Conductance, symbolized by G, is the measure of a material’s ability to conduct electricity. It represents the ratio of electric current flow to the voltage (potential difference) that causes that flow.
Conductance is a fundamental electrical property that defines how easily electric current passes through a given material or circuit. It is the reciprocal of resistance (R) and is measured in siemens (S), formerly known as mhos. In essence, while resistance quantifies how much a material opposes current flow, conductance expresses how effectively it allows that current to move.
In wire and cable engineering, conductance is directly influenced by a conductor’s material, cross-sectional area, temperature, and length. Copper, for example, is a preferred conductor in most commercial and industrial cabling applications because of its high conductance, which ensures efficient power transmission and minimal signal loss. Aluminum, though lighter, has lower conductance and therefore requires larger cross-sectional areas to carry equivalent current.
Conductance also plays a significant role in signal transmission performance for communication and control cables. In alternating current (AC) systems, the real part of the admittance (which combines conductance and susceptance) helps determine energy efficiency and losses. Maintaining high conductance minimizes voltage drop and energy dissipation, which is essential for consistent electrical and data performance across long cable runs in industrial facilities, AV networks, or automation systems.
Conductance principles and measurement standards are addressed by organizations such as the Institute of Electrical and Electronics Engineers (IEEE) and the International Electrotechnical Commission (IEC). These bodies define parameters for electrical performance, material conductivity, and cable testing methodologies.
The concept of conductance emerged alongside Ohm’s Law in the early 19th century, developed by Georg Simon Ohm, who described the relationship between voltage, current, and resistance. The reciprocal nature of conductance provided engineers with a simplified means to express how well materials and systems transmit electrical current. Over time, the measurement unit transitioned from the mho (ohm spelled backward) to the siemens (S), honoring German inventor and industrialist Ernst Werner von Siemens.