Resistivity of a typical metallic conductor as temperature increases:

1. In metals, ρ ≈ ρ₀ [1 + α(T − T₀)]; α positive. 2. Higher T means more phonon scattering of conduction electrons. 3. So ρ increases with T (opposite to semiconductors, which decrease). _Source: syllabus Physics Ch 3 §3.7 Temperature Dependence_