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magnetic_permeability [2020/03/07 16:27]
stan_zurek [Magnetic permeability]
magnetic_permeability [2020/12/07 00:08] (current)
stan_zurek
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 +====== Magnetic permeability ======
  
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 +| //[[user/Stan Zurek]], **[[Magnetic permeability]]**, [[http://Encyclopedia-Magnetica.com|Encyclopedia-Magnetica.com]], {accessed on @YEAR@-@MONTH@-@DAY@}// |
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 +**Magnetic permeability**, denoted by **μ** - a property of a given medium quantifying its magnetic response of [[flux density]] $B$  when subjected to [[magnetic field strength]] $H$.[(Jiles>[[http://google.com/books?isbn=9781482238884|David Jiles, Introduction to Magnetism and Magnetic Materials, Third Edition, CRC Press, 2015, ISBN 9781482238884, p. 11]])] 
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 +Permeabilities of [[magnetic material|magnetic materials]] (e.g. [[ferromagnets]]) are much higher than those of [[non-magnetic material|non-magnetic materials]] (e.g. [[permeability of free space|vacuum]], [[diamagnets]] and [[paramagnets]])
 +[[file/permeabilities_-_magnetica.png|{{permeabilities_-_magnetica.png}}]]
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 +[[Permeability of free space]] (or vacuum) is a universal physical constant defined in the [[international system of units]] (SI) denoted as $μ_0$ and its value defined exactly[(Jiles)][(BIPM_mu0>[[http://www.bipm.org/en/publications/si-brochure/ampere.html|Unit of electric current (ampere), SI Brochure: The International System of Units (SI) [8th edition, 2006; updated in 2014]], {accessed 2016-06-27})] as $μ_0 = 4 × π × 10^{-7}$ [[henry]] per [[metre]] which is approximately $μ_0 \approx 1.2566 × 10^{-6}$ H/m.
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 +The term "permeability" was proposed in 1885 by Olivier Heaviside.
 +
 +===== Practical significance of permeability =====
 +From a practical viewpoint permeability is one of the basic parameters which allows categorising all materials as "[[magnetic material|magnetic]]" (permeability much greater than that of vacuum $μ >> μ_0$) and "[[non-magnetic material|non-magnetic]]" (permeability similar to that of vacuum $μ \approx μ_0$). In reality all materials are magnetic because they always exhibit some magnetic response to the magnetic excitation so that:
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 +|  (1)  |  $$B = μ · H$$  |  (T)  |
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 +[[Ferromagnet|Ferromagnetic]] and [[ferrimagnet|ferrimagnetic]] materials have their permeabilities significantly greater than vacuum and are used for construction of [[magnetic core|magnetic cores]] in [[magnetic circuit|magnetic circuits]].
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 +However, at sufficiently high excitation all magnetic materials exhibit [[magnetic saturation]], with which the permeability reduces to that of vacuum.
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 +Permeability of [[ferromagnetic material|ferromagnetic materials]] is a non-linear function of the applied excitation and reduces when approaching saturation
 +[[file/permeability_of_ferromagnet_-_magnetica.png|{{permeability_of_ferromagnet_-_magnetica.png}}]]
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 +===== Types of permeability =====
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 +There are several types of magnetic permeability:
 +
 +==== Names ====
 +  * [[absolute permeability]]
 +  * [[AC inductance permeability]]
 +  * [[amplitude permeability]]
 +  * [[apparent permeability]]
 +  * [[bulk permeability]]
 +  * [[complex permeability]]
 +  * [[DC permeability]]
 +  * [[differential permeability]]
 +  * [[dynamic permeability]]
 +  * [[effective permeability]]
 +  * [[equivalent permeability]]
 +  * [[free space permeability]]
 +  * [[ideal permeability]]
 +  * [[imaginary permeability]]
 +  * [[impedance permeability]]
 +  * [[impulse permeability]]
 +  * [[incremental permeability]]
 +  * [[initial permeability]]
 +  * [[intrinsic permeability]]
 +  * [[linear permeability]]
 +  * [[magnetic constant]]
 +  * [[maximum permeability]]
 +  * [[non-linear permeability]]
 +  * [[peak permeability]]
 +  * [[post-saturation permeability]]
 +  * [[pulse permeability]]
 +  * [[quasi-permeability]]
 +  * [[quasi-static permeability]]
 +  * [[real permeability]]
 +  * [[recoil permeability]]
 +  * [[relative permeability]]
 +  * [[return permeability]]
 +  * [[reversible permeability]]
 +  * [[saturation permeability]]
 +  * [[scalar permeability]]
 +  * [[tensor permeability]]
 +  * [[universal magnetic constant]]
 +  * [[vacuum permeability]]
 +  * [[vector permeability]]
 +
 +==== Symbols ====
 +  * [[μ|$μ$]]
 +  * [[μ0|$μ_0$]]
 +  * [[μ0.08|$μ_{0.08}$]]
 +  * [[μ0.4|$μ_{0.4}$]]
 +  * [[μ4|$μ_4$]] 
 +  * [[μ4z|$μ_{4z}$]] 
 +  * [[μ5z|$μ_{5z}$]] 
 +  * [[μ_a|$μ_a$]] 
 +  * [[μ_core|$μ_{core}$]] 
 +  * [[μ_e|$μ_e$]] 
 +  * [[μ_eff|$μ_{eff}$]]
 +  * [[μ_gap|$μ_{gap}$]]
 +  * [[μ_i|$μ_i$]] 
 +  * [[μ_m|$μ_m$]] 
 +  * [[μ_max|$μ_{max}$]] 
 +  * [[μ_max_cc|$μ_{max\;cc}$]]
 +  * [[μ_max_dc|$μ_{max\;dc}$]]  
 +  * [[μ_p|$μ_{p}$]]
 +  * [[μ_p_max|$μ_{p\;max}$]] 
 +  * [[μ_r|$μ_r$]] 
 +  * [[μ_rev|$μ_{rev}$]] 
 +  * [[μ_s|$μ_s$]] ($μ_s'$ and $μ_s''$)   
 +  * [[μz8|$μ_{z8}$]] 
 +  * [[μ complex|$\bar{μ}$]] (μ complex)
 +  * [[mu]]
 +
 +===== References =====
 +~~REFNOTES~~
 +
 +{{tag>Permeability Counter}}

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