How does the conductivity of a metallic conductor vary with temperature?

Explanation

To understand how the conductivity of a metallic conductor varies with temperature, we can break down the explanation into several steps:

### Step-by-Step Solution:

1. **Understanding Conductivity**:
- Conductivity (σ) of a metallic conductor is a measure of how easily electrons can flow through the material. It is represented by the formula:
\[
\sigma = n \cdot e^2 \cdot \tau / m
...