If a resistor made of a metal is frequently used, will its resistance eventually go down? why?
Why do you ask? What is the context of the question? What type of resistor, what composition, what application, etc.?
As I mentioned, it was a metal resistor. I'm not exactly sure what kind of metal, etc, but the application was that we were doing a lab in school and just applying voltage to the resistor and seeing the resulting current. Our group found that the experimental resistance was consistently lower than the actual range of resistance (considering tolerance values), and I was just wondering if this is a general rule, that resistance goes down with use for metal resistors
Ah, you mean "metal film" resistors.
In general, no. The resistance will only vary with initial tolerance and with temperature. If the resistor is damaged by overheating or some mechanical problem, then the resistance can change (either up or down).
If you have a resistor in your lab that is out of tolerance, please show it to your professor or lab assistant -- it should be thrown away.
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