MH's ideal coil and voltage question

[MileHigh]

For Brad:

Don't get put off with what may look like a bunch of Engineering mumbo-jumbo talk.  I never intended to go in this direction.  All of the mumbo-jumbo talk can be expressed in ordinary simple English that anybody that wants to learn can truly learn.  I am glad that you are all fired up about this subject.

So I am going to ask you again to rethink your stance.  Accept the fact that at 3 seconds the current has climbed to 2.4 amps in a perfectly straight line.  Assuming that you do accept this fact, then the next step for you and your peers is to figure out how and why, and how you can apply this to real life.

I am still hoping that you and your peers will be able to answer the question and explain why.  At this point the thread has been littered with clues.  The best-case scenario would be for you to leverage off of this information and brainstorm with your friends and answer the simple question about the current waveform and demonstrate that you understand the how and why of what's going on.

MileHigh

[minnie]

   Oh, when I do 4/1.66666 I get something like 2.4A. Amazing!
                John.

[Magneticitist]

The Tau business is fairly simple to explain.

When you transition from a finite Tau to an infinite Tau the current waveform goes from an inverse exponential curve to a straight line.  Note that it is a straight line with a constant slope of V/L.

So Tau at infinity just means the current trace is a perfectly straight line.  Since it is a straight line the concept of "reaching 63% of the maximum value" does not apply anymore because that concept does not exist when the current waveform is a perfectly straight line.  i.e.; "There is no time constant."

So Tau being infinity does not mean stopping current flow, it means linearly increasing current flow.

Since we are discussing limits, the only possible way for the current to flat-line at zero "forever" would be for the inductance to be infinity.  Then you have a "more real" Tau = infinity because this time L/R becomes infinity/R.

So when Tau = infinity/R that gives you the horizontal current trace stuck at zero with a slope of zero (V/infinity), whereas when Tau = L/0, you get a current trace that is a straight line with with a slope of V/L.

is it really that simple to you? how can this not be construed as utterly confusing and even contradictory? I suppose I just have it completely backwards, but isn't our ability to calculate the current at a given time based upon the constant? but yet we remove the constant and un-tether it to infinity like what would happen to any normal inductor without a time constraint with which to calculate it? how do we know the rate of charge would follow a straight line incline, isn't the magnetic field supposed to be able to follow an equally opposing one making it just a flatline forever?

if you were to 'zoom in' at roughly the 99.5% point of the inductors charge you may see that you have only just begun charging it. it would almost be like looking at this examples straight incline with an infinite or 'no time constraint'.  the idea of 'infinity' or 'zero' seem to introduce some natural 'stalemate' as another user put it. we are expected to look at 0 as a balance of opposing forces, or a neutral. an at-rest. yet in this case the 0 is just supposed to represent a lack thereof as if there is a difference. it's not something I'm tying to argue to death it's just very counter intuitive in my opinion sorry of that offends you.

[EMJunkie]

Ok,im going to need help understanding this Poynt

The zero current meaning no load is no problem,but having an infinite load(a load of infinite proportions),would this not require a current flow of infinite magnitude?,and we have no current flow.


Brad

Personally I think the term: "infinite load" is just silly.

I would prefer the term: "infinite resistance" as Current (I) is directly proportional to the Resistance (R) of the load and the Voltage (V) applied accross the Load. Ohms Law Exquation: V/R = Current (I)

With: "infinite resistance", no current can flow.

I know this is what Poynt meant, but this mix in words is confusing for others that dont know.

    Chris Sykes
        hyiq.org

[MileHigh]

is it really that simple to you? how can this not be construed as utterly confusing and even contradictory? I suppose I just have it completely backwards, but isn't our ability to calculate the current at a given time based upon the constant? but yet we remove the constant and un-tether it to infinity like what would happen to any normal inductor without a time constraint with which to calculate it? how do we know the rate of charge would follow a straight line incline, isn't the magnetic field supposed to be able to follow an equally opposing one making it just a flatline forever?

if you were to 'zoom in' at roughly the 99.5% point of the inductors charge you may see that you have only just begun charging it. it would almost be like looking at this examples straight incline with an infinite or 'no time constraint'.  the idea of 'infinity' or 'zero' seem to introduce some natural 'stalemate' as another user put it. we are expected to look at 0 as a balance of opposing forces, or a neutral. an at-rest. yet in this case the 0 is just supposed to represent a lack thereof as if there is a difference. it's not something I'm tying to argue to death it's just very counter intuitive in my opinion sorry of that offends you.

For starters, just forget about all of the talk about an inductor being an infinite value.  The take away from this is as follows:  As the resistance gets lower and lower, the time constant gets longer and longer, and the inverse exponential curve for the current waveform gets flatter and flatter.  When the resistance drops to zero it becomes a straight line and then the concept of a time constant becomes invalid.

So, how much of a mind bender is it really to go from a sloped current waveform that is nearly perfectly flat and you only start to detect a slight curve in the waveform after five hours and a sloped current waveform that is perfectly straight?

What you really want to do if you are interested is work with your peers and focus on trying to understand what the circuit is doing and and answering the question.  Focus on doing the research and trying to answer the question.  If you know what you are talking about, this is a very simple problem with a very simple explanation.

Also as a side note, if you are serious, you have to work on your language and start using commonly accepted terms and phrases to describe electronic circuits.  You need to reign in the meaningless expressions and the mixing up of variables and concepts and use the proper term for the proper concept.