[Yahya (OP)]

 magnetizing reserve a specific amount of energy inside a magnet. I made this thread:
https://www.thenakedscientists.com/forum/index.php?topic=69591.0
but no-one was able to identify where does this energy come from, so I conclude that it is a specific amount of stored energy inside a magnet or a ferromagnetic material it appears in ferromagnetic material only when there is magnetic field.
and there is a relation between this stored energy and the potential energy outside, if this stored energy has a particular amount , then the possible potential energy due to this stored energy is also finite and equal this stored energy, because if the existence of this stored energy causes potential energy , then this potential energy can not exceed the specific amount of the stored energy. there also may be a relationship between gravitational potential energy and mass-energy.

[Bored chemist]

You say "but no-one was able to identify where does this energy come from"
That's because you never asked the question clearly enough.
The energy stored in a magnet is put in by the manufacturer.

[impyre]

I wouldn't say magnets store energy. Of course you could argue that a magnet has a higher energy level due to decreased entropy; however, that energy isn't responsible for the forces the magnet can produce. Those forces are the result of the field itself doing work.
Take, for example, a simple electric motor:
The simplest designs use stationary stator coils arranged around the rotor, while the rotor simply contains magnets carefully oriented around its axis.
Apply electricity and it turns. Apply nothing and it does nothing. The electricity carries energy from the power plant to the motor. Once applied it creates the fields necessary to interact with the rotor and cause it to spin. *IF* any energy is extracted from the magnets during this process it is miniscule enough to allow such a motor to function for many years without interference. I'm not saying it *does* lose energy during this process, I'm only saying it *could*. The truth is I don't know the answer to that question.
What I do know is that even if it does lose energy, it's such a tiny amount as to not be a worthwhile energy in itself.
For example, one couldn't mine natural magnets and produce power by "consuming" their naturally stored energy. If possible, it would produce far too little energy to be worthwhile. You'd spend far more energy digging them up, eventually you'd have to come to the conclusion that the better business model would be to simply sell them for use in generators, engines, etc.
In fact, it would prove far more lucrative to simply harvest wood to power a steam generator or simply erect a windmill.

As for where the energy comes from, it should be thought of like a form of potential energy due to the presence of the field. Not unlike gravity. It's simply a natural force present in the universe. The short answer: it just is.
https://en.wikipedia.org/wiki/Fundamental_interaction
The interaction of magnetic fields with other fields and with ferrous materials is considered part of the electromagnetic force.
As cool and strange as they may be, these forces still obey laws of conservation. Potential energy, kinetic energy, and work all still behave in the same way. This comes down the the response you received in the other thread about partial cycles. Basically, there's no cheating conservation.
Considering your example in that other thread we have to remember one important thing: in order for an action to be repeatable, the system must end up back in its starting position once all actions are complete. If this isn't the case then it's simply a one-time action. Like an asteroid falling, it releases a lot of energy, but it's not going to do it twice.
We can pick an arbitrary starting point, but since you chose to have a magnet and a piece of iron a distance away, I'll choose that point as well. Step by step:

• Iron piece is attracted to magnet. Potential energy is there.
• Iron piece is released, PE converted to kinetic energy. Distance decreases, work is done. (Z)
• Iron piece is at rest, kinetic and potential energies both exhausted.

Now at this point you have a couple of options:
The first:

• Iron piece is forced to move against field back to starting position. Work is done. (X)
• Iron piece is held in starting position and has same potential energy as before, cycle closed.

and the second:

• magnet is heated until field is lost, work is done(A)
• Iron piece is moved to starting position and is secured at rest. work is done (B)
• magnet is re-magnetized until field is regained, work is done (C)
• iron piece has potential energy again, cycle is closed

Either way, in order to get back to the starting point, you have to spend energy. In an *ideal* world, A+B+C would be the same amount of work as X. Due to inefficiencies, this is never the case. Energy is lost to friction, waste, etc. X and Z should be pretty close to the same, unless you use an inefficient method to move the magnet.

[Bored chemist]

I wouldn't say magnets store energy.

Others would.
https://en.wikipedia.org/wiki/Oersted#Stored_energy

[SeanB]

You have to use a lot of energy to create a magnet, and not all is lost as heat, so some is definitely stored in creating those aligned spins in the metal atoms ( or clusters of atoms) that make up each magnetic domain.

Consider stroking a strong magnet on a ferrous object, the energy you use to approach and remove it is not identical, some is lost in aligning domains in the ferrous item to give it a weak magnetic field. Also simply doing work on cold steel ( like drawing into a wire) will give it slight magnetism, simply from aligning the molecules slightly.

[GoC]

True alignment of molecules in a rotation causes magnetism. But there is more to the issue. It is energy c that spins outside of the magnet (causing what we recognize as a field) that attracts by the inverse square of the distance. Same as volume, gravity and view. There is a structure to energy causing the inverse square reality we measure.

Clockwise going in and clockwise going out  North to north and south to south is mirror images and spin is opposite. Gravity is a dilation of that energy where mass is attracted to a lower density of energy to move the electrons. This allows less friction between mass and c energy.

[Yahya (OP)]

I wouldn't say magnets store energy.

Others would.
https://en.wikipedia.org/wiki/Oersted#Stored_energy

that what I meant if there is stored energy or not , and not how this stored energy is put.

[nilak]

Anything that is different from a mathematical defined empty flat euclidean space has to have some energy.
If we take the case of a magnetic dipole, there is some energy associated to the magnetic field inside the volume of space it occupies. The energy is said to be potential.
The energy density is


Each atom inside a piece of magnet acts as a magnetic dipole. The magnetic field stores energy. But if you want to create such a magnet, you need to spend energy to align the atoms on a direction as close as possible to the north of the magnet. Inside such a magnet atoms will point more to the north. A perfect alignment would create a huge magnetic  field. Electromagnets can align atoms better than they are in a permanent magnet, because you can use very high currents to do that. The energy spent is lost in heat and electromagnetic radiation, and will not be recovered. After creating the magnet, the magnetic field will be stronger along the N-S axis, but the total value of the field will be the same, therefore, the energy stored within the magnet will be the same as before magnetizing it.

[hamdani yusuf]

Can we harvest energy from a magnet by demagnetising it?

I think that question is less ambiguous.

[nilak]

Can we harvest energy from a magnet by demagnetising it?

I think that question is less ambiguous.

I think not.
When you demagnetize a magnet it doesn't quite demagnetize. You just orient the atoms in random directions and the net field getting outside the north pole will be almost zero, but each atom keeps its own magnetic field as before.
You can play with a set of magnetic balls to see the effect. You put all magnets together and they will be in scrambled directions, but if you use a magnet you can orient the balls in one direction and the whole set will act like a single magnet.

[hamdani yusuf]

Can we harvest energy from a magnet by demagnetising it?

I think that question is less ambiguous.

I think not.
When you demagnetize a magnet it doesn't quite demagnetize. You just orient the atoms in random directions and the net field getting outside the north pole will be almost zero, but each atom keeps its own magnetic field as before.
You can play with a set of magnetic balls to see the effect. You put all magnets together and they will be in scrambled directions, but if you use a magnet you can orient the balls in one direction and the whole set will act like a single magnet.

why not?
analogy with electricity, battery store the energy by separating positively charged particles from negatively charged particles. If they are scrambled, the energy is lost from the system.

[Bored chemist]

Can we harvest energy from a magnet by demagnetising it?

Yes.
Imagine I get two identical magnets.
Then I heat one of them above its curie temperature  and  let it cool in the absence of a magnetic field so it is unmagnetised.

Then I take two  flasks full of acid and I add the magnet to one and the demagnetised "magnet" to the other.
The magnets dissolve and the reaction releases heat.
The magnet releases very slightly more heat so the acid in that flask gets slightly warmer.
I can run some sort of heat engine from the temperature difference.
So I can recover energy from the magnet and make it do work.
It's never going to make money, but there is energy which I can recover.

[nilak]

...

why not?
analogy with electricity, battery store the energy by separating positively charged particles from negatively charged particles. If they are scrambled, the energy is lost from the system.

Yes you are right.
In fact you can use a coil attached to a circuit, near the magnet, and as the magnetic field of the magnet gets lower, it will induce a current in the circuit. However, tbe amount of energy you retrieve is way lowet thant the energy spent to demagnetize it using heat.
But that doesn't mean the energy stored in the magnetic field of each atom is harvested. It is like separating two magnets using a certain amount of energy and getting like 90% of the energy back by lettig them attract again.

[PmbPhy]

magnetizing reserve a specific amount of energy inside a magnet. I made this thread:
https://www.thenakedscientists.com/forum/index.php?topic=69591.0
but no-one was able to identify where does this energy come from, so I conclude that it is a specific amount of stored energy inside a magnet or a ferromagnetic material it appears in ferromagnetic material only when there is magnetic field.
and there is a relation between this stored energy and the potential energy outside, if this stored energy has a particular amount , then the possible potential energy due to this stored energy is also finite and equal this stored energy, because if the existence of this stored energy causes potential energy , then this potential energy can not exceed the specific amount of the stored energy. there also may be a relationship between gravitational potential energy and mass-energy.

By definition, the energy stored in a magnetic field is done by the work done creating the magnetic field. Energy is not said to be stored in the magnet but in the magnetic field. In fact to calculate that energy one uses the entire magnetic field and nothing about the magnet itself is used other than its the magnet creating the field.

[Yahya (OP)]

That's because you never asked the question clearly enough.

I did.

[Bored chemist]

That's because you never asked the question clearly enough.

I did.

Where?

[evan_au]

It is energy c that spins outside of the magnet (causing what we recognize as a field) that attracts by the inverse square of the distance.

Unlike monopole fields like electric and gravitational fields, the dipole magnetic field strength declines as the inverse cube of the distance.

In other words, you can create an object which has a positive charge, but (as far as we know) every time you create a magnetic North pole, you also create a nearby South pole, and the two partially cancel each other out at large distances.

[Yahya (OP)]

nothing about the magnet itself is used other than its the magnet creating the field.

the electrons in uniform motion are inside the magnet, motion is energy so the energy is kept on the electrons themselves , it is possible that  uniform motion is like forces acting in the same direction to cause motion or kinetic energy while non-uniform motion is similar to forces in opposite directions or equilibrium in which no kinetic energy. then the kinetic energy is still inside the magnet ,  an example is the electric bell, electricity is energy , this energy is exerted on the arm via the field the energy is not in the field it is inside coil the field is just a connection to transfer this energy to the arm , the field has this feature of connectivity because it is a changeable force with respect to space. another thing is mass-energy causes the gravitational field , this gravitational field has the same mechanical properties of magnetic field and electric field which are the changeable force with respect to change in space and the inverse proportionality of force and square distance r^2,  if we consider the electric bell is a valid process for energy transfer between the coil ( electric energy ) and the bell arm ( kinetic energy), then gravity has this mechanical property the bell arm here is the potential energy on say a stone and the energy transferred is not the mass-energy itself but the energy added to the mass-energy when you moved the stone upward , i.e you add energy to the mass-energy by converting kinetic energy on the stone to potential energy. in all cases the gravitational field exists because it just a conserved connect to transfer energy.

induction is another thing , its a change in the magnetic force , change in magnetic force does need an AC current , moving a magnet close to a coil will cause induction because of the change in magnetic force. change in force also causes current flow in piezo-electric materials.

its the change in the field that causes energy and not the field itself, the change of the field caused by energy inside magnets. and field itself does not exist unless there is actual interaction, for gravity, magnetism and electrostatics the potential energy is stored inside the mass, magnet and charge.

force between magnets , objects and charges is just an effect without any medium , the other phenomena are a result of this force having the property of changeability with respect to space( distance r ).

[Yahya (OP)]

Once applied it creates the fields necessary to interact with the rotor and cause it to spin.

if there is not rotor what it will create? and what about places in space where the dimensions of the rotor does not cover ? will work be done there in that area of space ? will work be done when there is not rotor ?
if work is done by the field and there is field and  if there is not a rotor or a coil to absorb this energy , then in all cases work should be done in vacuum ?

[Horence]

Maybe it is, so you can explain how do it can work in such a strange way. But we can get more professional answers on Gogole. To know the truth about this question, we can search on Google.