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03-23-2008, 08:52 PM
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| Physics Question Light Bulbs and Power? A lightbulb marked 125 W [at] 128 V" is screwed into a socket at one end of a long extension cord in which each of the two con- ductors has a resistance of 0.826 ohms *. The other end of the extension cord is plugged into a 128 V outlet. Find the actual power of the bulb in this circuit. Answer in units of Watts.      |
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03-23-2008, 08:52 PM
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| W=V*V/R Effective resistance of the light is R=128^2/125=131.072? So total resistance is 0.826*2+131.072=132.724? Current will be 128/132.724 = 0.964407342 Amps Actual power will be 128*0.964407342=123.444W. In real life it will be nothing of the sort due to the non-linear negative temperature coefficient of indandescent lamps, |
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