Asked by TP

I'm doing a report on my experiment right now where you had to test out the voltage and current of 2 resisters and a light globe with an ammeter and voltmeter. We had to graph the results, and the reisistors had a linear relationship between voltage and current, but the light globe is either exponential or power. Can anyone explain why this is? Is it a systematic error?
Answered by drwls
Believe your data. The tungsten filament of a light bulb has a resistance that increases with temperature, and as you raise the voltage, the filament becomes much hotter.

Many materials have a resistance that varies with temperture, but the effect is more noticeable with light bulb filaments because they are designed to get very hot, in order to emit light.
Answered by TP
So basically, the light bulb's resistance varies?
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