MH's ideal coil and voltage question

[MileHigh]

How John?

Perhaps like this:

http://www.oxforddictionaries.com/definition/english/abstraction

The process of considering something independently of its associations or attributes.

"The question cannot be considered in abstraction from the historical context in which it was raised."

"When, for instance, we claim that water can freeze, we consider water simply as such, in abstraction from the conditions in which any given amount of water finds itself."

[MileHigh]

Brad:

Your postings #543, 544, 546, 547, 552, 553, 554 and 555 are all just useless trash talk.  Poor Brad is having difficulty understanding what an ideal voltage source is and how it works and he can't wrap his mind around a few concepts that are associated with the abstract concept of an ideal voltage source.

So we have to endure yet another ridiculous push-back and a whole litany of what are basically nonsensical statements from you.  You are trying to attach real and tangible properties to what is just an abstraction.  You are back trying to force pieces of a jigsaw puzzle together that don't fit because apparently that's the only way your brain can process it, or, it's an obstinate refusal to learn.

A discussion about a simple circuit that has an ideal voltage source in it should be about the operation of the circuit, not about how an ideal voltage source works.  You are just causing problems where there are no problems and in that sense your behaviour is the same as Wattsup's behaviour where he is freaking out about the very simple and straightforward question.

So that's eight postings that should never have even been made because they are all useless and don't deal with the question, as well as mostly being useless trash talk.

From the very start, there should have been no disagreement at all about what an ideal voltage source is, and how it works.  You have to do better than that, and it's time to move on.

MileHigh

[MileHigh]

I cannot agree to the ideal voltage source being able to absorb energy if it cannot contain it.
If any energy is absorbed by the ideal voltage source,and that ideal voltage source dose not dissipate energy,then the energy must now be contained in it(the ideal voltage source).

I cannot agree with MHs statement that the energy is just gone-disappears.
MHs question consists of two components only--the ideal voltage source,and the ideal inductor. He has made this apparent many times when he has stated that EMJ and Wattsup could not answer a simple question that involved on two components.
MH also states that the ideal voltage source can deliver energy,but dose not contain energy.

At T=5s, what would the solution below read?
And then again at T=7s,what would the solution below read?.

Brad

No Brad, we are asking you for what would be happening in the circuit at t=5 seconds and t=7 seconds.  And if you can't put numbers to it yet, we are asking you to tell us what you think should be happening and why it should be happening.  That is the whole point of this exercise, to learn how the circuit works and to understand the concepts and to demonstrate competency.

For example, let's back up for a second.  Look at the first three seconds where you have been given the answer.  Please explain why there is a linear ramp of increasing current up to 2.4 amps.  Why is that?  How do you explain it?  This is what this thread is all about, and I don't think you have even explained the answer to the first part of the question that has been given to you.  Can you explain the ramp up in current to us in your own words?  Why is it 2.4 amps at the end?  Why isn't it two amps or three amps?

It's too bad your peers have dropped out, I guess they don't know themselves and aren't comfortable trying to brainstorm with you.  The only brainstorming I can recall was the usual pie-in-the-sky brainstorming talk about electrons and electron drift and all that jazz that had nothing to do with the question.

It would be great if you met those two goals that I have posted several times.

MileHigh

[verpies]

At T=5s, what would the solution below read?
And then again at T=7s,what would the solution below read?.

I did not follow the discussion and I am not sure what the values for the inductance (L), exciting voltage(V) or resistance (R) are supposed to be in this case.  Without these values I cannot make the calculation.

Anyway, whatever these values are, I would use the first formula if R>0 and the second formula if R=0 to calculate the evolution of the current in time i_(t) flowing through the inductor.  This is because the first formula degenerates into the second formula when R approaches 0 Ohms.

P.S.
These formulas are accurate only when the inductance (L), exciting voltage (V) and resistance (R) do not vary in time.  If they do, than much more complicated formulas would need to be used. 
But if there is only an initial current I₀ already flowing at the time t₀, then its value should be simply added to the result.

[MileHigh]

Verpies:

Thanks for the two formulas.  Way back earlier in this thread I told Brad you use the appropriate formula for the appropriate circuit.  If there is no resistor in the circuit then you don't work with a formula that includes an undefined L/R (or V/R) of infinity.  Of course with Brad that was another battle.

The formulas are fine but of course, and just to repeat myself, the purpose of this thread is for Brad and his peers to actually understand the how and the why, and demonstrate full competency with respect to this subject matter.  As we know, there is a potential downside in providing formulas because then you rely on the formulas only without thinking.

MileHigh