Yes but temperature is affected by current which is affected by voltage so in some sense instantaneous resistance is a function of voltage. The instantaneous resistance will be a factor of of the base material, amount the resistance changes due to temperature and the current temperature. The current temperature is dependant on the voltage applied and for how long and how well the material can radiate heat and how well the environment can conduct heat away.
Hence I = V/R is not a very good approximation in this environment. While it may still hold for any given instantaneous moment in time it’s mostly useless as predictor when all of I, V and R vary with changes in all three values over time. You are better off to test the circuit and measure what it does. Lawrence > On Nov 5, 2015, at 1:12 PM, Peri Hartman via EV <[email protected]> wrote: > > I thought the resistance was dependent on temperature, not voltage. Sure, a > higher voltage means it will heat up quicker and increase in resistance > quicker. But initially, at least, for a given voltage, the resistance would > be low. Thus, resistance would not proportional to voltage. Did I miss > something? > > Peri > > ------ Original Message ------ > From: "paul dove via EV" <[email protected]> > To: "Lee Hart" <[email protected]>; "Electric Vehicle Discussion List" > <[email protected]> > Sent: 05-Nov-15 12:53:10 PM > Subject: Re: [EVDL] Suitable Load? > >> Yes, Ohms law applies in light bulbs. >> Instead of a linear graph you get a curve because of the changing >> resistance.As the voltage increases the current increase becomes smaller and >> smaller.Since it is not linear the change in current slows down as the >> voltage increases.Still, at low voltage you have low current and at high >> voltage you have high current as I said. >> >> >> >> >> From: Lee Hart <[email protected]> >> To: Paul Dove <[email protected]>; Electric Vehicle Discussion List >> <[email protected]> >> Sent: Thursday, November 5, 2015 11:01 AM >> Subject: Re: [EVDL] Suitable Load? >> >> Paul Dove via EV wrote: >>> Halogen bulbs are made in general for 6V, 12V, 24V... Using too low >>> a voltage will produce little current and too high a voltage will >>> produce high current and overheating of the filament >> >> Actually, light bulbs don't behave like resistors. Ohm's law doesn't >> apply. :-) >> >> A light bulb's apparent resistance changes drastically with temperature. >> The cold resistance (measured with an ohmmeter) is easily 1:10th that of >> its hot resistance (current divided by voltage at full rated voltage). >> Depending on the type of light, an 8-1 change in voltage only causes >> about a 2:1 change in current. >> >> This means that light bulbs can be used as crude constant-current loads. >> The current only changes slightly despite large changes in voltage. This >> characteristic is ideal for testing batteries, where you'd like the >> current to stay the same despite changes in cell or battery voltage. >> -- >> Any intelligent fool can make things bigger, more complex, and more >> violent. It takes a touch of genius, and a lot of courage, to move >> in the opposite direction. -- Albert Einstein >> -- >> Lee Hart, 814 8th Ave N, Sartell MN 56377, www.sunrise-ev.com >> >> >> >> -------------- next part -------------- >> An HTML attachment was scrubbed... >> URL: >> <http://lists.evdl.org/private.cgi/ev-evdl.org/attachments/20151105/00ba6a1a/attachment.htm> >> _______________________________________________ >> UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub >> http://lists.evdl.org/listinfo.cgi/ev-evdl.org >> Read EVAngel's EV News at http://evdl.org/evln/ >> Please discuss EV drag racing at NEDRA (http://groups.yahoo.com/group/NEDRA) >> >> > > _______________________________________________ > UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub > http://lists.evdl.org/listinfo.cgi/ev-evdl.org > Read EVAngel's EV News at http://evdl.org/evln/ > Please discuss EV drag racing at NEDRA (http://groups.yahoo.com/group/NEDRA) > _______________________________________________ UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub http://lists.evdl.org/listinfo.cgi/ev-evdl.org Read EVAngel's EV News at http://evdl.org/evln/ Please discuss EV drag racing at NEDRA (http://groups.yahoo.com/group/NEDRA)
