MH's ideal coil and voltage question

[tinman]

Brad, the honest truth is that I don't understand your explanation nor your questions. I can't make sense of them. So rather than spending my time trying to understand your theory, I asked you to plot out your current trace according to your understanding, which gives me instant insight into your thinking. Then I might have a chance of steering you in the right direction. But you state that you can not plot out the current according to your theory, while at the same time, rejecting the present accepted theory which is not only predicted by equation and simulation, but makes sense from the conceptual point of view. I think if you are going to reject a theory, you should have one the you feel is the correct one, and be able to explain it and prove that the existing one is incorrect. So far I have not seen this from you.

The inductance value is being used to calculate the peak current at T=7 seconds,but the induction process to make this calculation is not correct between the time period T=5 seconds to T=7 seconds. The inductance value being used to make this calculation is not correct. We have started at T=5 seconds,and ended at T=7 seconds to calculate the peak current reached at T=7 seconds. This is on the understanding that the induction process taking place at this time will start with no current flowing through the coil,and no existing magnetic field. We apply our voltage,and current starts to flow,and a magnetic field begins to build(induction). We calculate that using a 5H coil,the peak current value reached at T= 7 seconds will be 1.2 amp's. But as i said,this assumes that there is no current flowing through the coil. This assumes that a current will begin to flow,a magnetic field will begin to form,and the CEMF value will fall as the magnetic fields change in time reduces.

But what we actually have happening here is the opposite.
A current flow and magnetic field already exist .
The current dose the exact opposite to what the calculations we are using say it should.
The current dose not start from 0 and rise to 1.2 amps,it starts from 2.4 amps and falls.
The CEMF produced from this !once again! magnetic field that is changing in time,is now the same as the EMF that created it,and dose not appose it as it should the way we have made the calculation for the time period of T=5 seconds to T=7 seconds.

So we have used a calculation to gain a peak current value at T=7 seconds, that go's on the premise that there will be a Counter EMF--this give us our current rise over time value.
But what we actually have is a current value drop over time,not a rise,and no CEMF,but an EMF  working with the induced EMF.

So it would seem to me,that the formula used to calculate the peak current value at T-7 seconds,is not the correct formula to use.
If we have no CEMF but an EMF that is not apposing the inducing EMF,then there is no impedance/resistance to to the induced current flow.
So it makes sense that the current flow would sky rocket instantly,as there is no resistance/impedance to slow or stop it.


Brad

[MileHigh]

Brad:

Let's back up and discuss the inductor impedance over the first three seconds.  We all know the drill now, the five Henry inductor makes contact with the ideal voltage source, and for the first three seconds the voltage is four volts.

What is the impedance of the inductor over the fist three seconds?

MileHigh

[MileHigh]

I have taken the liberty of changing MH's original problem sightly so there is now a period following T3 to T5 from T5 to T8 with -4 volts applied to the 5H inductor. This is equal to but opposite the initial T0 to T3 so we can now see what happens to the inductor current.

One might find it easier to visualize the magnetic field around the inductor and how it varies in relation to the current.  I've included an algebraic proof of this relationship.

      𝑬𝒎𝒇 = - 𝑵 × 𝚫𝚽/𝚫𝒕    (Faraday's Law)
      𝑬𝒎𝒇 = - 𝑳 × 𝚫𝑰∕𝚫𝒕       (Inductance defined in terms of Emf)
      ∴ 𝑵 × 𝚫𝚽/𝚫𝒕 = 𝑳 × 𝚫𝑰∕𝚫𝒕   (Substitution)
      ∴ 𝑵 × 𝚫𝚽 = 𝑳 × 𝚫𝑰   (Reduce)
      ∴ 𝑳 = 𝑵 × 𝚫𝚽∕𝚫𝑰      (Inductance in terms of flux)
      ∴ 𝚫𝚽 = 𝑳 × 𝚫𝑰           (Flux over time verses inductance and current over time with 1 turn)

partzman

Thank you, excellent and very informative and enlightening post, especially the new voltage and current vs. time graph.

MileHigh

[Magluvin]

In spirit of the thread lets consider an ideal ferromagnetic as a break from the ideal voltage sources.
What properties would such material have?

For sure it wold not exhibit any hysteresis loss and it would not heat up at all when immersed in a changing magnetic flux.
It would not conduct electric current at all so Eddy currents could not form in it.
Would it have infinite permeability? - I don't think so, anymore than an ideal inductor needs to have an infinite inductance.

What are your thoughts?
What other properties would an ideal ferromagnetic have?

I understand fully. But its just pretend world. Anything can be whatever one may want it to be.

Ive been delving back into the resonance projects. Its not pretend. As Ive read over things here, Ive lost interest. Was thinking, as you just did above, of all the hows and whys of it all and it just plain isnt required as the rules are set. So pretty much all the ideal components and equipment are virtually limitless. Pioneer used to make a set of 6x9 speakers back in the early 80s. The magnets were bigger than any other that have been made. The max power handling was labeled 'Unlimited'. It wasnt that they were not telling the truth really. There just wasnt any car amplifiers in those days that exceeded or even came close to the real power handling of the speakers. So in that world back then, they were unlimited in power handling.  They were ideal in that world.

Mags

[tinman]

Brad:

Let's back up and discuss the inductor impedance over the first three seconds.  We all know the drill now, the five Henry inductor makes contact with the ideal voltage source, and for the first three seconds the voltage is four volts.

What is the impedance of the inductor over the fist three seconds?

MileHigh

Well,as the impedance is just a resistance to the current that wants to flow,is it correct to say that the impedance is a result of the CEMF?,--as we know,there is no ohmic resistance.