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### Author Topic: MH's ideal coil and voltage question  (Read 449261 times)

#### Magneticitist

• Full Member
• Posts: 131
##### Re: MH's ideal coil and voltage question
« Reply #150 on: May 10, 2016, 01:48:40 AM »
Read my posting again and understand it, I solved for R=0.001 ohm so I was not discussing an ideal inductor there.

Good Lord man... did you not just ever so thoroughly stress there is no real difference?
What is the point of this? Why would you even continue to prod him into solving for R=.001 if you are
satisfied with his answer for R=0? We are now practicing an exercise in futility.

I see maybe you are trying to prove a point? show that there is no real difference?
but once again, it wouldn't. you cannot compare two things by only having one of them.

#### tinman

• Hero Member
• Posts: 5363
##### Re: MH's ideal coil and voltage question
« Reply #151 on: May 10, 2016, 01:48:48 AM »
<<< Im sorry MH,but that dose not work either,as the V has no slope ,due to that fact that the voltage is ideal. >>>

The best thing you could do for yourself is follow-though and answer the complete question and demonstrate competence in the subject matter.  You have been given a very generous start, now it's up to you and your peers to follow through.  You still have a long way to go.

The question still has not been answered....

Quote
Read again, Poynt stated that his sim did not run right the first time and when he tweaked the R value it ran as expected and he is in agreement with me now.

That is correct,his sim ran correct the second time when he placed a very small resistance in with the ideal inductor,and the result was no flow of current.
I have not seen Poynt agree with you. I read- This dose not agree with the Tau being infinity,and--thank you for the explanation.

Quote
There is no slope associated with the voltage so I don't know what you are talking about.   Forget the Tau business for now, it's not relevant.

Your diagram shows a clear slope in the voltage across the inductor.
How can Tau not be relevant?.

#### tinman

• Hero Member
• Posts: 5363
##### Re: MH's ideal coil and voltage question
« Reply #152 on: May 10, 2016, 01:52:12 AM »
Read my posting again and understand it, I solved for R=0.001 ohm so I was not discussing an ideal inductor there.

Please solve for R=0,so as we are defined to the parameters of your original question,as i have shown you already the infinite difference this makes even at a resistance far less than .001 ohms

#### MileHigh

• Hero Member
• Posts: 7600
##### Re: MH's ideal coil and voltage question
« Reply #153 on: May 10, 2016, 01:56:00 AM »

Good Lord man... did you not just ever so thoroughly stress there is no real difference?
What is the point of this? Why would you even continue to prod him into solving for R=.001 if you are
satisfied with his answer for R=0? We are now practicing an exercise in futility.

I see maybe you are trying to prove a point? show that there is no real difference?
but once again, it wouldn't. you cannot compare two things by only having one of them.

If you read the posting again you will see that I compared the 5 Henry coil with no resistor (ideal) and the 5 Henry coil with a 0.001 ohm resistor (real) and I clearly show that the behaviour between the two coils is nearly identical at t=1 second.

#### Magneticitist

• Full Member
• Posts: 131
##### Re: MH's ideal coil and voltage question
« Reply #154 on: May 10, 2016, 01:58:26 AM »
Magneticitist:

Sorry for being picky but I am not going to discuss Joule Thieves on this thread.  For the main coil in a Joule Thief, there is no such thing as a "inductor voltage to current ratio" and I am making a point to you about communicating effectively.  How can you expect to talk shop about Joule Thieves if the person you are talking to is a beginner that would not have a clue what you are saying when you say "inductor voltage to current ratio" which itself doesn't really make sense.  I won't go after you anymore about this but now you are fully aware.

Note, this thread is all about the energizing of an inductor.  My advice to you is to forget about Joule Thieves on this thread and focus on trying to answer the question and understand what is going on.

MileHigh

well this is the golden point we have both made now. this thread was made out of respect to your question.. a question Brad never had to make any attempt at answering.. A question that was conceived by you to somehow prove your view on his circuit was correct and superior. That was a joule Thief circuit. at least, a circuit using a transformer.  Why you decided to then go into an inductors 101 is obviously beyond me as we have clearly discussed I am out of my element just here to throw around catch phrases and impress total strangers.

I have been trying to figure your reason for bringing up this inductor lesson since I first read about
your question and I still don't get how it could possibly relate to the original conversation.

I understand you want to knit pick such statements as 'voltage to current ratio' but I don't see how that is confusing.. at the time it seemed a fairly straightforward way to word it. I'm pretty sure I could come up with a number of ways to literate an inductor charging, and how it has a voltage unit and current unit we could measure.. I don't think you realize saying such things to me doesn't offend me. I can only gather that conclusion since you so frequently want to point out that all of my thoughts here are just random things I pulled out of my buttcrack on the spot for jollies that not even the most remedial of minds can understand.

#### MileHigh

• Hero Member
• Posts: 7600
##### Re: MH's ideal coil and voltage question
« Reply #155 on: May 10, 2016, 02:06:18 AM »
Please solve for R=0,so as we are defined to the parameters of your original question,as i have shown you already the infinite difference this makes even at a resistance far less than .001 ohms

You are shooting blanks, we are not discussing resistors.  What I did was compare the behaviour of the ideal 5 Henry coil and a real 5 Henry coil (0.001 series resistance) and showed you that their behaviour is nearly identical at t=1 second.  Do you get that?

If you get that then it proves to you that the formula for the current through the ideal coil of i = 0.8*t is correct.

In other words the explained behaviour for the ideal coil is not a short circuit or an open circuit, it's i = 0.8t.  Do you get that?

If you get all of this then you should move forward and try to answer the full question and demonstrate that you know what you are doing.

#### MileHigh

• Hero Member
• Posts: 7600
##### Re: MH's ideal coil and voltage question
« Reply #156 on: May 10, 2016, 02:12:07 AM »
Magneticitist:

Stop the psychobabble and the drama, ok?  The thread is here and Brad started it and that's all there is to it.

Do you want to contribute to it and learn?  Then work with Brad and see what you can come up with.  Try to answer the question and use that as a vehicle to learn.

MileHigh

#### tinman

• Hero Member
• Posts: 5363
##### Re: MH's ideal coil and voltage question
« Reply #157 on: May 10, 2016, 02:39:42 AM »
You are shooting blanks, we are not discussing resistors.  What I did was compare the behaviour of the ideal 5 Henry coil and a real 5 Henry coil (0.001 series resistance) and showed you that their behaviour is nearly identical at t=1 second.  Do you get that?

If you get that then it proves to you that the formula for the current through the ideal coil of i = 0.8*t is correct.

In other words the explained behaviour for the ideal coil is not a short circuit or an open circuit, it's i = 0.8t.  Do you get that?

If you get all of this then you should move forward and try to answer the full question and demonstrate that you know what you are doing.

Tau=L/R is how the time constant for the rise of current flow is determined,and that time constant has a value of infinity,and only changes to a finite value when a small amount of resistance is added to the inductor.

The second thing to ask your self,is how is the inductor defined as being a value of 5 Henry's when you have no resistive value to make that definition?. As you can see,the inductance in all three example in the link below,rely on measuring a voltage drop across a resistance to obtain the current flow to obtain inductive value. So how is this done when there is no resistance? When you work this out,you may begin to understand as to why an ideal inductor dose not dissipate any power,which also lines up with your very own statement that a voltage cannot be measured across an ideal inductor when a DC current if flowing through it,as current alone is not power,and hence the reason that an ideal inductor dose not dissipate power. But now your question also posses the problem that we !do! have an ideal voltage across the ideal inductor that you say has a DC current flowing through it. It can only have a voltage across it if there is no current flowing through it-and visa versa .
http://www.wikihow.com/Measure-Inductance

It is like my answer says it is--you cannot place an ideal voltage across an ideal inductor,as an ideal inductor dose not exist.
I have also shown that regardless of how little the resistance value may be,it will lead to a value that is infinitely different to that of an ideal inductor that has no R value.

#### MileHigh

• Hero Member
• Posts: 7600
##### Re: MH's ideal coil and voltage question
« Reply #158 on: May 10, 2016, 03:13:05 AM »
What does DC current have to do with anything when you put voltage across an ideal coil?   You will have to contemplate that.

You have been given more than enough information to do some hunting and researching on your own so that you answer the question correctly.  You still haven't taken a stab at the full question.

After all this, it still feels to me like there is faint hope that you are going to achieve those two tasks I listed for you with your current attitude.  You never know though like I already said.  I think that you are going to have to hope a guru comes in to help you because I am jumping off the train and switching to passive observer mode.

I hope one day in the not too distant future to see you follow-up on both tasks successfully and demonstrate full competence in this very important subject matter.

MileHigh

#### Magneticitist

• Full Member
• Posts: 131
##### Re: MH's ideal coil and voltage question
« Reply #159 on: May 10, 2016, 03:20:25 AM »
I'm just an oaf but I get what you're saying.. an inductor requires at least some form of 'resistance' to have a measurable inductance otherwise we are just saying "hey this is a 5H inductor" and base that entirely off of speculation.

#### tinman

• Hero Member
• Posts: 5363
##### Re: MH's ideal coil and voltage question
« Reply #160 on: May 10, 2016, 03:54:26 AM »
What does DC current have to do with anything when you put voltage across an ideal coil?   You will have to contemplate that.

You have been given more than enough information to do some hunting and researching on your own so that you answer the question correctly.  You still haven't taken a stab at the full question.

After all this, it still feels to me like there is faint hope that you are going to achieve those two tasks I listed for you with your current attitude.  You never know though like I already said.  I think that you are going to have to hope a guru comes in to help you because I am jumping off the train and switching to passive observer mode.

I hope one day in the not too distant future to see you follow-up on both tasks successfully and demonstrate full competence in this very important subject matter.

MileHigh

The fact that you have dismissed the L/R time constant to answer your original question is troubling.You have dismissed using this method-which is used in any other situation,based on the fact that there is no R value. You know that if you did use this conventional method,that the result would be exactly as myself and Poynt said it would be--there would be no flow of current,due to the infinite time constant value. You have dismissed the method that gives us the time constant required to answer your question correctly. This method (Tau=L/R) is the correct method to use in regards to your question. The fact that it results in no current flowing through the ideal inductor ,is inline with the fact that an ideal inductor dose not dissipate energy. Also to back it up is the fact that we have an ideal voltage of 4 volts across that inductor for a period of 3 seconds. This also states that during this time,no current can be flowing through that inductor,as there is a voltage across it,and as you your self have stated,if a DC current was flowing through that inductor,then there would be no voltage across it--but we have 4 volts across it,and so no current is flowing through it. This also falls in line with Poynts sim test.

All circuits used to make this definition are based around an ideal inductor,but with an added series resistor to simulate the resistance that would exist in a real world inductor. If we are to define the outcome of placing an ideal voltage across an ideal inductor,then there is no reason at all that the series resistor just be removed to obtain the correct evaluation for an ideal inductor.

The only reason you do not wish to use this method of Tau=L/R,is because that then puts you in a position of being incorrect. this being the case,i find that a sad time indeed in the history of this forum,where people come to learn and solve such problems using what we know and undderstand to be correct.

When a current is applied to an inductor it takes some time for the current to reach its maximum value, after which it will remain in a "steady state" until some other event causes the input to change. The time taken for the current to rise to its steady state value in an LR circuit depends on:
•The resistance (R)
This is the total circuit resistance, which includes the DC resistance of the inductor (RL) itself, plus any external circuit resistance.
• The inductance of L
Which is proportional to the square of the number of turns, the cross sectional area of coil and the permeability of the core.

I am standing firm on my answers,and i hope Poynt(and others) takes the time to have another look at this,and not just accept your example as a reality.

#### Magneticitist

• Full Member
• Posts: 131
##### Re: MH's ideal coil and voltage question
« Reply #161 on: May 10, 2016, 04:13:10 AM »
guys let's just make a deal and be honest. MH wants to act like you are a complete loony for believing what you do, but I'm fairly sure this is not some extremely rare argument and has been argued before, probably to this very day by many others.. there are others in this thread that share Brads view as well. does that mean MH is wrong? of course not. but until some kind of all ending smoking gun evidence can be presented (which it cannot) what is the point? ok let's say we're using a real R value then. still, what's the point? even plugging in the numbers and calculating for current or the rate of current change, or the voltage, or whatever.. at this point it's just going through the motions.

How about we agree to make a real conscious effort learning about inductors the same way MH did when he was being indoctrinated so long as he agrees to stop using circuit examples with values of 0 and expect a real provable formulaic outcome or omitting variables from formulas altogether.

Then hopefully we can go back to the original topic loool. I'm genuinely interested I mean when do you see me here, that's what I came for and for like 10 pages there it looked like you guys were creeping ever closer to a real provable answer which is what I thought MH had up his sleeve with this whole question thing but oh well can we move on now.

#### tinman

• Hero Member
• Posts: 5363
##### Re: MH's ideal coil and voltage question
« Reply #162 on: May 10, 2016, 04:27:24 AM »
guys let's just make a deal and be honest. MH wants to act like you are a complete loony for believing what you do, but I'm fairly sure this is not some extremely rare argument and has been argued before, probably to this very day by many others.. there are others in this thread that share Brads view as well. does that mean MH is wrong? of course not. but until some kind of all ending smoking gun evidence can be presented (which it cannot) what is the point? ok let's say we're using a real R value then. still, what's the point? even plugging in the numbers and calculating for current or the rate of current change, or the voltage, or whatever.. at this point it's just going through the motions.

How about we agree to make a real conscious effort learning about inductors the same way MH did when he was being indoctrinated so long as he agrees to stop using circuit examples with values of 0 and expect a real provable formulaic outcome or omitting variables from formulas altogether.

Then hopefully we can go back to the original topic loool. I'm genuinely interested I mean when do you see me here, that's what I came for and for like 10 pages there it looked like you guys were creeping ever closer to a real provable answer which is what I thought MH had up his sleeve with this whole question thing but oh well can we move on now.

I started this thread to remove the debate on MHs ideal coil and voltage question from the JT 101 thread,so as discussion on the topic of JTs could continue without unrelated topics being discussed there,and splitting up the thread. But it seems that now capacitors has also taken hold in that thread--perhaps a dedicated thread on capacitors should also be opened.

#### MileHigh

• Hero Member
• Posts: 7600
##### Re: MH's ideal coil and voltage question
« Reply #163 on: May 10, 2016, 04:35:11 AM »
I will drop in and say this out of frustration:

1.  Talking about DC current through an ideal coil and no resultant voltage drop is meaningless and has nothing to do with this exercise.

2.  When you apply voltage across an ideal coil you get changing and increasing current.  This simple fact is escaping you and as a result you are leading yourself down a garden path.  Just like when you apply voltage across a real coil you get changing and increasing current until the current levels off.

It's pull yourself up by your own bootstraps time, or stick in mud and be wrong and go nowhere time, or wait for a guru to save you time.

#### Magneticitist

• Full Member
• Posts: 131
##### Re: MH's ideal coil and voltage question
« Reply #164 on: May 10, 2016, 04:39:49 AM »
This is true I don't mean to disrespect this thread or MH's wishes to avoid further JT discussion... but I have to ask since you two are honestly the best people to ask at this point.. I was eagerly reading
your discussion in the JT thread before this topic and didn't quite realize how far off topic it was actually leading. I guess I may have to try to steal the JT thread back on topic but then I don't want to interrupt the capacitor talk after it has gained some charge. this topic actually has merit too though I suppose, I just don't see how one side could really disprove the other.