The watt is a unit of what quantity?

• A. Energy
• B. Power
• C. Force
• D. Velocity

Answer: (B)

Power is the rate at which work is done or energy is transferred. The watt is the unit that expresses that rate. One watt equals one joule per second, so it describes how quickly energy is used or moved. Energy, measured in joules, is the total amount of energy, while power tells you how fast that energy is being used. Force (newtons) describes push or pull, and velocity (meters per second) is speed; neither captures the idea of energy transfer rate. For example, a 60-watt bulb uses energy at 60 joules each second, so the total energy consumed grows with time as you run it.