Technical Glossary Volume Resistance

[Volume Resistance]

Volume resistance is the name of the electrical resistance value per unit volume. In other words, it is the resistance value between 2 facing surfaces of a 1m³ cube as indicated in Figure C. Units are indicated in Ohm ・ m. In addition, Ohm ・ cm is also used, though this will indicate the resistance value for a 1cm³ cube and not a 1m³ one, so 1 Ohm ・ m =100 Ohm ・ cm.
The resistance value for material as a whole is determined by multiplying the length by the volume resistance and dividing by the cross-sectional area. The volume resistance is a specific value (physical property) for a substance, so when comparing with the same dimensions, a substance with a large volume resistance will also have a large resistance value. In other words, a substance with a large volume resistance is preferred as an insulating material.
Insulators, semiconductors, and conductors can be classified based on the size of resistance. In terms of materials with larger numerical values,
insulators ＞ semiconductors ＞ conductors
Volume resistance is not a specific value for a substance and varies according to temperature. The volume resistance of metal, which is a conductor, increases with a rise in temperature, though it conversely tends to decrease for a semiconductor or insulator with an increase in temperature.