What is Permeability: Definition and 126 Discussions

Permeability in fluid mechanics and the Earth sciences (commonly symbolized as k) is a measure of the ability of a porous material (often, a rock or an unconsolidated material) to allow fluids to pass through it.
The permeability of a medium is related to the porosity, but also to the shapes of the pores in the medium and their level of connectedness. Fluid flows can be influenced in different lithological settings by brittle deformation of rocks in fault zones; the mechanisms by which this occurs are the subject of fault zone hydrogeology.

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  1. S

    Total Magnetic Flux Density Law Problem

    We know Total Magnetic Flux B = B_0 + B_m Where, B_0 is the external field and B_m is the field inside a material. Now, we get, B = B_0 + μ_0*M (M is the magnetization) My question is - Do I always have to use μ_0 ? If yes then Why? The material isn't free space, is it?& also B =...
  2. B

    Magnetic flux density calculation for high permeability material

    Hi to all of you, As the Biot-Savart-Law is based on experimentations in air, i like to know how to calculate the magnetic flux density in material with much greater permeability, where the circular like shape of the field distribution troughout the vicinity does not apply. Does anyone has a...
  3. D

    Problem in Magnetic Field and magnetic effect of electric current

    I read in class 10. I am having problem understanding magnetic fields, magnetic flux,magnetic flux density,magnetic field strength,magnetic permeability and strength of magnetic field produced due to a straight and closed loop current carrying conductor at a certain point at a certain distance...
  4. BINNOY.S.P

    Have i got the DIFFERENCE BETWEEN PERMITTIVITY AND PERMEABILITY Right?

    Hi, Just wanted to know the difference between permittivity and permeability. As far as I researched, permittivity is resistance to the creation of electric field and permeability is like an allowance of a medium to the creation of a magnetic field. Is it right? I get confused because in...
  5. A

    Magnetic coercivity and relative permeability

    So when looking at a hysteresis loop, the x-axis is the magnitude of H-field, and the y-axis is the magnitude of B-field. H is in units of electricity and B is in units of magnetic flux density. My question relates to how coercivity is determined if the material being magnetized has a...
  6. L

    Meaning Of Permeability Of Free Space

    When we talk about the permeability of free space, are we talking about something with physical meaning on its own? Or is it simply a useful constant? If it does have meaning on its own, what exactly is that meaning?
  7. M

    Magnetic susceptibility and relative permeability

    Homework Statement find the derivation of χm=μr-1 where Xm is the magnetic susceptibility and μ is the relative permeability. Homework Equations M=Xm.H M is the magnetization,H is the magnetic field μr=μ/μo where μo is the permeability of a vacuum, The Attempt at a Solution I...
  8. X

    Predict Magnetic Permeability?

    Is there any way to predict an approximation for the magnetic permeability of an alloy? I imagine that getting accurate results would be near impossible without creating the alloy and then testing it, so I'm looking more for just an order of magnitude (10x) or even a tolerance of maybe ± 50% or...
  9. S

    Why does altering permeability of an ion affect equilibrium potential

    It seems to me that change in permeability should not shift the equilibrium of entering and exiting ions, except how fast equilibrium is reached. Consider this: two compartments are separated by a membrane. 1st compartment holds 1mM Na+ and 10mM K+ and 2nd one holds 10mM Na+ and 1mM K+. Let's...
  10. Y

    Polymer low permeability for balls

    I have 2 interesting questions, I believe, regarding polymer properties. I am designing a ball (pretty much like a basketball in size and appearance) to be used inside pressure vessels for certain corrosive fluids. The ball is inflated with air to a certain pressure in order to cushion extreme...
  11. J

    Permittivity and Permeability affect propagation velocity?

    If I understand correctly in refraction, photon absorption and re-emission accounts for light taking "longer" to travel. Regarding Permeability and Permittivity, the below linked website states: "permittivity affects the speed of propagation of a wave through a medium"...
  12. B

    Experimental measurements of relative magnetic permeability

    I am trying to measure the relative permeability of a few materials, but the numbers I'm getting don't quite make sense. Maybe someone here can figure out what might be going wrong. My setup is as follows. I'm making solenoids using 30 AWG magnet wire wrapped around ferrite, steel and wood...
  13. T

    Magnetic Susceptibility VS. Relative Permeability

    What is the difference between the two and what are the applications of them in a magnetic material?
  14. A

    Magnetic permeability of air compared to ferrous materials

    The answer I'm hoping to achieve from this discussion is how high a field applied to air has to be in order for it's magnetic flux to match the magnetic flux of a ferrous material. As you may know, ferrous materials are used as magnetic cores, but once the applied field reaches a certain...
  15. E

    Use of tensors for dielectric permittivity and magnetic permeability

    Hello! In the study of electric and magnetic fields, two equations are called the constitutive relations of the medium (the vacuum, for example): \mathbf{D} = \mathbf{\epsilon} \cdot \mathbf{E}\\ \mathbf{B} = \mathbf{\mu} \cdot \mathbf{H} But in a generic medium (non linear, non...
  16. D

    Measuring the permeability of metallic objects

    Hello everyone. I'm working on a project where I have to do a finite element simulation of low frequency magnetic coupling. But my problem is that I don't know the permeability of all the objects involved. Can anyone suggest a good way to measure the permeability of these objects ? The objects...
  17. R

    Transformer output indepedent of core permeability

    I am having trouble pinning down why the relative permeability of a transformer core will not directly affect the output voltage. In fact the voltage is determined by the turns ratio and is independent of mu of core material. Given this where is the flaw in the following reasoning: Induced...
  18. I

    What is the magnetic permeability of clay?

    I am trying to apply the law of mixtures to a clay-steel magnetic composite. To determine the optimal ratio per unit mass I need the permeability of steel and clay and the density of steel and clay. The permeability permeability of steel and the density of steel and clay is easy enough to find...
  19. A

    Decrease permeability of ferromagnetic materials

    Hello. I know very few things about solid state physics, so my question is very basic.. I'm just searching for a clue.. Have some of you ever heard about, or imagine a way, of decreasing the permeability of a ferromagnetic material? Not by raising temperature, but with electric field or...
  20. D

    Vacuum Permeability: SI Base Units, Amps-2 Power

    I got the following for the units of Vacuum permeability: H•m−1 A2•s-2•kg•m T•m•A-1 N•A−2 V•s•A-1•m-1 Wb•A-1•m-1 Does anyone see anything wrong with these units? Are the SI base units correct? A2·s4·kg−1·m−3 in SI base units Should it be (Amps)-2 power?
  21. Roodles01

    Input of permeability of free space μ

    μμHomework Statement Permeability of free space: symbol: μ value: 4∏x10-7 Homework Equations How would this be input to a calculator? (4∏)x10-7 4x ∏x10-7 The Attempt at a Solution so the actual number is 1.2566x10-6 is it?
  22. U

    Relative Permitttivity & Relative Permeability Dependency

    Hi Everyone, I want to know that is there anyway to relate the relative permittivity (εr) & relative permeability (μr) ?... I am having relative permittivity of an material & i want to find out its relative permeability ... Like if εr = 2.2, then μr = ?... Please reply ...
  23. N

    Magnetic fields and Permeability

    Basically I just wanted to know how magnetic fields work when a highly Permeable material is placed close to a magnet. I mean normally a magnetic field as far as I know expands out it all directions whether it is from a wire or a coil or a magnet, but what happens when a Permeable material is...
  24. M

    Annealing mu-metal in hydrogen to retain max permeability?

    Mumetal is a high magnetic permeability alloy. It is known any kind of mechanical deformation changes its microstructure leading to loss of superior magnetic properties. Annealing of machined parts fabricated from mumetal is standard. I keep reading in literature, perhaps everyone getting...
  25. H

    Haow is magnetic permeability measured?

    My research is related to magnetism and I'm supposed to have a good understanding of permeability but I'm afraid I don't. My question is that how is permeability of a mater measured so that it becomes independent of the geometry and configuration? Thanks.
  26. B

    Speed of light, permeability and permitivity of free space

    See attachment for my text's explanation's on the permittivity and permeability of free space, if you want but it's not necessary. Anyway, after reading those explanations of the p & p of free space I'm having a very difficult time understanding why taking the inverse square root of the product...
  27. M

    Complex permeability and permittivity

    Hello All, I have a question regarding complex permeability and permittivity, in particular, regarding their use with the complex refractive index in Mie theory. If the material is not dielectric, the permeability/permittivity needs to be accounted for while calculating the scattering...
  28. L

    Speed of light - permeability?

    so what i am about to write is quite possibly wrong, but this is just how i was thinking about why the speed of light is different in a vacuum as it is in glass or water etc. i am writing this to see whether my train of thought is on the right lines, and if it isn't to hopefully get an insight...
  29. P

    Permeability of Free Space: Units & Value

    In Hartle's book on General Relativity, page 47 footnote 1, it says: "You might be used to thinking that quantities called \epsilon_0 and \mu_0 are the basic parameters in Maxwell's equations, but \mu_0 \equiv 4\pi \times 10^{-7} is a pure number, and \epsilon_0 = 1/(c^2 \mu_0)." But as far as...
  30. T

    Normal determination to estimate permeability

    "normal" determination to estimate permeability I'm working on a magnetic circuit using a cast steel rectangular core with a .0008m air gap. There is a hint the question that says, 'Use a "normal" determination to estimate μ from the graph.' What exactly is a "normal" determination...
  31. H

    Medical Why Does Permeability Alter Membrane Potential?

    I've just finished reading through the generally well-written Wikipedia article on membrane potential: http://en.wikipedia.org/wiki/Membrane_potential I found almost everything to be clear, but one question is nagging at me. Why do changes in membrane permeability directly affect membrane...
  32. S

    Does Magnetic Permeability Affect Magnet Lifting Power?

    Does a material's magnetic permeability affect how much of said material a magnet can lift? For example, say a magnet can lift 1 unit of weight of a material with a permeability of 2. If another material has a permeability of 4, could the same magnet instead lift 2 units of weight of this...
  33. C

    Why does the permeability of free space invoke pi?

    I'm not asking a question of what is permeability, but rather why is pi involved in its definition of 4pi x10^-7? As far as I know, pi is generally only used whenever dealing with a circle. How does the idea of magnetism relate to a circle?
  34. L

    Permeability, permittivity and susceptibility

    I got a little confused of these three things by my teacher and Griffiths. I am acquaintanced with Feynman's lectures on physics and what I get from there is \epsilon=\epsilon_{r}\epsilon_{0} = \left(1+\chi\right)\epsilon_{0} For some reason Griffiths, as well as my teacher, likes to use...
  35. N

    Understanding Permeability of Space

    I've always found this interesting especially because I never really knew what it means hehe. What is permeability of space? To me it sounds like the maximum speed that a wave can go through space, and space is assigned a constant for its ability in suppressing its magnitude of speed ...
  36. PolywellGuy

    What is Teflon's Magnetic Permeability?

    Hello, What is Teflon's Magnetic Permeability? It is very close to Chloroform's Magnetic Permeability. It is not easily found in a google search or on Wikipedia or in papers. It is measured in [Henrys/Meter] and is a measure of how well a material "conducts" magnetic fields. I have...
  37. A

    What is the relationship between permeability and dielectric constant?

    what is the difference between permeability and dielectric constant? advanced thanks.
  38. S

    Negative permeability of split ring resonators(SRR)

    Negative permeability of split ring resonators(SRR) is obtained between the resonant frequency and the Plasma frequency of the SRRs, then what is the meaning 'eigenfrequency' of split ring resonator(SRR). Is eigenfrequncy is that 'frequency' at what negative permeability occur ??
  39. J

    Changing/Controling relative permeability

    Hey everyone, I've been looking at metamaterials, and it's quite an overwhelming subtopic to be introduced to. Most of the stuff I'm finding has to do with negative permeabilities. I'm wondering how exactly we control what relative permeability a material has and how fine that control is, not...
  40. J

    Permeability of a Steel screw

    Hello All, I'm working on a project involving the use of electromagnets and I am trying to do some calculations to predict the B-Field strength of the coils I make. For the core, I'm just using some common 1/4-20 steel machine screws (the common ones you can get from Home Depot and Lowes) but...
  41. B

    What is the Permeability of Semi Porous Materials?

    Hi, I'm working on a presentation on Permeability. I need some basic information to start off. However, when i google permeability, all i get is magnetic permeability or permeability of the different types of soils. I'm more interested in the permeability of particles through semi porous...
  42. W

    Electron spin and magnetic permeability

    Well, This is my first post, I used to read topics here, time to make one! Consider we have an oscillating magnetic field acting on a paramagnetic material, would this cause the unpaired electrons to alter their spin with the same frequency ? If so, would this affect the magnetic...
  43. M

    Looking for a material with high mag. permeability, but low residual mag.

    Hi, I am trying to make a electromagnet to attract a ferrous material.. Currently I am using Iron and permalloy cores for my coil electromagnets, but the residual magnetism is higher than I'd like. Is there any material with a high magnetic permeability AND low residual magnetism? Thanks...
  44. F

    Metal Permeability - Definition & Properties

    Metal "permeability" I went to the Von Braun planetarium the other day and was surprised to find out that their planetarium dome was a prototype for the Saturn V's Fuel tank! As a result, it wasn't exactly hemi-spherical which threw off come constellations, but that's another story. I...
  45. J

    Equation for Permeability of an electromagnetic core

    well i hope I am posting this in the right section, I am new here. im making some electromagnets for a personal project I am doing but i want to get all the calculations done before i get all the materials and actually build the thing. i need to know what/if there is an equation to find...
  46. T

    Question about magnetizing field and recoil permeability

    Hey everyone, I'm trying to work out the current I would require to produce a 44kOe magnetizing field in a radial solenoid. From my understanding, in order to do this I need the relative permeability of my material, the inductance of my coil, as well as the number of turns in the coil and it's...
  47. O

    Magnetic Permeability: Definition & Meaning

    What is permeability? I know that it's the ratio between B and H but didn't understand exactly the physical meaning of this concept
  48. O

    Permeability and Permittivity of Free space versus particules

    We know for sure €0 and µ0 for free space. We know as well €r and µr for material Have theses values been calculated for stand alone particles like an electron, a proton or a neutron? Have somebody then connected theses values to an atom (of hydrogen for example) which is a combination of...
  49. C

    Electromagnet and core permeability

    A magnet is attached (or over a small airgap) to the end of an electromagnet (EM) with a steel core, then the EM is pulsed with just enough juice to get the magnet to drop off. (just negating the attraction) Which will require less energy input to get it to drop off? 1) a high permeability...
  50. K

    Confusing on permeability and relative permeability

    In some textbook of fundamental electromagnetism, the relation between magnetic field \vec{B} and so called magnetizing field \vec{H} is \vec{B} = \mu_0\vec{H} But later on, they introduce a so called relative permeability \mu_r = \frac{\mu}{\mu_0} I might be wrong but my...
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