Which quantity is defined as energy per unit time?

Which quantity is defined as energy per unit time?

• A. Power
• B. Energy
• C. Wavelength
• D. Frequency

Answer: (A)

Power is the rate at which energy is transferred or work is done. It is defined as energy per unit time, with the SI unit the watt (1 joule per second). This matches exactly what the question asks for. Energy, on the other hand, is a total amount rather than a rate. Wavelength and frequency describe wave properties—how long a wave is and how often cycles occur—not the speed of energy transfer. So the quantity defined as energy per unit time is power.

Power is the rate at which energy is transferred or work is done. It is defined as energy per unit time, with the SI unit the watt (1 joule per second). This matches exactly what the question asks for. Energy, on the other hand, is a total amount rather than a rate. Wavelength and frequency describe wave properties—how long a wave is and how often cycles occur—not the speed of energy transfer. So the quantity defined as energy per unit time is power.