An incandescent light bulb uses a coiled filament of tungstenthat is 580 mm long with a diameter of 46.0 μm. At 20.0∘C tungstenhas a resistivity of 5.25×10−8Ω⋅m. Its temperature coefficient ofresistivity is 0.0045 (C∘)−1, and this remains accurate even athigh temperatures. The temperature of the filament increaseslinearly with current, from 20∘C when no current flows to 2520∘C at1.00 A of current. What is the resistance of the light bulb at20∘C? What is the current through the light bulb when the potentialdifference across its terminals is 120 V? (Hint: First determinethe temperature as a function of the current; then use this todetermine the resistance as a function of the current. Substitutethis result into the equation V=IR and solve for the current I.)Express your answer to two significant figures and include theappropriate units. What is the resistance when the potential is 120V? Express your answer to two significant figures and include theappropriate units. How much energy does the light bulb dissipate in1 min when 120 V is supplied across its terminals? Express youranswer in kilojoules to two significant figures.
