Common light bulbs have a mental filament made of tungsten and when a current passes through it, it radiates visible light, as well as heat. If initially the filament's resistance is 2.45 Ω (6%) at 20 degrees Celsius and the temperature coefficient of resistivity α is 0.004403 (degrees Celsius)^-1 , what is its resistance at 40 degrees Celsius? And at 60 degree Celsius? (include the uncertainty of the result)

Question

As the filament's temperature increases, does its resistance stay the same, increase or decrease?

Answer 1

The resistance will increase with temperature, since the coefficient of resistivity is positive.

I assume you know how to compute the resistance at 40 and 60 C, knowing the value of 20 C and the coefficient. Just multiply the temperature change by the coefficient and add it to the value of the resistance at 20 C.

As for the uncertainty analysis, perhaps your (6%) number will provide a clue. It seems like a large uncertainty when three significant figures are being quoted.