For a 3 horsepower, 100 V DC motor that is 85% efficient, what is the input power in watts?

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Multiple Choice

For a 3 horsepower, 100 V DC motor that is 85% efficient, what is the input power in watts?

Efficiency tells us how much of the input power becomes useful output. Input power equals output power divided by efficiency. The motor’s mechanical output is 3 horsepower. Convert that to watts: 1 horsepower is 746 watts, so 3 hp = 3 × 746 ≈ 2238 W of output. With 85% efficiency, the input power is 2238 W ÷ 0.85 ≈ 2633 W. So the input power is about 2633 watts, which matches the given option. If you ever need current, you could divide this input power by the voltage: 2633 W / 100 V ≈ 26.3 A.

Efficiency tells us how much of the input power becomes useful output. Input power equals output power divided by efficiency.

The motor’s mechanical output is 3 horsepower. Convert that to watts: 1 horsepower is 746 watts, so 3 hp = 3 × 746 ≈ 2238 W of output.

With 85% efficiency, the input power is 2238 W ÷ 0.85 ≈ 2633 W. So the input power is about 2633 watts, which matches the given option. If you ever need current, you could divide this input power by the voltage: 2633 W / 100 V ≈ 26.3 A.

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