Question 26.66: The headlights of a moving car require about 10 A from the 1......

Instructor Solution Manual for Fundamentals of Physics [1361627]

The headlights of a moving car require about 10 A from the 12 V alternator, which is driven by the engine. Assume the alternator is 80% efficient (its output electrical power is 80% of its input mechanical power), and calculate the horsepower the engine must supply to run the lights.

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The horsepower required is $P={\frac{i V}{0.80}}={\frac{(10\,\mathrm{A})(12\ \mathrm{V})}{(0.80)(746\ \mathrm{W/hp})}}=0.20\ \mathrm{hp}.$

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