MH's ideal coil and voltage question

[tinman]

 author=MileHigh link=topic=16589.msg483572#msg483572 date=1462810403]
Thank you partzman for running the simulation. 

MileHigh


Partzmans answer dose not represent your original question.
If partzman runs the same simulation with the resistance value removed,so as the circuit represents your ideal inductor,he will derive the same answer as myself and Poynt.

I am hoping that this gives Brad and others enough information to answer the full question and demonstrate that they understand the concepts and show competence in the subject matter.

The rest of us are hoping that MH learns that when you add ideals into questions,it changes everything drastically,and the situation in no way represents real worl outcomes.

In that sense please refrain from providing further answers to the complete question that defines a multi-part voltage waveform.  The hope is that the interested parties undertake to teach themselves as apposed to being spoon fed the answers.

All the information i have provided has been under my own understandings and research. There has been no spoon feeding thank you very much MH.


Brad

[MileHigh]

Brad:

<<< If the voltage increases,then it is not an ideal voltage,as an ideal voltage dose not change in time. >>>

Actually, that's a "rule" that you seem to have made up for yourself.  An ideal voltage source can be a function of time.  i.e.; v(t) = 7*sin(omega*t).

That's a +/-7-volt sine wave at the angular frequency omega that has a zero output impedance.

I can't fathom how you "lock" yourself sometimes.  An ideal voltage source is a voltage source that has a zero output impedance.  It has nothing to do with it possibly varying in time.

Like I said before, you can have an ideal voltage source that outputs an Ozzy Osbourne song or The Star Spangled Banner - it's still an ideal voltage source.

MileHigh

[tinman]

I just want to point out this argument started over an actual inductor. like, a non imaginary, real world, coil that is part of a real circuit.
The argument began when the group was discussing just how the circuit operated. Now I'm no expert, but I'm fairly sure
this inductor has an inductance and a resistance, and I'm sure some capacitance in the windings.. I'm also pretty sure we can track down
the rest of the factors in the circuit such as source voltage.. frequency.. etc.. I have seen no one do that. Instead days have been spent
arguing over a completely fictitious scenario that basically boils down to a basic philosophical argument about duality or the chicken and the egg.

At this point I don't see how we are any closer to agreeing just how the JT circuit originally in question fires below 300mV.

Instead we have moved to the fantasy realm of an ideal hypothetical scenario because MH want's to prove that
Brad just blindly threw the circuit together and has no idea how it works.

At least I learned something.. I learned that even though one can understand the characteristics of an inductor, how to use it
in a circuit, how it behaves in comparison to other components, and how to work out its role in a circuit over time.. none of that
has absolutely anything to do with how an inductor really works unless you can answer some ambiguous question about a
hypothetical coil.

what happens after T=0? well, there's a dog somewhere that probably took a dump, someone's favorite tv show probably came on,
somewhere along the lines the inductor started charging.. oh and it also continued to display characteristics of any other inductor even though
we have to assume that entirely of faith.

I'm assuming since MH has finished his little test exercise, can we go ahead and start figuring out
what's going on in the actual circuit now?

MH ask this question to a couple of members of this forum,and he has been ranting on ever since how they could not answer his question correctly.

I decided to have a go at answering the question,which is posted in the first post of this thread.
I opened this thread to discuss this original question,and not MHs modified version that now has a non ideal inductor.

I told MH that his question is more complicated than he believes it is.
It has already been established that from T=0 to T=13 seconds,nothing will happen,as current will not flow through an ideal inductor. This opens cans of worms all over the place,as you can see in my previous 4 to 5 posts.


Brad

[Magneticitist]

MH you have to understand, the problems I have with your 'ideal' argument and your test question are entirely based upon the context in which you are using them..

As I said I totally understand the entire use of this circuit theory. Why would I argue that? Of course, by knowing the nature of what you are playing with, you can use certain tools to approximate possible outcomes.. essentially design a functioning circuit on paper and know how it will work before even having to wire it.. I get it..  The argument I have against the 'ideal' 0 resistance situation is simple.. we don't know for sure how a circuit would act with 0 resistance. we just don't. we lie to ourselves and say once we get to a point where from our perspective things become far too 'small' to say they matter anymore, we can just go ahead and say they don't exist.

Anyway like I said it seemed as if you had presented this question like it somehow related to the circuit that was originally being discussed. I'm trying to explain how your pop quiz had entirely nothing to do with the real world circuit in question and you take that as me trying to crap on the basic circuit theory you had to learn and have grown to respect as a useful tool in EE, all talks of 0 resistance aside.


If it would make you feel any better we can dispense with the trivial motions we are sure to play out.. I'm dumb, you're smart. I have absolutely no idea what an inductor is and you're the master of the electronic universe. I resign to the fact that I am utterly incapable of designing even the simplest functional circuit so long as it contains an inductor, and you know them inside out, top to bottom, with no mysteries to uncover.

Now that we have all that out of the way, I'd really like to get back to the joule thief discussion myself.. Didn't you and Brad have a disagreement about the circuit operation?
Is there some further explanation that proves your reasoning somewhere buried underneath this pop quiz question we have spent pages and pages discussing?

[tinman]

The formula for the voltage source that connects to the coil is v = 20*t^2.   Therefore when t=0 the voltage is zero.  This is like setting the voltage on your bench power supply to zero and connecting up a coil.  Then you turn the knob to increase the voltage, and you turn it faster as time progresses.  So the question is what is the current through the coil when you do this?

Do you perhaps think that is a dumb thing to do?  Millions would disagree with you.  What if you play the Star Spangled Banner across the coil?  Well, there will be a current waveform in that case also, and it would not be that hard to determine.  Notice that I say "determine" and NOT "measure."  You don't need to measure the current when the Star Spangled Banner is playing across the coil, you can determine what it is using your brain and a few tools.  That's the whole point in this discussion.  Note that sometimes you simply can't measure the current, you need to use your wits instead to determine the current.

  Please check with Brad first and get his take on how to answer the question.  He should know how to respond to that.  If it is still not clear after that then I will answer you.

The way the question was posed was intentional.  You are supposed to have the electronics aptitude and experience to know what to say for the answer.  I am not saying this to give you a hard time.  Rather, I am just stating this to illustrate how far many bench experimenters have to go to get to a better and more productive place.  There is no point in playing with coils if you don't really know what you are doing.  It might be tough medicine to say that but it is good medicine.  And that brings us full circle back to the question that I asked EMJunkie being repeated here.  He had been playing with coils on his bench for ten years and he couldn't answer the question either.

MileHigh

At this point how to answer the original question should be pretty obvious to most.

Except to you MH.

The first answer we have so far is--nothing will happen.
I am awaiting Poynts review on the reasons for my second theoretical answer-and my theories on the rest of it.

Brad


Brad