What is the relationship between mechanical power and electrical power?

• A. 1 Horsepower = 746 Watts
• B. 1 Horsepower = 1 Watt
• C. 1 Horsepower = 0.746 Watts
• D. 1 Horsepower = 1000 Watts

Answer: (B)

Power is the rate at which energy is transferred or work is done. When you compare mechanical power to electrical power, you’re looking at the same quantity expressed in different forms of energy transfer. One horsepower is defined as 746 watts, so a machine delivering 1 horsepower of mechanical power corresponds to about 746 watts of power, assuming energy is converted to electrical form with no losses. In real systems, efficiencies are less than 100%, so the electrical power available would be mechanical power times the efficiency. The other options—1 watt, 0.746 watt, or 1000 watts—don’t match the established conversion between horsepower and watts.