R = ρ ρ ℓ ℓ A . The resistance of a given element is proportional to the length, but inversely proportional to the cross-sectional area. For example, if A = 1 m, ℓ ℓ = 1 m (forming a cube with perfectly conductive contacts on opposite faces), then the resistance of this element in ohms is numerically equal to the resistivity of the material it is made of in Ω⋅m.