|MadSci Network: Engineering|
OK, Erik -- Here's what to expect. Metals have a postive temperature coefficient. This means, for a fixed length of wire, you will measure, let us say, 10.0 ohms at room temperature (27 degrees Celsius). If you heat the wire, this temperature should go up -- perhaps to 10.3 ohms at 100 degrees. If you cool it, it should go down. You should be measuring the wire resistance -- not its voltage. Also, make effort to heat and cool the length of wire uniformly. Boiling and freezing water would do the job. So make an R versus T graph. It is true (I^2)*R is the power dissipated in a resistance R carrying current I. But unless you wish to heat the wire with electric current, I don't think it applies. You'd also have great difficulty in measuring the wire temperature. "Temperature coefficient of resistivity" is what you want to look up in the library. It is usually represented by a lower case alpha. This number is fairly constant over common temperatures but it is not absolutely constant. Devices called Resistance Temperature Detectors take on different resistance at different temperatures. The graph of resistance versus temperature is almost a straight line, but it is actually a very mildly curved parabola. Here's a site where a student has done what you are trying to do -- to find the slope of the R versus T curve. The student did it for a copper resistor. http://stupendous.rit.edu/classes/phys273/lab5_extra.html The student uses a instead of alpha in this paper. Hope this helps. Larry Skarin
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