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Author Topic: Magnetic force without local magnetic field  (Read 328 times)
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Following the Smudge's thread on the Marinov generator, it appears that a magnetic field can be zero at the position where a supposedly magnetic force is exerted on charges.
This tends to think of an explanation using the magnetic vector potential, which is never zero around a magnetic field even confined.

The purpose of this thread is to better define this principle and to imagine new contexts where it could be used, which seem to be numerous.

But first we have to verify the facts. In this experiment, video here, Peng Kuan uses a long solenoid (2 m). In the middle and outside, the magnetic field is almost nil. Despite this, by placing there another coil connected in series with the solenoid so that the currents are in phase and therefore the possible force remains in a single direction, Peng Kuan shown that a force tends to make the coil rotate.
This experiment confirms the facts.

It should be noted that Peng Kuan presents a whole bunch of electromagnetic paradoxes on his blog. While I think that most of them are paradoxical only apparently and can be explained, it remains very interesting and of a good level.

My next project is a new verification by replacing the mechanical device with a solid state system. A commonplace Hall effect sensor of the electronics industry, for example Allegro's A1324 (pdf) works by using the Lorentz force on a semiconductor, linked to a magnetic field. If this component is placed near the middle of the long solenoid and outside, such as in Peng Kuan's experiment, or outside a toroidal coil, and detects a signal, then we will have a new proof of concept.




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Buy me some coffee
Following the Smudge's thread on the Marinov generator, it appears that a magnetic field can be zero at the position where a supposedly magnetic force is exerted on charges.
This tends to think of an explanation using the magnetic vector potential, which is never zero around a magnetic field even confined.

The purpose of this thread is to better define this principle and to imagine new contexts where it could be used, which seem to be numerous.

But first we have to verify the facts. In this experiment, video here, Peng Kuan uses a long solenoid (2 m). In the middle and outside, the magnetic field is almost nil. Despite this, by placing there another coil connected in series with the solenoid so that the currents are in phase and therefore the possible force remains in a single direction, Peng Kuan shown that a force tends to make the coil rotate.
This experiment confirms the facts.

It should be noted that Peng Kuan presents a whole bunch of electromagnetic paradoxes on his blog. While I think that most of them are paradoxical only apparently and can be explained, it remains very interesting and of a good level.

My next project is a new verification by replacing the mechanical device with a solid state system. A commonplace Hall effect sensor of the electronics industry, for example Allegro's A1324 (pdf) works by using the Lorentz force on a semiconductor, linked to a magnetic field. If this component is placed near the middle of the long solenoid and outside, such as in Peng Kuan's experiment, or outside a toroidal coil, and detects a signal, then we will have a new proof of concept.

Should it be an air core solenoid or toroidial transformer,or one with an iron or ferrite core ?


Brad


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Should it be an air core solenoid or toroidial transformer,or one with an iron or ferrite core ?


Brad

It doesn't matter, but the larger B is, the larger A is, the greater the effect, so a core should improve the effect. A toroidal coil with a core, rather than a long solenoid, would be ideal because it confines the field better.

Although the theoretical principle seems solid, I must admit that I am uncertain about the result because why should it not already have been seen?
I am currently studying the datasheets of Hall effect censors to find out what is best to order.

In any case, if we have a result with the Hall effect, another component that the electronics industry has recently released, the TMR, will have to be tried instead. This component is also very sensitive to the magnetic field, but by a completely different effect, a variation in resistance by tunneling between two ferromagnetic layers (tunnel magnetoresistance, wikipedia). Exemple of component, TMR2503 (pdf). It will be very interesting to see if there is a difference in the effects for the two components. I am also looking for what to buy in this area.

Anecdotally, I recently discovered through the above-mentioned article in wikipedia that the discoverer of the tunnel magnetoresistance in 1975, Michel Jullière, was teaching at the same time and at the same institute at the University of Rennes, France, where I was studying. I could have had him as a professor. Its discovery at the time, I have not heard of it, it has gone completely unnoticed! :( It took more than 30 years before the great interest of the effect was understood and improved to be used in practice.


---------------------------
"Open your mind, but not like a trash bin"
   

Group: Elite Experimentalist
Hero Member
*****

Posts: 3651


Buy me some coffee
It doesn't matter, but the larger B is, the larger A is, the greater the effect, so a core should improve the effect. A toroidal coil with a core, rather than a long solenoid, would be ideal because it confines the field better.

Although the theoretical principle seems solid, I must admit that I am uncertain about the result because why should it not already have been seen?
I am currently studying the datasheets of Hall effect censors to find out what is best to order.

In any case, if we have a result with the Hall effect, another component that the electronics industry has recently released, the TMR, will have to be tried instead. This component is also very sensitive to the magnetic field, but by a completely different effect, a variation in resistance by tunneling between two ferromagnetic layers (tunnel magnetoresistance, wikipedia). Exemple of component, TMR2503 (pdf). It will be very interesting to see if there is a difference in the effects for the two components. I am also looking for what to buy in this area.

Anecdotally, I recently discovered through the above-mentioned article in wikipedia that the discoverer of the tunnel magnetoresistance in 1975, Michel Jullière, was teaching at the same time and at the same institute at the University of Rennes, France, where I was studying. I could have had him as a professor. Its discovery at the time, I have not heard of it, it has gone completely unnoticed! :( It took more than 30 years before the great interest of the effect was understood and improved to be used in practice.

Is there any chance that the electric field could skew these tests in anyway,and give a false indication of an A field causing the effect ?.

I only ask due to the fact that it is the electric field that induces a secondary,and not the magnetic field.


Brad


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Is there any chance that the electric field could skew these tests in anyway,and give a false indication of an A field causing the effect ?.

I only ask due to the fact that it is the electric field that induces a secondary,and not the magnetic field.


Brad

Electric and magnetic field are the same physical reality, the difference is only a question of observer. This is not easy to explain because there are two charge displacements to take into account, that of the electrons of the magnetic field source, and that of the test-charge that moves in this field.

When the charges are at rest, their electric field (Coulomb field) is isotropic. When the charges move in a current, their field is compressed in front of them and strengthened transversely, effect of length contraction, it is no longer isotropic.
Since only electrons move and the positive charges of the conductor are at rest, the deformed electron field can no longer systematically compensate the positive charge field.
This anisotropy of the electric field is the magnetic field. Nevertheless, the conductor remains globally neutral, so that a test-charge at rest in this magnetic field is not subjected to any force.

On the other hand, when this test-charge moves, it "sees" this difference between the electric field of the positive and negative charges of the source of the so-called magnetic field, and it is attracted or repulsed by the resultant of this electric field. For it, it's only an electric field. For the resting observer who sees the test-charge deviate, it is the magnetic field, and the force, the Lorentz force.

The Lorentz force is F=q.VxB (vector product of the velocity of the charge and the field). By writing E=VxB, we find the Coulomb force F=q.E, where E is the electric field seen by the charge, and B is the magnetic field seen by the observer who also sees the charge at the speed V. So even without talking about relativity, the Lorentz force that reduces to Coulomb's force shows us that the electric and magnetic fields are the same physical reality, as well as the electric field from induction and the electric Coulomb field are of same nature also, contrary to what we often read, only their topology differs.


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...... the electric field from induction and the electric Coulomb field are of same nature also, contrary to what we often read, only their topology differs.
Whist I don't disagree with your teaching leading up to this sentence I do think that to others not familiar with relativity that sentence can give the wrong message.  A closed circuit within the electric Coulomb field cannot get an induced voltage.  A closed circuit within the electric field from induction can get an induced voltage.  Therefore they are not of the same nature.
Smudge   
   
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Whist I don't disagree with your teaching leading up to this sentence I do think that to others not familiar with relativity that sentence can give the wrong message.  A closed circuit within the electric Coulomb field cannot get an induced voltage.  A closed circuit within the electric field from induction can get an induced voltage.  Therefore they are not of the same nature.
Smudge   

An induced voltage is an electric field with field lines in a loop instead of being opened like field lines of a charge. The difference is not nature but the way the field is distributed in space.
There is only one electric field defined as E=F/q. A charge in an induced field or in a field deriving from a potential is subjected to the same force, it cannot feel a difference. The absence of difference is the only need to affirm identity and identity comes from the definition of E.
So where does the apparent difference come from? E is only a property of space at a point position, not of an extended volume where the electric field can be "shaped" at will. It is only this distribution of the field and its time evolution that makes the difference.

To make this better understood, I have a mechanical analogy of the difference.
Case 1: A ball rolling on an inclined plane driven by gravity is the equivalent of the electron in a difference in electrical potential.
Case 2. If now you have a large wheel (the red wheel, see picture) that is rotated around its inclined axis, and that this inclined axis is connected by a gearbox to a vertical axis around which a second rotation will be driven by the first, then the yellow ball will roll in the rim flange of the red wheel and turn endlessly at the same height around the vertical axis.
As in the case of the inclined plane, it is indeed the one and only gravity that will cause the ball to be driven. There are no two fields of different nature for each case, yet the two cases are very different. It is clear that the ball moves in the second case under the effect of gravity, but without any difference in gravitational potential. This is how I see the difference between the effect of an electric field deriving from a potential and that of induction.

This is not to be taken literally, the comparison has obvious limits, in particular that induction is carried out with a variable field, unlike my mechanical example, and that it is not the field topology but the mechanical constraints that differ here.


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"Open your mind, but not like a trash bin"
   
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Order done.

The Hall effect censor is a SS496A. As it is sensitive to the Lorentz force, it should allow to replace any moving conductors of mechanical experiments, it's the easy way when we're trying to highlight a force. In the above-mentioned experiment of Peng Kuan, this component used to replace his small mobile coil placed near the middle of the long solenoid, should indicate a signal as if it were in a magnetic field when there is none and there is only the magnetic vector potential A. 

The TMRs are a TMR2104P and a TMR2005 (more sensitive). I bought them to test this new kind of components (Tunnel magnetoresistance). I don't know yet how the magnetism changes the resistance but it seems that it's not with the Lorentz force. If the first experiment is positive, it will be interesting to see if a TMR detects also A when B=0.

I won't be able to experiment until early July.
If someone has already experimented with this type of component, I am interested in feedback. Thanks.


---------------------------
"Open your mind, but not like a trash bin"
   
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