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John Fields wrote:
On Mon, 13 Jun 2005 15:55:33 -0800, (Floyd L. Davidson) wrote: No discussion John. I don't waste time teaching basics to grown men who have temper tantrums in public. You're confusing a temper tantrum with getting a dressing down you thoroughly deserve. You're a poser pretending to knowledge and skills you don't have, for the purpose of elevating yourself to a station which you yearn to occupy, but can't. If you wish to end the discussion or exit the thread, then just do it. There's really no need for parting shots unless you find it necessary to have the last word before you run away. -- John Fields Professional Circuit Designer ^^^^^^^^^^^^ Posting public articles like the above may well cost you employment in the future. -- Floyd L. Davidson http://web.newsguy.com/floyd_davidson Ukpeagvik (Barrow, Alaska) |
On Mon, 13 Jun 2005 11:49:58 GMT, "daestrom"
wrote: "Floyd L. Davidson" wrote in message ... "operator jay" wrote: It is not changing polarity. I would hesitate to call it alternating current. On the "dc sine wave" issue, I wouldn't even get into that debate. To me the terms involved are open to too many interpretations. As evidenced in this thread, I suppose. Where *do* you get this requirement for changing polarity? We don't call it "Alternating Polarity", we call it "Alternating Current". If the current is being altered, it's AC. You keep talking about AP, and it isn't the same. 'Alternating' is not the same as 'altering'. "Alternating current" is an electrical current where the magnitude and *direction* [emphasis added] varies cyclically. http://en.wikipedia.org/wiki/Alternating_current One may 'alter' the magnitude of a DC current without it becoming 'alternating current' The problem with that definition is that it is unnecessarily limiting. You can find other sources where the definition reads "magnitude *or* direction," the latter which I believe to be more correct. If the signal is steady state, then the current that changes magnitude but never direction is simply an AC signal with a DC component greater in positive amplitude than the negative peak of the AC component. -- 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 |
On Mon, 13 Jun 2005 10:14:41 -0500, Mike Berger wrote:
The freezing point and boiling point of water are both have a clearly defined intrinsic meaning to a chemist. [snip] Well, "intrinsic" may be a bit to strong of a word. Boiling and freezing points very considerably with pressure. --Mac |
"Kitchen Man" wrote in message ... On Sun, 12 Jun 2005 22:59:18 -0500, "operator jay" wrote: You are the one with the requirements, assertions, and definitions, not me. Actually, the ones with the requirements, assertions, and definitions are codes and organizations such as the NEC and the IEEE, and the bothersome universities that teach the stuff. 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". On this point: Picture my flashlight, battery powered. Generally this is considered a dc circuit. When I turn it on or off, there is 'change'. So is it in fact an AC flashlight? If the battery starts to die there is a change so is it in fact an AC battery? Etcetera. (These questions are rhetorical by the way). I know better than to try to pin a strict name on these things where there is not an (adequately) universal and strict definition. You are talking about transients, and if you intend for the questions to be rhetorical, then I think you should demonstrate some expertise in the subject matter that shows why the questions' answers must be obvious. I don't think they are, so I will answer the questions: "show why the answers must be obvious" sounds like a peculiar concept. An obvious answer inherently needs no explaining. The behavior of the flashlight in your example is neither AC nor DC, it is transient. The first case is the instantaneous step function caused by the closing of a source to a circuit. The second case is a long-term curved ramp caused by the decay of a voltage source. AC and DC analyses are steady-state. AC analysis will never apply to the example. DC analysis must be performed prior to the transient analysis in order to provide a steady state model for the application of time-sensitive mathematics. You feel that neither AC nor DC is correct as a description for the flashlight behavior. I wonder whether there is a sufficiently definitive (and also agreeable) meaning of "AC" or of "DC" that would merit this position. I infer from other posts that there are people who would say it is DC. There may be others who would say it is AC. So a statement of fact that it is neither AC nor DC is suspect. By the way, my rhetorical questions were actually whether it is an AC flashlight and whether it is an AC battery. The point of this was (I thought obviously) to illuminate the difficulty in declaring some things to be AC or to be DC. There is a certain ridiculousness (I thought obviously) in calling a flashlight AC or in calling a battery AC. Yet it would be awkward (I thought obviously) in adhering to calling it DC if one's description of DC was that the (voltage / current) would essentially remain constant. Thus my (possibly obvious) point and my rhetoricals. I'll work on them. Your response did not seem to conradict my point. There is quite a bit of information available on the web about circuit analysis. Your curiosity is to be commended; you might consider a web crawling adventure, or even an education in the field. The web has lots of information and lots of misinformation, I think you'd agree. I'm not sure that I have displayed curiosity in these posts. An education in the field of circuit analysis? No, thanks, you go ahead. And hey operator jay, what do you operate? Not electrical substations, I wouldn't guess. That's remarkably funny. What do you operate? Not your brain I wouldn't guess. j |
On Mon, 13 Jun 2005 04:14:08 GMT, ehsjr
wrote: Kitchen Man wrote: On Sun, 12 Jun 2005 14:33:39 -0500, John Fields wrote: It's a shame that those of us who give of our time in an effort to edify the ignorant are often abused by imbeciles who can't take correction gracefully. It is equally a shame that there are those that are sometimes incapable of offering correction gracefully, eh, John? If it pains you so much to engage in your ungracious edifying, perhaps you would do well to bugger off, and leave the stress of educating imbeciles to those with more patience. Interesting! I thought John's response to the op was called for. The OP is going to get himself into trouble with the attitutde he's exhibited. In my opinion, John saw through the BS and called a spade a spade. I don't know whether the OP got it or not - but John made it clear that the BS wasn't fooling anybody. I'll have to go back and read it again in light of your post. I simply feel it's prudent to carefully consider all responses, as I've grown rather un-fond of the taste of my foot in my mouth. I agree that the poster's attitude is obtuse at best, but flinging off-hand insults is risky. I should know. Besides, right now I'm the new guy in a new job after 30 years in electronics, so I have to practice restraint. Practice, practice, practice! :-) -- 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 |
"Mac" wrote in message ... On Mon, 13 Jun 2005 10:14:41 -0500, Mike Berger wrote: The freezing point and boiling point of water are both have a clearly defined intrinsic meaning to a chemist. [snip] Well, "intrinsic" may be a bit to strong of a word. Boiling and freezing points very considerably with pressure. And purity and other factors. N |
On Mon, 13 Jun 2005 12:11:31 -0800, (Floyd L. Davidson) wrote:
The Phantom wrote: On Mon, 13 Jun 2005 07:58:46 -0800, (Floyd L. Davidson) wrote: *Snip* Either that or we are back to Don Lancaster's correct statement that they are meaningless terms anyway. They certainly are if that is the way they are defined! Don first said: --------------------------------------- '"DC" is simply the first (or "offset" term in the Fourier expression of any repetitive waveform. "AC" are all of the remaining components.' ---------------------------------------- Then he said: ---------------------------------------- '"AC" or "DC" are gross and meaningless oversimplifications.' ---------------------------------------- Which are we to believe? There is no contradiction, so what is wrong with understanding both statements? The difficulty is understanding just what Don was getting at. His first post in its entirety was: -------------------------------- Bob Penoyer wrote: 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. Total and utter horse****. "DC" is simply the first (or "offset" term in the Fourier expression of any repetitive waveform. "AC" are all of the remaining components. Changing the relative amplitude of the terms does NOT in any manner change which is the first term and which are the remaining terms. DC, of course, cannot exist at all ever. Because it would have to be unvarying through infinite time. Tutorials on my website. --------------------------------- In this post he seems to be suggesting that Bob Penoyer's definitions of AC and DC were "Total and utter horse****", and follows with a couple of definitions which appear to be offered as alternative definitions which presumably Don thought were *not* "Total and utter horse****". But then in his next post, he says: --------------------------------- "AC" or "DC" are gross and meaningless oversimplifications. --------------------------------- If he thinks "AC" and "DC" are gross and meaningless oversimplifications, why would he offer alternative definitions of AC and DC to those given by Penoyer which Don thinks are "Total and utter horse****"? Why offer definitions of AC and DC at all if he thinks so poorly of the terms? Because when people see him first disparaging someone else's definitions and then offering definitions of his own, they're going to think he believes his own definitions are good ones. |
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". There are really only two definitions put forth in this thread. One is that AC refers to all non-zero frequency components of a signal, and DC refers to the zero frequency (average) component of a signal. The other camp believes that DC means a current whose direction doesn't change, and AC means a current whose direction does change. For me, the fact that a Voltage can be called DC proves that the other camp is not right, or not entirely right. In fact, the OP was talking about a DC Voltage. There was no mention of current at all. --Mac |
Mac wrote:
There are really only two definitions put forth in this thread. One is that AC refers to all non-zero frequency components of a signal, and DC refers to the zero frequency (average) component of a signal. The other camp believes that DC means a current whose direction doesn't change, and AC means a current whose direction does change. For me, the fact that a Voltage can be called DC proves that the other camp is not right, or not entirely right. In fact, the OP was talking about a DC Voltage. There was no mention of current at all. When the context is clear, people sometimes use the same word (especially, informally) to mean one of several different things in different contexts. The problem with the original post was that the poster meant the opposite of what most of us would have assumed the context implied, so we tried to explain that to him. Then he told us either we were wrong or that it didn't matter, if we were capable of figuring out what he meant. Some people are harder to help than others. ;-) |
"NSM" wrote:
"Mac" wrote in message ... On Mon, 13 Jun 2005 10:14:41 -0500, Mike Berger wrote: The freezing point and boiling point of water are both have a clearly defined intrinsic meaning to a chemist. [snip] Well, "intrinsic" may be a bit to strong of a word. Boiling and freezing points very considerably with pressure. And purity and other factors. Not to mention with *what* it is! 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. He then proceeded to boil the ni-cad coating off the screws, which plated the expensive ceramic insulators and shorted out his thermionic diode. Danged, several weeks of work shot because it just hadn't occurred to him that ni-cad would boil at room temperature. He eventually made it work though, using stainless steel hardware, and when he wrote a thesis about what his diode did and didn't do, they awarded him a PhD in Nuclear Engineering. -- Floyd L. Davidson http://web.newsguy.com/floyd_davidson Ukpeagvik (Barrow, Alaska) |
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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! Damned fast too! And no, you wouldn't fit into the 18" vacuum jar this was in. The way to get ni-cad to boil at room temperature is simply reduce the pressure to something significantly below its vapor pressure. We did it knowingly with gold too once, and that was nothing short of beautiful as far as the results went. The entire inside of the bell jar was very faintly plated with gold. That particular experiment was testing the voltage breakdown of ceramic wafers, so in addition to the gold plating there was the bluish white glow from a high voltage arc too. Really great visual effects! That was 40 years ago... -- Floyd L. Davidson http://web.newsguy.com/floyd_davidson Ukpeagvik (Barrow, Alaska) |
Don Bowey wrote:
On 6/13/05 10:01 PM, in article , "The Phantom" wrote: DC, of course, cannot exist at all ever. Because it would have to be unvarying through infinite time. Horse pucky. I think I can afford to miss the tutorials on your website. Pure DC, or something close to it, is actually pretty rare stuff. Even on battery power plants, which are extremely good filters, there is some AC on the leads of just about anything powered from the battery unless either the battery or the load is all but embedded in the other. For example, the 48 volt battery plants that telephone companies have, use some rather large cables to supply voltage to equipment. Yet a filter is required at every fuse bay to decouple the AC noise on the supply cable from the equipment in the bay. Even then, the supply lines have an astounding amount of AC noise on them. That was particularly true back in the days of mechanical switches, when a telco switch was filled with "DC" switched lines that had mechanical contacts, and most of the loads being switched were inductive. There is even more of the same going on in modern digital switching systems, minus the inductive kick, but those are filtered much more effectively because unlike the old mechanical monster, these new ones will malfunction themselves if the noise isn't filtered out. -- Floyd L. Davidson http://web.newsguy.com/floyd_davidson Ukpeagvik (Barrow, Alaska) |
Floyd L. Davidson wrote:
Don Bowey wrote: On 6/13/05 10:01 PM, in article , "The Phantom" wrote: DC, of course, cannot exist at all ever. Because it would have to be unvarying through infinite time. Horse pucky. I think I can afford to miss the tutorials on your website. Pure DC, or something close to it, is actually pretty rare stuff. snip And is pretty cold - ask Thevenin. -- Sue |
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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. John |
On Tue, 14 Jun 2005 02:49:32 +0000, NSM wrote:
"Mac" wrote in message On Mon, 13 Jun 2005 10:14:41 -0500, Mike Berger wrote: The freezing point and boiling point of water are both have a clearly defined intrinsic meaning to a chemist. [snip] Well, "intrinsic" may be a bit to strong of a word. Boiling and freezing points very considerably with pressure. And purity and other factors. No, the "intrinsic" _meaning_ (in case you'd care to check the original post) of "boiling" or "freezing" doesn't change, no matter what the temperature and pressure you're applying. You're confusing _meaning_ with _parameters_. I have seen water freeze and boil simultaneously in a single container. Anybody can do this - just get a decent bell jar and a good vacuum pump. The "boiling point" certainly changes with ambient pressure, but that does not change the intrinsic nature of _what boiling is_. I think this might have been Mike Berger's point here. Thanks, Rich |
On Tue, 14 Jun 2005 00:41:47 -0700, Don Bowey
wrote: On 6/13/05 10:01 PM, in article , "The Phantom" wrote: DC, of course, cannot exist at all ever. Because it would have to be unvarying through infinite time. Horse pucky. I think I can afford to miss the tutorials on your website. He has tutorials? You've got to be kidding. John |
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. -- Floyd L. Davidson http://web.newsguy.com/floyd_davidson Ukpeagvik (Barrow, Alaska) |
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 ****. -- John Fields Professional Circuit Designer |
On Tue, 14 Jun 2005 11:42:15 -0500, 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 ****. -- John Fields Circuit Designer |
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 ****. I think he is confusing boiling with sputtering. |
On Tue, 14 Jun 2005 09:45:52 -0700, John Larkin
wrote: -- John Fields Circuit Designer --- LOL :-) Slow day and nothin' better to do than to edit folks' dotsigs, huh?^) -- John Fields Professional Circuit Designer |
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: 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 ****. I think he is confusing boiling with sputtering. --- Ahhhh! I think you're right!-) -- John Fields Professional Circuit Designer |
On 6/14/05 2:28 AM, in article , "Floyd L.
Davidson" wrote: Don Bowey wrote: On 6/13/05 10:01 PM, in article , "The Phantom" wrote: DC, of course, cannot exist at all ever. Because it would have to be unvarying through infinite time. Horse pucky. I think I can afford to miss the tutorials on your website. Pure DC, or something close to it, is actually pretty rare stuff. Even on battery power plants, which are extremely good filters, there is some AC on the leads of just about anything powered from the battery unless either the battery or the load is all but embedded in the other. For example, the 48 volt battery plants that telephone companies have, use some rather large cables to supply voltage to equipment. Yet a filter is required at every fuse bay to decouple the AC noise on the supply cable from the equipment in the bay. Even then, the supply lines have an astounding amount of AC noise on them. That was particularly true back in the days of mechanical switches, when a telco switch was filled with "DC" switched lines that had mechanical contacts, and most of the loads being switched were inductive. There is even more of the same going on in modern digital switching systems, minus the inductive kick, but those are filtered much more effectively because unlike the old mechanical monster, these new ones will malfunction themselves if the noise isn't filtered out. 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. Don |
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: 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. I had a feeling that something like this would be his response. 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. 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? |
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. -- Many thanks, Don Lancaster Synergetics 3860 West First Street Box 809 Thatcher, AZ 85552 voice: (928)428-4073 email: Please visit my GURU's LAIR web site at http://www.tinaja.com |
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. |
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. 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. -- Floyd L. Davidson http://web.newsguy.com/floyd_davidson Ukpeagvik (Barrow, Alaska) |
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? I went looking on the IEEE website for a standard that would define the terms. There is a standard, 100-1992 "IEEE Dictionary of Electrical and Electronics Terms" that probably has their definition of AC and DC, but it isn't available on the web. I wonder if anybody participating in this thread has access to it? Even though I couldn't find the dictionary referred to above, I did look at a number of their standards, and they are quite happy to use the terms AC and DC. I guess they don't realize that those terms are "Total and utter horse****". Someone should tell them! John |
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. |
On Tue, 14 Jun 2005 10:58:11 -0700, 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. Please give us the correct definitions. In an earlier post you said: '"DC" is simply the first (or "offset" term in the Fourier expression of any repetitive waveform. "AC" are all of the remaining components.' But then in your next post you said: '"AC" or "DC" are gross and meaningless oversimplifications.' Does this comment apply to your own earlier definitions? Are you saying that even you can't give definitions to AC and DC that aren't "gross and meaningless oversimplifications"? |
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. 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. 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... -- Floyd L. Davidson http://web.newsguy.com/floyd_davidson Ukpeagvik (Barrow, Alaska) |
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's the vapor pressure of zinc at 20C? 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 10:11:03 -0800, Floyd L. Davidson wrote:
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. In a case like this, "out-gas" would definitely be a better term, or even "sublimate", which means to go right from solid to gas. Only liquids can boil, and then only when the uneven heat causes bubbles of vapor to form. _That's_ what boiling is, regardless of the temp., material, or anything else. You should have seen the LN2 seethe when they opened the valve on the sorption pump! Cheers! Rich |
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