Conductivity ↔ Resistivity

Formula

Description

Conductivity and resistivity are reciprocal material properties: conductivity measures how easily a material carries current, resistivity how strongly it opposes it. They are intrinsic to the material and independent of its shape, unlike resistance. Conductivity is convenient for good conductors, resistivity for insulators and for computing resistance from geometry (R = ρ·L/A).

Variables

• σ — Conductivity (S/m)
• ρ — Resistivity (Ω·m)

Practical Notes

Copper: ρ ≈ 1.72×10⁻⁸ Ω·m, σ ≈ 5.8×10⁷ S/m. Both vary with temperature; conductivity falls as a metal heats up. Resistance follows from R = ρ·L/A = L/(σ·A).