Electric Conductance

The Ease of Flow: Understanding Electric Conductance

Electrical conductance is a measure of how easily electric current flows through a material or an electrical component. It is the direct reciprocal of electrical resistance. While resistance quantifies the opposition to current flow, conductance quantifies the 'easiness' of that flow. A component with high conductance allows current to pass through it with very little opposition, whereas a component with low conductance significantly impedes the flow of current. The concept provides an alternative and sometimes more convenient perspective for analyzing electrical circuits, particularly in parallel circuits where the total conductance is simply the sum of individual conductances.

The standard unit of conductance is the Siemens (S), named after the German inventor and industrialist Ernst Werner von Siemens. An older, more whimsical name for the same unit is the 'mho', which is 'ohm' spelled backwards, graphically illustrating its inverse relationship with the unit of resistance, the Ohm. A conductor has a conductance of one Siemens if a potential difference of one volt across it results in a current of one Ampere. Understanding conductance is essential for electrical engineers and physicists when analyzing circuit behavior, characterizing materials, and designing electronic components where facilitating current flow, rather than resisting it, is the primary goal.

Relevant Formulas in Science and Mathematics

• Definition of Conductance (Physics): Conductance (G) is the reciprocal of resistance (R): G = 1 / R.
• Ohm's Law in terms of Conductance (Physics): Ohm's Law (V=IR) can be rewritten to feature conductance. Since I = V/R, and G = 1/R, then I = GV. This shows that for a given voltage, the current is directly proportional to the conductance.
• Conductance in Parallel (Physics): For resistors connected in parallel, the total conductance is the sum of the individual conductances: G_total = G₁ + G₂ + G₃ + .... This is often simpler than calculating the total resistance using the formula 1/R_total = 1/R₁ + 1/R₂ + ...
• Relationship to Conductivity (Physics): Conductance (G) of a specific object is related to the intrinsic conductivity (σ, sigma) of its material by its geometry: G = σ * (A / L), where 'A' is the cross-sectional area and 'L' is the length of the conductor.

A Deep Dive into Common Electric Conductance Units

• Siemens (S): The SI unit of electrical conductance. It is defined as the reciprocal of an Ohm (1 S = 1 Ω⁻¹). It is the standard unit for all scientific and engineering applications.
• Mho (℧): An older, non-SI name for the same unit as the Siemens. The name 'mho' and its symbol, the upside-down capital omega (℧), were proposed by the British scientist Lord Kelvin in 1883 to cleverly emphasize the inverse relationship with the Ohm (Ω). While officially replaced by the Siemens in 1971, the term 'mho' is still occasionally encountered in older texts and in some fields out of tradition.
• Abmho: The unit of conductance in the CGS-EMU (electromagnetic) system. 1 abmho is equal to 1 billion Siemens (10⁹ S). It is an obsolete unit.