Material conductivity refers to the ability of a material to conduct electricity. It is a measure of how easily electrons can flow through a material. Materials with high conductivity allow electricity to flow freely, while materials with low conductivity resist the flow of electricity.
Material conductivity is measured in units of siemens per meter (S/m) or mhos per meter (mho/m). These units represent the inverse of ohms, which is the unit of resistance. The higher the conductivity, the lower the resistance and vice versa.
Conductivity and resistivity are inversely related. This means that as conductivity increases, resistivity decreases and vice versa. This relationship is described by the equation: σ = 1/ρ, where σ is conductivity and ρ is resistivity.
Variable ohmic resistance refers to a material's ability to change its resistance in response to an external stimulus, such as temperature or an electric field. This type of resistance is often seen in materials with semiconductor properties, where the flow of electrons can be controlled by changing the material's properties.
Some common materials with variable ohmic resistance include semiconductors such as silicon, germanium, and gallium arsenide. Other materials that exhibit variable resistance include conductive polymers, amorphous materials, and certain metal oxides.