Question

What is Electrical Conductance? Definition, Formula, and Units Explained

Answer 1

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What is Electrical Conductance? Definition, Formula, and Units Explained

In the world of electronics and physics, we often talk about resistance—how much a material opposes the flow of electricity. But what about the opposite? The measure of how easily an electric current can flow is known as conductance.

Understanding conductance is key to analyzing circuits and materials. Here's a complete breakdown of its definition, formulas, units, and a simple analogy to help you grasp the concept.

Definition of Conductance

At its core, electrical conductance is a fundamental property of a material.

• Definition: Conductance (symbol: G) is the measure of how easily electric current flows through an object or material.
• Opposite of Resistance: It is the direct opposite, or reciprocal, of electrical resistance (R). If a material has high resistance, it has low conductance, and vice-versa.

Key Conductance Formulas

Conductance can be calculated using several important formulas, depending on the context.

1. From Resistance

The most basic formula for conductance defines its relationship with resistance:

G = 1 / R

Where:
G is the conductance in Siemens (S).
R is the resistance in Ohms (Ω).

2. Ohm's Law Form

Ohm's Law (V = I ⋅ R) can be rearranged to express current (I) in terms of conductance:

I = G ⋅ V

Where:
I is the current in Amperes (A).
G is the conductance in Siemens (S).
* V is the voltage in Volts (V).

3. For a Physical Conductor

The conductance of a specific conductor (like a wire) depends on its material properties and physical dimensions:

G = σ ⋅ (A / L)

Where:
G is the conductance.
σ (sigma) is the electrical conductivity of the material (in S/m).
A is the cross-sectional area of the conductor.
L is the length of the conductor.

Units of Conductance

• SI Unit: Siemens (S)
  The modern, standard international (SI) unit for conductance is the Siemens, abbreviated with the symbol S.

• Old Symbol: Mho (℧)
  In older textbooks and references, you may find conductance measured in mho. This name is simply "ohm" spelled backward, and its symbol is an upside-down omega (℧).

A Simple Analogy: Water in a Pipe

To make the concept intuitive, think of electric current as water flowing through a pipe:

• High Conductance: This is like a wide, thick pipe. Water flows through it easily with very little restriction.
• High Resistance: This is like a clogged or very narrow pipe. It restricts the flow of water, making it difficult to pass through.

Summary Table: Conductance vs. Resistance vs. Conductivity

This table provides a quick reference for the related concepts, symbols, units, and formulas.

| Concept | Symbol | Unit | Formula |
| :--- | :---: | :---: | :---: |
| Conductance | G | Siemens (S) | G = 1/R |
| Resistance | R | Ohms (Ω) | R = 1/G |
| Conductivity | σ | S/m | G = σ ⋅ (A/L) |