A: When temperature of a metallic wire is increased, its resistance increase .
R : As the temperature is increaed , average relaxtion time increase.

Options

A. If both Assertion & Reason are true and the reason is the correct explanation of the assertion , then mark
B. If both Assertion & Reason are true but the reason is not the correct explanation of the assertion then mark.
C. If Assertion is ture statement but Reason is false , then mark
D. If both Assertion and Reason are false statements then mark.

Answer

To solve the question, we need to analyze both the assertion and the reason provided.

### Step 1: Analyze the Assertion
The assertion states: "When the temperature of a metallic wire is increased, its resistance increases."

- **Explanation**: In metallic conductors, as the temperature increases, the lattice ions in the metal vibrate more vigorously. This increased vibration leads to more frequent collisions between the conduction electrons and the lattice ions. As a result, the resistance of the metallic wire increases with temperature.

### Step 2: Analyze the Reason
The reason states: "As the temperature is increased, average relaxation time increases."

- **Explanation**: The average relaxation time (τ) is the average time between two successive collisions of the conduction electrons. When the temperature increases, the energy of the electrons increases, leading to an increase in their velocity. However, this increased velocity results in a decrease in the average relaxation time because the electrons collide more frequently with the vibrating lattice ions. Therefore, the statement that the average relaxation time increases is incorrect.

### Step 3: Conclusion
- **Assertion**: True (Resistance increases with temperature).
- **Reason**: False (Average relaxation time decreases with temperature).

### Final Answer
The correct option is that the assertion is true, but the reason is false.

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