MH's ideal coil and voltage question

[MileHigh]

Here we go again.  Who said that ideal voltages have to be fixed and can't change in time?  It's an ideal voltage, I can say it does whatever I want it to do.  In my second example I state that the ideal voltage v = 20*t^2.  So the ideal voltage increases in value proportional to the square of the time.  There is nothing stopping me from saying that.

What about your function generator when you set it to a triangle wave and you connect it to your circuit?  Supposing that the triangle wave is somewhat attenuated especially at the peaks because of the load on it from the circuit.  Well, what if I said that my "ideal voltage source" had an identical waveform to the somewhat attenuated triangle wave output from your function generator?  Under those static load conditions then the ideal voltage source that clones your function generator output and the function generator output are indistinguishable.  That means you can look at the output from your function generator as being a time-variable ideal voltage source as long as the load condition remains static and unchanging.

[verpies]

Why would you equate a time variable with ideal voltage, when ideal voltages do not change?

I don't know what an "ideal voltage" is and I think that MH does not know either.
Perhaps you had an "ideal voltage source" in mind.

If "yes, then consider these questions:
Does an "ideal voltage source" need to output a constant voltage all the time?
Can a voltage source still be ideal if it outputs an alternating voltage ?

[wattsup]

@MH - @verpies

Common guys. We have been through this how many times.

Here is a common definition.
"An ideal voltage source is a voltage source that supplies constant voltage to a circuit despite the current which the circuit draws."

In this definition, one can summarize that there is no variability in the voltage source. If you adjust your voltage at 4 volts, it stays at 4 volts regardless of any current draw.

In the video I posted on my shorting a wire over a battery, the battery is not an ideal voltage source so the voltage will drop as I short it with that wire. But in that case it is still backed up with 100 amps so that wire went zap in a few seconds. This for @tinman and myself and many others was the complete basis of why the question of ideal voltage on an ideal inductor was more then moot, it approached ludicrous because for us, like I said in my post, come hell or high water, that voltage should never change. This for us signifies a DC voltage holding a fixed straight line as in @partzman's graph showing the first three seconds as a straight 4 volts. Where is the variable in time there for the voltage. None. Yes it will show a variable current rise from t0 onward.

This is why I was stating that for any voltage to change across the terminals of the ideal voltage, it has to come from the inductor.

This was the whole basis of my prior post and of most posts from @tinman and the root of all this commotion that started with an innocent JT circuit.

A time variable ideal voltage source, for me, is not a DC fixed ideal source but either an AC ideal source or a DC ramped ideal source. Totally different animal. But in either of these three, using the term IDEAL will still signify that once they are set, they are set for life. No change possible and thus they become the fixed anchor to other variables that one can experiment with.

Hmmmmmmm.

wattsup

[poynt99]

I don't know what an "ideal voltage" is and I think that MH does not know either.
Perhaps you had an "ideal voltage source" in mind.

This is what MH actually said:

As an example, I somehow doubt we are going to get any more challenges about the concept of a time-variable ideal voltage source.

It's quite clear to me what he is referring to.

If "yes, then consider these questions:
Does an "ideal voltage source" need to output a constant voltage all the time?
Can a voltage source still be ideal if it outputs an alternating voltage ?

It is perplexing to me to see these questions 

To clarify for all interested, one simple answer to cover all questions as to what an ideal voltage source is:

An ideal voltage source is a source that outputs a voltage according to what it is set to, no matter what load is connected to it. This does not preclude ideal function generators.

I trust you can now answer both of your questions.

[partzman]

@MH - @verpies

This for us signifies a DC voltage holding a fixed straight line as in @partzman's graph showing the first three seconds as a straight 4 volts. Where is the variable in time there for the voltage. None. Yes it will show a variable current rise from t0 onward.

wattsup

Wattsup,

Yes, I created that ideal voltage source and applied it to the ideal inductor for three seconds and that voltage source was faithful to it's duty and it did not change for that duration.  I could however, create a new ideal voltage source of 0 volts in magnitude and replace the original 4 volt ideal voltage source and it too will do it's job. In a sim, I can do this in few ns of time and maintain a duration of my choosing.

I can continue to replace each ideal voltage source with another as I choose since there is no law I am aware of which prevents me from doing so.  Each ideal voltage source I create has the ability to maintain it's magnitude no matter the load.  Proceeding in this manner allows us to be able to solve MH's problem.

partzman

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