Which option is NOT listed as a basic energy unit in the material?

• A. Watt
• B. Joules
• C. Btu
• D. Calories

Answer: (A)

Energy versus power is what this question tests. Energy is the amount of work that can be done and is measured in joules, calories, and BTUs. Power is the rate at which energy is used or transferred and is measured in watts. One watt equals one joule per second, so a watt is a unit of power, not energy.

Since the basic energy units listed are joules, BTUs, and calories, they quantify energy. Watt does not; it describes how quickly energy is used. For example, a light bulb rated at 60 watts uses energy at a rate of 60 joules per second, and the total energy consumed depends on the run time.

So the option that does not fit as a basic energy unit is the one that measures power.