Post by: Yahya on 15/04/2017 08:38:13
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.
Post by: Bored chemist on 15/04/2017 09:28:45
That's because you never asked the question clearly enough.
The energy stored in a magnet is put in by the manufacturer.
Post by: impyre on 15/04/2017 16:58:26
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.
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.
- 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.
Post by: Bored chemist on 16/04/2017 13:37:42
I wouldn't say magnets store energy.Others would.
https://en.wikipedia.org/wiki/Oersted#Stored_energy
Post by: SeanB on 16/04/2017 14:36:44
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.
Post by: GoC on 16/04/2017 15:52:12
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.
Post by: Yahya on 17/04/2017 20:11:55
that what I meant if there is stored energy or not , and not how this stored energy is put.I wouldn't say magnets store energy.Others would.
https://en.wikipedia.org/wiki/Oersted#Stored_energy
Post by: nilak on 17/04/2017 21:27:20
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.
Post by: hamdani yusuf on 18/04/2017 14:00:55
I think that question is less ambiguous.
Post by: nilak on 18/04/2017 14:20:31
Can we harvest energy from a magnet by demagnetising it?I think not.
I think that question is less ambiguous.
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.
Post by: hamdani yusuf on 18/04/2017 17:37:09
why not?Can we harvest energy from a magnet by demagnetising it?I think not.
I think that question is less ambiguous.
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.
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.
Post by: Bored chemist on 18/04/2017 18:43:49
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.
Post by: nilak on 18/04/2017 19:54:07
...Yes you are right.
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.
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.
Post by: PmbPhy on 21/04/2017 05:28:22
magnetizing reserve a specific amount of energy inside a magnet. I made this thread: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.
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.
Post by: Yahya on 02/05/2017 18:40:17
That's because you never asked the question clearly enough.I did.
Post by: Bored chemist on 18/05/2017 20:48:16
Where?That's because you never asked the question clearly enough.I did.
Post by: evan_au on 19/05/2017 12:14:45
Quote from:
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.
Post by: Yahya on 19/05/2017 17:12:28
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 ).
Post by: Yahya on 19/05/2017 17:56:41
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 ?
Post by: Horence on 22/05/2017 10:45:12
Post by: puppypower on 22/05/2017 11:33:50
In magnetic iron, for example, the outer most electrons are not in the lowest energy state. Rather a number of electrons spread out over extra orbitals, will all these elections having the same spin. The result is the individual magnetic fields of these electrons reinforce each other, instead of cancel, as they do at minimum atomic energy.
The energy stored in the magnet is connected to the outer electrons of individual atoms being in stable, but higher energy levels, where the magnetic fields are all reinforcing each other. The energy of the magnet is based on this stable arrangement of electrons, relative to the stable arrangement called the ground state.
What makes this higher energy state stable is connected to the electrostatic force. Electrons wish to repel each other since they all have negative charges. The movement of the electrons, creates magnetic fields with certain arrangement in space, magnetically attractive. This magnetic attraction can induce the electrons to get closer, making the electrostatic repulsion get worse, until the two opposing forces balance.
In the case of magnetism, the magnetic fields are repelling each other; reinforcing, spreading out the electrons into extra orbitals, allowing the electrostatic repulsion to drop. Iron ends up with two sweet EM spots, with the magnetic sweet spot higher in overall energy.
Post by: Yahya on 23/05/2017 14:32:50
there should be a relation between electron kinetic energy and gravity , assuming the gravity will be zero if electrons are at rest, gravity will increase by the increase in the sum of kinetic energy for electrons.
in this case gravity will depend on the mass of the electron as well as its speed. just like magnetism depends on the charge value and its speed.
Post by: Yahya on 23/05/2017 16:46:37
Post by: Bored chemist on 23/05/2017 22:20:05
Not really, they are dimensionally distinct.
, in Newtonian mechanics a net force with acceleration "a" will cause some kinetic energy ,
No, the force and acceleration may be like the "centrifugal" force there's no change in energy unless the force move through a distance along its length.
the opposite is also true kinetic energy of a moving object will cause force .
No. not really.
Post by: Bored chemist on 23/05/2017 22:20:37
I think I added a new view for gravity and its cause.I think you wrote stuff that makes no sense.
Post by: Yahya on 24/05/2017 10:50:49
, in Newtonian mechanics a net force with acceleration "a" will cause some kinetic energy ,I did not say there would be change in energy I said it causes energy to exist, the object first was at rest then what causes it to rotate is a force , there is still an object rotating around with kinetic energy , you misunderstand what I write and claim I do not clarify things , for your knowledge , there is not in physics a thing called centrifugal force , its just centripetal force , when the centripetal force disappears , the object does not move outward , instead it moves tangential to the circular path. towards its direction of motion at that time.
No, the force and acceleration may be like the "centrifugal" force there's no change in energy unless the force move through a distance along its length.
Post by: Yahya on 24/05/2017 13:49:11
There is changeability between kinetic energy and forcethe word changeability means they have ability to change , changeability between two things is they change and become one another , i.e when a moving object stops it looses its kinetic energy and a force appears , the kinetic energy changed to force and another kind of energy. if I have a spring with potential energy it can exert force on a ball to cause it to move , the spring force no longer exists and kinetic energy appeared.
Not really, they are dimensionally distinct.
Post by: Yahya on 24/05/2017 13:52:04
the opposite is also true kinetic energy of a moving object will cause force .when the object stops . But in the case of electron it does not stop but it cause a special kind of force i.e magnetic field
No. not really.
Post by: Colin2B on 24/05/2017 14:06:20
when a moving object stops it looses its kinetic energy and a force appearsCan you give an example of what you mean?
Usually an object stops because a force has caused it to decelerate.
Post by: Yahya on 24/05/2017 14:41:25
if I exert a force to throw a ball to hit the wall , then I exert the force by my hand on the wall but not directly.
Post by: Bored chemist on 24/05/2017 20:29:38
I know what the words mean.There is changeability between kinetic energy and forcethe word changeability means they have ability to change , changeability between two things is they change and become one another
Not really, they are dimensionally distinct.
It's just that you are wrong.
Post by: PmbPhy on 25/05/2017 21:41:08
the electrons in uniform motion are inside the magnet, motion is energy so the energy is kept on the electrons themselves , ...etc.You asked where the energy is "stored." I explained that the energy is stored in the field. It is not stored in the kinetic energy of the electrons. The energy comes from the work done in creating the magnetic field. As such it's said that the energy is stored in the field.
How do I know this? Simple. Its not only a well established fact in physics but can easily be shown. All one has to do to find the derivation is pick up an advanced text on EM like those used in an EM course in college.
Post by: Yahya on 29/05/2017 17:55:33
Post by: PmbPhy on 29/05/2017 18:45:56
congratulations for becoming a global moderator!Thanks.
Do you have an objection or disagreement for what I've explained in my response to your question?
Post by: Yahya on 29/05/2017 19:18:02