Which of the following is the biggest unit of energy?

Options

A. Juole
B. Kilowatt hour
C. Erg
D. Electron volt

Answer

To determine which of the following is the biggest unit of energy, we will compare the given options: joule, kilowatt-hour (kWh), erg, and electron volt (eV).

### Step-by-Step Solution:

1. **Understanding the Units**:
- **Joule (J)**: The basic unit of energy in the International System of Units (SI).
- **Kilowatt-hour (kWh)**: A unit of energy equivalent to one kilowatt (1 kW) of power used for one hour.
- **Erg**: A unit of energy in the centimeter-gram-second (CGS) system, where 1 erg = \(10^{-7}\) joules.
- **Electron volt (eV)**: A unit of energy equal to the amount of kinetic energy gained by a single electron accelerating through an electric potential difference of one volt. 1 eV = \(1.6 \times 10^{-19}\) joules.

2. **Convert Each Unit to Joules**:
- **Joule**: 1 J = 1 J (itself).
- **Kilowatt-hour**:
\[ 1 \text{ kWh} = 1 \text{ kW} \times 1 \text{ hour} = 1000 \text{ W} \times 3600 \text{ s} = 3.6 \times 10^6 \text{ J} \]
- **Erg**:
\[ 1 \text{ erg} = 10^{-7} \text{ J} \]
- **Electron volt**:
\[ 1 \text{ eV} = 1.6 \times 10^{-19} \text{ J} \]

3. **Comparison of the Energy Values**:
- **Joule**: 1 J
- **Kilowatt-hour**: \(3.6 \times 10^6\) J
- **Erg**: \(10^{-7}\) J
- **Electron volt**: \(1.6 \times 10^{-19}\) J

4. **Identify the Largest Value**:
- Comparing the values:
- Joule: 1 J
- Kilowatt-hour: \(3.6 \times 10^6\) J
- Erg: \(10^{-7}\) J
- Electron volt: \(1.6 \times 10^{-19}\) J
- Clearly, \(3.6 \times 10^6\) J (kilowatt-hour) is the largest.

5. **Conclusion**:
- The biggest unit of energy among the options provided is **kilowatt-hour (kWh)**.

### Final Answer:
The biggest unit of energy is **kilowatt-hour (kWh)**.

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