MH's ideal coil and voltage question

[Magneticitist]

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?

[Magneticitist]

Here is the harder version of the question and the answer:

You have an ideal voltage source and an ideal coil of 5 Henrys.  At time t=0 seconds the coil connects to the ideal voltage source.  The voltage source waveform is 20*t^2.  So as the time t increases, the voltage increases proportional to the square of the time.

The question is what happens starting at t = 0

The answer:

The current through the ideal coil starts from zero at time t = 0 and then increases with this formula:  i = 1.33*t^3.

Time..........Voltage.........Current
0...............0.................0
1...............20...............1.33
5...............500.............166.67
10.............2000............1333.33
20.............8000............10666.67
50.............50000..........166666.7

Brad, you need to try to get up the learning curve such that you get to the point where you come back and acknowledge the answer given above is correct.

look.. I'm just some dude that loves electronics tinkering and never claimed to be any kind of electrical engineer, but this version actually seems a simpler question.  Though I'm extremely confused as to how there is 0 voltage at 0 seconds when at 0 seconds the coil is connected to the source.

For those of us who are trying to interpret your original question properly out of simple respect, any more details as to 'how' you wanted the question answered would be of great help.

[MileHigh]

Magneticitist:

You are way off.  For starters, you threw a lot of mumbo-jumbo talk at this subject earlier when discussing this test.  You are talking more mumbo-jumbo talk now.

Like I already clearly stated to you in an earlier posting, this example has many applications in the real world of your bench.  What we are talking about is real, and there are no philosophical arguments to be made.

We are not interested in the resistance or the capacitance between the windings, at all.  That just makes everything more complicated.  We are not talking about frequency at all.  Nor are we talking about a Joule Thief.  Forget about the usual buzz words and the usual box of tricks, time to get real.

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.

It has every damn thing to do with how an inductor really works.  Your problem is that you have been taken out of your comfort zone.  You like to fire off philosophical musings when it comes to coils and circuits, it gives the impression that you have a "higher order" discussion going on about electronics.  The problem here is that we were trying to figure out how a very simple circuit works and you had no idea yourself.  Don't be dismissive of real solid knowledge and make silly cracks about a dog taking a dump.

The message to you is to come down to Earth and if you want to do better work on your bench, then you want to understand this stuff and have complete mastery over it.  Pay attention and try to learn something important.  Drop the mumbo-jumbo talk and be real.

The question still has not been answered, do you want to take a shot at it?

MileHigh

[Magneticitist]

well at least we can agree, that both sides of this argument feel as if they are speaking to a brick wall that's reading a magazine.


(btw that was sarcasm about the inductor..)

[MileHigh]

look.. I'm just some dude that loves electronics tinkering and never claimed to be any kind of electrical engineer, but this version actually seems a simpler question.  Though I'm extremely confused as to how there is 0 voltage at 0 seconds when at 0 seconds the coil is connected to the source.

For those of us who are trying to interpret your original question properly out of simple respect, any more details as to 'how' you wanted the question answered would be of great help.

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.

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