MH's ideal coil and voltage question

[poynt99]

I've already stated this and I know it did not register, so here it is again:

With a non-ideal inductor, the instant Vin is applied, all the voltage appears across the inductance, and nothing across the resistance (assuming a lumped inductance and resistance model), therefore Vin=cemf, and lo and behold, current still begins to flow. In fact this is the moment the A/s is the highest rate!

Now, what happens if we were able to make R smaller and smaller?

The above is germane to the argument, yet no comments.

[tinman]

 author=MileHigh link=topic=16589.msg487413#msg487413 date=1467212939]

I asked you a couple of times to give a concrete example of where the CEMF must be less than the EMF for current to flow using a simple example with a coil and voltage source with actual numbers and you refused.  You can't actually put substance to your beliefs.

Well Mr resonance,i have done this by way of showing that when the BackEMF in a DC PM motor equals the applied EMF,then no current flows,and no BackEMF voltage can be measured--the same applies for every other electronic component. Show me just one other component that will allow for current flow,when there is no potential difference across it's terminals.

So, we often hear, "This is what I believe but I can't really explain it and I cannot give you a concrete example illustrating my theory with numbers."  And that is just plain bogus.  Here is a classic example, "Repeatedly shorting a coil gives extra energy."  The thread name is , "Shorting coil gives back more power."

And you know this is bogus by experimentation MH?

Quote:Additional phenomenon has also been discovered in atomic physics and has created a lot of confusion and speculation about how the atom fundamentally works. An example of this atomic phenomenon is based on the fact that all atoms are considered to have orbiting electrons, which in theory should radiate electromagnetic energy as they orbit the positive nucleus. This theoretical loss of un-replenished radiated electromagnetic energy should result in the negative electron eventually spiralling inwards and collapsing into the positive nucleus. But in reality this loss of radiated energy is not observed as happening. Scientists are still unclear as to why this is so.

With respect to the discussion, there is more than one way to skin a cat and so different ways of explaining the whole EMF/CEMF business have been explored.  Then there is the pure reality of doing tests on your bench.  And within that reality you must have the full conscious realization that within the real coil on your bench, there is actually an ideal coil, and that ideal coil is functioning exactly like the EE equations state it should function like.  Saying, "I only deal with real stuff on my bench" is almost a strange thing to say because the exponential response of the real coil comes directly from the ideal coil that is the basis for the real coil.

It is funny to watch you tried to compare real and ideal as one in the same,where one will dissipate energy,and the other will not. All your electrical models which include inductors,have a series resistor,and that is to show that there is a resistance associated with real world inductors. It also clearly shows there will be losses associated with that inductor.

Perhaps you would like to have a go at the diagrams below--which is correct?



Brad

[tinman]

Actually MH doesn't every scope shot of an inductor with a voltage applied across it's terminals generating a linear current rise give proof that Emf = L*dI/dt or rearranging di = Emf*dt/L? Where is the evidence of Cemf? So, anyone adhering to the notion that Emf = Cemf in a single inductor has the burden of proof IMO to show by experiment or math derivation that it exists.

By definition, Cemf is opposite to Emf.  The current increase in the above example is in phase with the applied Emf and follows Faraday's law without Lenz. How do we justify any amount of negative Cemf to be added to the Emf and still adhere to Faraday's law? I am willing to change my view if and when I see something convincing.

pm

Edit

Faradays own Faraday disk generator dosnt even follow his own law.
Here we have no rate of change in time between the magnetic field and conductor,but current still flows. We can have the magnets stationary to the rotating conductor,or we can have them spining with the conductor--it makes no difference.
But im sure there has been some tweaking to the laws to account for this--as they often do.


Brad

[picowatt]

But as we are dealing with an ideal coil,and none of that negative feedback energy is dissipated

You are correct, it is not dissipated.  That which cannot be dissipated is either stored in, or retrieved from, the magnetic field.  It is what inductors do using and obeying the laws of inductance...

We are going on what, 130 years or so of modern man investigating, defining, and verifying the operation of inductors?  All manner of wire types, geometries, resistance and capacitance, use at frequencies into the THz region, study of inductance in the realm of nano-length conductors, inductors using zero resistance conductors, and all manner of core types have been investigated over those years.

PW

[tinman]

The above is germane to the argument, yet no comments.

This seems to go against what we discussed before Poynt.
We agreed that the CEMF is what limits the current,and stops it from going straight to its steady state value. A voltage appears across a resistor as soon as it is placed across that resistor. The only reason the current value is far less than that steady state value at T=0,is because we have the added series resistance generated by the CEMF ,that is added to the coils winding resistance. We know this to be true,because if there was no CEMF(as we discussed),then the current would go straight up to the steady state value.


Brad