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Magnetic Permeability

Magnetic permeability:

\mu= \frac{B}{H}


\muμ = Magnetic Permeability (Henries/meter)

B = Magnetic Flux Density (Tesla)

H = Magnetizing Force


Relative Magnetic Permeability:

\mu_{r}= \frac{\mu}{\mu_{0}}


μr = Relative Magnetic Permeability (dimensionless)

μ = Any Given Magnetic Permeability (H/m)

μo = Magnetic Permeability in Free Space (H/m), which is 1.257 x 10-6 H/m

Magnetic permeability is the ease with which a material can be magnetized. It is a constant of proportionality that exists between magnetic induction and magnetic field intensity. This constant is equal to approximately 4π x10-7 henry per meter or 1.257 x 10-6 H/m in free space (a vacuum). In other materials permeability

 can be much different, often substantially greater than the free-space value, which is symbolized µo.

In engineering applications, permeability

 is often expressed in relative, rather than in absolute , terms. If µo represents the permeability  of free space and µ represents the permeability  of the substance in question (also specified in henrys per meter), then the relative permeability , µr, is given by the equation above. Relative permeability  is dimensionless since it is the ratio of two permeability  values expressed in the same units.


Example 1

What is the relative permeability

 of a material with an absolute  permeability  of 5.63x10-5H/m?

Simply plug the materials permeability

 and the free space permeability  values in the equation and solve.

\mu_{r}= \frac{\mu}{\mu_{0}}

\mu_{r}=\frac{5.63\times10^{-5}}{1.257 \times 10^{-6}}


Example 2

What is the absolute

 permeability  of a materials with a relative permeability  of 1.05

Given the equation and the permeability

 of free space (µo) of 1.257x10-6 H/mm Rearranging this equation to solve for absolute  permeability  results in:

\mu_{r}= \frac{\mu}{\mu_{0}}


Plugging the given values into the equation produces an absolute

 permeability  value.


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