Permeance

Permeance, in general, is the degree to which a material admits a flow of matter or energy.

Electromagnetism

In Electromagnetic theory, permeance is the inverse of reluctance. Permeance is a measure of the quantity of flux for a number of current-turns in magnetic circuit. A magnetic circuit almost acts as though the flux is 'conducted', therefore permeance is larger for large cross sections of a material and smaller for longer lengths. This concept is analogous to that of electrical conductance.

Measuring Permeance

The equation for permeance is:

${\frac {\Phi }{NI}}=\Lambda$

Where:

Λ=Permeance

Φ=Flux

NI=Current-turns (current x number of coils)

Alternatively, similar to the equation for electric conductance:

${\frac {\mu \mathrm {A} }{l}}=\Lambda$

Where:

Λ=Permeance

μ=Permeability of Material

A=Cross Sectional Area

l=Length of Circuit

Units of Permeance

The SI unit of permeance is 'webers per ampere-turn' given as Wb A^-1.

Materials science

In Materials science, permeance is the degree to which a material transmits another substance.

See also

• Reluctance
• Dielectric complex reluctance

External articles and references

Electromagnetism

• Properties of Magnetic Materials (units of magnetic permeance)

Material science

• Bombaru, D., Jutras, R., and Patenaude, A., "Air Permeance of Building Materials". Summary report prepared by, AIR-INS Inc. for Canada Mortgage and Housing Corporation, Ottawa, 1988.
• Don Mills, "The Details of Air Barrier Systems for Houses". Ontario New Home Warranty Program, 1993.