As I continue to state, that is Lenz exclusion. And it will occur regardless of the permeability of the material the flux is within.
No. You are confusing permeability of the path with focusing of the flux. The effect is more noticeable over the faucet valve wrench because it has gathered the flux such more of it is going through the pipe ring. All four of your readings are entirely consistent with what I have been saying all along.
An excellent test, thank you for the effort. I've made two copper rings for the exact same inductor, but have to test Tuesday lunch.
If you examine your ring in coil picture, you will notice that you have a significant amount of area between the coil ID and the half inch copper pipe sleeve. That will lessen the effect as flux will simply go around the ring. The rings I've made using .003 inch copper foil, I put two layers of masking tape over the inductor, then wrapped the copper foil two full turns soldering it where it first overlaps both layers. That way the ring is about 5-10 mils from the coil surface. ID I just winged it. These are close enough that there is little room for flux to go around.
However, your inductor (and mine) are multilayer, maybe ten layers thick with all aspect ratio close to 1. This allows lots of flux to divert within the winding themselves, so the ring effect is lessened. A voice coil will have an aspect ratio in the 20 to 50 range, so a close sleeve will indeed be more effective. I plan on repeating these measurements on my speaker vc once I've disassembled it.
My explanation is not a truncated idealized situation, it is designed to cover every effect in the system. Remember, the gross magnetic structure inductance needs to be removed from the equation if one has any hope of seeing the more subtle effects, such as Lenz based dissipation, eddy braking, the much smaller contributions to speaker distortion. I note you did not include Rs in the meter readings. My intent is to do that as well for a better look at what is happening.
My father taught me what a faucet wrench was..
I learned all about the left hand rule about 15 years ago.
Transformer theory is fine and dandy, but falls significantly short when moving parts and time and position dependent reluctance come into play within a dynamic loudspeaker. Many who try to shoehorn a speaker structure into simple transformer theory ignore the effects I am trying to measure. If I simply use transformer theory, I might as well quit now.
Jn
Think of a shorting ring as a restrictor only for time varying flux. In a speaker, the iron is channeling the flux, and any time you put the ring around the path, it tries to prevent flux change.
For a speaker, the ring does not have to be in the voice coil on the pole piece, it just has to surround the magnetic flux path somewhere. Early on, it was done external to the vc. Years ago someone realized that the system inductance still changed due to vc position, so figured out to include the shorting ring there, that helps to control Le(x).
Jn
Using a small series resistor between a solid-state amplifier and a conventional two or three way loudspeaker has always been a legitimate option. It might not be to everyones liking, but.....
At this point there seems to be a misunderstanding, as - according to John Atkinson - Carver took the modified amplifier back with him after finishing the Carver challenge with Stereophile.
They tested some time later a production model (which should sound allegedly like the CJ amp, but did not; John Atkinson said he measured the achieved null between the two amplifiers at a max. of 35 dB but only in the midrange while considerably lower at the extremes.
Both Carver challenges (Stereophile and Audio Critic two years before) are quite interesting reads, especially when considering the various listening methods.....
Just don't try to put several together with heat shrink, I've heard it said that they can be demagnetized..😉
Bonsai; some manu's do, some don't. Depends on what they wish to optimize.
Jn
So, I know this is "so 5 pages ago", but I figured I would clarify that the LF inductance of a driver increases as the coil enters the magnet assembly. However the 10KHz inductance may at the same time fall due to the coil getting closer to the pole piece and/or shorting ring. You could say that the permeability of the coil environment can be above or below that of free air depending on voice coil position, shorting ring position, etc.
The idea with shorting ring linearization is that the permeability of the gap can be made to be the same as free air, so that as the coil enters the gap it's inductance does not change. However the writeups often don't care to mention that the linearization only works at one frequency due to eddy currents in the shorting ring changing the coupling at all other frequencies.
Now what if instead of using a solid shorting ring, we used a shorted coil? With greatly reduced conductor size you now have much less eddy currents in the shorting coil and it's effect is more constant with frequency. Thus maybe you could get the inductance linearization to work within a larger frequency range?
The idea with shorting ring linearization is that the permeability of the gap can be made to be the same as free air, so that as the coil enters the gap it's inductance does not change. However the writeups often don't care to mention that the linearization only works at one frequency due to eddy currents in the shorting ring changing the coupling at all other frequencies.
Now what if instead of using a solid shorting ring, we used a shorted coil? With greatly reduced conductor size you now have much less eddy currents in the shorting coil and it's effect is more constant with frequency. Thus maybe you could get the inductance linearization to work within a larger frequency range?
Notice the yellow bumpers on the magnets. The ones I had where much larger and if a finger gets between them by accident they can draw blood.
There appears to be a widespread misinterpretation about the meaning of Lenz' law.
Lenz' law is actually not any law of its own but just the mere minus sign that appears in Faraday's law. Faraday's law states that the EMF induced in a loop of wire is the opposite of the rate of change of flux through the loop:
EMF = -d(phi)/dt
This means that the flux generated by the induced EMF current in the loop follows the opposite of the time derivative of the excitation flux. With sinusoidal signals, this means that the ring (loop) flux comes 90 degrees behind the excitation flux.
The fallacy is to infer that since the ring flux opposes the rate of change of the original flux, it tries to keep the flux constant. Namely, 'opposing the rate of change' does not oppose or exclude the magnitude at all.
Consider the two sinusoidal fluxes, the ring flux (RF) lagging 90 degrees the original flux (OF). When OF is increasing, RF is on the negative side, yes; and when OF is decreasing, RF is positive, yes; but when OF is at maximum, RF is zero; and when OF is at minimum, RF is also zero! So, there is NOT any reduction in amplitude, as there never can be when two signals in phase quadrature are summed. Also, in two quarters of the wave, RF and OF have the same polarity, and in the other two they are in opposite polarity.
If such a mistaken form of Lenz' law would really be imposed upon us, all transformers would be rendered pretty useless, as their magnetizing flux would be soon eaten up by the load current.
Lenz' law is actually not any law of its own but just the mere minus sign that appears in Faraday's law. Faraday's law states that the EMF induced in a loop of wire is the opposite of the rate of change of flux through the loop:
EMF = -d(phi)/dt
This means that the flux generated by the induced EMF current in the loop follows the opposite of the time derivative of the excitation flux. With sinusoidal signals, this means that the ring (loop) flux comes 90 degrees behind the excitation flux.
The fallacy is to infer that since the ring flux opposes the rate of change of the original flux, it tries to keep the flux constant. Namely, 'opposing the rate of change' does not oppose or exclude the magnitude at all.
Consider the two sinusoidal fluxes, the ring flux (RF) lagging 90 degrees the original flux (OF). When OF is increasing, RF is on the negative side, yes; and when OF is decreasing, RF is positive, yes; but when OF is at maximum, RF is zero; and when OF is at minimum, RF is also zero! So, there is NOT any reduction in amplitude, as there never can be when two signals in phase quadrature are summed. Also, in two quarters of the wave, RF and OF have the same polarity, and in the other two they are in opposite polarity.
If such a mistaken form of Lenz' law would really be imposed upon us, all transformers would be rendered pretty useless, as their magnetizing flux would be soon eaten up by the load current.
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Wow, just wow.
Emil Lenz is rolling in his grave.
You are attempting to re-write history.
Go to any textbook and review what Lenz's law is.
No matter how much you protest and hand wave, it still exists.
Edit.. To respond to your first statement, it is not a "widespread misinterpretation" of Lenz law.
It appears to be just you.
Jn
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Thanks mark4. Fig 2 shows a lot. Edit, top of page 9.
But I fear the textual understanding will be beyond most here, as the description of power flow is buried in the explanation, as well as the concept of conservation of energy.
Jn
Are you also trying to erase Lenz's law from the books?
To do that, first you have to recall basically every physics and E/M textbook ever written. Then, have the servers remove all those pesky references to it.
Or perhaps, a better understanding of power flow in a transformer, mark4's link is good but may be a little bit over most heads here.
Re-examine the concept of mutual inductance. It explains why the secondary''s opposing flux causes the primary to pull more power from the source.
It is the basis for the lowering of inductance seen by the primary as a result of the increased power draw of the secondary.
Jn
Ps.. Richard, your response surprises me.
But I fear the textual understanding will be beyond most here, as the description of power flow is buried in the explanation, as well as the concept of conservation of energy.
Jn
An incomplete understanding of transformers does lead to incorrect thinking.
Are you also trying to erase Lenz's law from the books?
To do that, first you have to recall basically every physics and E/M textbook ever written. Then, have the servers remove all those pesky references to it.
Or perhaps, a better understanding of power flow in a transformer, mark4's link is good but may be a little bit over most heads here.
Re-examine the concept of mutual inductance. It explains why the secondary''s opposing flux causes the primary to pull more power from the source.
It is the basis for the lowering of inductance seen by the primary as a result of the increased power draw of the secondary.
Jn
Ps.. Richard, your response surprises me.
Sigh...IPad dropped another post..sigh, no joy yet..
Typing a post should not be like build-a-bear...
I was busy this weekend making metal chips. I made an aluminum winding mandrel using 2 inch aluminum round with cuts just like an ER collet. It expands to about 2.15 inches. I made a brass dead center, and am almost finished with a dog to turn the mandrel..it slips easily, and wire tension would stop it. When I load the end with the live center, I can set the OD of the mandrel.
Next are side discs to contain the wind, and a Teflon split ring to keep a bit of the former clear for wire entry and exit.
I have 2 mil calandered nomex, so can wrap several times to buildup to whatever thickness I want.
First coil set will be a co-wound two layer with an ID of 2.025 inches that will slide over my 2 inch round aluminum stock. I am going to watch what the inductance meter does when I slide the coil over the bar with 1khz excitation.
I should be able to use 5 minute epoxy to make the former, but for wet winding I will use some west system with the tropical hardener, it's pot life is far better...there is never a good reason to rush a job on a lathe, and ten very good reasons to take it slowly.
I'll post the pics I've taken when I'm not using this infernal IPad.
As I gain experience making these things, I'll be better poised to make the 1 inch mandrel for the 8 incher I dissect. Since I don't know the vc ID, it will wait till it's apart.
Jn
Typing a post should not be like build-a-bear...
I was busy this weekend making metal chips. I made an aluminum winding mandrel using 2 inch aluminum round with cuts just like an ER collet. It expands to about 2.15 inches. I made a brass dead center, and am almost finished with a dog to turn the mandrel..it slips easily, and wire tension would stop it. When I load the end with the live center, I can set the OD of the mandrel.
Next are side discs to contain the wind, and a Teflon split ring to keep a bit of the former clear for wire entry and exit.
I have 2 mil calandered nomex, so can wrap several times to buildup to whatever thickness I want.
First coil set will be a co-wound two layer with an ID of 2.025 inches that will slide over my 2 inch round aluminum stock. I am going to watch what the inductance meter does when I slide the coil over the bar with 1khz excitation.
I should be able to use 5 minute epoxy to make the former, but for wet winding I will use some west system with the tropical hardener, it's pot life is far better...there is never a good reason to rush a job on a lathe, and ten very good reasons to take it slowly.
I'll post the pics I've taken when I'm not using this infernal IPad.
As I gain experience making these things, I'll be better poised to make the 1 inch mandrel for the 8 incher I dissect. Since I don't know the vc ID, it will wait till it's apart.
Jn
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The stikin' Lenz law has no business to stand against a former LLNL project manager with Q clearance.
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