Author Topic: Does Kirchhoff's Law Hold? Disagreeing with a Master  (Read 63088 times)

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Offline ogden

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Re: Does Kirchhoff's Law Hold? Disagreeing with a Master
« Reply #725 on: February 01, 2019, 08:14:25 pm »
I can't do better.

I did not ask to do better. Answer using your own words.
 

Offline bsfeechannel

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Re: Does Kirchhoff's Law Hold? Disagreeing with a Master
« Reply #726 on: February 01, 2019, 09:08:32 pm »
I don't know how to answer your question without further investigation. Let's suppose that we have a varying magnetic field so that going from point A and returning to it again via the path indicated by the dashed line, we find an EMF = 1V like in the picture below.

Now consider that we introduce a piece of wire along the same path so that we have 3/4 of a turn, 1/2 a turn and 1/4 of a turn. What would be the voltages VAB, VAC and VDC following their respective dashed lines indicated in the picture?

« Last Edit: February 01, 2019, 09:11:12 pm by bsfeechannel »
 

Offline Berni

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Re: Does Kirchhoff's Law Hold? Disagreeing with a Master
« Reply #727 on: February 01, 2019, 11:03:59 pm »
Im talking about the field around it due to us all agreeing that circuit analysis (And with that also KVL) works when there is no field.

What 1V jump is there? Its simply voltages measured across the wires inside the magnetic field by taking a different path with the voltmeter. The voltages are there in Dr. Lewins experimental circuit if you probe it just the right way.

The lumped model simply has a different way of expressing the effects of magnetic fields, that's it. The whole circuit still acts identical and that's what matters. Cirucit mesh models are supposed to model the high level behavior of circuits, not model physical electrons moving trough wires and the fields they make around them. As long as the circuit behaves the same its considered a accurate model.
 

Offline bsfeechannel

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Re: Does Kirchhoff's Law Hold? Disagreeing with a Master
« Reply #728 on: February 02, 2019, 12:23:35 am »
What 1V jump is there? Its simply voltages measured across the wires inside the magnetic field by taking a different path with the voltmeter. The voltages are there in Dr. Lewins experimental circuit if you probe it just the right way.

And that's what he did. There is 0.9V across one resistor, and 0.1 across the other. Those are the only voltages present in the circuit. If you're measuring anything else, it's because you are choosing a different path than that of the circuit.

Simple as that.

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The lumped model simply has a different way of expressing the effects of magnetic fields, that's it.

This is impossible since the lumped model is derived from Maxwell. That's explained by Feynman in his chapter 22.

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The whole circuit still acts identical and that's what matters. Cirucit mesh models are supposed to model the high level behavior of circuits, not model physical electrons moving trough wires and the fields they make around them.

When Maxwell published his equations, they didn't know about the existence of electrons. Maxwell is about fields and geometry. Every time your circuit is affected by fields or geometry, you'll have to use them.

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As long as the circuit behaves the same its considered a accurate model.

Unfortunately your "model" doesn't behave the same as Lewin's circuit nor is accurate. In fact it is aberrant. And, if you pardon me, asinine. It proposes the existence of 250mV across a wire that has a resistance of about zero ohms carrying a current of 1mA.

250mV = 0Ω · 1mA !!!!!!!!!!!!!

Besides, your model contradicts Faraday's law that states that any circuit under varying magnetic will have its voltages adding up to a value different from zero.

To help you avoid those gross errors, I prepared a quick guide to lumpiness. I hope that it will be useful for you.

 

Offline ogden

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Re: Does Kirchhoff's Law Hold? Disagreeing with a Master
« Reply #729 on: February 02, 2019, 12:59:15 am »
I don't know how to answer your question without further investigation. Let's suppose that we have a varying magnetic field so that going from point A and returning to it again via the path indicated by the dashed line, we find an EMF = 1V like in the picture below.

Now consider that we introduce a piece of wire along the same path so that we have 3/4 of a turn, 1/2 a turn and 1/4 of a turn. What would be the voltages VAB

I was talking about 1/4 (part) of the winding/turn. No need to introduce anything. It was simple question. - Transformer with single winding/turn with 1/4-turn tap. What's voltage on it if full winding gives 1V?

 

Offline ogden

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Re: Does Kirchhoff's Law Hold? Disagreeing with a Master
« Reply #730 on: February 02, 2019, 01:02:24 am »
Unfortunately your "model" doesn't behave the same as Lewin's circuit nor is accurate. In fact it is aberrant. And, if you pardon me, asinine. It proposes the existence of 250mV across a wire that has a resistance of about zero ohms carrying a current of 1mA.

250mV = 0Ω · 1mA !!!!!!!!!!!!!

You say you mastered Maxwell's equations?  :-DD :-DD :-DD :-DD :-DD :-DD
 

Offline bsfeechannel

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Re: Does Kirchhoff's Law Hold? Disagreeing with a Master
« Reply #731 on: February 02, 2019, 01:25:54 am »
I was talking about 1/4 (part) of the winding/turn. No need to introduce anything. It was simple question. - Transformer with single winding/turn with 1/4-turn tap. What's voltage on it if full winding gives 1V?

Can you please provide a schematic of how you get a 1/4 tap from a transformer with a single-turn winding?
« Last Edit: February 02, 2019, 01:33:46 am by bsfeechannel »
 

Offline bsfeechannel

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Re: Does Kirchhoff's Law Hold? Disagreeing with a Master
« Reply #732 on: February 02, 2019, 01:32:08 am »
Unfortunately your "model" doesn't behave the same as Lewin's circuit nor is accurate. In fact it is aberrant. And, if you pardon me, asinine. It proposes the existence of 250mV across a wire that has a resistance of about zero ohms carrying a current of 1mA.

250mV = 0Ω · 1mA !!!!!!!!!!!!!

You say you mastered Maxwell's equations?  :-DD :-DD :-DD :-DD :-DD :-DD

Isn't that hilarious? A static wire with a next to zero ohm internal resistance sporting 250mVDC and 1mA!!!

It doesn't need to be a Maxwell expert to realize how moronic that conclusion is. I agree with you.


 
 

Offline ogden

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Re: Does Kirchhoff's Law Hold? Disagreeing with a Master
« Reply #733 on: February 02, 2019, 01:32:26 am »
I was talking about 1/4 (part) of the winding/turn. No need to introduce anything. It was simple question. - Transformer with single winding/turn with 1/4-turn tap. What's voltage on it if full winding gives 1V?

Can you, please provide a schematic of how you get a 1/4 tap from a transformer with a single-turn winding?

This one is good enough. There are loads of 1/4 windings, with voltmeters attached:

 

Offline ogden

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Re: Does Kirchhoff's Law Hold? Disagreeing with a Master
« Reply #734 on: February 02, 2019, 01:35:43 am »
Unfortunately your "model" doesn't behave the same as Lewin's circuit nor is accurate. In fact it is aberrant. And, if you pardon me, asinine. It proposes the existence of 250mV across a wire that has a resistance of about zero ohms carrying a current of 1mA.

250mV = 0Ω · 1mA !!!!!!!!!!!!!

You say you mastered Maxwell's equations?  :-DD :-DD :-DD :-DD :-DD :-DD

Isn't that hilarious? A static wire with a next to zero ohm internal resistance sporting 250mVDC and 1mA!!!

It doesn't need to be a Maxwell expert to realize how moronic that conclusion is. I agree with you.

Right. So you agree that you do not know what EMF actually is.
 

Offline bsfeechannel

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Re: Does Kirchhoff's Law Hold? Disagreeing with a Master
« Reply #735 on: February 02, 2019, 01:38:41 am »
This one is good enough. There are loads of 1/4 windings, with voltmeters attached:



Where is the transformer?
 

Offline bsfeechannel

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Re: Does Kirchhoff's Law Hold? Disagreeing with a Master
« Reply #736 on: February 02, 2019, 01:39:47 am »
Right. So you agree that you do not know what EMF actually is.

What is the EMF?
 

Offline ogden

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Re: Does Kirchhoff's Law Hold? Disagreeing with a Master
« Reply #737 on: February 02, 2019, 01:59:27 am »
 

Offline bsfeechannel

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Re: Does Kirchhoff's Law Hold? Disagreeing with a Master
« Reply #738 on: February 02, 2019, 02:16:58 am »
https://en.wikipedia.org/wiki/Electromotive_force

Thank you.

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Dr.Lewin's experiment is transformer. Didn't you notice?  :palm:

So any circuit under a varying magnetic field is a transformer?
 

Offline ogden

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Re: Does Kirchhoff's Law Hold? Disagreeing with a Master
« Reply #739 on: February 02, 2019, 02:20:49 am »
Isn't that hilarious? A static wire with a next to zero ohm internal resistance sporting 250mVDC and 1mA!!!

It doesn't need to be a Maxwell expert to realize how moronic that conclusion is. I agree with you.

Take any Li-Ion battery and put it into your reasoning ;)
 

Offline ogden

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Re: Does Kirchhoff's Law Hold? Disagreeing with a Master
« Reply #740 on: February 02, 2019, 02:25:13 am »
Quote
Dr.Lewin's experiment is transformer. Didn't you notice?  :palm:

So any circuit under a varying magnetic field is a transformer?

I did not say any circuit. I said that Dr.Lewin's experiment is transformer. You are clearly avoiding my quite straight and simple question:

Transformer with single winding/turn with 1/4-turn tap. What's voltage on it if full winding gives 1V?
 

Offline bsfeechannel

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Re: Does Kirchhoff's Law Hold? Disagreeing with a Master
« Reply #741 on: February 02, 2019, 02:30:00 am »
Isn't that hilarious? A static wire with a next to zero ohm internal resistance sporting 250mVDC and 1mA!!!

It doesn't need to be a Maxwell expert to realize how moronic that conclusion is. I agree with you.

Take any Li-Ion battery and put it into your reasoning ;)

Got it. I'll replace the batteries of my cell phone with a piece of wire. Why didn't i think of that before?
« Last Edit: February 02, 2019, 02:38:20 am by bsfeechannel »
 

Offline bsfeechannel

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Re: Does Kirchhoff's Law Hold? Disagreeing with a Master
« Reply #742 on: February 02, 2019, 02:35:19 am »
I did not say any circuit. I said that Dr.Lewin's experiment is transformer.

Well, it is a circuit, innit? It has two resistors and wires connecting them so that current can flow.

But since you said it is a transformer, what are the criteria to consider a circuit under a varying magnetic field a transformer?

Quote
You are clearly avoiding my quite straight and simple question:

Transformer with single winding/turn with 1/4-turn tap. What's voltage on it if full winding gives 1V?

Maybe you're asking the wrong questions.
 

Offline ogden

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Re: Does Kirchhoff's Law Hold? Disagreeing with a Master
« Reply #743 on: February 02, 2019, 02:37:02 am »
Isn't that hilarious? A static wire with a next to zero ohm internal resistance sporting 250mVDC and 1mA!!!

It doesn't need to be a Maxwell expert to realize how moronic that conclusion is. I agree with you.

Take any Li-Ion battery and put it into your reasoning ;)

Got it. I'll replace the batteries of my cell phone by a piece of wire. Why didn't i think of that before?

In case you did not know - batteries have low internal resistance. That was my point.
 

Offline bsfeechannel

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Re: Does Kirchhoff's Law Hold? Disagreeing with a Master
« Reply #744 on: February 02, 2019, 02:40:18 am »
Batteries have electric fields inside them.
 

Offline ogden

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Re: Does Kirchhoff's Law Hold? Disagreeing with a Master
« Reply #745 on: February 02, 2019, 02:42:21 am »
But since you said it is a transformer, what are the criteria to consider a circuit under a varying magnetic field a transformer?

Since you do not know what is transformer - why do you even participate in this discussion?

Quote
Maybe you're asking the wrong questions.

You just pretend that you do not understand what I am asking.
 

Offline ogden

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Re: Does Kirchhoff's Law Hold? Disagreeing with a Master
« Reply #746 on: February 02, 2019, 02:46:18 am »
Batteries have electric fields inside them.

So what? How does it changes Ohm's law you mentioned?

Isn't that hilarious? A static wire with a next to zero ohm internal resistance sporting 250mVDC and 1mA!!!
 

Offline bsfeechannel

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Re: Does Kirchhoff's Law Hold? Disagreeing with a Master
« Reply #747 on: February 02, 2019, 03:05:31 am »
Since you do not know what is transformer - why do you even participate in this discussion?

I don't know. Perhaps because you could tell me what a transformer is.

Quote
You just pretend that you do not understand what I am asking.

I'm trying to be polite.
 

Offline bsfeechannel

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Re: Does Kirchhoff's Law Hold? Disagreeing with a Master
« Reply #748 on: February 02, 2019, 03:08:51 am »
So what? How does it changes Ohm's law you mentioned?
Wires are not batteries.
 

Offline Sredni

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Re: Does Kirchhoff's Law Hold? Disagreeing with a Master
« Reply #749 on: February 02, 2019, 03:48:35 am »
Note: I should be sleeping but...

Im talking about the field around it due to us all agreeing that circuit analysis (And with that also KVL) works when there is no field.

EDIT
This post has been shortened and cleansed to avoid upsetting other children.
Whatever was written here can be found in one or more of the following books (in no particular order, and without mentioning the usual suspects Feynman, Purcell, Griffiths, Ohanian, Jackson):

Nayfeh, Brussel
Electricity and Magnetism

Kip
Fundamentals of Electricity and Magnetism 2nd ed

Lorrain, Courson
Electromagnetic Fields and Waves 2nd ed

Panofsky, Phillips
Classical Electricity and Magnetism 2nd ed

John Kraus
Electromagnetism 2nd to 4th ed

Ramo, Whinnery, VanDuzer
Fields and Waves in Communication Electronics 2nd or 3rd ed

Bleaney
Electricity and Magnetism 3rd ed


« Last Edit: February 13, 2019, 07:38:06 am by Sredni »
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