# Electrical Conductivity Definition

## Understand Electrical Conductivity Electrical conductivity is a measure of how readily a material transmits an electrical current. KTSDESIGN/Getty Images

Electrical conductivity is the measure of the amount of electrical current a material can carry or it's ability to carry a current. Electrical conductivity is also known as specific conductance. Conductivity is an intrinsic property of a material.

## Units of Electrical Conductivity

Electrical conductivity is denoted by the symbol σ and has SI units of siemens per meter (S/m). In electrical engineering, the Greek letter κ is used. Sometimes the Greek letter γ represents conductivity. In water, conductivity is often reported as specific conductance, which is a measure compared to that of pure water at 25°C.

## Relationship Between Conductivity and Resistivity

Electrical conductivity (σ) is the reciprocal of the electrical resistivity (ρ):

σ = 1/ρ

where resistivity for a material with a uniform cross section is:

ρ = RA/l

where R is the electrical resistance, A is the cross-sectional area, and l is the length of the material

Electrical conductivity gradually increases in a metallic conductor as the temperature is lowered. Below a critical temperature, resistance in superconductors drops to zero, such that an electrical current could flow through a loop of superconducting wire with no applied power.

In many materials, conduction occurs by band electrons or holes. In electrolytes, entire ions move, carrying their net electrical charge. In electrolyte solutions, the concentration of the ionic species is a key factor in the conductivity of the material.

## Materials With Good and Poor Electrical Conductivity

Metals and plasma are examples of materials with high electrical conductivity. The element that is the best electrical conductor is silver -- a metal. Electrical insulators, such as glass and pure water, have poor electrical conductivity. Most of the nonmetals on the periodic table are poor electrical and thermal conductors. The conductivity of semiconductors is intermediate between that of an insulator and a conductor.

Examples of excellent conductors include:

• Silver
• Copper
• Gold
• Aluminum
• Zinc
• Nickel
• Brass

Examples of poor electrical conductors include:

• Rubber
• Glass
• Plastic
• Dry Wood
• Diamond
• Air

Pure Water (not salt water, which is conductive)

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