Which does not has the same unit as others

Options

A. watt-s
B. kilowatt-hour
C. eV
D. J-s

Answer

To determine which unit does not belong with the others, we need to analyze the units provided in the context of energy.

### Step-by-Step Solution:

1. **Identify the Units**: The units we are considering are:
- Watt (W)
- Kilowatt-hour (kWh)
- Electron volt (eV)
- Joule-second (J·s)

2. **Understand Each Unit**:
- **Watt (W)**: This is the SI unit of power. It is defined as one Joule per second (1 W = 1 J/s). Thus, it relates to energy.
- **Kilowatt-hour (kWh)**: This is a unit of energy. It is calculated as 1 kW (which is 1000 W) multiplied by the time in hours (1 hour = 3600 seconds). Therefore, 1 kWh = 1000 W × 3600 s = 3.6 × 10^6 J. This confirms that kWh is also a unit of energy.
- **Electron volt (eV)**: This is a unit of energy commonly used in physics, particularly in atomic and particle physics. It is defined as the amount of kinetic energy gained by an electron when it is accelerated through a potential difference of one volt. It can be converted to Joules (1 eV = 1.6 × 10^-19 J), confirming that it is indeed a unit of energy.
- **Joule-second (J·s)**: This is a unit that combines energy (Joule) and time (second). It does not represent energy on its own but rather is used in contexts such as action in quantum mechanics (Planck's constant). Therefore, it does not fit with the other units that represent energy.

3. **Conclusion**: From the analysis, we see that:
- Watt, Kilowatt-hour, and Electron volt are all units of energy.
- Joule-second is not a unit of energy but rather a unit of action.

Thus, the unit that does not have the same meaning as the others is **Joule-second (J·s)**.

### Final Answer:
The correct answer is **Joule-second (J·s)**.

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