# Answer to Question #6450 in Electric Circuits for Fainah

Question #6450

For a three-way bulb (60 W, 100 W, 160 W) that is designed to operate at 120 V, find the resistance of each of the two filaments. Assume that the wattage ratings are not limited by significant figures and ignore any heating effects on the resistances.

60 W filament________Ohms

100 W filament__________Ohms

60 W filament________Ohms

100 W filament__________Ohms

Expert's answer

Power

P=V

60W filament 240 Ohms

100W filament 144 Ohms

P=V

^{2}/R whence R=V^{2}/P60W filament 240 Ohms

100W filament 144 Ohms

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