nonconductivity

Nonconductivity is the property of a material to resist the flow of electric current. Materials with high electrical resistivity are commonly described as insulators or nonconductors, in contrast to conductors such as metals. The degree of nonconductivity is quantified by electrical resistivity (rho) or, inversely, electrical conductivity (sigma).

Electrical conduction in a homogeneous material is described by Ohm's law: J = sigma E, where J is current density and E is the electric field. Materials with very low conductivity impede charge flow and are regarded as nonconductive under ordinary conditions. Common insulators include dry air, glass, rubber, porcelain, and many plastics. Conductivity is strongly influenced by temperature, moisture, impurities, and the frequency of the applied field; for instance, humidity or dissolved ions increase conductivity.

Nonconductivity is not absolute. At sufficiently high electric fields, many insulators undergo dielectric breakdown and begin to conduct, potentially leading to arcing. Aging, mechanical damage, contamination, and radiation can degrade insulating performance by reducing resistivity.

Applications include electrical insulation for cables, wires, and equipment; insulating coatings; and safety barriers. In design, engineers specify dielectric strength—the maximum field the material can withstand before breakdown. Nonconductivity is thus a practical property supporting safety and reliability in electrical systems.