Choose the correct statement(s)

Options

A. Work done by the system is taken as negative
B. In expansion , there is work done by the system
C. `W_("reversible") gt W_("irreversible")`.
D. All of these

Answer

To solve the question, we need to analyze each statement provided and determine whether they are correct or not based on the principles of thermodynamics.

### Step-by-Step Solution:

1. **Understanding Work Done by the System**:
- The work done by the system is defined as negative when the system expands. This is due to the convention that when the system does work on the surroundings (like expanding gas), it loses energy, hence the work is considered negative.
- **Hint**: Remember that work done by the system is negative during expansion.

2. **Work Done During Expansion**:
- In the case of expansion, the volume of the gas increases (V2 > V1). The work done by the system can be expressed as \( W = -P \Delta V \) where \( \Delta V = V2 - V1 \). Since \( \Delta V \) is positive during expansion, the work done is negative.
- **Hint**: Expansion means the system does work on the surroundings, leading to negative work.

3. **Work Done During Compression**:
- Conversely, when work is done on the system (compression), the volume of the gas decreases (V2 < V1). In this case, the work done is considered positive because the system gains energy.
- **Hint**: Compression leads to positive work done on the system.

4. **Comparison of Reversible and Irreversible Work**:
- It is a well-established principle that the work done in a reversible process is greater than that done in an irreversible process. This is because reversible processes are more efficient and minimize energy loss.
- **Hint**: Reversible processes are ideal and maximize work done compared to irreversible processes.

5. **Conclusion**:
- Based on the analysis:
- Statement 1: Work done by the system is negative during expansion - **Correct**.
- Statement 2: Work done during expansion is by the system - **Correct**.
- Statement 3: Work done reversible is greater than work done irreversible - **Correct**.
- Statement 4: All of these - **Correct**.

Thus, the correct answer is **All of these**.

### Final Answer:
The correct statements are:
1. Work done by the system is taken as negative.
2. In expansion, there is work done by the system.
3. Work done reversible is greater than work done irreversible.
4. Therefore, the answer is **All of these**.