`q=-w` is not true for :-

Options

A. Isothermal process
B. Adiabatic process
C. Cyclic process
D. Options (1) and (3)

Answer

To solve the question "q = -w is not true for:", we will analyze the different thermodynamic processes mentioned in the options: isothermal, adiabatic, cyclic, and a combination of isothermal and cyclic.

### Step-by-Step Solution:

1. **Understanding the First Law of Thermodynamics**:
The first law of thermodynamics states that the change in internal energy (ΔU) of a system is equal to the heat added to the system (Q) plus the work done on the system (W):
\[ \Delta U = Q + W \]

2. **Rearranging the Equation**:
From the first law, we can rearrange the equation to express Q in terms of W:
\[ Q = \Delta U - W \]
If we want to find when \( Q = -W \), we can set \( \Delta U = 0 \):
\[ Q = -W \implies \Delta U = 0 \]

3. **Analyzing Different Processes**:
- **Isothermal Process**:
In an isothermal process, the temperature remains constant, which means the change in internal energy (ΔU) is zero (ΔU = 0). Therefore:
\[ Q = -W \quad \text{(True for isothermal process)} \]

- **Adiabatic Process**:
In an adiabatic process, there is no heat exchange with the surroundings (Q = 0). The first law becomes:
\[ \Delta U = W \quad \text{(Q = 0)} \]
Thus, we cannot say \( Q = -W \) because \( Q \) is zero and \( W \) is not necessarily zero. Therefore:
\[ Q \neq -W \quad \text{(Not true for adiabatic process)} \]

- **Cyclic Process**:
In a cyclic process, the system returns to its original state, which means the change in internal energy (ΔU) is also zero (ΔU = 0). Thus:
\[ Q = -W \quad \text{(True for cyclic process)} \]

4. **Conclusion**:
The statement \( Q = -W \) is not true for the adiabatic process. Therefore, the correct answer is:
- **Adiabatic Process** (Option 2).

### Final Answer:
The statement \( Q = -W \) is not true for the **adiabatic process**.