convert watts to hpThe headlights of a moving car draw about 9 A from the 12 V alternator, which is driven by the engine. Assume the alternator is 85% efficient (its output electrical power is 85% of its input mechanical power), and calculate the horsepower the engine must supply to run the lights.

Question

Physics

Koen Greene

13 November, 17:39

convert watts to hpThe headlights of a moving car draw about 9 A from the 12 V alternator, which is driven by the engine. Assume the alternator is 85% efficient (its output electrical power is 85% of its input mechanical power), and calculate the horsepower the engine must supply to run the lights.

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Answers (1)

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Imani Butler · Answer 1

Answer: 0.17hp

Explanation:

Power output = power input * 85%

Power output = power input * 0.85

Power input = IV/0.85

Power input = 9*12/0.85

Power input = 108/0.85

= 127.058 watts

Converting to horse power = 127.058W * 1horse power/745.7W

= 127.058 * 0.001341

= 0.17hp