If a motor produces 746 watts of mechanical power from an input of 1500 watts, what is its efficiency?

If a motor produces 746 watts of mechanical power from an input of 1500 watts, what is its efficiency?

• A. 24.9%
• B. 49.7%
• C. 74.6%
• D. 100%

Answer: (B)

Efficiency is the ratio of useful mechanical power produced to the power supplied, expressed as a percentage. It’s found by dividing the output power by the input power and multiplying by 100. In this case, 746 W of output from 1500 W of input gives: (746 / 1500) × 100 ≈ 49.7%. That result makes sense because some of the input energy is always lost to inefficiencies like heat and friction. An efficiency of 74.6% would require a larger output for the same input, while 100% would imply no losses, which isn’t the case here.

Efficiency is the ratio of useful mechanical power produced to the power supplied, expressed as a percentage. It’s found by dividing the output power by the input power and multiplying by 100. In this case, 746 W of output from 1500 W of input gives: (746 / 1500) × 100 ≈ 49.7%. That result makes sense because some of the input energy is always lost to inefficiencies like heat and friction. An efficiency of 74.6% would require a larger output for the same input, while 100% would imply no losses, which isn’t the case here.