MH's ideal coil and voltage question

[partzman]

Below are two models showing the relationship between Emf, Cemf, and an inductor. One is the current model that PW, Poynt, MH, and others are promoting and the remaining is my proposal which simply relocates the Cemf source to be in series rather than in parallel with the inductor.

The notations require some explanation and are as follows:

A) Definitions for Emf and Cemf.*

B) Equation for di.

C) Value of Cemf when di reaches it's stable value in A/s for any given inductor.

D) Description of the negative feedback correction for di.

Where there is a question mark, it simply means that I have either not seen or understood any answer given regarding these aspects of the current model. If answers are given, the blanks will be filled.

* Notice I am using the same definition for Cemf as the current model which is a mathematical fudge to make the feedback loop work in my model conceptually. True Cemf opposes or is opposite the change in di so should contain a negative on one side or the other of the equation.

So, the model I propose differs from the current model mostly in the definition of Cemf.  Cemf does not equal Emf but rather equals zero when an inductor reaches it's calculated di. This seems to verify what is seen experimentally which also satisfies Faraday's equation and is easier to understand IMO.

pm

[picowatt]

Below are two models showing the relationship between Emf, Cemf, and an inductor. One is the current model that PW, Poynt, MH, and others are promoting and the remaining is my proposal which simply relocates the Cemf source to be in series rather than in parallel with the inductor.

The model that you "propose" is the model we have been discussing and "promoting" all along...

However, your notation for "C" should read "When di=.8A/s, Cemf=4 volts"

PW

[partzman]

The model that you "propose" is the model we have been discussing and "promoting" all along...

However, your notation for "C" should read "When di=.8A/s, Cemf=4 volts"

PW

No, what you state above is correct for your model but not mine. My notation is correct. That is the big difference between the two models.

pm

Edit: I will add that your model's feedback node is at Emf and mine is at zero.

[picowatt]

No, what you state above is correct for your model but not mine. My notation is correct. That is the big difference between the two models.

pm

Edit: I will add that your model's feedback node is at Emf and mine is at zero.

I am unaware of anyone claiming or discussing that the CEMF is in parallel with di as you depict it in your left hand drawing.  Your right hand model is what has been discussed all along.

The only apparent difference in your model seems to be that in "C)", you state that when di=.8A/s the CEMF=0.

Now think about that a minute.  How can a di of .8A/s result in a CEMF that equals zero volts?  Anytime current is changing in a condutor, there is also a changing magnetic field and a subsequently induced non-zero CEMF.

If CEMF=0 when di=8A/s, then your formula for CEMF in "A)" must also be incorrect.

Perhaps, for discussion, you could post two identical versions of your "proposed" model side by side but with one stating:

C) When di=.8A/s, Cemf=4 volts

With that correction, the model depicts what I and others have been discussing.

Thanks...

PW

[partzman]

I am unaware of anyone claiming or discussing that the CEMF is in parallel with di as you depict it in your left hand drawing.  Your right hand model is what has been discussed all along.

That is correct in the fact that when I have asked for a model or math derivation, none was given. However with the statement that Emf=Cemf when di = .8A/s, the parallel model with L as shown has to be assumed for any di to flow thru L. Please diagram schematically how this would be accomplished otherwise.

The only apparent difference in your model seems to be that in "C)", you state that when di=.8A/s the CEMF=0.

My model is correctly noted and defined and "C)" is correct as compared to yours.  Please explain how your position of Emf=Cemf when di=.8A/s fits in my series connected model.

Now think about that a minute.  How can a di of .8A/s equal zero volts?  Anytime current is changing in a condutor, there is also a changing magnetic field and a subsequently induced non-zero CEMF.

I didn't say that. What I did say in B) is that di=(Emf-Cemf)*dt/L implying that Cemf=0. I don't have a problem with that as I use Cemf for feedback correction only and follow Faraday's law as I stated in B).

I will say here that I have somewhat conceded with this model that Emf/Cemf feedback is required to achieve the .8A/s di in this example which I am not absolutely convinced is the case. Even my own model needs the math fudge to make this happen so something is still wrong here but that is another subject

If CEMF=0 when di=8A/s, then your formula for CEMF in "A)" must also be incorrect.

You are right because in the Cemf in "A" is missing the minus sign.  I don't see a problem with Cemf=0 due to di=Emf*dt/L using conventional current flow. Are you saying that Cemf is inherent in Faraday's original derivation of this formula?

Perhaps, for discussion, you could post the two identical models side by side but with one stating:

C) When di=.8A/s, Cemf=4 volts

With that correction, the model depicts what I and others have been discussing.

Thanks...

PW

I'm sorry PW but I can't seem to justify changing C) to what you state because it makes no electrical sense in the series connected configuration. However, I am certainly open to see how this can be logically achieved.

pm