Name one material whose resistivity decreases with rise in temperature. Explain briefly on the basis of free electron theory why the resistivity decreases.

Explanation

### Step-by-Step Solution:

**Step 1: Identify a Material**
- One material whose resistivity decreases with an increase in temperature is **semiconductors**.

**Step 2: Understand the Concept of Resistivity and Conductivity**
- Resistivity (ρ) and conductivity (σ) are related by the equation:
\[
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