Which of the following is not the unit of energy ?

Options

A. calorie
B. joule
C. electron volt
D. watt

Explanation

To determine which of the following options is not a unit of energy, we will analyze each option step by step.

1. **Identify the options**: We need to look at the given options to evaluate them. The options are:
- A) Calorie
- B) Joule
- C) Electron Volt
- D) Watt

2. **Evaluate Calorie**:
- The calorie is a unit of heat energy. It is defined as the amount of energy needed to raise the temperature of 1 gram of water by 1 degree Celsius.
- Since heat is a form of energy, the calorie is indeed a unit of energy.

3. **Evaluate Joule**:
- The Joule is the SI unit of energy. It is defined as the amount of work done when a force of one newton displaces an object by one meter in the direction of the force.
- Therefore, the Joule is also a unit of energy.

4. **Evaluate Electron Volt**:
- The electron volt (eV) is a unit of energy commonly used in the field of atomic and particle physics. It is defined as the amount of kinetic energy gained by a single electron when it is accelerated through an electric potential difference of one volt.
- Thus, the electron volt is also a unit of energy.

5. **Evaluate Watt**:
- The watt (W) is the SI unit of power. It is defined as one joule per second (1 W = 1 J/s). Power measures the rate at which energy is transferred or converted.
- Since the watt measures power and not energy, it is not a unit of energy.

6. **Conclusion**:
- Based on the evaluations, the option that is not a unit of energy is **D) Watt**.

### Final Answer: D) Watt