Rezistivity

Rezistivity is an intrinsic electrical property of a material that quantifies how strongly it resists the flow of electric current when an electric field is applied. Denoted by the symbol ρ (rho), it is measured in ohm-meters (Ω·m) and is the reciprocal of electrical conductivity (σ). For isotropic materials, ρ = 1/σ; in anisotropic substances, resistivity is more correctly represented as a tensor ρ_ij, relating current density J to electric field E via J_i = ∑ σ_ij E_j.

In practice, resistivity is determined from a measured resistance R by accounting for geometry: R = ρ L / A for a uniform bar of length L and cross-section A. For samples with complex shapes, geometry factors or specialized methods such as the four-point probe, Van der Pauw technique, or impedance spectroscopy are used.

Temperature strongly affects rezistivity. In metals, ρ typically increases with temperature due to enhanced electron-phonon scattering, described by a positive temperature coefficient α. In semiconductors, ρ often decreases with rising temperature as carrier concentration increases. At high frequencies, ac resistivity may differ from dc due to dielectric and inductive effects, especially in thin films or composite materials.

Applications span electronics, materials science, and geology, including characterizing metallic alloys, conducting films, and determining subsurface properties via apparent resistivity measurements. Etymology varies by language; some languages render it as rezistivitas or rezistivity, but in English the standard term is resistivity.