The P-V diagram in Fig 21-8 a represents a series of processes performed by an ideal gas , comprising a cylic process of operations . Fil in the table in Fig 21-8 b for this cycle using "+" to indicate an increase in the quantity listed "-" to indicate a decrease , and "0" to indicate no change .

Explanation

To solve the problem regarding the P-V diagram and the cyclic processes for an ideal gas, we will analyze each segment of the cycle (A-B, B-C, C-D, D-A) and determine the changes in temperature, enthalpy, internal energy, and work done. We will fill in the table with "+" for an increase, "-" for a decrease, and "0" for no change.

### Step-by-Step Solution:

1. **Process A to B:**
- **Type of Process:** Isobaric (constant pressure).
- **Change in Volume:** The volume increases (VB > VA).
- **Change in Temperature:** Since volume increases at constant pressure, temperature must also increase (TB > TA).
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