Permeability

Electromagnetism and formation of magnetic fields

Permeability is the ability to support formation of magnetic fields in a material.

Permeability is measured in H/m (henries/m) or newtons/ampere2 (N/A2).

The Permeability of Free Space

The permeability of free space µ0 (the permeability constant or the magnetic constant) is

µ0 = 4π 10−7 (H/m)

    ≈ 1.257 10−6 (H/m, N/A2)

The Relative Permeability

The relative permeability is the ratio of the permeability of a specific medium to the permeability of free space µ0

µr = µ / µ0                       (1)

where

µr = the relative permeability

µ = permeability of the medium (H/m)

MediumPermeability
- µ -
(H/m)
Relative permeability
- μ / μ0 -
Air 1.25663753 10−6 1.00000037
Aluminum 1.256665 10−6 1.000022
Austenitic stainless steel 1.260 10−6 - 8.8 10−6 1.003–7
Bismuth 1.25643 10−6 0.999834
Carbon Steel 1.26 10−4 100
Cobalt-Iron (high permeability strip material) 2.3 10−2 18000
Copper 1.256629 10−6 0.999994
Ferrite (nickel zinc) 2.0 10−5 – 8.0 10−4 16 – 640
Ferritic stainless steel (annealed) 1.26 10−3 - 2.26 10−3 1000 – 1800
Hydrogen 1.2566371 10−6 1
Iron (99.8% pure) 6.3 10−3 5000
Iron (99.95% pure Fe annealed in H) 2.5 10−1 200000
Martensitic stainless steel (annealed) 9.42 10−4 - 1.19 10−3 750 – 950
Martensitic stainless steel (hardened) 5.0 10−5 - 1.2 10−4 40 – 95
Nanoperm 1.0 10−1 80000
Neodymium magnet 1.32 10−6 1.05
Nickel 1.26 10−4 - 7.54 10−4 100 – 600
Permalloy 1.0 10−2 8000
Platinum 1.256970 10−6 1.000265
Sapphire 1.2566368 10−6 0.99999976
Superconductors 0 0
Teflon 1.2567 10−6 1
Vacuum 0) 4π 10−7 1
Water 1.256627 10−6 0.999992
Wood 1.25663760 10−6 1.00000043

Related Topics

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  • Material Properties - Material properties for gases, fluids and solids - densities, specific heats, viscosities and more

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