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Concept

Problem: You buy a 75-W lightbulb in Europe, where electricity is delivered to homes at 240 V. If you use the lightbulb in the United States at 120 V (assume its resistance does not change), how bright will it be relative to 75-W 120-V Bulbs? [ Hint: assume roughly that brightness is proportional to power consumed]

FREE Expert Solution

The bulb's resistance is found by:

$\overline{)\begin{array}{rcl}{\mathbf{R}}& {\mathbf{=}}& \frac{{\mathbf{V}}^{\mathbf{2}}}{\mathbf{P}}\end{array}}$

When used in Europe, R = 2402/75 = 768Ω

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Problem Details

You buy a 75-W lightbulb in Europe, where electricity is delivered to homes at 240 V. If you use the lightbulb in the United States at 120 V (assume its resistance does not change), how bright will it be relative to 75-W 120-V Bulbs? [ Hint: assume roughly that brightness is proportional to power consumed]

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