Electrical conductivity describes how well a material allows electric current to pass through it. This characteristic is a fundamental aspect of many substances, influencing their applications in various technologies, from simple wiring to complex electronic components. Understanding this property helps differentiate between materials that are good conductors, like metals, and those that are poor conductors, known as insulators.
What Are Intensive and Extensive Properties?
Properties of matter are categorized based on their dependence on the amount of substance present. An intensive property is a characteristic that does not depend on the quantity or size of the matter. For example, the temperature of a substance remains the same regardless of how much of it you have. Density, color, and melting point are other common examples of intensive properties.
Conversely, an extensive property is a characteristic that directly depends on the amount of matter in a sample. If the amount of substance changes, the value of an extensive property will also change proportionally. Mass and volume are classic examples of extensive properties; a larger sample of a material will have both greater mass and greater volume.
What is Electrical Conductivity?
Electrical conductivity indicates how readily electric charge can flow through a substance when an electrical potential difference is applied. Materials with high electrical conductivity, such as copper and silver, allow electricity to flow easily, making them suitable for electrical wires.
Materials with low electrical conductivity, like rubber or glass, resist the flow of electric current and are therefore used as electrical insulators. The standard international (SI) unit for electrical conductivity is Siemens per meter (S/m).
Why Electrical Conductivity is an Intensive Property
Electrical conductivity is an intensive property because its value does not change with the amount or size of the material. For instance, a small piece of copper wire will have the same electrical conductivity as a much longer or thicker piece of the same copper wire. This is because conductivity is an inherent characteristic of the material itself, determined by its atomic structure and the availability of free charge carriers, such as electrons.
If you were to cut a conductive material in half, each half would still possess the same conductivity as the original whole. This consistency across different sample sizes confirms its classification as an intensive property.
The Difference Between Conductivity, Conductance, and Resistance
Distinguishing electrical conductivity from related concepts like electrical conductance and electrical resistance is important.
Electrical conductance, in contrast, is an extensive property that measures how easily electricity flows through a specific object or component. Conductance depends not only on the material’s conductivity but also on the object’s physical dimensions, such as its length and cross-sectional area. For example, a shorter, wider wire made of a conductive material will have higher conductance than a longer, thinner wire of the same material.
Electrical resistance is the inverse of conductance and is also an extensive property. It quantifies the opposition a specific object offers to the flow of electric current. Resistance is influenced by the object’s dimensions and the material’s resistivity. A longer or thinner wire will have higher resistance, even if made from the same material.