MH's ideal coil and voltage question

[verpies]

I thought that the self-inductance was a physical property,

On the most basic level it is a simple ratio that tells you how many Webers you get per Ampere.
L=Φ/i

[MileHigh]

How about trying to state inductance in something a bit more tangible that people can relate to?  It's all basically the inertia of the current flow when passing through an inductor.

If you have one Henry of inductance and you put a voltage of one volt across it, you get one amp of current after one second.
If you have two Henrys of inductance and you put a voltage of one volt across it, you get one-half amp of current after one second.
If you have one Henry of inductance and you put a voltage of two volts across it, you get two amps of current after one second.

More Henrys = less amps.
More voltage = more amps.

When you think about that hard you realize that one Henry is one volt-second per amp.

It's perhaps easier to think about the inverse of that, which is one amp per volt per second.

So, one Henry of inductance gives you one amp per volt per second.
One-half of a Henry of inductance is less inertia, so you get two amps per volt per second.
Two Henrys of inductance is more inertia, so you get one-half of an amp per volt per second.

It's really as simple as that.  It's like pushing on a bloody shopping cart, the lighter the shopping cart, the faster it will accelerate, the heavier the shopping cart, the slower it will accelerate.  The speed of the shopping cart is the current flow.  The mass of the shopping cart is the inductance.

It's all very simple and very understandable if you choose friendly concepts like inertia and friendly units like amps per volt per second.

But unfortunately this simplicity was destroyed by a positively insane argument that no current would flow in an ideal inductor.  It's a travesty.

Travesty:  1. a false, absurd, or distorted representation of something.  2. represent in a false or distorted way.

[tinman]

How about trying to state inductance in something a bit more tangible that people can relate to?  It's all basically the inertia of the current flow when passing through an inductor.

If you have one Henry of inductance and you put a voltage of one volt across it, you get one amp of current after one second.
If you have two Henrys of inductance and you put a voltage of one volt across it, you get one-half amp of current after one second.
If you have one Henry of inductance and you put a voltage of two volts across it, you get two amps of current after one second.

More Henrys = less amps.
More voltage = more amps.

When you think about that hard you realize that one Henry is one volt-second per amp.

It's perhaps easier to think about the inverse of that, which is one amp per volt per second.

So, one Henry of inductance gives you one amp per volt per second.
One-half of a Henry of inductance is less inertia, so you get two amps per volt per second.
Two Henrys of inductance is more inertia, so you get one-half of an amp per volt per second.



Travesty:  1. a false, absurd, or distorted representation of something.  2. represent in a false or distorted way.

It's really as simple as that.  It's like pushing on a bloody shopping cart, the lighter the shopping cart, the faster it will accelerate, the heavier the shopping cart, the slower it will accelerate.  The speed of the shopping cart is the current flow.  The mass of the shopping cart is the inductance.
It's all very simple and very understandable if you choose friendly concepts like inertia and friendly units like amps per volt per second.
But unfortunately this simplicity was destroyed by a positively insane argument that no current would flow in an ideal inductor.  It's a travesty.

It's really not that simple MH. And the travesty is you have not taken the time to draw out your own circuit,or realize what you have described. Most every other EE guy has just followed your lead,without thinking or doing the same.

It is like i said,you cannot place an ideal voltage from an ideal voltage source across an ideal inductor. The reason you dont understand this,is because you dont understand your own two component circuit.

Verpies was the only one to touch on why you cannot have or place an ideal voltage across an ideal inductor(quote: Since an ideal inductor must have a zero resistance, this means that it must be shorted (if it ain't shorted, it ain't ideal) and it becomes physically impossible to connect any real voltage sources in series with it.),but i think that your circuit may have past him by as well. Your circuit is an oxymoron-a paradox,and cannot work in reality,as one cancels out the other. If you took the time to draw out your own circuit,and write down all the values of that circuit,and applied all that you have stated in this(and the JT)thread,then you would see the error of your ways.

But as you continue to try and relate ideal coils to non ideal coils,and ideal voltage sources with non ideal sources,you havnt a hope in hell in seeing what your circuit represents.

I can debunk your circuit in just 5 lines of text,but i will give you and the other EE guys here say-4 to 8 weeks lol,--just kidding,say 4 days to think about it.


Brad

[MileHigh]

The travesty continues.

Unfortunately Brad you are not understanding what Verpies is stating or you simply are not reading his actual text properly and/or it is not registering in your brain.

He does NOT say that you cannot place an ideal voltage source across an ideal inductor.  He clearly states that you cannot place a real voltage source across an ideal inductor.  This is the second time I am telling you what he said in an attempt to correct your misunderstanding.

If you are still confused, then please take it up with Verpies.

[tinman]

I have no issue with that representation because it helps to explain a mathematical
way we can calculate charge/discharge using the constant, at the very least. It also
seems like a great presentation so I will definitely give it a look and thank you for
providing it.

I also have no issue with Poynt99's statement :
"Tau has no bearing on whether current can/will flow or not.
The effect it has is how "curvy" the rise of current is, relative to
the timing of your test. With an infinite tau, the curve is going to
be a straight line,"

beat my
head against the wall until I no longer see it that way? You can't quite
prove to me that current would flow over 0 resistance unless we are
talking mathematical constructs. and even then, you say you can use
that math to prove this theory but with R=0 I don't see how it could
possibly result in any answer that is not 'undefined', even if you claim
we are using formulas that do not even require a relationship with a unit
of resistance. Somewhere along the lines, a unit of resistance has to matter
in quantum mechanics. The only 'constant' which I see available for us to
make the determination that current will flow, is the assumption it would
do so because it does indeed flow with very little resistance.


In all honestly I don't wholeheartedly believe in hardly any of this
electron theory. I give it the respect it deserves by not completely
dismissing it and attempting to gain an understanding of it because
as far as I know it retains a complex level of mathematical continuity
across the board but that doesn't mean I'm ready to completely
and absolutely accept every aspect of these theories.

they are not totally tangible to me and a lot of times
just flat out go against my better judgement and intuition.

if I had a specific capacitor charged to a certain voltage
and said it had discharged to x volts over a period of time,
and someone was to tell me they did the math and that wasn't
possible.. chances are I was wrong somewhere because as I said
it's been figured out to a complex level of mathematical continuity.

but what if I wasn't wrong? what if all my units were correct?
what would be the real reality of my capacitor? would that need
investigation or should it be immediately dismissed as wrong?
what if I so immediately dismissed it as wrong only to overlook
a possibility that the math was not accounting for an additional
variable? what if? an important discovery or revelation could be
made, or a lot of freaking time could be wasted having a severe
brain fart cause a decimal was where it shouldn't be. to each his own.

the issue I have is when trying to imagine what would 'actually'
happen if this 'ideal inductor' question was suddenly made reality.
It gets into the atomic model and the more detailed aspects of ultra
complicated quantum physics where I am so lost in the grand scheme of things
I can't say I really know how to make heads or tails of it..
I see a more paradoxical issue where we just wouldn't be able to
'see' or 'observe' the current in any way in the real world so it might
as well not exist as 'flowing'. My position is almost agreeing that current
will flow, but flow just as much as it wouldn't. I know this doesn't seem
to make any logical sense to others but what am I left to do?

It makes perfect logical sense. It is only those here that are trying to relate real world device with ideal devices,and the transition just dose not exist .

PW mentioned the real world superconductors we use today,like in MRI scanners. The problem with that is,they are not charged by an ideal voltage source,and so we only have half the circuit MH has proposed.

Current may flow through a shorted ideal inductor,but like you said--how is it measured?,and how can a voltage  placed across an ideal shorted inductor induce a current flow through a shorted ideal inductor?.   !!Hopefully Poynt will stand back,and look at the circuit MH poses,as MH seems to refuse to do that)

I told MH in the JT thread,that i did not know the answer to the question,in the hope that he would move on,and the JT thread would return back to it's original discussion. But no-MH insist that i continue on with the question,and says the first part has been answered. Truth is,it has not been answered-non of it.

So i stand by my answer due to MHs insistence.

You cannot place an ideal voltage from an ideal voltage source across an ideal inductor.


Brad