User talk:Sbyrnes321

Your transmission line animation

It's great.

I'd like to suggest an animation of a pulse reflecting off an open termination would be very interesting.Constant314 (talk) 22:01, 4 August 2012 (UTC)

Thanks! The pulse is a good idea ... I put it on my list of things to do someday. --Steve (talk) 23:18, 4 August 2012 (UTC)

spin-orbit interaction...

This sentence is from you, if I traced that correctly: In quantum physics, the spin-orbit interaction (also called spin-orbit effect or spin-orbit coupling) is any interaction of a particle's spin with its motion.

I agree, that there is a interaction a particle with its motion in a magnetic field, like in the described spin-orbit interaction effects, but I can not find that this is also called spin-orbit interaction in a case were you do not have an orbit. Can you give a book or article where this definition is used. Where is the orbit, if we just assume a free particle with magnetic moment and an electric field. --Do ut des (talk) 16:26, 28 August 2012 (UTC)

I know that the term "spin-orbit" is frequently used in solid-state physics (eg spintronics), where it is applied to valence electrons moving over mesoscopic distances. [1] [2] etc. etc. etc. These electrons are not "orbiting" anything.

For a particle in vacuum, I agree, the spin can affect motion, and I agree, nobody seems to calls that effect by the term "spin-orbit". You should change it....sorry for my mistake... --Steve (talk) 21:26, 28 August 2012 (UTC)

I disagree with you revert at Fourier transform infrared spectroscopy in Conceptual introduction

I really understand what you mean but the problem is that viewing a Michelson interferometer as a wavelength filter is not right at all. In fact, that is how a spectrometer works. More over the usual mistake about the Michelson interferometer is to compare it to a spectrometer which it is not. You must know that all wavelengths are passing through a Michelson interferometer and that what you see on one of the output ports is the sum of the interference pattern of each wavelength for a certain optical path difference. I know that the way a Michelson interferometer works is not easy to understand but it may be better to avoid false description (I am sorry for my poor english). This is a description taken from Michelson interferometer : "The Michelson interferometer's detector in effect monitors all wavelengths simultaneously throughout the entire measurement, increasing the integration time and the total number of photons monitored"

Oh, I already wrote a message at Talk:Fourier_transform_infrared_spectroscopy#Conceptual_introduction ... I will copy this message and we can keep talking there :-)

Quasiparticle

Hi,

why did you undo my version of "quasiparticles"?. If you think it is not clear, then you could put your own version of why they are different from "standard" particles because it is not clear from the article.

Rolancito (talk) 11:02, 21 October 2012 (UTC)

Thanks for asking, sorry I didn't leave you a note. I explained at Talk:Quasiparticle (scroll to the bottom).

You're right, it's a good idea to have some basic discussion that precedes the mention of many-body quantum mechanics. I will try based on your example, and you can let me know if I am at all successful :-) --Steve (talk) 15:28, 21 October 2012 (UTC)

OK I tried ... did that help at all??? --Steve (talk) 16:42, 21 October 2012 (UTC)

Thanks for your consideration, I answered your post in the talk page. Regards, Rolancito (talk) 16:24, 22 October 2012 (UTC)

Faraday's Law / Maxwell-Faraday eqn

You reverted my correction to the wrong statement "a changing magnetic field creates an electric field". I appreciate that my wording could be improved, but that is no excuse for retaining a mistake. If you want to revert, please provide (as I did) an explicit reference in the scientific literature supporting "a changing magnetic field creates an electric field"; i.e., one with an explicit causality-based reasoning, not just the statement itself. — Preceding unsigned comment added by 2001:630:12:10C6:217:8FF:FE2A:A8ED (talk) 09:01, 23 October 2012 (UTC)

I did not revert it. "Reverting" means undoing an edit word-for-word to restore what was there before. I didn't do that. Your reference convinced me that the article should not say that a changing magnetic field creates an electric field, therefore I did not put that statement back.

In my new version, the text neither asserts nor denies that either thing causes the other. It just doesn't discuss it. This is in accordance with standard textbook discussions, which do not analyze causality in detail. Indeed, it is possible to be an electrical engineer or physicist with an excellent working knowledge of Faraday's law, the ability to apply it in all situations to better understand the world, etc., despite having never considered the issue of which side of the equation is the cause and which side is the effect (in the sense of the paper that you cited). I know of no one who has seriously considered the issue before 2011 (the date of your citation), surely a sign that it is not vitally important to understand this issue. In your version, the causality analysis is discussed before even writing down what the equation is! Surely that's undue emphasis. We shouldn't distract from the most important points.

For the record, I don't think that the technical definition of "cause" used in the paper you cite is the only possible valid definition. I think it is used in a looser sense in everyday life, related to intentions etc. For example, when I rotate a bar magnet with my hand, Paul Kinsler would say: "You're creating a curl in the electric field, which in turn is changing the magnetic field." But I would say "My spinning the magnet is the cause of both the curl in the electric field and the changing magnetic field." It is strange and confusing (in my opinion) to imagine that the immediate cause of the changing magnetic field is anything but my decision to spin the magnet. I am not a philosopher, I am only trying to picture what a typical person would find confusing versus helpful.

I hope that clarifies what I was up to... Let me know your thoughts.  :-) --Steve (talk) 12:26, 23 October 2012 (UTC)

I misread the details of your change, for which I apologise.

I agree my change was arguably inelegant, but there is value in explicitly rebutting the (not uncommon, but wrong) view of cause and effect as contained in the original statement - which after all has persisted for some time without comment. Perhaps the clarification could put in a footnote?

As regards a failure to consider causality being typical of textbooks, that is certainly true in my experience; but why should wikipedia inherit that failing? The prior use of "creating" already strongly implied a certain (incorrect) cause and effect - if that was OK, why is a different (but now systematically justified) statement of cause and effect not OK? Note that the EJP paper is not claiming novelty in its approach to causality (see e.g. the existing wording of http://en.wikipedia.org/wiki/Causality#Engineering ).

In regards to "original causes", such as your argument where you decide to move a magnet, Faraday's law has no mechanism to include decisions to wave magnets about - it only has dB/dt = curl E. Thus within the narrow scope of Faraday's law, curl E is the cause of a temporal change in B - there is nothing else there to consider (although there might be in some putuative extension, to be later known as the Byrnes-Faraday Law :-) — Preceding unsigned comment added by 2001:630:12:10C6:217:8FF:FE2A:A8ED (talk) 17:10, 23 October 2012 (UTC)

I am working on an edit and I am struggling with the wording. Can you help?

This is in the context of a very basic introduction to Faraday's law, and how it applies to an electric generator. Last week I would have said something like

Rotating a bar magnet changes the magnetic field around it. According to Faraday's law, this changing magnetic field creates ("induces") an EMF in the wire.

Today, I'm not sure what to say. Maybe something like

If a bar magnet is rotated, the magnetic field around it changes. According to Faraday's law, a changing magnetic field is always accompanied by an EMF in the wire.

Or something like

Rotating a bar magnet changes the magnetic field around it. According to Faraday's law, this changing magnetic field creates ("induces") an EMF in the wire.[Note 1]

[Footnote 1:] Strictly speaking, it is incorrect to say that the magnetic field is the cause and the EMF is the effect. The rotating magnet is the true cause of both. It has been argued that it is valid to say that a curl in the electric field is the (proximal) cause of a changing magnetic field, but not the other way around. See Kinsler, P. (2011)....

I like the third best, although I imagine you would object to it. What do you think? Is there a better way?

The trouble is, it is intuitively obvious to everyone that rotating bar magnet should change the magnetic field, but it is not intuitive or obvious why a rotating bar magnet should directly create a curl in the electric field. --Steve (talk) 18:41, 23 October 2012 (UTC)

If you want to wave a bar magnet about, then you need to start with the source of the magetization (eg current loops). But since that seems a bit over the top, we might instead simply specify a time varying B(t). What changes might that induce? For "changes" (aka effects) we need a time derivative, so we see that the equation to use when we have a pre-specified B(t) is not dB/dt=curl E but instead dD(rt)/dt=curl B(rt), as we can then calculate induced changes in E field using E = D/epsilon. That is, we shouldn't use the Maxwell-Faraday eqn. at all, but Maxwell-Ampere (!) I suspect that in practice the typical interpretation works because the two curl Maxwell's eqns are coupled and support waves, thus in many cases a solution to one is a solution to the other.

It might be best to go with your (3) for the moment, but I'd strengthen the wording, e.g.:

Rotating a bar magnet changes the magnetic field around it. A common usage of Faraday's law in this situation is to say that this changing magnetic field creates ("induces") an EMF in the wire (but see[Note 1])

[Footnote 1:] Strictly speaking, the Faraday-Maxwell equation treats the electric field as a cause of a changing magnetic field; it is the Maxwell-Ampere's equation that has the magnetic field causing changes in the electric field (See Kinsler, P. (2011)....).

Although I think my footnote wording has the advantage of being more specific, it does beg the question as to why the existing interpretation is not right, even if in principle we imagine all things are answered in the EJP. And since that existing view is to an extent embedded in the rest of the article, it's hard to make a localised fix, as opposed to recasting the entire article in the more careful way. 2001:630:12:10C6:217:8FF:FE2A:A8ED (talk) 09:33, 25 October 2012 (UTC)

Hmm ... food for thought ... will respond later ... --Steve (talk) 12:24, 25 October 2012 (UTC)

This chain of events is quite strange. I start rotating the bar magnet. Rotating the bar magnet causes the magnetic field to change ("obviously" - or is this inference not allowed??) Now I am supposed to use Ampere's law:

$\nabla \times B=(1/c^{2}){\frac {\partial E}{\partial t}}$

The answer is supposed to be "it creates an EMF", i.e. the curl of E becomes nonzero. Let me try ... from Ampere's law:

${\frac {\partial }{\partial t}}(\nabla \times E)=c^{2}\nabla \times \nabla \times B=-c^{2}\nabla ^{2}B$

I want to argue that the left-hand-side is nonzero, so I suppose I should be arguing that the right-hand-side has to be nonzero. But why? It's not clear to me in any way!

Well, I find myself back where I started. If we know that one side of the Faraday's law equation is nonzero, then we can always infer that the other side is nonzero. If it is obvious from external events that one side has to be nonzero, we can speak loosely of that side "causing" the other side to be nonzero. Generations of physicists and engineers have imagined that a changing magnetic field "causes" a curl in the electric field, and never has it caused anyone to design a faulty transformer, or even come to an incorrect answer in a homework problem. Finally, now, when I tried to explain an extremely simple phenomenon in a way that rigorously follows the EJP cause-and-effect restrictions, I found that it was impossible (at least, too hard for me).

So what's the point? I am back to thinking that we should acknowledge and even embrace the fact that people can use cause-and-effect in a loose, flexible way in their everyday lives and when learning and understanding physical phenomena. Another example: Talk to an expert analog circuit designer. When a resistor is driven by a current source, they will have no problem saying "there is a current through this resistor, which causes a voltage drop across it". When a resistor is driven by a voltage source, they will have no problem saying "there is a voltage drop across this resistor, which causes a current to flow through it". Again, they are describing logical relations. The EJP article is fun, but is not really relevant to anything, because it is discussing cause-and-effect in a highly specific, technical way, not related to how people discuss cause-and-effect in real life. That explains why humanity was extremely successful at using the laws of electromagnetism even before the EJP article was published in 2011. --Steve (talk) 14:24, 31 October 2012 (UTC)