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Dr. Polemic wrote:
On Tue, 14 Jun 2005 10:11:03 -0800, (Floyd L. Davidson) wrote: Note the relative vapor pressure of cadmium compared to other metals. Then think about "a nice little vacuum pump". Think about why the graphs on that web page don't go below 10^-7 torr. Then think about cadmium's (extrapolated) vapor pressure of 10^-12 torr at 30 degrees. http://www.veeco.com/learning/learni...orelements.asp This is quite OT, but might be of interest, since we're so far OT anyway! Note the strange behavior of mercury. This makes it possible to use mercury vapor to make "a nice little vacuum pump". When I first started using vacuum pumps, mercury pumps were common. They were displaced by oil diffusion pumps and more recently by ion pumps. I don't know of any that would make cadmium "boil" at anywhere near "room temperature". -- Virg Wall |
Dr. Polemic wrote:
The information on this web page doesn't indicate directly what the vapor pressure of cadmium is at 20 degrees, but extrapolating the numbers in the table gives a value of 10^-12 torr at 30 degrees. It takes more than a "nice little vacuum pump" to achieve this. But I see that you're waffling now; you now say that "I'm not sure what the actual temperature was". I said it was 40 years ago! And I make *no* claims about any absolute accuracy of any specific detail. I'm *not* making a point of what the specific material was, what the exact temperature was, what the exact pressure was. I appreciate corrections to what would obviously have to be the correct parameters. Clearly at 70 some degrees C cadmium will out-gas if the pressure is down to 10^-8 Torr. The point was about apparently solid things simply vaporizing without being raised to some significantly high temperature, because *pressure* is just as significant. And the results can come as an expensive surprise too. The idea that water boils at 100C and freezes at 0C, without some mention of pressure, has little meaning. Water can "boil" at 0C too. -- Floyd L. Davidson http://web.newsguy.com/floyd_davidson Ukpeagvik (Barrow, Alaska) |
On Tue, 14 Jun 2005 11:44:02 -0700, Dr. Polemic
wrote: On Tue, 14 Jun 2005 10:11:03 -0800, (Floyd L. Davidson) wrote: John Fields wrote: On Tue, 14 Jun 2005 08:32:09 -0800, (Floyd L. Davidson) wrote: Dr. Polemic wrote: On Tue, 14 Jun 2005 01:14:42 -0800, (Floyd L. Davidson) wrote: Dr. Polemic wrote: Danged, several weeks of work shot because it just hadn't occurred to him that ni-cad would boil at room temperature. I doubt that it *boils* at room temperature; evaporates slowly, maybe. At least, not at the temperature of any rooms I've been in. Oh, it boiled off! So, tell me, what is the vapor pressure of Cadmium at 20 degrees C? I don't know. Look it up. Takes a nice little vaccuum pump to do it though. --- Yer fulla ****. Well John, it probably was cadmium plating, not ni-cad. And I'm not sure what the actual temperature was, though it certainly wasn't much above room temperature (the experiment failed before it was exposed to significant nuclear radiation, which would have provided heat). However, the metal plating on the hardware boiled! Here's a chart you might want to look at. The information on this web page doesn't indicate directly what the vapor pressure of cadmium is at 20 degrees, but extrapolating the numbers in the table gives a value of 10^-12 torr at 30 degrees. It takes more than a "nice little vacuum pump" to achieve this. But I see that you're waffling now; you now say that "I'm not sure what the actual temperature was". I would certainly agree that cadmium can be made to boil if the temperature is high enough, but you claimed "room temperature". One thing is pretty certain; you weren't "boiling" cadmium at 20 degrees because you have to get the pressure below the vapor pressure of cadmium at 20 degrees before it "boils" and a "nice little vacuum pump" of 40 years ago couldn't do that under a bell jar. Note the relative vapor pressure of cadmium compared to other metals. Then think about "a nice little vacuum pump". Think about why the graphs on that web page don't go below 10^-7 torr. Then think about cadmium's (extrapolated) vapor pressure of 10^-12 torr at 30 degrees. http://www.veeco.com/learning/learni...orelements.asp My point, since it went right over your head Did this go over your head, John? when stated as a puzzle, is that temperature alone is not what defines when something "boils", and some materials that you wouldn't normally think of in terms of a vapor can in fact "boil". "Out-gas" might be a better term. --- Not at all. Even Betty Crocker (last time I looked) had baking altitude adjustments on her boxes of cake mix. -- John Fields Professional Circuit Designer |
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apparently you have not seen the equations governing reactance to make the
statements you do about deh said the "AC" equations are rigorous, and apply equally well to your one-voltage DC when the frequency drops to zero- the reactance term of the changing magnitude [current equation] then goes to zero. fld said That is an hilarious idea! If the magnitude is zero all the way around... we aren't talking about AC or DC... maybe about blown breakers or taking a coffee break, but not about current. nor have you ever designed a switch carrying power loads, to say that in non-DC rated switches, arc quenching does not rely on current reversal. Or to ground fault design, I might add. deh said Because the reactance equations only apply to varying magnitude, and they do not apply to reversing direction. fld said Then why would we be concerned at all about this reversing direction, and give it a specific name and have a whole separate field of study for it? Sounds like we need to be concerned with varying magnitude, *not* with reversing direction. (Which is what I've been saying...) As I said, your position works only if you are in one corner of one part of all electrical phenomena, and if you use technicians tools rather than engineers and scientists tools. You will just have to live with what the big boys in academia say is alternating current - they are not going to change the widely applicable proven rigorous for a circuit design technician's philosophical musings. "Floyd L. Davidson" wrote in message ... "--" wrote: "Floyd L. Davidson" wrote: "--" wrote: Strictly speaking, I believe the reactance (part of impedance) equations apply to any variation in current magnitude. Their appropriate application does not in any way require reversing the charge. Exactly. 1) I think one needs to define the term "alternating current" by its phenomena rather than define it by what applies to "AC". In other words, define AC as alternating current -rather than defining AC as "anything requiring an impedance calculation because of its magnitude variation". What value does that have? The problem is circuit analysis, No, rather the problem is that many of the fundamental physical sciences and most of electrical engineering use the concept, and it is not used merely by a small corner of circuit analysis. The definition has to work for all the sciences where it may be used. E.g., many switches use the "AC as reversing" concept for quenching contact arcs during switching (as the current passes thru zero as direction reverses) and the defintion of AC as varying DC falls flat for that purpose. Install an AC designed switch on a varying DC circuit, and you may well have a safety switch contacts welded shut. Here, AC DEFINITELY means reversing direction. Bad example. That does *not* require a direction reversal. All it requires is understanding that it is relative to the static state. you really don't know much about power switches, do you? It does happen that the static state in that specific case is when a polarity reversal takes place, but in the general case it is not required. In other examples both sides of the switch might well be at some DC potential, that happens to be equal on both sides at the time the switch is made, even though there is no direction reversal. which requires the division between DC and AC, I believe the equations are not DC-AC specific - the "AC" term drops to zero if the change in magnitude drops to zero. Your rationale of using the equations does not hold up. Everything concerned with reactance is AC specific. Nothing concerned with reactance requires a polarity reversal. Reactance is the essence of the difference between DC and AC, not some notion of reversing polarity. AC is defined as: charge flow that changes direction. which leaves the calculations for reactance out of the definition. Which means it is worthless. Reactance *is* the significance. 3) In the definition approach to a phenomena, one deals with the descriptive term and the phenomena itself and ignores the present attached The problem is defining something with no practical value. We define air, and black holes, and impracticality. All of which *does* have practical value. And if memory serves me correctly, the "AC" equations are rigorous, and apply equally well to your one-voltage DC when the frequerncy drops to zero- the reactance term of the changing magnitude goes to zero. That is an hilarious idea! If the magnitude is zero all the way around... we aren't talking about AC or DC... maybe about blown breakers or taking a coffee break, but not about current. And "varying DC" is a contradiction in terms to begin with. Do we actually need *four* states: 1 -- DC 2 -- Varying DC 3 -- AC 4 -- Steady AC no, just two - reversing flow direction, and varying magnitude. Oh? DC doesn't exist? What about "steady AC"? (That's two exactly equal signals 180 degrees out of phase, combined in that capacitor which can generate AC mentioned by John Fields, perhaps???) Because the reactance equations only apply to varying magnitude, and they do not apply to reversing direction. Then why would we be concerned at all about this reversing direction, and give it a specific name and have a whole separate field of study for it? Sounds like we need to be concerned with varying magnitude, *not* with reversing direction. (Which is what I've been saying...) As I understood, scienctific method is designed to remove personal views from science. Thus the definition,must stand alone, and since we can't see all that is ahead, science has to fall in behind a definition of that phenomena in pure terms. imho....... A nice goal. ---------------- Alternating-direction Current, aka Alternating Current Except that alternating direction has no significance. Changing magnitude does. Why bother with alternating-direction at all, it is just an insignificant, though interesting, part of the more general case of changing magnitude. All of the same equations apply. Direction-specific Current, aka Direct Current. And if you claim that only alternating direction current is AC, then you have to have two sets of equations for DC, one for non-varying magnitude and one for varying magnitude. That doesn't make a lick of sense. -- Floyd L. Davidson http://web.newsguy.com/floyd_davidson Ukpeagvik (Barrow, Alaska) |
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Dr. Polemic wrote in
: On Tue, 14 Jun 2005 08:12:33 -0500, John Fields wrote: On Mon, 13 Jun 2005 23:15:06 -0800, (Floyd L. Davidson) wrote: I knew a fellow one time who put together a nice little experiment where he bolted everything together with nice shiny nickel-cadmium plated screws. --- Nickel-cadmium usually refers to the metals used in fabricating a family of secondary cells used in redchargeable batteries, while cadmium, by itself, was once used to plate mechanical fasteners. Just one more inconsistency in his postings. I didn't even mention the nickel component in his alleged plating because it, like gold, has a vapor pressure of about 10^-11 torr at around 800 degrees, and thus won't boil at 20 degrees even in interstellar space. But I think you're right. I've never heard of Nickel-cadmium plating of screws, but I used to use cad plated hardware all the time. It has dropped out of favor and its use may now be prohibited for that purpose due to its toxicity and effect on the environment. Yea, I'd have to call BS on that one... ----== Posted via Newsfeeds.Com - Unlimited-Uncensored-Secure Usenet News==---- http://www.newsfeeds.com The #1 Newsgroup Service in the World! 120,000+ Newsgroups ----= East and West-Coast Server Farms - Total Privacy via Encryption =---- |
"--" wrote:
apparently you have not seen the equations governing reactance to make the statements you do about Your descriptions apply to *your* comments, not mine! deh said the "AC" equations are rigorous, and apply equally well to your one-voltage DC when the frequency drops to zero- the reactance term of the changing magnitude [current equation] then goes to zero. fld said That is an hilarious idea! If the magnitude is zero all the way around... we aren't talking about AC or DC... maybe about blown breakers or taking a coffee break, but not about current. nor have you ever designed a switch carrying power loads, to say that in non-DC rated switches, arc quenching does not rely on current reversal. Or to ground fault design, I might add. So your one single point of exposure defines the entire field? I don't think so at all. You are trying to say that specific instance is the general case. I was saying that it isn't, and that the general case is *much* larger. deh said Because the reactance equations only apply to varying magnitude, and they do not apply to reversing direction. fld said Then why would we be concerned at all about this reversing direction, and give it a specific name and have a whole separate field of study for it? Sounds like we need to be concerned with varying magnitude, *not* with reversing direction. (Which is what I've been saying...) As I said, your position works only if you are in one corner of one part of all electrical phenomena, and if you use technicians tools rather than engineers and scientists tools. That describes *your* position very well! You will just have to live with what the big boys in academia say is alternating current - they are not going to change the widely applicable proven rigorous for a circuit design technician's philosophical musings. Actually, getting too deep into either one, or into any single field in either one, is what causes these assumptions like yours, that specific instances are the entire general case. One of the problems with academia, for example, is this specialization. Whereas someone who works in the field runs into whatever each project coughs up. The exposure is significantly greater. And no that does not mean that academics is bad, wrong, poor, unnecessary, less that useful or any other silly thing you are likely to try twisting it into. It does mean that it necessarily, for any one individual, has a narrower scope, and people with field experience have a broader view, generally (which also often lacks as much depth too). Both are necessary. "Floyd L. Davidson" wrote: Bad example. That does *not* require a direction reversal. All it requires is understanding that it is relative to the static state. you really don't know much about power switches, do you? Well, I certainly do lack depth in that particular subject! But knowing about power switches doesn't define understanding AC vs DC, even if that is your field of expertise. In fact, it might be the cause of your confusion. Power switches may in fact operate at the moment of direction reversal, but that is merely one specific example of the broader "relative to the static state" general description that I gave. The switch can happen at any time there is no current flow (or rather, when the phase angle and rate of change is appropriate) across the "contacts". But that can be at some DC potential which is equal on both sides of the switch, or at a zero voltage, either of which is *not* at a current direction reversal. Maybe those circumstances don't happen with AC distribution power switching, but they most certainly do in other fields. The requirement is *not* that a direction reversal be taking place. That is just a collateral circumstance that happens to exist in AC power distribution systems at the same time the necessary phase relationship exists. The very same general principle is used in video switching... except not at a time when there is any change in current direction! -- Floyd L. Davidson http://web.newsguy.com/floyd_davidson Ukpeagvik (Barrow, Alaska) |
Floyd L. Davidson wrote:
(snip) The idea that water boils at 100C and freezes at 0C, without some mention of pressure, has little meaning. Water can "boil" at 0C too. Unless it is a solid. Then it sublimates. Boiling only happens to liquids. |
On Tue, 14 Jun 2005 18:58:46 GMT, Rich Grise wrote:
On Tue, 14 Jun 2005 10:54:37 -0700, Dr.Polemic wrote: On Tue, 14 Jun 2005 13:07:05 -0400, John Popelish wrote: John Fields wrote: On Tue, 14 Jun 2005 08:32:09 -0800, (Floyd L. Davidson) wrote: Dr. Polemic wrote: On Tue, 14 Jun 2005 01:14:42 -0800, (Floyd L. Davidson) wrote: Dr. Polemic wrote: snip No way did he "...get ni-cad to boil at room temperature (by) simply reduc(ing) the pressure to something *significantly* below its vapor pressure. We did it knowingly with gold too once..." Gold has a vapor pressure of 10^-11 torr at about 800 degrees. I don't think gold will boil even in interstellar space (10^-17 torr) at 20 degrees. It *will* evaporate, though; so will tungsten! Slowly! Takes a nice little vaccuum pump to do it though. Yer fulla ****. I think he is confusing boiling with sputtering. But he says it *boiled*; he couldn't be mistaken, could he? Or maybe just sublimation. And he didn't say the chamber was held at room temperature. What he said was: "Danged, several weeks of work shot because it just hadn't occurred to him that ni-cad would boil at room temperature." I suppose I could say that tungsten exaporates at room temperature and then say that I didn't say that the filament wan't held at room temperature; I just meant that the room was at room temperature. What's the vapor pressure of zinc at 20C? 10^-8 torr at 123 degrees C. And, of course it will evaporate at 10^-8 torr and 20 degrees, but it *won't* boil. At 10^-8 torr, it will *boil* at 123 degrees. I once worked at a place where their product used a UHV bell jar - that's "Ultrahigh vacuum". They didn't even have an oil-based pump in the building. They started with an ordinary sorption pump, then they had ion pumps and molecular inertial pumps, and getter pumps, and the sexiest was the cryopump. One day one of the vacuum engineers came into the shop from the line, fit to be tied. It seems someone had supplied feedthroughs with brass contacts. The zinc ruined some stuff, and wasted about a week from having to clean out the bell jar. Cheers! Rich |
On Tue, 14 Jun 2005 14:19:24 -0500, John Fields wrote:
On Tue, 14 Jun 2005 10:11:03 -0800, (Floyd L. Davidson) wrote: John Fields wrote: On Tue, 14 Jun 2005 08:32:09 -0800, (Floyd L. Davidson) wrote: Dr. Polemic wrote: On Tue, 14 Jun 2005 01:14:42 -0800, (Floyd L. Davidson) wrote: Dr. Polemic wrote: Danged, several weeks of work shot because it just hadn't occurred to him that ni-cad would boil at room temperature. I doubt that it *boils* at room temperature; evaporates slowly, maybe. At least, not at the temperature of any rooms I've been in. Oh, it boiled off! So, tell me, what is the vapor pressure of Cadmium at 20 degrees C? I don't know. Look it up. Takes a nice little vaccuum pump to do it though. --- Yer fulla ****. Well John, it probably was cadmium plating, not ni-cad. And I'm not sure what the actual temperature was, though it certainly wasn't much above room temperature (the experiment failed before it was exposed to significant nuclear radiation, which would have provided heat). --- So now we don't even know whether it was cadmium or not, we also don't know what the temperature or the pressure was in the chamber, _and_ we learn that the sample was being subjected to ionizing radiation! What next? Well, now he has informed us that: "And I make *no* claims about any absolute accuracy of any specific detail." --- However, the metal plating on the hardware boiled! Uh-huh... sure it did. --- Here's a chart you might want to look at. Note the relative vapor pressure of cadmium compared to other metals. Then think about "a nice little vacuum pump". http://www.veeco.com/learning/learni...orelements.asp My point, since it went right over your head when stated as a puzzle, is that temperature alone is not what defines when something "boils", and some materials that you wouldn't normally think of in terms of a vapor can in fact "boil". "Out-gas" might be a better term. --- Blah, blah, blah, ****ing blah. More posturing, platitudes and crapola. 'Outgassing' is an entirely different phenomenon which manifests itself as the extraction of gas entrained in a material by and into a vacuum surrounding the gassy material. A good example is the frothing that occurs when a two-part epoxy is mixed and then placed in a vacuum. After the release of the gas and the collapse of the froth, it would still be possible for the epoxy to boil in the vacuum if the vacuum were hard enough and the temperature high enough, but that would then be true boiling and _not_ outgassing. Just so you won't have to extrapolate to 20°C from those charts of yours, here's Dr. Polemic's data: "The CRC handbook indicates that the vapor pressure of cadmium is about 10^-12 torr at room temperature (20 degrees). This is better than the vacuum at the moon. The best vacuum pumps available today can't hit that in a bell jar, much less 40 years ago." |
On Tue, 14 Jun 2005 10:51:11 -0800, (Floyd L.
Davidson) wrote: Don Bowey wrote: On 6/14/05 2:28 AM, in article , "Floyd L. Davidson" wrote: I agree with your examples of DC power supplies and AC noise. Been there, done that. Defining how may angels can dance on a DC power cable without having to redefine it is pointless, however. Everyone I knew in the telco industry had good, workable terms for the cause of the need for filters, not only at the FB, but at the equipment rack too; it was noise, trash, crap. spikes....., but the 48V and 130V "power" were always DC and we knew the noise had to be dealt with as AC riding the DC. No other esoteric, mindless definitions are needed even though the terms AC and DC may be misnomers. They are historic and work very well. Exactly. --- LOL, instead of grasping at straws you're now grasping for the coattails of someone who knows what he's talking about, and you're using that "Exactly" crack to make it seem like what you've been positing all along has finally been iterated by someone with some credibility. --- But look at all the people claiming it *isn't* AC! Very clearly anyone who claims the various "noise, trash, crap, spikes" etc are *not* AC, needs a reality check on their definition of AC. --- And here, now, you're using your newly found unilateral alliance to vehemently try to add credence to your error-plagued hypotheses and to pooh-pooh your naysayers. It won't work. Got some circuits? Got some numbers? Post 'em and end the bull**** or else get the **** out of Dodge. --- On the other hand, while their definition and understanding of it is clearly invalid, there is no lack of wide spread belief that it is correct. Which I do find somewhat amazing... --- Only because it's at odds with what you think is correct which, because of your obvious lack of technical training, has you in blinders. However, you do seem to have a nice command of the language, so there may be hope for you yet. :-) -- John Fields Professional Circuit Designer |
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John Fields wrote:
On Tue, 14 Jun 2005 11:21:21 -0800, (Floyd L. Davidson) wrote: The idea that water boils at 100C and freezes at 0C, without some mention of pressure, has little meaning. Water can "boil" at 0C too. --- As John Popelish remarked, boiling is only possible if the medium in which the boiling is occurring is a liquid, so if the water has turned into ice at 0°C, sublimation is the mechanism which water molecules will use to evaporate from their parent structure. Since this a technical forum and we _do_ have ground rules, I believe we generally agree that, unless otherwise specified, standard pressure is defined as 760 millimeters of mercury and standard temperature is defined as zero degrees celcius. While the boiling point of water is dependent on pressure, the freezing point, I believe, is not. At least, not to a great extent. I don't have any data to support that position, but I'd love to see some, if it's out there. Handbook of Chemistry and Physics, Twenty Fifth Edition, Table p.1696. 1 kg/sq.cm. = 0.0 deg C. to 2200 kg/sq.cm = -22.1 deg C. All you have to do is go ice skating! You skate on a thin layer of water, produced by the pressure of the skates. Water is also one of the few liquids that expands when it freezes, which is fortunate for life on this earth! :-) -- Virg Wall, K6EVE |
"John Fields" wrote in message ...
Since this a technical forum and we _do_ have ground rules, I believe we generally agree that, unless otherwise specified, standard pressure is defined as 760 millimeters of mercury and standard temperature is defined as zero degrees celcius. I believe that in this forum we assume temperature is a variable that must be accommodated in design, unless otherwise stated. I cannot imagine why any unstated temperature would be assumed to be 0 oC. I suppose sea-level atmospheric pressure is often assumed, but where it matters, it should not be assumed at all. While the boiling point of water is dependent on pressure, the freezing point, I believe, is not. You might want to consider the "triple point" of water, below which pressure "melting point" is meaningless and the "freezing point" varies considerably with pressure. At least, not to a great extent. I don't have any data to support that position, but I'd love to see some, if it's out there. See: http://www.lsbu.ac.uk/water/phase.html -- --Larry Brasfield email: Above views may belong only to me. |
On Tue, 14 Jun 2005 11:12:09 -0700, Dr. Polemic
wrote: On Tue, 14 Jun 2005 07:44:13 -0700, John Larkin wrote: On Mon, 13 Jun 2005 22:01:12 -0700, The Phantom wrote: Total and utter horse****. "DC" is simply the first (or "offset" term in the Fourier expression of any repetitive waveform. DC, of course, cannot exist at all ever. Because it would have to be unvarying through infinite time. So, the first Fourier term is always zero. Got it. Damn, this thread will hit 200 posts soon. The less the content, the bigger the thread. Amazing isn't it? We're actually witnessing a dispute over what AC and DC are? And whether such things even exist? There seems to be a consensus that, since no signal is absolutely stable with time, then DC must not exist. That does simplify life. John |
DIE THREAD!!!!!!!
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Larry Brasfield wrote: "John Fields" wrote in message ... Since this a technical forum and we _do_ have ground rules, I believe we generally agree that, unless otherwise specified, standard pressure is defined as 760 millimeters of mercury and standard temperature is defined as zero degrees celcius. I believe that in this forum we assume temperature is a variable that must be accommodated in design, unless otherwise stated. I cannot imagine why any unstated temperature would be assumed to be 0 oC. I suppose sea-level atmospheric pressure is often assumed, but where it matters, it should not be assumed at all. While the boiling point of water is dependent on pressure, the freezing point, I believe, is not. You might want to consider the "triple point" of water, below which pressure "melting point" is meaningless and the "freezing point" varies considerably with pressure. At least, not to a great extent. I don't have any data to support that position, but I'd love to see some, if it's out there. See: http://www.lsbu.ac.uk/water/phase.html Using the usual meaning of "freezing" which is the transition from liquid to solid, that graph shows "freezing" occurring at 273K over a million to one range in pressure. I would say that the statement "While the boiling point of water is dependent on pressure, the freezing point, I believe, is not" is essentially true- to all except a nitwit like you. |
"Kevin Aylward" wrote in message ... Floyd L. Davidson wrote: Bob Penoyer wrote: On Sat, 11 Jun 2005 10:36:54 -0400, "Tam/WB2TT" wrote: snip Yes. DC by definition is zero frequency. Um, no. DC is Direct Current, i.e., current that flows in one direction. For example, the output from a rectifier is DC but it certainly isn't "zero frequency." Actually, DC from a rectifier *is* "zero frequency", to the degree that it is DC. Of course until the AC is filtered out, it has both AC and DC components. The output of a rectifier contains both AC and DC. You put a filter on it to get close to pure DC. That is *precisely* correct. (It just doesn't tell enough of the story to explain the confusion of this "flows in one direction" definition of DC.) A rectified AC waveform contains DC and AC components but if the current isn't changing direction, it isn't alternating current. And, if it isn't AC, it's DC. The output of a rectifier until filtered *does* have both AC and DC, which actually is another way of saying that yes it *does* change directions. What? you say! The problem is that "direction" only has meaning when measured in comparison some specific point of reference. If you have three different reference points, one at the DC level, one at the peak positive swing and one at the peak negative swing, you have three very different views of "direction" for current flow: Since we are quibbling her on terms, lets get this bit straight shall we. "Current flow" is wrong. Its simply "current" or "charge flow". "Current" already contains the notion of "flow". Atta boy, Kevin. Ratch Kevin Aylward http://www.anasoft.co.uk SuperSpice, a very affordable Mixed-Mode Windows Simulator with Schematic Capture, Waveform Display, FFT's and Filter Design. |
"Fred Bloggs" wrote in
message ... Larry Brasfield wrote: "John Fields" wrote in message ... Since this a technical forum and we _do_ have ground rules, I believe we generally agree that, unless otherwise specified, standard pressure is defined as 760 millimeters of mercury and standard temperature is defined as zero degrees celcius. I believe that in this forum we assume temperature is a variable that must be accommodated in design, unless otherwise stated. I cannot imagine why any unstated temperature would be assumed to be 0 oC. I suppose sea-level atmospheric pressure is often assumed, but where it matters, it should not be assumed at all. While the boiling point of water is dependent on pressure, the freezing point, I believe, is not. You might want to consider the "triple point" of water, below which pressure "melting point" is meaningless and the "freezing point" varies considerably with pressure. At least, not to a great extent. I don't have any data to support that position, but I'd love to see some, if it's out there. See: http://www.lsbu.ac.uk/water/phase.html Using the usual meaning of "freezing" which is the transition from liquid to solid, that graph shows "freezing" occurring at 273K over a million to one range in pressure. It does not. The straight part of the liquid/solid phase boundary covers less than 5 orders of magnitude. "Over a million to one" would be more than 6 orders of magnitude. I would say that the statement "While the boiling point of water is dependent on pressure, the freezing point, I believe, is not" is essentially true In a discussion that has involved sublimation, to exclude that part of the phase space would be essentially silly. - to all except a nitwit like you. Off your meds again, Fred? I expect you to be more careful with your graph reading before breaking into your frothing-at-the-mouth modes. -- --Larry Brasfield email: Above views may belong only to me. |
John Fields wrote:
Since this a technical forum and we _do_ have ground rules, I believe .... While the boiling point of water is dependent on pressure, the freezing point, I believe, is not. At least, not to a great extent. I don't have any data to support that position, but I'd love to see some, if it's out there. What happened to the ground rules you mentioned? Being correct isn't one of them? Tell us more about AC, so we can laugh again. Then come back to this, for more! -- Floyd L. Davidson http://web.newsguy.com/floyd_davidson Ukpeagvik (Barrow, Alaska) |
John Fields wrote:
On Tue, 14 Jun 2005 10:51:11 -0800, (Floyd L. Davidson) wrote: Don Bowey wrote: On 6/14/05 2:28 AM, in article , "Floyd L. Davidson" wrote: I agree with your examples of DC power supplies and AC noise. Been there, done that. Defining how may angels can dance on a DC power cable without having to redefine it is pointless, however. Everyone I knew in the telco industry had good, workable terms for the cause of the need for filters, not only at the FB, but at the equipment rack too; it was noise, trash, crap. spikes....., but the 48V and 130V "power" were always DC and we knew the noise had to be dealt with as AC riding the DC. No other esoteric, mindless definitions are needed even though the terms AC and DC may be misnomers. They are historic and work very well. Exactly. --- LOL, instead of grasping at straws you're now grasping for the coattails of someone who knows what he's talking about, and you're using that "Exactly" crack to make it seem like what you've been positing all along has finally been iterated by someone with some credibility. What's the matter John, are you bitter that several people, who do understand the theory and practice, have said you are wrong... -- Floyd L. Davidson http://web.newsguy.com/floyd_davidson Ukpeagvik (Barrow, Alaska) |
John Fields wrote:
(snip) While the boiling point of water is dependent on pressure, the freezing point, I believe, is not. At least, not to a great extent. I don't have any data to support that position, but I'd love to see some, if it's out there. If you are willing to consider extreme conditions, not only does the freezing point change, but there are many ice phases, each structurally distinct and with temperature and pressure boundaries. http://www.lsbu.ac.uk/water/phase.html |
wrote: 2 questions about a fully DC Sine Wave....let's suppose you have a DC Sine wave which varies from +5V to +15V peak-to-peak going into a load with R, L, and C components..... Question #1: Is the load's impedance a function of R, L, and C (and wave frequency) or is it simply just R (i.e. Z=R)? In other words does non-resistive impedance (L + C) really only matter with an AC signal OR anytime voltage varies periodically (even if it is all DC)? Question #2: Would a "regular" negative peak detector ciruit, like shown he http://www.elektroda.net/cir/index/D...CTOR.htmgative work for the DC Wave described? Will it output +5V or do negative peak detectors only work for AC signals? Thank you. Ladies and Gentlemen--jackbruce9 has left the building. ;-)) Tut |
On Mon, 13 Jun 2005 21:28:49 -0500, operator jay wrote: [snip] If you have definitions of AC and DC handy from IEEE or someone, stick them on here. I'd say that the (apparent) widespread disagreement means that, functionally, there is no single pervasive definition for these terms, but it would be interesting to see if some of these bodies have published definitions. It would be really interesting if they had definitions, and they didn't quite agree with one another, or if they were "wishy-washy". Didn't see this response, so piggy-backing my reply. There are literally hundreds of references on the web about DC, AC and Transient Analyses. Browse some of the simpler overviews, and you will see that the mathematical differences are clearly defined, and that's what it's all about. The math determines the signal type. It is my belief that the widespread disagreement is due to participants that just like to argue a lot. -- Al Brennan "If you only knew the magnificence of the 3, 6 and 9, then you would have a key to the universe." Nicola Tesla |
Bob Penoyer wrote:
There are certainly AC components in the waveform. But the sum of all the components, including the DC component, never changes direction, so the total signal is a DC signal. Here, "DC" does NOT mean "constant"; it means unidirectional. Anyone who went to university studying a natural science will know the meaning of all of these terms and the others expose their ignorance by speculating and making up instead. You clearly belong to the last category. -- ciao Ban Bordighera, Italy |
Larry Brasfield wrote: "Fred Bloggs" wrote in message ... Larry Brasfield wrote: "John Fields" wrote in message ... Since this a technical forum and we _do_ have ground rules, I believe we generally agree that, unless otherwise specified, standard pressure is defined as 760 millimeters of mercury and standard temperature is defined as zero degrees celcius. I believe that in this forum we assume temperature is a variable that must be accommodated in design, unless otherwise stated. I cannot imagine why any unstated temperature would be assumed to be 0 oC. I suppose sea-level atmospheric pressure is often assumed, but where it matters, it should not be assumed at all. While the boiling point of water is dependent on pressure, the freezing point, I believe, is not. You might want to consider the "triple point" of water, below which pressure "melting point" is meaningless and the "freezing point" varies considerably with pressure. At least, not to a great extent. I don't have any data to support that position, but I'd love to see some, if it's out there. See: http://www.lsbu.ac.uk/water/phase.html Using the usual meaning of "freezing" which is the transition from liquid to solid, that graph shows "freezing" occurring at 273K over a million to one range in pressure. It does not. The straight part of the liquid/solid phase boundary covers less than 5 orders of magnitude. "Over a million to one" would be more than 6 orders of magnitude. Bull- it goes from 10^3 to 10^9 Pa, idiot. I would say that the statement "While the boiling point of water is dependent on pressure, the freezing point, I believe, is not" is essentially true In a discussion that has involved sublimation, to exclude that part of the phase space would be essentially silly. There is no discussion- the statement was about water "freezing", pseudo-intellectual. - to all except a nitwit like you. Off your meds again, Fred? I expect you to be more careful with your graph reading before breaking into your frothing-at-the-mouth modes. More of your parroting insults from other mediocre and pretentious garbage like yourself? Like I say- you are typical USENET garbage, all mouth and heap of worthless garbage in the physical world. My, how that keyboard empowers unskilled nobodies... |
Ban wrote: Bob Penoyer wrote: There are certainly AC components in the waveform. But the sum of all the components, including the DC component, never changes direction, so the total signal is a DC signal. Here, "DC" does NOT mean "constant"; it means unidirectional. Anyone who went to university studying a natural science will know the meaning of all of these terms and the others expose their ignorance by speculating and making up instead. You clearly belong to the last category. That is the pseudo-intellectuals for you, speculating about elementary definitions- and later on you find even a second order network is hopelessly beyond their abilities of computation. They are worthless zeroes of the highest order. The original weakling who started the thread with his ignorant question offered no discussion about direct responses to its question, preferring instead to pseudo-intellectualize about the fundamental principles of terminology, in a weak and ineffective way- OP=ZEROID. |
On Tue, 14 Jun 2005 20:34:41 -0700, Kitchen Man
wrote: On Mon, 13 Jun 2005 21:28:49 -0500, operator jay wrote: [snip] If you have definitions of AC and DC handy from IEEE or someone, stick them on here. I'd say that the (apparent) widespread disagreement means that, functionally, there is no single pervasive definition for these terms, but it would be interesting to see if some of these bodies have published definitions. It would be really interesting if they had definitions, and they didn't quite agree with one another, or if they were "wishy-washy". Didn't see this response, so piggy-backing my reply. There are literally hundreds of references on the web about DC, AC and Transient Analyses. Browse some of the simpler overviews, and you will see that the mathematical differences are clearly defined, and that's what it's all about. The math determines the signal type. It is my belief that the widespread disagreement is due to participants that just like to argue a lot. --- No, they don't. ;^) -- John Fields Professional Circuit Designer |
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On Tue, 14 Jun 2005 22:32:48 -0400, John Popelish
wrote: John Fields wrote: (snip) While the boiling point of water is dependent on pressure, the freezing point, I believe, is not. At least, not to a great extent. I don't have any data to support that position, but I'd love to see some, if it's out there. If you are willing to consider extreme conditions, not only does the freezing point change, but there are many ice phases, each structurally distinct and with temperature and pressure boundaries. http://www.lsbu.ac.uk/water/phase.html --- Interesting. Thanks, John! BTW, from another thread and just as an aside, I went over to my friend's sign shop and checked some known-good neon sign transformers using the same meters I used to check the ones I have here, and it turns out my transformers are defective. :-( -- John Fields Professional Circuit Designer |
John Fields wrote:
--- Not at all. I'm always grateful when someone takes the time to correct me and show me where I went wrong, since that increases my store of stuff I know is right. John, you can't have it both ways. You say the above is what you do, but what you actually *do* is the next paragraph: But when a self-important know-nothing windbag like you comes along making baseless proclamations and spouting opinions like they were gospel it _does_ annoy me. John Fields Professional Circuit Designer ^^^^^^^^^^^^ When will that begin? -- Floyd L. Davidson http://web.newsguy.com/floyd_davidson Ukpeagvik (Barrow, Alaska) |
"Don Bowey" schreef in bericht
... On 6/14/05 10:58 AM, in article , "Don Lancaster" wrote: Don Bowey wrote: No other esoteric, mindless definitions are needed even though the terms AC and DC may be misnomers. They are historic and work very well. Don The only tiny problem is that the definitions are wrong. As with many historic terms, they may be off the mark by today's understanding, but they are not necessarily wrong. For example, I have no problem using the term DC even when there is no current (flowing). Is that bad that I can assume DC is valid for static and dynamic states? It didn't cause me any problem when I first began to learn about electricity. How about we assume the term DC is a set with many subsets? That beats defining DC in a manner that says if there is a constant, never-ending load on a EMF, then it is DC, but if it is EVER interrupted, then it never was DC but was some form of AC? The more I learn, the more I find fault with some definitions. I find more fault (pointing the finger nowhere specific), however, with people who want to redefine things before they have studied long enough to understand what they are doing. Go on folks, this is all very bloody important. -- Thanks, Frank. (remove 'q' and 'invalid' when replying by email) |
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John Fields wrote:
On Tue, 14 Jun 2005 17:49:11 -0800, (Floyd L. Davidson) wrote: John Fields wrote: LOL, instead of grasping at straws you're now grasping for the coattails of someone who knows what he's talking about, and you're using that "Exactly" crack to make it seem like what you've been positing all along has finally been iterated by someone with some credibility. What's the matter John, are you bitter that several people, who do understand the theory and practice, have said you are wrong... --- Not at all. I'm always grateful when someone takes the time to correct me and show me where I went wrong, since that increases my store of stuff I know is right. But when a self-important know-nothing windbag like you comes along making baseless proclamations and spouting opinions like they were gospel it _does_ annoy me. Er..the gospels are the biggest pile of erroneous nonsense one can come up with. Its all about those imaginary beings, that can do anything, be everywhere at once, knows everything etc... Kevin Aylward http://www.anasoft.co.uk SuperSpice, a very affordable Mixed-Mode Windows Simulator with Schematic Capture, Waveform Display, FFT's and Filter Design. |
On Wed, 15 Jun 2005 03:36:15 -0500, John Fields
wrote: It is my belief that the widespread disagreement is due to participants that just like to argue a lot. --- No, they don't. ;^) Look, this isn't an argument, it's just contradiction! -- Al Brennan "If you only knew the magnificence of the 3, 6 and 9, then you would have a key to the universe." Nicola Tesla |
John Popelish writes:
John Fields wrote: BTW, from another thread and just as an aside, I went over to my friend's sign shop and checked some known-good neon sign transformers using the same meters I used to check the ones I have here, and it turns out my transformers are defective. :-( Sorry to hear that. I was surprised that I couldn't simply Google this. But the elusive neon sign transformer voltage current curve remains uncaptured. No curve but some info: http://repairfaq.ece.drexel.edu/sam/...lp.htm#clpnstc --- sam | Sci.Electronics.Repair FAQ Mirror: http://repairfaq.ece.drexel.edu/ Repair | Main Table of Contents: http://repairfaq.ece.drexel.edu/REPAIR/ +Lasers | Sam's Laser FAQ: http://repairfaq.ece.drexel.edu/sam/lasersam.htm | Mirror Sites: http://repairfaq.ece.drexel.edu/REPAIR/F_mirror.html Note: These links are hopefully temporary until we can sort out the excessive traffic on Repairfaq.org. Important: Anything sent to the email address in the message header above is ignored unless my full name is included in the subject line. Or, you can contact me via the Feedback Form in the FAQs. |
John Fields wrote:
BTW, from another thread and just as an aside, I went over to my friend's sign shop and checked some known-good neon sign transformers using the same meters I used to check the ones I have here, and it turns out my transformers are defective. :-( Sorry to hear that. I was surprised that I couldn't simply Google this. But the elusive neon sign transformer voltage current curve remains uncaptured. |
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