A solenoid plus a wire-loop-coil, has it been tested?

[PhysicsProf]

    The long current-carrying solenoid is interesting.  The B field is almost entirely contained INSIDE the solenoid, yet the EFFECTS can be felt by a wire-loop (multiple wires allowed) OUTSIDE the solenoid, where essentially no B-field lines actually "cut" the wires in the external wire-loop.
    I made an effort at putting some diagrams together to help one SEE what I'm discussing here - see attached.
    Questions -
1. --  If the current in the solenoid is CHANGING, so the flux INSIDE the wire loop is changing, will a current be produced in the external wire loop?  The answer is surely YES, even though essentially no B-field lines actually "cut" the wires in the external wire-loop.

2 - How does this happen physically, that is, how does the external wire-loop (red) "FEEL" the change in the magnetic flux down inside the solenoid?

3 - If this system is now working as a transformer, a voltage will be produced in the external wire loop -- and a current in a closed circuit to which the "red wires" in the diagram are attached (not shown).  But note that the FLUX due to current in the external wire loop is NOT ALL contained inside the solenoid.  In the diagram (and depending on geometries) - perhaps 1/3 of the FLUX inside the external wire loop is contained inside the solenoid, as an example.  Thus, the "LENZ effect" will be asymetrical between the wire loop and the solenoid.  Will this result in a "reduced Lenz effect" (RLE)?
Has this ever been measured?

4 - Note (see diagram) that the field inside the wire loop but OUTside the solenoid, due to reaction-current in the wire loop, is in the SAME direction as the weak B-field OUTSIDE the solenoid, due to the solenoid - right?

I'm much more interested in experimental results than in theoretical analysis, although the latter can be helpful.
--Steve

[PhysicsProf]

  I want to acknowledge that Partzman (Jon) has done a lot of work on RLE, and his work has re-awakened my interest in the subject!

[Jerry Volland]

The direction of the current in the red loop isn't designated.  Would this coil's sence determine the flux loop's direction, relative to that of the solenoid?

[PhysicsProf]

The direction of the current in the red loop isn't designated.  Would this coil's sence determine the flux loop's direction, relative to that of the solenoid?

B field lines (Reacting to change in flux) in the red loop are to the right, while the B lines inside the solenoid are to the left.  Lenz's law states that the reaction field in the secondary, the red loop, OPPOSES the CHANGE in flux through the red loop, so we can tell that the B field in the solenoid is INCREASING in strength.

[Jerry Volland]

I was also considering a non passive application using the loop as a ring radiator.  This type of antenna has a preferred frequency, and if fed with a miss matched signal, a nodal point will "walk" around the ring.  This will twist the solenoid flux.  Twisting and untwisting the flux should produce a Faraday effect with a copper disk centered in the solenoid. Electrons would oscillate between going to the rim and going to the central region.  The output potential should be measurable.

[PhysicsProf]

I was also considering a non passive application using the loop as a ring radiator.  This type of antenna has a preferred frequency, and if fed with a miss matched signal, a nodal point will "walk" around the ring.  This will twist the solenoid flux.  Twisting and untwisting the flux should produce a Faraday effect with a copper disk centered in the solenoid. Electrons would oscillate between going to the rim and going to the central region.  The output potential should be measurable.

Thank you for reminding me of the Faraday disk and Faraday "paradoxes." 

[Jerry Volland]

I consider the Faraday Disc to be an important opportunity for research.  (Even different geometries).  I'm thinking you might have some interesting ideas.

[PhysicsProf]

I consider the Faraday Disc to be an important opportunity for research.  (Even different geometries).  I'm thinking you might have some interesting ideas.

Thank you, Jerry.  I'm pursuing a few paths right now.
If something breaks through to novel information - I'll let you know.
Steve

[Smudge]

I am not clever enough to put my reply to the first post here so it is in the attached pdf document.

Smudge

[PhysicsProf]

Thank you smudge!
Pondering.

[PhysicsProf]

Smudge, when I click on the link you provided in the last paragraph of your PDF, I get the following message (see below).   Any idea why I cannot access your link?

[Smudge]

Smudge, when I click on the link you provided in the last paragraph of your PDF, I get the following message (see below).   Any idea why I cannot access your link?

Here is the link to the topic
https://www.overunityresearch.com/index.php?topic=2609.msg41587#msg41587
The paper is attached to the first post.

Smudge

[PhysicsProf]

   Very good - thank you, Smudge.

   While we're doing thought-experiments (although I much prefer REAL experiments) - can we agree that the B field outside a long solenoid can approach zero by making the solenoid longer and longer? 

[Jerry Volland]

   Very good - thank you, Smudge.

   While we're doing thought-experiments (although I much prefer REAL experiments) - can we agree that the B field outside a long solenoid can approach zero by making the solenoid longer and longer?

This is a difficult concept for me to muddle through.  It would help if I could see some calculations pointing to the effect.

[Smudge]

   Very good - thank you, Smudge.

   While we're doing thought-experiments (although I much prefer REAL experiments) - can we agree that the B field outside a long solenoid can approach zero by making the solenoid longer and longer?

Yes.  And hopefully we can agree that the B field outside a magnetized ring core (toroidal transformer core) is also zero if the primary magnetizing winding is equally spaced around the whole core.  So you could have the same question, how does the secondary coil "feel" the changing flux in the core?  Answer of course it "feels" the changing A field.  What is quite interesting to explore is having conductors inside the core, something our classical electrical domain model can't handle.  Tinman has done some work there potting his own toroidal cores with inside coils, using iron powder loaded epoxy for the cores.

Smudge 

[PhysicsProf]

Yes, I agree also:  "And hopefully we can agree that the B field outside a magnetized ring core (toroidal transformer core) is also zero if the primary magnetizing winding is equally spaced around the whole core. "

Yes.  And hopefully we can agree that the B field outside a magnetized ring core (toroidal transformer core) is also zero if the primary magnetizing winding is equally spaced around the whole core.  So you could have the same question, how does the secondary coil "feel" the changing flux in the core?  Answer of course it "feels" the changing A field.  What is quite interesting to explore is having conductors inside the core, something our classical electrical domain model can't handle.  Tinman has done some work there potting his own toroidal cores with inside coils, using iron powder loaded epoxy for the cores.

Smudge

Yes, very interesting to have conductors INSIDE the toroidal core. 
I think Mike Nunnerley has also worked on that.
Thank you.

[F6FLT]

...So you could have the same question, how does the secondary coil "feel" the changing flux in the core?  Answer of course it "feels" the changing A field.  What is quite interesting to explore is having conductors inside the core, something our classical electrical domain model can't handle.  Tinman has done some work there potting his own toroidal cores with inside coils, using iron powder loaded epoxy for the cores.

Smudge

The flux variation is not the cause of the induced current, the secondary coil does not feel it. If it were the case, it would be a non-local phenomenon, we would no longer be in classical physics but in quantum mechanics.
The use of flux is only a practical means of calculation, a consequence of Gauss' theorem.
∫E.dl = - ∂Φ/∂t: the only cause is the effect of the electric field E on the charge in its closed path.  -∂Φ/∂t can be used instead of ∫E.dl when the circuit is closed and its dimensions are small compared to the wavelengths of the signals used (quasi-stationary regime, no propagation phenomena).

At the link you indicate above, you say "There appear to be few people who treat magnetic circuits in the same way that we treat electric circuits". This seems quite normal to me. Electrons circulate in an electric circuit, forming a current. But there is no "magnetic current" in a magnetic circuit, nothing moves along a magnetic circuit. A flux variation is transverse, it's field lines that are always looped around an electric current, and that enter or leave the magnetic circuit, but without moving along it.

[Jerry Volland]

The flux variation is not the cause of the induced current, the secondary coil does not feel it. If it were the case, it would be a non-local phenomenon, we would no longer be in classical physics but in quantum mechanics.
The use of flux is only a practical means of calculation, a consequence of Gauss' theorem.
∫E.dl = - ∂Φ/∂t: the only cause is the effect of the electric field E on the charge in its closed path.  -∂Φ/∂t can be used instead of ∫E.dl when the circuit is closed and its dimensions are small compared to the wavelengths of the signals used (quasi-stationary regime, no propagation phenomena).

At the link you indicate above, you say "There appear to be few people who treat magnetic circuits in the same way that we treat electric circuits". This seems quite normal to me. Electrons circulate in an electric circuit, forming a current. But there is no "magnetic current" in a magnetic circuit, nothing moves along a magnetic circuit. A flux variation is transverse, it's field lines that are always looped around an electric current, and that enter or leave the magnetic circuit, but without moving along it.

This is some really interesting information, F6FLT, and I got a screenshot of your post, for subsequent consideration.

When you say that "magnetic current" doesn't move - through a circuit - does this have any correlation to the flux lines around a conductor?  These loops are shown with directional arrows, but this might indicate an impetus rather than rotation.  I have a side project with a magnetic funnel antenna, and I'd like to be able to predict if the funnel is rotating.

[Smudge]

At the link you indicate above, you say "There appear to be few people who treat magnetic circuits in the same way that we treat electric circuits". This seems quite normal to me. Electrons circulate in an electric circuit, forming a current. But there is no "magnetic current" in a magnetic circuit, nothing moves along a magnetic circuit.

Of course nothing moves, but that does not prevent there being formula relating mmf, flux and reluctance to be identical to formula relating emf, current and resistance.  In fact "magnetic ohm's law" has been used forever (well, for over a century) when dealing with air gaps in magnetic cores.  And there is nothing wrong in extending that into dynamic situations to understand how fields in magnetic circuits respond in the time domain.  Take the classical Lenz's Law, the the magnetic field from the current in the secondary creates a field that opposes the change of field from the primary.  That's OK until you realize that the current in the secondary relates not just to the (rate of change of) field from the primary, but to the (rate of change of) total field, that is the field from both the primary and secondary current.  Many people are either unaware of this and simply think the secondary is only seeing the field from the primary that would exist if the secondary were not there (which in good transformers is almost true but in bad transformers is certainly not true) or they give up on trying to solve the dilemma of how the secondary really responds to the two summed fluxes.   For sine waves the phase vectors of the two separate fluxes and the sum form a right angled triangle and that gives a clear picture of how they change with frequency which is normally hidden from view.   And how many people realize that in a power transformer running at full load the primary current on its own , or secondary current on its own, would drive the core well beyond saturation?  That cancellation of fluxes from the primary and secondary load currents, leaving only the primary magnetizing current to create the working flux, is a vital feature that has to be provided by the transformer system and the magnetic domain analysis tells you how this is achieved and how good it is for any perceived design.  In the classical electrical transformer model that cancellation is inherent in the "perfect transformer" at the heart of the model that magically works without any magnetic field, then other components are added to account for the need of a magnetic field and its practical imperfections such as leakage.  That is OK until you are interested in transformers that could have unusual characteristics, where you would resort to making something, measuring it, then putting the results into an electrical model.  Far better to use the magnetic domain model to forecast the results that then allows you to build the best model.

Smudge

[PhysicsProf]

Thank you smudge.
I have to ask you, Does any of this discussion apply to a Tesla coil?

[F6FLT]

@Smuge

I agree with everything you say above.

My point was just to emphasize that nothing moves along a magnetic flux, which the idea of a magnetic current might wrongly suggest.

[F6FLT]

...
When you say that "magnetic current" doesn't move - through a circuit - does this have any correlation to the flux lines around a conductor?  These loops are shown with directional arrows, but this might indicate an impetus rather than rotation.  I have a side project with a magnetic funnel antenna, and I'd like to be able to predict if the funnel is rotating.

Yes, there is a complete connection.

It is the name "flux" that is misleading. We think of the flux or flow of water when it is a purely mathematical concept, which also applies in statics, it is "the surface integral of the perpendicular component of a vector field over a surface".
In our case, this surface is the section of a magnetic circuit, therefore transverse. And this flux is conservative, we will always have the same flux whatever the surface which will cut the magnetic circuit, except of course if there are leaks, but then by widening the surface to "capture" the leaks, we will find again this flux constancy.

I think the best method is to reason with the image of the field lines. When an electron moves, it creates a magnetic field whose field lines (equipotentials) surround it in closed loops, in a plane perpendicular to its speed vector.  If the electrons form a current, these loops encircle the conductor. If the velocity increases, we say that the number of lines increases. If the conductor passes near a ferromagnetic core, these loops will tend to concentrate inside, and very little in the air. It is the number of these closed lines that can be seen as the intensity of the flux. These lines are unbreakable, without beginning or end, never cross each other, and nothing moves along them.

To answer your question, the arrows only indicate the orientation of the field to know where north and south are, which tells us the direction of the velocity vector of the electrons that generate it. The only conventional force I know and that could rotate a funnel is the Lorentz force F=q.VxB.

In fact there is no mystery around all this when we reason by relativity. A charge seen in motion by an observer has its electric field compressed in the direction of the motion because of the contraction of the lengths. So its coulombic field is no longer seen isotropic around the charge. It is this anisotropy that causes the magnetic effects. The magnetic forces are only due to the electric forces of the coulombic field of the charge, deformed because of its motion.
The electric field, coulombic, is the primordial reality, and the relativity applied to the coulombic field of the moving charge is enough to explain all magnetism. Maxwell's equations + the Lorentz force, to which electromagnetism is generally summarized, are only a calculation facility, but which blurs the mental representation, paradoxically simpler, that one can make of the phenomenon thanks to relativity.

[Jerry Volland]

That information is concise and well presented.  Thank you for taking the time to consider my question and provide the answer.

I'll post my work with that project in its own thread.

[Jerry Volland]

What might we suppose will happen when the loop is moved to the end of the coil or beyond?  Still considering a mismatched signal, will a funnel form at the end of the solenoid?  If it does, could  the original configuration be used to make the coil's field fatter around the middle?

[Jerry Volland]

And there was the televised experiment involving a 20 hp three phase motor with an unloaded shaft pointing straight up through the middle of a four foot degaussing coil held above the end of the motor.  The ring coil apparently had a walking signal.  Afterwards, something was said about an "angel in the whirlwind", perhaps the observer's higher awareness?