A system undergoes a reversible adiabatic process. The entropy of the system

Options

A. Remains constant
B. May increase or may decrease
C. Increases
D. Decreases

Answer

To solve the problem regarding the entropy of a system undergoing a reversible adiabatic process, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Process**: The question states that the system undergoes a reversible adiabatic process. In thermodynamics, an adiabatic process is one where no heat is exchanged with the surroundings.

2. **Identify Key Concepts**: For a reversible process, the change in entropy (ΔS) can be expressed using the formula:
\[ \Delta S = \frac{\Delta Q}{T} \]
where ΔQ is the heat exchanged and T is the temperature.

3. **Apply the Adiabatic Condition**: Since the process is adiabatic, we know that:
\[ \Delta Q = 0 \]
This means there is no heat transfer during the process.

4. **Substitute into the Entropy Formula**: Plugging the value of ΔQ into the entropy change formula gives:
\[ \Delta S = \frac{0}{T} = 0 \]
This indicates that the change in entropy is zero.

5. **Conclude the Results**: Since the change in entropy (ΔS) is zero, we can conclude that:
\[ S_f - S_i = 0 \implies S_f = S_i \]
This means that the final entropy (S_f) is equal to the initial entropy (S_i), indicating that the entropy remains constant during the process.

6. **Final Answer**: Therefore, the entropy of the system remains constant during a reversible adiabatic process.