Peter T. Daniels ran out of electrical outlets; states rewiring entire house to be the only feasible solution.
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From: Hatunen on 30 Mar 2010 13:57 On Mon, 29 Mar 2010 14:36:53 -0400, Doctroid <doctroid(a)mailinator.com> wrote: >In article <nq6787-qkc.ln1(a)mail.specsol.com>, jimp(a)specsol.spam.sux.com >wrote: > >> All things obey Ohm's law exactly because R=V/I is the definition of >> resistance. > >In that case I hereby announce Doctroid's Law which states that > > V = D * C > >where V is the electrical potential across a device, and C is the total >mass of chocolate consumed in the past year by the person who measures >V. D is the device's Doctroidance, which is in fact defined by D = V / >C, and of course is not constant. Therefore Doctroid's law always holds >for all circumstances. > >It is also perfectly useless. As is Ohm's Law, if you consider it to be >solely a definition of resistance: it has no predictive power. Sure it does, if you know the emf and current. -- ************* 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 14:00 On Tue, 30 Mar 2010 08:48:42 -0400, Doctroid <doctroid(a)mailinator.com> wrote: >In article <7uq3r59afg17p63gsvitp4qbm6uh3032f8(a)4ax.com>, > barbara(a)bookpro.com wrote: > >> On Tue, 30 Mar 2010 18:26:04 +1200, "PaulJK" >> <paul.kriha(a)paradise.net.nz> wrote: >> >> >A homework for Doctroid and P.Moylan >> >http://www.allaboutcircuits.com/worksheets/diode1.html >> > >> >just trying to help you to stop embarrassing yourself with >> >high school physics. >> >> P'raps you should ask Doctroid what he is a doctroid of. >> >> BW > >See, the thing about high school physics is, it's taught by high school >teachers out of high school textbooks to high school students. > >High school physics teachers usually do not have advanced training in >physics. Often neither do the authors of high school physics textbooks. >Even when they do, they recognize the necessity of presenting a >simplified picture to high school students, who are not ready for >differential equations, surface integrals, and deep questions about the >meaning of physical law. Agreed. But youseem to be refusing to accept the applicability of all those other things. In ohter words, thus far your argument seems to be based on high school physics. >So what gets taught is "Ohm's law is V = IR". The ones who go on to >earn degrees in physics are taught there's more to it than that. (And >some of them learn it.) The ones who major in English Lit or Business >or Electrical Engineering? Might not. I doubt tehy will ever understand quantum theory, either. (I used to teach Physics for Nurses and so-called "Physics for Poets" at McGill University and University of Arizona; kind of hopeless.) -- ************* 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 14:03 On Mon, 29 Mar 2010 19:40:33 +0100, Adam Funk <a24061(a)ducksburg.com> wrote: >On 2010-03-29, Doctroid wrote: > >> In article <ruOdna7WF6m71C3WnZ2dnUVZ7o5i4p2d(a)westnet.com.au>, >> Peter Moylan <gro.nalyomp(a)retep> wrote: > >>> It's true that a great many resistors are nearly linear, i.e. they can >>> be said to obey Ohm's law to a reasonable degree of accuracy, provided >>> that you don't go beyond their design limits. > >Well, another way to look at it is that the resistance changes in >various situations, such as, erm, higher voltages. The most familiar example is the common incandescent lamp, which has a low resistance when first turned on. See http://www.sylvaniaautocatalog.com/sylvania/imgs/resistance_vs_temp.gif -- ************* DAVE HATUNEN (hatunen(a)cox.net) ************* * Tucson Arizona, out where the cacti grow * * My typos & mispellings are intentional copyright traps *
From: jimp on 30 Mar 2010 13:53 In sci.physics Hatunen <hatunen(a)cox.net> wrote: > On Sun, 28 Mar 2010 20:18:39 -0400, dbd(a)gatekeeper.vic.com (David > DeLaney) wrote: > >>PaulJK <paul.kriha(a)paradise.net.nz> wrote: >>>Doctroid wrote: >>>> "PaulJK" <paul.kriha(a)paradise.net.nz> wrote: >>>>> Voltage and current are proportional to each other. >>>>> It is therefore sufficient to say that damage is proportional >>>>> to one of them. >>>> >>>> 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. > > Obviously, some cases will be intractable to solution, but the > fact that we can't solve it doesn't mean Ohm's Law doesn't remain > true; there are approximation methods that can yield useful > results. And, yes, Ohm's law is applicable to bulk materials as > well as the idealized linear forms. > > This is all quite practical and not theoretical out in the real > world. There are qutie a few eingineers that cope with this sort > of stuff on a daily basis. > > In other word, Ohm's Law is always true and you should avoid > making such statements unless you know what you're talking about. Ohm's law is not V = IR, but rather deals with the special case of V = IR where the R is constant as in a metallic conductor. -- Jim Pennino Remove .spam.sux to reply.
From: Hatunen on 30 Mar 2010 14:05
On Tue, 30 Mar 2010 17:57:10 +1200, "PaulJK" <paul.kriha(a)paradise.net.nz> wrote: >Peter Moylan wrote: >> PaulJK wrote: >>> Doctroid wrote: >>>> In article <homphq$91l$1(a)news.eternal-september.org>, >>>> "PaulJK" <paul.kriha(a)paradise.net.nz> wrote: >>>> >>>>> Voltage and current are proportional to each other. >>>>> It is therefore sufficient to say that damage is proportional >>>>> to one of them. >>>> 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. >>> >> Except when it isn't - which is most of the time. >> >> It's true that a great many resistors are nearly linear, i.e. they can >> be said to obey Ohm's law to a reasonable degree of accuracy, provided >> that you don't go beyond their design limits. >> >> It's equally true that some resistive devices are *deliberately* made to >> be nonlinear. A semiconductor diode, for example, would be totally >> useless if it obeyed Ohm's law. > >I see you didn't have Ohm's law in your high school? >What has nonlinearity to do with it? Absolutely nothing. > >At every point in time and at every point inside the body >of a resistive conductor the Ohm's law applies with 100% >accuracy. It is applicable even when the conductors are >never completely homogeneous and never absolutely linear. Importantly, it still applies even in cases where it is very difficult to determine or that present intractable solutions. -- ************* DAVE HATUNEN (hatunen(a)cox.net) ************* * Tucson Arizona, out where the cacti grow * * My typos & mispellings are intentional copyright traps * |