the power rating on a light bulb indicates how much power it would dissipate whe
ID: 2187178 • Letter: T
Question
the power rating on a light bulb indicates how much power it would dissipate when it is hooked up to the standard household voltage of 120V (t his rating does not mean that the light bulb always dissipates the same amount of water, assume that the resistance is constant in this case).A) how much power is dissipated in a light bulb that is normally rated at 100W, if instead we hook it up to a potential difference of 60V?
B) how much power is dissipated in a light bulb that is normally rated at 100W, if instead we hook it up to a potential difference of 240V?
Explanation / Answer
Since P = V^2 / R, R = V^2 / P The 100W bulb offers a resistance of R = 120^2 / 100 = 144ohms A) P = V^2 / R = 60^2 / 144 = 25 W B) P = V^2 / R = 240^2 / 144 = 400 W
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