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Author Topic: MH's ideal coil and voltage question  (Read 477573 times)

minnie

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Re: MH's ideal coil and voltage question
« Reply #450 on: May 16, 2016, 12:57:34 PM »



  Have you had a gander at the Waterloo induction analogy?
            J.

partzman

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Re: MH's ideal coil and voltage question
« Reply #451 on: May 16, 2016, 02:25:55 PM »
Something that keeps coming to mind as i think....

When we see the demo of a magnet being suspended above a superconductor, It is said that as we put the magnet in place, I suspect a particular height above the super conductive object, that as the field of the magnet sets up lenz currents in the superconductor that are set in motion indefinitely and it sets up an opposing field against the mags field and it floats. So in that case the lenz field is even stronger than the mags field at float as to hold up the weight of the magnets mass, let alone just be equal to the field of the magnet. So is it not possible that this balancing act could be inherent in the ideal perfect inductor? Still thinking on it all. Which is good I suppose.  Have some work to do tonight. Will see what I figure on it all

Mags

Mags,

Let me say again that I'm no expert on superconductivity however, I would like to comment on your thoughts above.

In a type I superconductor, all the magnetic flux is outside the superconducting material. If you approach the type I with a magnet, the magnet will be repelled into space because the magnetic field can not penetrate the type I superconductor.

In a type II superconductor however, the levitating magnet is held in place via flux pinning.  In a type II superconductor, magnetic flux penetration is possible and it produces quantum current vortexes or tubes. These penetrating flux tubes loop around the magnet and hold it in fixed position above the superconductor. Wikipedia shows a good representation of this plus a good explanation.

partzman


poynt99

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Re: MH's ideal coil and voltage question
« Reply #452 on: May 16, 2016, 02:40:26 PM »
You mean like the benefit of doubt that he gave me regarding the ICE having resonant systems?. Guessed you missed all that. This is the very same situation. He told me i had no idea what i was talking about,when Internal combustion engines are my forte--my area of expertise.
The difference is,i backed up my knowledge with provided fact's,and this is something no one here can do with an actual test,as we are talking about ideals we do not have. What we are doing is placing a theory based around !best guesses!.

So i have given MH no more than he has given me,and in fact,i have never used the foul language he has toward me.
Not once did i see you,or any other EE guy here tell MH to calm it down when the roll was reversed,but i see you are quick to jump on me when i do the same that has been done to me.

I have seen this very same thing with other members that disagree with MHs analogy.
It's an !agree with me! or your wrong attitude MH has--plane and simple.
As i said in the other thread,i will now treat him as he treats me.

As i said,there is a pattern that is followed on this forum,and that is the EE guys stick together--bar one,that being (as i have always said) verpies. I would also put vortex1 in there with verpies,but he dosnt frequent this forum much-sadly.
As verpies said in reply to this question,Quote : The equivalent circuit model for an ideal inductor is not an inductor with a wire shorting across its ends.
verpies-Just because most of the world does it wrong does not mean that we have to.


Brad
All I will say Brad is that posts like you made inferring that MH did not know the answer to his question are just not good, for you, nor the forum, especially since it is a question having to do with electrical fundamentals.

And you are right, MH is not infallible, nor am I, TK, nor anyone I know on this forum. But you are wrong about the techies always sticking together. We do sometimes disagree, and that is ok. Like you, if I see something that I feel is incorrect or nonsense, I will point it out, regardless of who posted it. And I expect the same of others too, in regards to what I post.

Brad, if anyone can build a 50:1 L/R ratio inductor, I feel it is you. I would encourage you to try to get one together and give this thing a go so you can see for yourself what the circuit current does. For the supply voltages, you could build a 4V and -3V, and 0.5V supply with reasonable ease, and just use a rotary switch to change the voltages manually while monitoring a stop watch. It won't be exactly precise, but close enough to get the gist of what will happen at each transition.

Going with 5H and a 50:1 ratio however would be difficult to achieve without liquid nitrogen cooling I would think, so perhaps the ratio could be reduced and the resulting error taken into account?

What do you say?

Guitar pickups are on the order of 5H, but their R is on the order of 8k Ohms :(

tinman

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Re: MH's ideal coil and voltage question
« Reply #453 on: May 16, 2016, 04:04:41 PM »








Quote
All I will say Brad is that posts like you made inferring that MH did not know the answer to his question are just not good, for you, nor the forum, especially since it is a question having to do with electrical fundamentals.

The first thing i will say is--have you said the same thing to MH,when he said i did not know what i was talking about and was wrong,when it came to the ICE,which is my speaciality ?
Secondly-can you say without doubt tha MH would have been able to answer the question correctly,without having proof to back it up.
Thirdly- Regardless of any answer being considered to be correct,it is just theory based around real world examples. As we cannot make such an ideal voltage source to test the theory,then it remains just that-a theory. Lust as verpies said--just because th erest of the world dose it wrong,dose not mean we have to.

Quote
Brad, if anyone can build a 50:1 L/R ratio inductor, I feel it is you. I would encourage you to try to get one together and give this thing a go so you can see for yourself what the circuit current does. For the supply voltages, you could build a 4V and -3V, and 0.5V supply with reasonable ease, and just use a rotary switch to change the voltages manually while monitoring a stop watch. It won't be exactly precise, but close enough to get the gist of what will happen at each transition.

And there in lies a problem. What about that ideal voltage source,where the current is free to flow during the 0 volt cycle. A rotary switch would mean an open circuit in between contacts,and there go's your current flow.
Why not simulate it Poynt,using the lowest value resistance you can.
We have to remember,it is going to be -3 volt's,not a build up of voltage as the current drop's from 2.8 amp's down to the lower value,the ideal voltage source will place -3 volts across that ideal loop regardless of the current. So lets see if you can get your sim to do that.

Quote
Going with 5H and a 50:1 ratio however would be difficult to achieve without liquid nitrogen cooling I would think, so perhaps the ratio could be reduced and the resulting error taken into account?

What do you say?

Guitar pickups are on the order of 5H, but their R is on the order of 8k Ohms :(

Why would it have to be a set value of inductance. Could we not see the effect with any decent inductor?.


Brad

tinman

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Re: MH's ideal coil and voltage question
« Reply #454 on: May 16, 2016, 04:11:31 PM »


  Have you had a gander at the Waterloo induction analogy?
            J.

And as you can see from that very example minnie,that my prediction is correct. The water wheel being the inductor will keep pumping the water against the pump when the direction of the pump is reversed. This works against the pump,it dose not store it's energy in the pump at Poynt said.


Brad

Magneticitist

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Re: MH's ideal coil and voltage question
« Reply #455 on: May 16, 2016, 04:37:27 PM »
still reading this but have been wrapped up tinkering hardcore with some stuff someone sent me.
just wanted to leave this here for Mags and Bill.  interesting stuff regarding electron movement.
http://hyperphysics.phy-astr.gsu.edu/hbase/electric/ohmmic.html

partzman

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Re: MH's ideal coil and voltage question
« Reply #456 on: May 16, 2016, 04:46:33 PM »


And there in lies a problem. What about that ideal voltage source,where the current is free to flow during the 0 volt cycle. A rotary switch would mean an open circuit in between contacts,and there go's your current flow.
Why not simulate it Poynt,using the lowest value resistance you can.
We have to remember,it is going to be -3 volt's,not a build up of voltage as the current drop's from 2.8 amp's down to the lower value,the ideal voltage source will place -3 volts across that ideal loop regardless of the current. So lets see if you can get your sim to do that.

Why would it have to be a set value of inductance. Could we not see the effect with any decent inductor?.


Brad

Brad,

Trust me when I say that a sim using an ideal voltage source and an inductor with a really, really small resistance will properly demonstrate the point that MH and others are trying to get across.  The question is, would you believe it and accept it?  To understand this may open up new horizons for you in your quest for OU.

I am not a 'EE' or an 'E' or even an 'e', but I have studied greatly to show myself approved. This is a difficult way to go but one can get an education either formally or informally but we all must be willing to learn.  For example, I could raise a rucus here by stating that Distinti's magnetic theory says Maxwell's equations for electromagnetic waves are incomplete. I would guess that the EEs here would/will take issue with this. The point is, we must all be willing to learn.

Poynt or myself could post a sim showing the answer to the question but I chose not to do so out of respect to MH because he asked me not to.

partzman

minnie

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Re: MH's ideal coil and voltage question
« Reply #457 on: May 16, 2016, 04:57:56 PM »



  As I understand it in the analogy the torque of the pump is the voltage.
  Am I correct?
           Having a bad day "at the office".
        J.

poynt99

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Re: MH's ideal coil and voltage question
« Reply #458 on: May 16, 2016, 07:02:41 PM »
The first thing i will say is--have you said the same thing to MH,when he said i did not know what i was talking about and was wrong,when it came to the ICE,which is my speaciality ?
Yes, in private I have talked to MH about keeping his tone in check, and yes I would agree that he still goes a little too far sometimes.

Quote
Secondly-can you say without doubt tha MH would have been able to answer the question correctly,without having proof to back it up.
Absolutely. It perplexes me why you would even question this.

Quote
Thirdly- Regardless of any answer being considered to be correct,it is just theory based around real world examples. As we cannot make such an ideal voltage source to test the theory,then it remains just that-a theory. Lust as verpies said--just because th erest of the world dose it wrong,dose not mean we have to.
Not sure what you mean by "theory based around real world examples", but as I've already explained, and MH did also a while back, we don't need a perfectly ideal source nor inductor to prove out the equation that MH posted, which determines the final value of current in the inductor, based on the L and t, and initial current Io.

Quote
And there in lies a problem. What about that ideal voltage source,where the current is free to flow during the 0 volt cycle. A rotary switch would mean an open circuit in between contacts,and there go's your current flow.
Most voltage sources are close enough to ideal for this test. Yes, a rotary switch may cause some loss due to an imperfect transition.

Quote
Why not simulate it Poynt,using the lowest value resistance you can.
I have already done so. A number of posts back I gave a recommendation as to the L/R ratio that would still provide results "close to ideal", at least close enough for our purposes. I established this level (50:1) by using the sim with various values of R to get 5% error on the final current. Did you miss that post? It was done with the simulation. I have already posted a partial plot of the current, did you miss that also?

Quote
We have to remember,it is going to be -3 volt's,not a build up of voltage as the current drop's from 2.8 amp's down to the lower value,the ideal voltage source will place -3 volts across that ideal loop regardless of the current. So lets see if you can get your sim to do that.
As I said above, I have already fully simulated the circuit, as has Partzman. I am sure our results are identical.

Quote
Why would it have to be a set value of inductance. Could we not see the effect with any decent inductor?.
If you followed my posts on establishing the L/R ratio for a "close to ideal" inductor, you would know that any value of inductance can work, as long as we are aware that a 50:1 L/R ratio will present a 5% error in the current values. The current will be 5% (or thereabouts) less than the value predicted by MH's equation.

MileHigh

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Re: MH's ideal coil and voltage question
« Reply #459 on: May 16, 2016, 07:17:24 PM »
I already discussed simulating this in the real world on another thread.  Say you had a 2x1000-watt car audio amp.  I am pretty sure they have huge voltage inverters in them so the run off a bipolar supply.  They are giant ideal voltage sources within certain bandwidth and IV limits.  If you could hack into one so that you insert a current viewing resistor at the output such that the voltage sense is on the far side of the current viewing resistor then you should be good to go.  You just need a scope channel for the CVR and I am assuming that the car audio amp is being powered by a car battery.  You connect up your arbitrary waveform generator (or iPhone) to the amplifier.

Then perhaps go to the hardware store and buy a bunch of looped hollow copper pipe for your inductor.  There is probably a better way of doing the coil but that's the one that comes to my mind.

All that you have to do is shorten the timing and lower the voltages and you should be able to do a setup that is a very good facsimile of what we are discussing here.  As long as you don't exceed the IV capabilities of the beefy car audio amplifier you should be fine.

But of course, measurements like these were probably made thousands of times already.  What's of more value is the intellectual understanding and solving the problem on paper.  That's what we are trying to do here.

MileHigh

verpies

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Re: MH's ideal coil and voltage question
« Reply #460 on: May 16, 2016, 07:33:20 PM »
As I understand it in the analogy the torque of the pump is the voltage.
Am I correct?
Yes.
It is interesting to consider, which way the energy flows when the pump rotates against that torque.

MileHigh

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Re: MH's ideal coil and voltage question
« Reply #461 on: May 16, 2016, 07:41:59 PM »
If the question in this thread is ever answered properly or not, I strongly advise anybody interested to go back and read it again from the beginning.  You can decide for yourselves.

As an example, I somehow doubt we are going to get any more challenges about the concept of a time-variable ideal voltage source.  Nor will we get any admissions that this was all just silliness and a useless and nonsensical waste of time and energy from the main players.

I will also repeat the main goals for this thread:

1.  Brad gets up the learning curve and understands the original question and then answers it correctly all by himself and clearly demonstrates that he understands the concepts and understands what he is doing.
2.  Brad admits that he was wrong when he stated that my response to the harder question was wrong.

I would really hope that Brad successfully achieves those two goals.

verpies

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Re: MH's ideal coil and voltage question
« Reply #462 on: May 16, 2016, 07:48:43 PM »
I see no difference in what i said,and what you have stated above.
The motor that drives the positive displacement pump you have used,will still encounter the force of the water moving in the opposite direction to that of the applied torque to the pump.
You have simply separated the pump from the motor. But any force placed upon the pump will be transferred to the motor.
The difference is huge because now the torque is not synonymous with the rotational direction of the impeller and the pump can rotate with or against the torque.

Thus, we can have a typical 4-quadrant operation:
1) The pump moving CW with a CW torque.
2) The pump moving CW against a CCW torque.
3) The pump moving CCW with a CCW torque.
4) The pump moving CCW against a CW torque.

In two of these cases, the energy is transferred to the pump, and in two other cases, the energy is transferred from the pump.
Can you assign the direction of energy flow in these four cases?


As the motion of the pump/motor combo i was using to represent the voltage(our force),then i included the bypass valve to represent no motion of the motor/pump--the equivalent of the 0 volt level in the question. Having the impeller still moving,would be seen as a resistance against the flow of water,and in our ideal loop,we have no resistance to the flow of the current,and so the bypass valve was included for that reason also.
In an ideal pump, as well as in an ideal pipe, there is no resistance to the water's motion and lately we've been considering an analogy of an ideal L circuit here, so all the analogical hydraulic components must be ideal, too.
Thus, the water can move the impeller without any friction ...and the impeller can move the water without any friction, too.

MileHigh

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Re: MH's ideal coil and voltage question
« Reply #463 on: May 16, 2016, 07:58:35 PM »
Yes.
It is interesting to consider, which way the energy flows when the pump rotates against that torque.

I am just going to offer up simplified analogies and perhaps they will help.

The water pump in this case never impedes the water flow, but what it does do is create an increase in pressure in that water itself.   So you don't necessarily have to think about a tangible water pump, just what it does.  So if the pressure is 10 psi on one side of the pump, then the pressure is 14 psi on the other side of the pump.  Or perhaps the pump drives the pressure the other way:  the pressure is 10 psi on one side of the pump, and 7 psi on the other side of the pump.

That's the type of water pump we are talking about in this example, a constant-pressure pump.  You don't care about the water flow rate or even the direction of the flow, the only thing that counts is that the pump establishes a difference in water pressure from one side to the other side.  You can even block the water flow, and the pump still does the same thing.

However there is another type of water pump you can also imagine, a constant-flow pump.  It's easy to imagine perhaps a large diesel engine with a transmission that lowers the shaft output speed that drives some small pistons that pump water at a certain flow rate.

In this pump, you don't care at all what the water pressure is on either side of the pump.  The only thing  you care about is that the pump pumps say six gallons of water per minute.  The pressure at the output side of the pump could be 100 psi or 1000 psi, it doesn't matter and the pump will pump at a constant water flow rate.

wattsup

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Re: MH's ideal coil and voltage question
« Reply #464 on: May 16, 2016, 08:30:19 PM »
If the question in this thread is ever answered properly or not, I strongly advise anybody interested to go back and read it again from the beginning.  You can decide for yourselves.

As an example, I somehow doubt we are going to get any more challenges about the concept of a time-variable ideal voltage source.  Nor will we get any admissions that this was all just silliness and a useless and nonsensical waste of time and energy from the main players.

I will also repeat the main goals for this thread:

1.  Brad gets up the learning curve and understands the original question and then answers it correctly all by himself and clearly demonstrates that he understands the concepts and understands what he is doing.
2.  Brad admits that he was wrong when he stated that my response to the harder question was wrong.

I would really hope that Brad successfully achieves those two goals.

Where did the bold words in your post come from? Seems this is the first time this is used in front of the words "ideal voltage source" since this was not in your initial question of ideal voltage on an ideal inductor. If so then why is that graph showing a straight line at 4 volts for 3 seconds? Why would you equate a time variable with ideal voltage, when ideal voltages do not change?

Hmmmmmmmmm (with my wet index finger pointing upwards) did the wind change directions? Or do I sense a hurricane is about to form.

wattsup