Answer to Question #65353 in Electric Circuits for Helen

Question

A Tungsten filament for a light bulb is found to have a resistance of 0.25 Ω when
measured at a temperature of 20◦ C. When the light bulb has been on for a substantial
period of time, the filament has heated up and the resistance is found to be 3.50 Ω.
What is the temperature of the heated filament? Tungsten’s temperature coefficient
of resistivity is 4.5 × 10−3 per degree C, and do not consider thermal expansion of the
filament.