MH's ideal coil and voltage question

[poynt99]

I do not know,nor do i have the means to find out.

You have the ability to think and ponder, correct? Perhaps you could use your knowledge to surmise what the traces may look like? For example, would there be anything to "charge" if there were no capacitance? If not, then would that current bump be present?

My point is this--
We would assume that we would not see this with an ideal coil,and we know we do have this situation with a non ideal coil,and so the two will not act in the same manor.

As far as i can see from bench tests,the CEMF dose not equal the EMF at T=0 ,with real world inductors--am i incorrect in saying that?,and if so,what is the initial current spike at T=0,if it is not the charging of coil capacitance ?.

Your point is understood and accepted. However, it seems you are missing the forest for the trees.

[tinman]

 author=poynt99 link=topic=16589.msg487809#msg487809 date=1467724879]

You have the ability to think and ponder, correct? Perhaps you could use your knowledge to surmise what the traces may look like? For example, would there be anything to "charge" if there were no capacitance? If not, then would that current bump be present?

One could speculate that there would be no bump due to the charging of capacitance with an ideal coil.
But one would also wonder as to how that may effect the outcome of the results.
If we remove one part of a system,then it may just make the outcome a whole lot different than thought.

Your point is understood and accepted. However, it seems you are missing the forest for the trees

An interesting saying,as without the tree's,there is no forest.

I know what your saying Poynt,and chances are you are right. But one thing has become of this so far,and that is,for the first time,i have seen the capacitance being charged in an inductor.

I would rather look at things far more closely, and observe everything that is taking place,rather than just look at the forest from afar.
Better to be amongst the trees i think,that way we see all that exist in the forest


Brad

[poynt99]

One could speculate that there would be no bump due to the charging of capacitance with an ideal coil.
But one would also wonder as to how that may effect the outcome of the results.
If we remove one part of a system,then it may just make the outcome a whole lot different than thought.

One can also use their knowledge gained from prior experience to confidently predict certain outcomes.

[MileHigh]

My point is this.
At T=0,with regard to a real world inductor,the CEMF is not equal to the EMF,due to capacitance charging. This means that the ideal coil will react differently to that of a real world coil that has parasitic capacitance.

I think that you are making up one of your "ruel's" but unfortunately it doesn't make any sense.  Even if you add a parasitic capacitance in parallel with an inductor model that consists of an ideal inductor with added wire resistance only, the CEMF will still be equal to the EMF.  You have to think these things through.

once again we see the current trace track the voltage trace,and for a short time,the current actually leads the voltage. This would mean a clear indication of capacitance being charged.

It does look like a capacitance being charged but you typically only talk about current leading the voltage in a case where the excitation is a repeating sine wave.  You can even extend the concept and apply this for things like say a repeating square wave.  But you are not in that territory at all.  You are really just looking at the response to a single pulse and therefore you are misapplying the concept of current leading or lagging the voltage.  It does not apply when you look at the response to a pulse.

Beyond that, you are simply leading yourself down a garden path.  When you look at the scope shot the current does not "actually lead the voltage."  All that you are seeing is that part of the current waveform is higher than the voltage waveform on the scope capture.  You could easily change the gain settings on the scope and then the "current actually leading the voltage" would go away.  One more time, you have to think these things through.

[partzman]

Pursuant to simulating an inductance, I have some questions and comments.

In our ideal inductor of 5H, it is stated that Emf = Cemf when di = .8A/s. Can we then say di = Emf-Cemf?

It is interesting to read Wiki's definition of Counter-electromotive force and I quote in part  "For example, the voltage drop across an inductor is due to the induced magnetic field inside the coil.[1][2] The voltage's polarity is at every moment the reverse of the input voltage.[1][3]"  Is this not contradictory?

pm