Which statement about horsepower and watts is correct?

Which statement about horsepower and watts is correct?

• A. Watts are larger than horsepower.
• B. Horsepower is dimensionally different from watt.
• C. One horsepower equals 746 watts.
• D. Watts measure energy.

Answer: (C)

Power is the rate at which energy is transferred or work is done. Watts and horsepower are both units for this quantity, so they measure the same kind of thing—power. One mechanical horsepower is defined as 746 watts. That means if something is delivering 1 horsepower of power, it’s delivering 746 joules per second. Because of this, the statement equating horsepower to 746 watts is correct. The other statements don’t fit because: watts are not larger than horsepower; horsepower and watts are simply different scales for the same concept of power, so it’s not a matter of one being dimensionally different. And watts do not measure energy themselves; they measure power, the rate of energy transfer. Energy is measured in joules (or watt-hours when you’re looking at energy over time).

Power is the rate at which energy is transferred or work is done. Watts and horsepower are both units for this quantity, so they measure the same kind of thing—power.

One mechanical horsepower is defined as 746 watts. That means if something is delivering 1 horsepower of power, it’s delivering 746 joules per second. Because of this, the statement equating horsepower to 746 watts is correct.

The other statements don’t fit because: watts are not larger than horsepower; horsepower and watts are simply different scales for the same concept of power, so it’s not a matter of one being dimensionally different. And watts do not measure energy themselves; they measure power, the rate of energy transfer. Energy is measured in joules (or watt-hours when you’re looking at energy over time).