User talk:Alfred Centauri

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Contents 1 Geodesics comment 2 Sympathy 3 Comments requested 4 Inductance Proposed change of defn 5 Agreement 6 Inductance Article 7 Grounding 8 Current status 9 Very interesting page 10 Has Electric flux actually been observed? 11 Your recent work 12 New Discussion 13 Look whose talking 14 WikiProject Electronics 15 Tom Bearden 16 Order of replies 17 Time for bed 18 Equivalent series resistance-- can AC look at it please? 19 Welcome! 20 Is the DC voltage across an inductor zero? 21 Talk Ivor Catt 22 My beliefs & Merry Xmas 23 A favour 24 Thanks (put other thanks here) 25 Transformer 25.1 E X H and transformers 25.2 Flux in a transformer core 26 Ground or common? 27 Re: Clock synchronization question. 28 Opinion needed

[edit] Geodesics comment

Thank you for supporting at least some of my edits. The people who removed them seem to be practically vandals. I mean, for gosh sakes, if you have a mass bobbing up and down on a spring in a freshman lab it's not on a geodesic! My other item, also removed by the vandals or ostrogoths or people's great cultural revolution gave meaning to a spacelike geodesic. Do you see anything wrong with that part? Seems to me if you stretch a practically weightless fiber (maybe silk or catgut) over the shoulder of "The Thinker" and let it remain there, under tension, an instantaneous shot of it is a spacelike geodesic. But to define "instantaneous" you need clock synchronization over a "space section" which is why I threw in the stuff about the Killing vector.

It appears that Linas was thinking worldline when he read geodesic and he has since apologized for the revert. However, I must confess that I don't understand the spacelike geodesic stuff you wrote either as I am still a novice relativist. Let's see, the worldline of a free particle is a timelike geodesic. To 'see' a spacelike geodesic, would not the fiber above also need to be freely falling? Alfred Centauri 22:32, 7 Jun 2005 (UTC)

Not sure what to do - edit back what I had in or report vandalism as well. I don't know how to do a "revert" without mouse-copying and re-editing, do you? Pdn 15:36, 6 Jun 2005 (UTC)

Simply view your last edit, and then select edit, enter a comment that you are reverting and save. Alfred Centauri 22:32, 7 Jun 2005 (UTC)

Thanks, AC. I admit my material on spacelike geodesic was not very clear. I am trying to say, perhaps too mathematically, what "everybody knows" about geodesics in 3-space or even 2-space (like the surface of a spheroid e.g.) but it gets complicated exactly because of that timelike dimension. Maybe you can advise how to put it in simpler terms. Imagine you and a friend are making an old-fashioned toy telephone system across a street, as I did in 1949. You each have a stiff paper cup, and you get some cord that is very light and strong, and put it under tension between the two cups, across the street dividing your apartments. Imagine passing to a limit where the string is virtually massless (actually, the tension in it would interact with gravity, but let the mass ->0 faster than the tension, but the tension -> 0 also! ). That string, which I called a "filament" - confusing Linas - does indeed have a timelike aspect, too. Each particle composing it is moving into the future. So to the relativist it is a sheet and is not a candidate for a geodesic, which has to be a line. But if we synchronize clocks suitably and grab an instantaneous "snapshot" of that string, we have a spacelike geodesic. There are some further problems just below the surface here, however. Due to the rotation of the Earth, one has to synchronize the clocks from a central source, not by exchanging light signals between them, unless the string is oriented exactly North-South. In that case synchronizing to WWV for example, will agree with synchronizing by light signals. (If one goes East-West one runs into the Sagnac effect, and in fact even if North-South there is a small error due to the Earth's motion around the Sun). I am probably being too rigorous. The "problem" I refer to is the "snapshot" issue. If one does not make the assumption I mentioned about a Killing vector (see Killing vector field) one faces the difficulty that the "snapshot" is really a family of short segments, sort of like the fibers one can see in the feathers of a bird - they do not connect because one has not handled the simultaneity issue correctly. One can still construct a spacelike geodesic representing a slice through the sheet that is the string (as explained before), but one has to allow a tiny time variation along it by following those little feathery segments in a continuous way. I was trying to avoid time varying along the spacelike geodesic, but I am probably introducing too many caveats in trying to get a simple static entity (constant time slice). Maybe I can just say that a tightly stretched string taken at one instant is a spacelike geodesic and let the "user" worry about the meaning of "instant." But I have another problem in nomenclature: Linas found the term "filament" confusing. Now I do not want to use "string" because we have string theory nowadays, and ordinary household strings are heavy, and I do not want to use "fiber" because we have "fibre bundle topology" so I tried "filament". I just checked it in Merriam-Webster and it looks OK. And I used to fish with a "nylon filament leader" [[1]] so I am stumped. Seems like a light fibre or cord one could stretch quite a ways and get a good approximation to a space geodesic (remembering to use the snapshot idea rather than to follow the world-lines of each particle making up the filament).

I do hope you get the picture now (you may of course disagree). A tightly stretched filament is a collection of particles each of which has a timelike world-line. Orthogonal to that family of world lines, let's call it a "warp" (not a space-warp and hyperdrive, but a warp) one has a "woof" or weft . If the warp is the set of timelines, the weft lines are the spacelike geodesics (provided the filament or fibre is tightly stretched, and essentially massless). Pdn 01:45, 8 Jun 2005 (UTC)

[edit] Sympathy

My sympathy to you, now you know how I felt trying to explain the dreaded bootstrap cct to 'R'!! I wish I had not bothered. There are none so deaf as those who will not hear. Regards ;-)Light current 04:28, 16 August 2005 (UTC)

[edit] Comments requested

Hi again Alfred, I noticed you've had a lot of input on the operational amplifier talk page and wondered if you could comment on my recent musings on the internals on Talk:Operational amplifer.(funny, cant link to it properly) I am most interested to hear your views. Light current 13:09, 30 August 2005 (UTC)

[edit] Inductance Proposed change of defn

Alfred, I wonder if you could have a look at Talk:Inductance when you have some time. Im not happy with the existing defn. and have proposed an alternative which I think is more scientific/basic and doesnt need to mention inductors as such. The other things like Lenz law maybe could be kept to the other pages where they are mentioned. Also my proposal fits with the analogous defn of capacitance. What do you think? Please post any reply on Talk:Inductance page. THanks! Light current 14:49, 2 September 2005 (UTC)

[edit] Agreement

Alfred, I'm so glad we seem to have reached some sort of agreement on capacitance/inductance. I'm hoping to further integrate (bind together) these ideas and I would really value your help in my attempts. Once again , many thanks for your educated insight into these knotty questions!! Light current 23:57, 3 September 2005 (UTC)

[edit] Inductance Article

Alfred, I have spent some(a lot) time trying to simplify and segregate the topics in inductance, especially by splitting 'induced voltages in inductors' from 'applied voltages to inductors' thereby avoiding the confusion of signs and back emf and all that stuff. I would appreciate your comments on this severely modified page before I tidy into its final(?) form. THanks once more. Light current 07:42, 4 September 2005 (UTC)

[edit] Grounding

Yes ,I agree with you here. 'Ground' seems to be an American term. Over here we use the word 'Earth'. Again not all electronics systems have their reference connected to earth (although for safety reasons many do indirectly). I have always shown the reference on my circuit diagrams (schematics) as 0v. So: Anal 0v, Dig 0v etc. Then, if 0v is connected to chassis, show the connection to the chassis symbol. If the chassis needs to be 'earthed', then this is shown as a wire connected from chassis to the earth pin of the mains plug. I suppose the word 'common' is good too. I could live with that! But the 5v 'return' would normally be connected to 'common' wouldnt it? Light current 21:06, 4 September 2005 (UTC)

[edit] Current status

Thanks for letting me know what youre doing. My current status is reviewing pages for any new material/talk Light current 20:40, 5 September 2005 (UTC)

[edit] Very interesting page

Alfred, wondered if you had seen this [2] before. You may be interested

[edit] Has Electric flux actually been observed?

You say magnetic charge has not been observed, but magnetic flux has. Correct.

Now consider this: Electric charge has been observed. However, I would argue that, whilst we are all familiar with the concept, electric flux( ie flux meaning flow) is an imaginary concept that cannot be observed directly (same as magnetic charges cant). Is this any help in your thinking?? Light current 15:58, 6 September 2005 (UTC)

Well, that's not correct! Magnetic charge may exist but it has not been observed (yet). Further, if it does exist, it will be directly observable with, for example, a particle detector.

Now, contrast this with the question of observability of electric flux or any other field associated with EM. The answer may be suprising to you!

The magnetic flux has, in the absence of magnetic charge, zero divergence. Thus, it can be thought of as the curl of some other vector field we call the A field or vector potential. I once asked my EM professor whether the A field is physical or just a mathematical construct. His answer was "a mathematical construct". In other words, he claimed that the A field was not directly observable. However, I later found out that this isn't true. If you pass a current through a solenoidal inductor, the magnetic flux density B is zero outside the inductor. However, the A field can be non-zero outside the inductor as long as the curl of A outside the inductor is zero. This A field external to an energized solenoidal inductor has been observed by the effect it has on the phase of the wave function of electrons passing near but outside the inductor Aharonov-Bohm effect. Thus, it appears that A is the physical field and B is the mathematical construct!

It is likely the same for the scalar potential. That is, V is the physical (scalar) field and E is the mathematical construct. BTW, if magnetic charge does exist, then there should be an electric vector potential and a magnetic scalar potential too. Alfred Centauri 16:20, 6 September 2005 (UTC)

[edit] Your recent work

Although your recent work is extremely interesting and ,I think, important to the greater understanding of EM field theory, you probably wont be able to publish it on Wikipedia as recent/new work and self citing is not allowed. However, I feel that insights of this type are to useful to be 'hidden under the bed' and I wondered if Bill Beatty (to whose page I referred you) might be interested in your ideas. After all, his pages are full of unconventional ways of teaching people about 'electricity'. Just a thought! BTW Thanks for the tutorials! Light current 02:36, 7 September 2005 (UTC)

Yes, I would definitely encourage you to communicate your ideas to Bill. I think he will be most interested. Maybe he could even incorporate them on his pages!! Light current 17:18, 7 September 2005 (UTC)

[edit] New Discussion

Thought you may be interested in a new discussion just breaking on Talk:Capacitor ;-)--Light current 01:18, 11 September 2005 (UTC)

[edit] Look whose talking

Alfred, I think you have been talking to 'O' the past 30 mins. I havent been addessing you. I have just replied to 'O' on the talk page. Someone has not been signing his posts so it gets a bit dfficult to know whos who.--Light current 15:28, 12 September 2005 (UTC)

Hint: look at earlier posts again....(A friend!)

[edit] WikiProject Electronics

I am wondering if we should start a WikiProject for Electronics. What do you think? — Omegatron 00:21, 15 September 2005 (UTC)

The project was already started by another user, though I think we can consider it a prototype. You should bring up any concerns on the talk page. — Omegatron 13:41, 22 September 2005 (UTC)

[edit] Tom Bearden

Can I just ask you seriously what your view is on Tom Bearden. I had not heard of him till you mentioned him. I dont know if you were joking or not (I suspect you were) in your last post to David on Talk:Displacement current. Do you think he's a crank or what? Serious answer appreciated!--Light current 22:02, 16 September 2005 (UTC)

[edit] Order of replies

If you don't interrupt my replies with your replies, I will stop rearranging your replies. Deal?--Light current 21:47, 17 September 2005 (UTC)

[edit] Time for bed

look Alfred, as much as I enjoy these little chats of ours, I think its time for bed. BTW I dont mean ay offence to you. Lets just say were having a robust agrument and try to remain friends. What do you say?--Light current 01:06, 18 September 2005 (UTC)

[edit] Equivalent series resistance-- can AC look at it please?

Alfred, could you please have a quick look at this page when you have time.Equivalent series resistance. There seems to be some silly statements in it. Can you confirm/deny. THanks--Light current 04:40, 20 September 2005 (UTC)

[edit] Welcome!

Welcome Alfred to the Electronics project. I'm so glad you have decided to join us. I enjoy our little discussions so much! So, I'll probably see you over on WikiProject: electronics quite soon!--Light current 02:15, 24 September 2005 (UTC)

[edit] Is the DC voltage across an inductor zero?

Hi Alfred,

In your User page, under this question you first wrote, "In DC steady state, all circuit voltages and currents are constant." This is also the meaning I understand for the term "DC". That is, not just currents, but also voltages are constant in DC analysis.

You then say, "a constant (DC) voltage across an inductor can exist if the current through the inductor changes at a constant rate." and therefore "the answer [to the titular question] is no." But you've contradicted the definition of DC, which requires that all currents are constant. A current that changes at a constant rate is not constant; it is changing.

To say it another way, for a value (current) to be constant, its derivative must be zero. Therefore the definition of DC requires that all dv/dt and di/dt are zero. Therefore, from the inductor equation v = L(di/dt), we have v=L*0, v=0.

There is probably an analogy here to the question of whether current "flows" or whether current is a flow of charge.

--The Photon 02:31, 14 November 2005 (UTC)

Hi again,

You wrote (on UserTalk:The Photon):

There is not contradiction. You have equated DC steady state and DC which is incorrect. A circuit consisting of an inductor and a DC voltage source has no DC steady state solution yet the voltage across the inductor is constant (DC). Alfred Centauri 11:27, 14 November 2005 (UTC)

I suppose you are right. You have been very subtle about the terminology difference between "DC" and "DC steady state". Your solution is a time-varying solution to a circuit with only DC sources. (But I think it would be confusing to students to call it a DC circuit or DC solution).

Also when you said, "It is commonly said that an inductor is a 'short circuit at DC'", this implies you define "at DC" to mean "in a DC analysis." not "in a circuit with only DC sources." The statement "an inductor is a short at DC" is obviously not correct if "at DC" means "the sources are constant in the time period of interest" in a transient analysis.

I guess I accept that "at DC" means either "in a DC analysis" or "in the limit as t -> infinity in a transient analysis", or "in the limit as f -> 0 in an AC analysis". I haven't heard the term "at DC" used to mean "in a time-varying circuit with only DC sources."

If I took the perfect capacitor and perfect inductor, with nonzero i and v, as described in your page, and put them together to make an ideal lossless oscillator, would you still say the circuit is "at DC"?

--The Photon 17:17, 14 November 2005 (UTC)

[edit] Talk Ivor Catt

Alfred, you may be interested to learn that some idiot on that talk page is again claiming that all capacitors are TLs and that Ivor Catt was in fact totally correct in his 1978 Wireless World article!--Light current 17:21, 21 April 2006 (UTC)

[edit] My beliefs & Merry Xmas

I have changed my wholesale acceptance of Maxwell's equations now. I now believe that displacement current does not in fact exist as a flow of anything at all. Current does appear to be transferred from one plate to the other in a capacitor, but this is purely an effect of the em energy flow down the distributed (TL) structure. NB displacement current I of course admit in dielectrics- but not in vacuum.--Light current 07:23, 1 January 2006 (UTC) As far as em propagation in space is concerned, I believe no current (flow of anything at rt angles to direction of propagation) happens there either, but that the changing electric field creates (by an as yet unknown process) the required magnetic field and vice versa.

My reasonings are outlined on Talk:displacement current

Of course, it may turn out that Maxwell was correct all along, if the theory of vacuum polarisation can be proved. But until then, I think I'll stick with this explanation, which whilst probably not satisfying everyone, satisfies me at the moment. You may not agree with my view, but I would ask you to respect it. Merry Xmas!!--Light current 03:59, 25 December 2005 (UTC)

[edit] A favour

Alfred, I am doing some editing of education and training of electrical and electronics engineers and Im short of syllabus content (mainly final year stuff) for the power engineering/machines/heavy current stuff. Would you be able to oblige us with an up to date syllabus please? --Light current 07:08, 1 January 2006 (UTC)

[edit] Thanks (put other thanks here)

Thanks for the triva on PFM. That'll be a useful term in my major (hint, its your major ; ). Fresheneesz 20:21, 8 February 2006 (UTC)

[edit] Transformer

Alfred, do you know how transformers work - I mean really know how they work?. If so see Talk:Transformer. I think we could do with some insights! 8-)--Light current 01:14, 19 May 2006 (UTC)

[edit] E X H and transformers

Alfred, do transformers depend on Poynting vector for energy transfer? If so, how does it come into play? 8-)--Light current 01:04, 22 May 2006 (UTC)

[edit] Flux in a transformer core

Alfred I am trying to reopen discussion on the important topic of whether or not there is substantial flux (due to increased secondary loading,say) in the core of a transformer aside from the magnetising flux. I am basing my present thoughts on the interesting paper by Edwards and Saha and it seems to me that they are in fact saying something about core flux, but not explicitly stating the magnitude of flux in the actual core. I would value your educated comments if you have time at Talk:transformer. --Light current 13:45, 1 June 2006 (UTC)

[edit] Ground or common?

On your user page, you say:

The so-called 'ground' symbol is ubiquitous in virtually any schematic diagram. Yet, rarely is this node actually connected to 'ground'. Further, in many circuits, there is more than one 'ground', i.e., analog ground, digital ground, rf ground, etc. But technically, the term 'grounded' means connected to the Earth. If this node is not actually connected to ground, a more appropriate name might be 'common' or 'return', i.e., +5V return, analog common, etc.

Another commonly-used (sorry!) term is "reference", so "logic reference", "analog reference", and so on.

Atlant 13:56, 22 May 2006 (UTC)

[edit] Re: Clock synchronization question.

I have posted a response of my talk page. --EMS | Talk 21:15, 23 May 2006 (UTC)

[edit] Opinion needed

Alfred, do you know how magnetic guitar pickups work? I say they work on the variable reluctance principle, but many refs disagree. Even one supposed Univerity paper seems to say that the string must be 'magnetised' to work. Would you be able to spare some time to comment please at Talk:Pickup. THanks 8-)--Light current 18:43, 18 June 2006 (UTC)