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From: Doctroid on 30 Mar 2010 12:28 In article <hot6pr$fal$1(a)news.eternal-september.org>, "PaulJK" <paul.kriha(a)paradise.net.nz> wrote: > J. Clarke wrote: > > On 3/30/2010 10:27 AM, Doctroid wrote: > >> In article<ebv3r55bt7v35nvejvpplqhr51dlpkklhi(a)4ax.com>, > >> barbara(a)bookpro.com wrote: > >> > >>> On Tue, 30 Mar 2010 09:29:17 -0400, "J. Clarke" > >>> <jclarke.usenet(a)cox.net> wrote: > >>> > >>>> On 3/30/2010 8:07 AM, Doctroid wrote: > >>> > >>>>> Anyone wishing to take this up with me further may write to me at > >>>>> rsholmes at physics dot syr dot edu. > >>>> > >>>> Would you be kind enough to provide us an example of the equation that V > >>>> and I follow for a material that does not obey ohm's law and tell us for > >>>> what material that equation is valid? > >>> > >>> Oopsie, looks like you posted this accidentally to Usenet. > >>> > >>> BW > >> > >> 'sOK, I can take this one. > >> > >> Zener diode: > >> > >> http://www.reuk.co.uk/OtherImages/current-voltage-graph-zener-diode.gif > > Well? The semiconductors exhibit highly nonlinear relationship > between voltage and their resistance resulting in nonlinear > relationship between voltage and the current. > > However, no matter in which region of the graph you happen > to be in each point in time, the Ohm's law is always perfectly > applicable. The relationship between voltage, current, and > resistance at each moment cannot help but conform to the > law, since that's how their relationship is defined. > > Indirectly, you can measure the resistance at each region > of the graph by the heat the diod generates. > > pjk > > > The requirement was for the equation and the material, not a link to a > > Web site. Ineducable. Plonk. -- Sig available on request. - Doctroid
From: jimp on 30 Mar 2010 12:18 In sci.physics Doctroid <doctroid(a)mailinator.com> wrote: > In article <hot3lv02v8c(a)news3.newsguy.com>, > "J. Clarke" <jclarke.usenet(a)cox.net> wrote: > >> On 3/30/2010 10:27 AM, Doctroid wrote: >> > In article<ebv3r55bt7v35nvejvpplqhr51dlpkklhi(a)4ax.com>, >> > barbara(a)bookpro.com wrote: >> > >> >> On Tue, 30 Mar 2010 09:29:17 -0400, "J. Clarke" >> >> <jclarke.usenet(a)cox.net> wrote: >> >> >> >>> On 3/30/2010 8:07 AM, Doctroid wrote: >> >> >> >>>> Anyone wishing to take this up with me further may write to me at >> >>>> rsholmes at physics dot syr dot edu. >> >>> >> >>> Would you be kind enough to provide us an example of the equation that V >> >>> and I follow for a material that does not obey ohm's law and tell us for >> >>> what material that equation is valid? >> >> >> >> Oopsie, looks like you posted this accidentally to Usenet. >> >> >> >> BW >> > >> > 'sOK, I can take this one. >> > >> > Zener diode: >> > >> > http://www.reuk.co.uk/OtherImages/current-voltage-graph-zener-diode.gif >> >> The requirement was for the equation and the material, not a link to a >> Web site. > > Sorry, I figured you were capable of "clicking" on the "link" with your > "mouse". I'd've pasted the graph here, but Usenet is a text medium. > There isn't an equation; the behavior is complex and more easily > understood from a graph. But do feel free to do a fit if you can come > up with a suitable function. Material specified above. And at any point on your graph, the relationship R=V/I is true as is P=V^2/R. What is not true is that a zener diode has any particular value of resistance, which is why the R=V/I relationship is shown as a curve. -- Jim Pennino Remove .spam.sux to reply.
From: Doctroid on 30 Mar 2010 12:33 In article <g2k987-ktn.ln1(a)mail.specsol.com>, jimp(a)specsol.spam.sux.com wrote: > In sci.physics 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. > > > > 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. > > Since R=V/I is a definition, care to elaborate on when the relationship > does not hold? > > Your Nobel awaits. I refuse to enter into further public discussion with people with no reading comprehension skills. As before, you can write me at rsholmes dot physics dot syr dot edu, if you are genuinely interested in learning. -- Sig available on request. - Doctroid
From: Peter Duncanson (BrE) on 30 Mar 2010 12:43 On Tue, 30 Mar 2010 16:11:11 -0000, jimp(a)specsol.spam.sux.com wrote: >In sci.physics "Peter Duncanson (BrE)" <mail(a)peterduncanson.net> wrote: >> On Tue, 30 Mar 2010 17:57:10 +1200, "PaulJK" >> <paul.kriha(a)paradise.net.nz> wrote: >> >>> >>>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. >>> >>>(Excepting conditions in the super conductive environment.) >> >> That assumes that the current results from a potential difference, a >> voltage. > >Wrong, R=V/I is a definition. > >> If a closed circuit, a resistive ring for instance, is put in a varying >> magnetic field an induced current will flow but no potential difference >> will be created. > >True if, and only if, the "resistive" ring is an ideal superconductor >with zero resistivity, otherwise there will be a potential difference >between any two given points on the ring. > Are you absolutely sure of that? If the resistive ring is of uniform thickness and electrical properties and is uniformly "bathed" in a varying magnetic field how is one to determine which two points to consider? If the ring is circular and you take two points at the opposite ends of a diameter (A and B) and the current flows A -> B -> A ... what happens? If there is a potential difference between A and B, say Vab, there is also through the other half of the ring a potential difference Vba. It is many years since I considered anything like this but I think that mneans that Vab = -Vba. The only obvious way in which that can be true is Vab = Vba = 0. Obviously, attempting to measure any potential difference between two points will modify the conditions and my result in a non-zero measurement if the points are not diametrically opposite. -- Peter Duncanson, UK (in alt.usage.english)
From: jimp on 30 Mar 2010 13:05
In sci.physics Doctroid <doctroid(a)mailinator.com> wrote: > In article <g2k987-ktn.ln1(a)mail.specsol.com>, jimp(a)specsol.spam.sux.com > wrote: > >> In sci.physics 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. >> > >> > 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. >> >> Since R=V/I is a definition, care to elaborate on when the relationship >> does not hold? >> >> Your Nobel awaits. > > I refuse to enter into further public discussion with people with no > reading comprehension skills. As before, you can write me at rsholmes > dot physics dot syr dot edu, if you are genuinely interested in learning. > 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." Check the library at physics dot syr dot edu if you have further questions. -- Jim Pennino Remove .spam.sux to reply. |