Assertion : A pure semiconductor has negative temperature coefficient of resistance.
Reason: On raising the temperature, more charge carriers are released,. conductance increases and resistance decreases.

Answer

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

### Step 1: Understand the Assertion
The assertion states that "A pure semiconductor has a negative temperature coefficient of resistance."

- **Explanation**: A negative temperature coefficient of resistance means that as the temperature increases, the resistance of the material decreases. This is characteristic of semiconductors.

### Step 2: Understand the Reason
The reason given is: "On raising the temperature, more charge carriers are released, conductance increases and resistance decreases."

- **Explanation**: In a pure semiconductor, as the temperature increases, thermal energy allows more electrons to jump from the valence band to the conduction band. This increases the number of charge carriers (electrons and holes), which in turn increases the conductance (the ability to conduct electricity). Since conductance and resistance are inversely related, an increase in conductance results in a decrease in resistance.

### Step 3: Conclusion
Both the assertion and the reason are correct. The assertion correctly states that a pure semiconductor has a negative temperature coefficient of resistance, and the reason correctly explains why this is the case.

### Final Answer
Both the assertion and the reason are correct.

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