A 0.2-horsepower, 24-volt motor with 75 percent efficiency requires approximately how many watts of input power?

A 0.2-horsepower, 24-volt motor with 75 percent efficiency requires approximately how many watts of input power?

• A. 199 watts
• B. 149 watts
• C. 174 watts
• D. 240 watts

Answer: (A)

Efficiency links input power to output power: input power must be larger than what’s delivered as useful output. Use P_in = P_out / η. First convert the output from horsepower to watts: 0.2 hp × 746 W/hp ≈ 149.2 W. Then divide by the efficiency: 149.2 W / 0.75 ≈ 198.9 W, which rounds to about 199 W of input power. If you check the motor at 24 V, the current would be roughly 199 W / 24 V ≈ 8.3 A. So the input power is about 199 watts because the 75% efficiency means only 75% of the input becomes useful output, with the rest lost as heat.

Efficiency links input power to output power: input power must be larger than what’s delivered as useful output. Use P_in = P_out / η.

First convert the output from horsepower to watts: 0.2 hp × 746 W/hp ≈ 149.2 W.

Then divide by the efficiency: 149.2 W / 0.75 ≈ 198.9 W, which rounds to about 199 W of input power.

If you check the motor at 24 V, the current would be roughly 199 W / 24 V ≈ 8.3 A.

So the input power is about 199 watts because the 75% efficiency means only 75% of the input becomes useful output, with the rest lost as heat.