Which of the following items is NOT a common unit of energy?

• A. Electronvolt (eV)
• B. Calorie (cal)
• C. Joule (J)
• D. Watt (W)

Answer: (D)

Verified step by step guidance

1. Understand that energy is a measure of the capacity to do work or produce heat, and it is expressed in various units depending on the context.
2. Recall that the Joule (J) is the SI unit of energy, defined as one Newton meter (N·m), which is a standard unit used universally in physics and chemistry.
3. Recognize that the Calorie (cal) is a unit of energy commonly used in chemistry and nutrition, defined as the amount of energy needed to raise the temperature of 1 gram of water by 1 degree Celsius.
4. Know that the Electronvolt (eV) is a unit of energy used primarily in atomic and particle physics, representing the energy gained by an electron when it moves through an electric potential difference of one volt.
5. Identify that the Watt (W) is a unit of power, not energy. Power is the rate at which energy is transferred or converted, defined as one Joule per second (J/s), so Watt is not a unit of energy itself.