Select the incorrect statement

Options

A. For isothermal process of ideal gas, `DeltaU=0`
B. For isochoric process, W=0
C. For Adiabatic process, `DeltaU=-DeltaW`
D. For cyclic process, `DeltaU=-DeltaW`

Answer

To solve the question of selecting the incorrect statement regarding thermodynamic processes, we will analyze each option step by step.

### Step-by-Step Solution:

1. **Understanding Isothermal Process:**
- In an isothermal process, the temperature of the system remains constant.
- For an ideal gas, the internal energy (U) is a function of temperature. Therefore, if the temperature does not change, the change in internal energy (ΔU) is zero.
- **Conclusion:** ΔU = 0 for an isothermal process. This statement is **correct**.

2. **Understanding Isochoric Process:**
- In an isochoric process, the volume of the system remains constant.
- Work done (W) is defined as W = PΔV. Since ΔV = 0 (no change in volume), the work done is also zero.
- **Conclusion:** ΔW = 0 for an isochoric process. This statement is **correct**.

3. **Understanding Adiabatic Process:**
- In an adiabatic process, there is no heat exchange with the surroundings (ΔQ = 0).
- According to the first law of thermodynamics: ΔQ = ΔU + ΔW. Since ΔQ = 0, we have ΔU = -ΔW.
- **Conclusion:** ΔU = -ΔW for an adiabatic process. This statement is **correct**.

4. **Understanding Cyclic Process:**
- In a cyclic process, the system returns to its initial state after completing the cycle.
- Since internal energy is a state function, the change in internal energy (ΔU) over a complete cycle is zero (ΔU = 0).
- From the first law of thermodynamics: ΔQ = ΔU + ΔW. Since ΔU = 0, we have ΔQ = ΔW.
- The statement in option 4 claims ΔU = -ΔW, which contradicts our conclusion that ΔU = 0.
- **Conclusion:** The statement is incorrect.

### Final Answer:
The incorrect statement is option 4: "For cyclic process, ΔU = -ΔW."