

Conservation of energy is on pretty solid ground. What modern science resists is nonsense explanations like yours. Science prefers sound theories with experimental verification.

 

 

[Charles 3781]

3 minutes ago, swansont said:

The fields have a constant energy, so they do not “produce” energy. It does not take a source of energy to sustain the field of a permanent magnet, because the energy in the field doesn’t “go” anywhere.

 

What if the magnet is attached to the door of a refrigerator.  The door has a smooth glossy coat of paint, which offers very little frictional resistance to the downward pull of gravity. 

Why doesn't this constant downward pull make the magnet gradually slide down the door, until it falls off at the bottom onto the floor?