What is electrical resistivity ? How does it depend om temperature. Give its `SI` unit.

Explanation

### Step-by-Step Solution

1. **Definition of Electrical Resistivity**:
Electrical resistivity (ρ) is defined as a measure of how strongly a material opposes the flow of electric current. It is an intrinsic property of the material, meaning it does not depend on the shape or size of the conductor but only on the material itself.

2. **Mathematical Expression**:
The resistivity can be expressed mathematically using the formula for resistance (R):
\[
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