STATEMENT 1: A free rod when heated experiences no thermal stress.
STATEMENT 2: The rod when heated increases in length.

Options

A. Statement 1 is true, Statement 2 is true, Statement 2 is the correct explanation of statement 1.
B. Statement 1 is true, Statement 2 is true
C. Statement 1 is true, Statement 2 is false
D. statement 1 is true, Statement 2 is true, Statement 2 is not the correct explanation of statement 1.

Answer

To solve the question, we need to analyze both statements regarding the behavior of a free rod when it is heated.

### Step 1: Analyze Statement 1
**Statement 1:** A free rod when heated experiences no thermal stress.

- When a rod is heated, it tends to expand due to an increase in temperature. However, if the rod is free (not constrained), it can expand without any restrictions.
- Since there are no external forces acting on the rod to prevent this expansion, it does not experience any thermal stress.

**Conclusion for Statement 1:** This statement is **True**.

### Step 2: Analyze Statement 2
**Statement 2:** The rod when heated increases in length.

- According to the principle of linear expansion, when a material is heated, its length increases. This is a fundamental property of materials.
- Therefore, as the temperature of the rod increases, it will indeed increase in length.

**Conclusion for Statement 2:** This statement is **True**.

### Step 3: Determine the Relationship Between the Statements
- While both statements are true, we need to check if Statement 2 explains Statement 1.
- Statement 1 explains that a free rod does not experience thermal stress because it is free to expand. Statement 2 simply states that the rod increases in length when heated, but it does not explain why there is no thermal stress in the case of a free rod.

### Final Conclusion
- Both statements are true, but Statement 2 does not serve as a correct explanation for Statement 1. Therefore, the correct answer is that both statements are true, but Statement 2 is not the correct explanation for Statement 1.

### Answer:
- Statement 1 is true.
- Statement 2 is true.
- Statement 2 is not the correct explanation for Statement 1.