Peter T. Daniels ran out of electrical outlets; states rewiring entire house to be the only feasible solution.
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From: Otto Bahn on 30 Mar 2010 15:46 "Hatunen" <hatunen(a)cox.net> wrote >>Out of curiosity, is the resistance of charred skin the same as >>the resistance of normal skin? > > If it's charred I would imagine it's lower. I'd guess the absence of water would make it go up. More Resistance! Less current! More Resistance! Less current! More Resistance! Less current! --oTTo--
From: Hatunen on 30 Mar 2010 16:36 On Tue, 30 Mar 2010 19:31:20 +0100, Jonathan de Boyne Pollard <J.deBoynePollard-newsgroups(a)NTLWorld.COM> wrote: >Xe most definitely did argue that "it is therefore sufficient". The >words are right there. Have a read. Xe's been arguing all along that >voltage is the one pertinent factor. It of course isn't. There are >other dimensions, as already explained. Xe stated that there were two >forms of damage (there are in fact four), the one "directly related to >voltage" and the other also proportional to voltage. As I've said, >there are dimensions missing, there, not least the physical dimensions >of the body tissues involved and the length of the shock, as well as >other missing factors such as the A.C. frequency. it also depends on the impedance ("resistance") of the source of electricity. A connection that reads 4000 volts on a high impedance voltmeter may not deliver enough current to even feel when you use your body in place of the meter. It also depends on how high the voltage is. There's the classic classrooom demonstration of the Van de Graff generator where the globe is charged up to thousands of volts and the teacher simply toughtes the globe, to little effect except tht his hair is standing on end. -- ************* DAVE HATUNEN (hatunen(a)cox.net) ************* * Tucson Arizona, out where the cacti grow * * My typos & mispellings are intentional copyright traps *
From: Hatunen on 30 Mar 2010 16:54 On Tue, 30 Mar 2010 14:15:12 -0400, barbara(a)bookpro.com wrote: >>From Fundementals of Physics by Halliday and Resnick: >> >>"The relationship V = i/R remains as the derfinition of the resistance of >>a conductor whether or not the conductor obeys Ohm's law." > >So the conductor might not obey Ohm's law. Even though the relationship remains as the definition. That doesn't make much sense. >Some of these mokes have >been claiming that everything always obeys Ohm's law. It is too bad that the authors didn't give an example of a conductor that doesn't "obey" [*] Ohm's Law. I suspect it may turn out to be less than it appears. [*] "Obey" makes it seem to be that a conductor can choose whether or not Ohm's Law applies. -- ************* DAVE HATUNEN (hatunen(a)cox.net) ************* * Tucson Arizona, out where the cacti grow * * My typos & mispellings are intentional copyright traps *
From: Jerry Friedman on 30 Mar 2010 17:01 On Mar 30, 2:36 pm, Hatunen <hatu...(a)cox.net> wrote: > On Tue, 30 Mar 2010 19:31:20 +0100, Jonathan de Boyne Pollard > > <J.deBoynePollard-newsgro...(a)NTLWorld.COM> wrote: > >Xe most definitely did argue that "it is therefore sufficient". The > >words are right there. Have a read. Xe's been arguing all along that > >voltage is the one pertinent factor. It of course isn't. There are > >other dimensions, as already explained. Xe stated that there were two > >forms of damage (there are in fact four), the one "directly related to > >voltage" and the other also proportional to voltage. As I've said, > >there are dimensions missing, there, not least the physical dimensions > >of the body tissues involved and the length of the shock, as well as > >other missing factors such as the A.C. frequency. > > it also depends on the impedance ("resistance") of the source of > electricity. A connection that reads 4000 volts on a high > impedance voltmeter may not deliver enough current to even feel > when you use your body in place of the meter. But that's just because it doesn't deliver its nominal voltage. > It also depends on how high the voltage is. There's the classic > classrooom demonstration of the Van de Graff generator where the > globe is charged up to thousands of volts and the teacher simply > toughtes the globe, to little effect except tht his hair is > standing on end. Teacher? I make my students do it. (Or did--I should get that thing fixed up.) And I make them stand on a milk crate, though disobedient students who step off haven't been harmed. Only one student has ever reported feeling much of an effect--someone who has some bone in his leg replaced with metal. I really wonder what was going on there. Could his discomfort have been physical? Could it have been psychological? Careful study of middle schoolers on the Van de Graaff has shown that they will accept considerable pain to cause an equal amount to their friends. With giggling. -- Jerry Friedman
From: Hatunen on 30 Mar 2010 17:44
On Tue, 30 Mar 2010 10:19:13 -0400, dbd(a)gatekeeper.vic.com (David DeLaney) wrote: >Hatunen <hatunen(a)cox.net> wrote: >>dbd(a)gatekeeper.vic.com (David DeLaney) wrote: > >>>>> Only in materials and voltage/current ranges where Ohm's "law" is >>>>> obeyed. And if damage is occurring, it probably isn't. >>>> >>>>Ohm's law is always obeyed in all aparatus made by humans. >>> >>>... ... Okay, so you're not an engineer AND are not an experimentalist. >>>Meaning you're a theorist. This explains some things. >>> >>>(Tell the court, please, how long ago it was that humans made the first >>>material that had exactly the same resistance at every interior point, and >>>how to get current to go through an object in such a way as to have the same >>>current density everywhere inside the object...) >> >>As taught in high school science classes, Ohm's Law is the >>familiar V = IR. but in the real world Ohm's Law is valid for all >>kinds of cases of non-constant factors, writte in lower case, v = >>ir to indicate the values are non-constant. In gneral, Ohm's law >>is expressed e = iz, where, as I note in another post, z is >>impedance, which can be resistive or reactive and therefore >>contain an imaginary component, and e is the term usually used >>for "voltage". In fact, in the generic case the for Ohm's Law is >>a differential equation with time dependency. > >Oh, certainly. Except that the law-as-given-earlier-in-the-thread was being >used to find "the resistance of" a fairly large, squishy object. I didn't take it that way. The resistance of a large squishy obeject is likely to be a tensor or soomething, but it will be a very sohisticated application of Ohm's Law. >To do so >you've got to integrate over the various internal resistances at various points >weighted by the various paths the current density can be taking through said >screaming object; at each of those points there'll be a value of R you could >measure, if your nanabots (day-o, day-ay-ay-o ... nanobot come and I wan' go >home!) were small enough, good for that particular temperature and pressure and >other conditions local to that point. I'vw tried to make it clear that Ohm's Law applies even when we complexity makes it intractable to apply. >The original claims were more of the >form that "This large squishy object has an R, and V = IR is the definition of >that R, which has one value, and is a number, which you can find". Which, not >so much. I suppose someone thought that was said, but I sure didn't. But some posters were assuming that V = IR ois e be-all and end-all of Ohm's Law which would require some sort of constants for V, I and R. >You're actually arguing the other side of that, I believe, and are in violent >agreement with the Doctroid. The second(?)-joining perpetrator of the thread >appears to be jumping on the "V=IR At Every Point So Of Course It's A Natural >Law" bandwagon without fully understanding either what that means, or how this >disagrees with the first perpetrator. Huh? > >>In other word, Ohm's Law is always true and you should avoid >>making such statements unless you know what you're talking about. >As long as you're doing it on a point-by-point basis and are prepared to have >your overall R be a function of quite a lot of variables. Both the people >getting schooled in this thread (there may be three by now, I've lost count) >are missing Important Parts of that qualification in their assertions. Because they learned V = IR in high school or some sort of freshman science course. A little bit of knowledge can be a, um, well, not dangerous, but very misleading. -- ************* DAVE HATUNEN (hatunen(a)cox.net) ************* * Tucson Arizona, out where the cacti grow * * My typos & mispellings are intentional copyright traps * |