Conductivity and resistance are inversely proportional to each other. When conductivity is low, resistance is high. When the resistance is low, the conductivity is high. Since conductivity is the measure of how easily electricity flows, electrical resistivity measures how much a material resists the flow of electricity.
Volume resistivity, also known as bulk resistivity or electrical resistivity, is the ability of a material to resist the movement of electricity from one end of the material to the other. The lower the volume resistance, the higher the movement and the more conductive the material will be.
Volume resistivity refers to conductivity, which measures the electrical resistance from a sample of material. This process typically involves placing a sample of material between two electrodes and applying voltage to one electrode and measuring the electrical current flowing through the other electrode. The movement captured between opposing sides is equal to the volume resistance measured in ohms. In general, results will vary depending on applied voltage and environmental factors.
In these tests, the ASTM D257 standard developed by the American Testing and Materials Organization (ASTM) is followed. This standard, whose full name is "ASTM D257-14 Standard test methods for DC resistance or conductivity of insulating materials", describes direct current test methods for the measurement of direct current insulation resistance, volume resistance and surface resistance. From such measurements and the geometric dimensions of the sample and electrodes, both the volume and surface resistance of electrical insulating materials as well as the corresponding conductivities are calculated. These test methods are not suitable for use in measuring the electrical resistance/conductivity of moderately conductive materials. The test method defined in the ASTM D4496 standard is used to evaluate such materials.
These test methods include several general alternative methodologies for measuring resistance (or conductivity). Specific materials are optimally tested using standard ASTM test methods applicable to the specific material, which define both voltage stress limits and finite electrification times, as well as sample configuration and electrode geometry.
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