How do the electrical conductivity and resistivity of the following classes of materials vary with temperature ?
Semiconductors, metallic conductors, superconductors.

Explanation

To analyze how electrical conductivity and resistivity vary with temperature for semiconductors, metallic conductors, and superconductors, we can break down the solution into clear steps:

### Step-by-Step Solution:

1. **Understanding Electrical Conductivity and Resistivity**:
- Electrical conductivity (σ) is a measure of a material's ability to conduct electric current.
- Resistivity (ρ) is the reciprocal of conductivity, represented as ρ = 1/σ. This means that as conductivity increases, resistivity decreases, and vice versa.

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