Magnetic permeability- physical quantity, coefficient (depending on the properties of the medium) characterizing the relationship between magnetic induction texvc not found; See math/README for setup help.): (B) and magnetic field strength Unable to parse expression (Executable file texvc not found; See math/README for setup help.): (H) in matter. For different environments this coefficient is different, so they talk about the magnetic permeability of a particular medium (meaning its composition, state, temperature, etc.).
First found in Werner Siemens's 1881 work "Beiträge zur Theorie des Elektromagnetismus" ("Contribution to the Theory of Electromagnetism").
Usually denoted Greek letter Unable to parse expression (Executable file texvc . It can be either a scalar (for isotropic substances) or a tensor (for anisotropic substances).
In general, the relationship between magnetic induction and magnetic field strength through magnetic permeability is introduced as
Unable to parse expression (Executable filetexvc not found; See math/README for setup help.): \vec(B) = \mu\vec(H),
And Unable to parse expression (Executable file texvc not found; See math/README for setup help.): \mu in the general case, this should be understood as a tensor, which in component notation corresponds to:
texvc not found; See math/README - help with setup.): \ B_i = \mu_(ij)H_j
For isotropic substances the ratio:
Unable to parse expression (Executable filetexvc not found; See math/README for setup help.): \vec(B) = \mu\vec(H)
can be understood in the sense of multiplying a vector by a scalar (magnetic permeability is reduced in this case to a scalar).
Often the designation Unable to parse expression (Executable file texvc not found; See math/README for setup help.): \mu is used differently than here, namely for relative magnetic permeability (in this case Unable to parse expression (Executable file texvc not found; See math/README for setup help.): \mu coincides with that in the GHS).
The dimension of absolute magnetic permeability in SI is the same as the dimension of the magnetic constant, that is, Gn / or / 2.
Relative magnetic permeability in SI is related to magnetic susceptibility χ by the relation
Unable to parse expression (Executable filetexvc not found; See math/README - help with setup.): \mu_r = 1 + \chi,
Classification of substances by magnetic permeability value
The vast majority of substances belong either to the class of diamagnets ( Unable to parse expression (Executable file texvc not found; See math/README for setup help.): \mu \lessapprox 1), or to the class of paramagnets ( Unable to parse expression (Executable file texvc not found; See math/README for setup help.): \mu \gtrapprox 1). But a number of substances (ferromagnets), for example iron, have more pronounced magnetic properties.
In ferromagnets, due to hysteresis, the concept of magnetic permeability, strictly speaking, is not applicable. However, in a certain range of changes in the magnetizing field (so that the residual magnetization can be neglected, but before saturation), it is still possible, to a better or worse approximation, to present this dependence as linear (and for soft magnetic materials the lower limit may not be too significant in practice), and in In this sense, the value of magnetic permeability can also be measured for them.
Magnetic permeability of some substances and materials
Magnetic susceptibility of some substances
Magnetic susceptibility and magnetic permeability of some materials
| Medium | Susceptibility χ m (volume, SI) |
Permeability μ [H/m] | Relative permeability μ/μ 0 | A magnetic field | Maximum frequency |
|---|---|---|---|---|---|
| Metglas (English) Metglas ) | 1,25 | 1 000 000 | at 0.5 T | 100 kHz | |
| Nanoperm Nanoperm ) | 10×10 -2 | 80 000 | at 0.5 T | 10 kHz | |
| Mu metal | 2.5×10 -2 | 20 000 | at 0.002 T | ||
| Mu metal | 50 000 | ||||
| Permalloy | 1.0×10 -2 | 70 000 | at 0.002 T | ||
| Electrical steel | 5.0×10 -3 | 4000 | at 0.002 T | ||
| Ferrite (nickel-zinc) | 2.0×10 -5 - 8.0×10 -4 | 16-640 | 100 kHz ~ 1 MHz [[K:Wikipedia:Articles without sources (country: Lua error: callParserFunction: function "#property" was not found. )]][[K:Wikipedia:Articles without sources (country: Lua error: callParserFunction: function "#property" was not found. )]] | ||
| Ferrite (manganese-zinc) | >8.0×10 -4 | 640 (or more) | 100 kHz ~ 1 MHz | ||
| Steel | 8.75×10 -4 | 100 | at 0.002 T | ||
| Nickel | 1.25×10 -4 | 100 - 600 | at 0.002 T | ||
| Neodymium magnet | 1.05 | up to 1.2-1.4 T | |||
| Platinum | 1.2569701×10 -6 | 1,000265 | |||
| Aluminum | 2.22×10 -5 | 1.2566650×10 -6 | 1,000022 | ||
| Tree | 1,00000043 | ||||
| Air | 1,00000037 | ||||
| Concrete | 1 | ||||
| Vacuum | 0 | 1.2566371×10 -6 (μ 0) | 1 | ||
| Hydrogen | -2.2×10 -9 | 1.2566371×10 -6 | 1,0000000 | ||
| Teflon | 1.2567×10 -6 | 1,0000 | |||
| Sapphire | -2.1×10 -7 | 1.2566368×10 -6 | 0,99999976 | ||
| Copper | -6.4×10 -6 or -9.2×10 -6 |
1.2566290×10 -6 | 0,999994 | ||
| Water | -8.0×10 -6 | 1.2566270×10 -6 | 0,999992 | ||
| Bismuth | -1.66×10 -4 | 0,999834 | |||
| Superconductors | −1 | 0 | 0 |
see also
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Notes
Excerpt characterizing Magnetic permeability
I felt so sorry for him!.. But, unfortunately, I was not in my power to help him. And I honestly really wanted to know how this extraordinary little girl helped him...- We found them! – Stella repeated again. – I didn’t know how to do it, but my grandmother helped me!
It turned out that Harold, during his lifetime, did not even have time to find out how terribly his family suffered while dying. He was a warrior knight, and died before his city fell into the hands of the “executioners,” as his wife predicted.
But as soon as he found himself in this unfamiliar, wondrous world of “gone” people, he was immediately able to see how mercilessly and cruelly they treated his “only and loved ones” evil fate. Afterwards, like one possessed, he spent an eternity trying somehow, somewhere to find these people, the most dear to him in the whole wide world... And he searched for them for a very long time, more than a thousand years, until one day, some completely unfamiliar person, sweet girl Stella didn’t offer to “make him happy” and didn’t open that “other” door to finally find them for him...
- Do you want me to show you? - the little girl suggested again,
But I was no longer so sure whether I wanted to see something else... Because the visions she had just shown hurt my soul, and it was impossible to get rid of them so quickly to want to see some kind of continuation...
“But you want to see what happened to them!” – little Stella confidently stated the “fact”.
I looked at Harold and saw in his eyes complete understanding of what I had just unexpectedly experienced.
– I know what you saw... I watched it many times. But they are happy now, we go to look at them very often... And at their “former” ones too... - the “sad knight” said quietly.
And only then I realized that Stella, simply, when he wanted it, transferred him to his own past, just like she had just done!!! And she did it almost playfully!.. I didn’t even notice how this wonderful, bright girl began to “tie me to her” more and more, becoming for me almost a real miracle, which I endlessly wanted to watch... And whom I didn’t want to leave at all... Then I knew almost nothing and couldn’t do anything except what I could understand and learn myself, and I really wanted to learn at least something from her while there was still such an opportunity.
- Please come to me! – Stella, suddenly saddened, whispered quietly, “you know that you can’t stay here yet... Grandma said that you won’t stay for a very, very long time... That you can’t die yet.” But you come...
Everything around suddenly became dark and cold, as if black clouds had suddenly covered such a colorful and bright Stella world...
- Oh, don’t think about such terrible things! – the girl was indignant, and, like an artist with a brush on a canvas, she quickly “painted over” everything again in a light and joyful color.
- Well, is this really better? – she asked contentedly.
“Was it really just my thoughts?..” I didn’t believe it again.
- Surely! – Stella laughed. “You’re strong, so you create everything around you in your own way.”
– How then to think?.. – I still couldn’t “enter” the incomprehensible.
“Just shut up and show only what you want to show,” my amazing friend said, as a matter of course. “My grandmother taught me that.”
I thought that apparently it was time for me, too, to “shock” my “secret” grandmother a little, who (I was almost sure of this!) probably knew something, but for some reason did not want to teach me anything yet.. .
“So you want to see what happened to Harold’s loved ones?” – the little girl asked impatiently.
To be honest, I didn’t have too much desire, since I wasn’t sure what to expect from this “show.” But in order not to offend the generous Stella, she agreed.
– I won’t show you for a long time. I promise! But you should know about them, right?.. – the girl said in a happy voice. - Look, the son will be first...
To my great surprise, unlike what I had seen before, we found ourselves in a completely different time and place, which was similar to France, and the clothes were reminiscent of the eighteenth century. A beautiful covered carriage was driving along a wide cobbled street, inside of which were sitting a young man and a woman in very expensive suits, and apparently in a very bad mood... The young man stubbornly proved something to the girl, and she, not listening to him at all, hovered calmly somewhere in her dreams, which really irritated the young man...
- You see, it’s him! This is the same " a little boy“... only after many, many years,” Stella whispered quietly.
- How do you know that it’s really him? – still not quite understanding, I asked.
- Well, of course, it’s very simple! – the little girl stared at me in surprise. – We all have an essence, and the essence has its own “key” by which each of us can be found, you just need to know how to look. Here look...
She showed me the baby again, Harold's son.
– Think about his essence, and you will see...
And I immediately saw a transparent, brightly glowing, surprisingly powerful entity, on whose chest an unusual “diamond” energy star was burning. This “star” shone and shimmered with all the colors of the rainbow, now decreasing, now increasing, as if slowly pulsating, and sparkled so brightly, as if it had really been created from the most stunning diamonds.
– Do you see this strange inverted star on his chest? - This is his “key”. And if you try to follow him, like a thread, then it will lead you straight to Axel, who has the same star - this is the same essence, only in its next incarnation.
I looked at her with all my eyes, and apparently noticing this, Stella laughed and cheerfully admitted:
– Don’t think that it was me myself – it was my grandmother who taught me!..
I was very ashamed to feel like a complete incompetent, but the desire to know more was a hundred times stronger than any shame, so I hid my pride as deeply as possible and carefully asked:
– But what about all these amazing “realities” that we are seeing here now? After all, this is someone else’s, specific life, and you don’t create them in the same way as you create all your worlds?
- Oh no! – the little girl was again glad to have the opportunity to explain something to me. - Of course not! This is just the past in which all these people once lived, and I’m just taking you and me there.
- And Harold? How does he see all this?
- Oh, it’s easy for him! He’s just like me, dead, so he can move wherever he wants. After all, he no longer has a physical body, so his essence does not know any obstacles here and can walk wherever it wants... just like me... - the little girl finished more sadly.
I sadly thought that what was for her just a “simple transfer into the past”, for me, apparently for a long time will be a “mystery behind seven locks”... But Stella, as if hearing my thoughts, immediately hurried to reassure me :
- You'll see, it's very simple! You just have to try.
– And these “keys”, are they never repeated by others? – I decided to continue my questions.
“No, but sometimes something else happens...” for some reason, the little one answered, smiling funny. “That’s exactly how I got caught at the beginning, for which they even beat me up very badly... Oh, that was so stupid!..”
- But as? – I asked, very interested.
Stella immediately answered cheerfully:
- Oh, that was very funny! - and after thinking a little, she added, “but it’s also dangerous... I was looking on all the “floors” for the past incarnation of my grandmother, and instead of her, a completely different entity came along her “thread”, which somehow managed to “copy” my grandmother’s “ flower" (apparently also a "key"!) and, just as I had time to rejoice that I had finally found it, this unfamiliar entity mercilessly hit me in the chest. Yes, so much that my soul almost flew away!..
- How did you get rid of her? – I was surprised.
“Well, to be honest, I didn’t get rid of it...” the girl became embarrassed. - I just called my grandmother...
– What do you call “floors”? – I still couldn’t calm down.
– Well, these are different “worlds” where the essences of the dead live... In the most beautiful and highest live those who were good... and, probably, the strongest too.
- People like you? – I asked, smiling.
- Oh, no, of course! I probably got here by mistake. – The girl said completely sincerely. – Do you know what’s most interesting? From this “floor” we can walk everywhere, but from the others no one can get here... Isn’t that interesting?..
Yes, it was very strange and very excitingly interesting for my “starved” brain, and I really wanted to know more!.. Maybe because until that day no one had ever really explained anything to me, but just sometimes someone - gave (like, for example, my “star friends”), and therefore, even such a simple childish explanation already made me unusually happy and made me delve even more furiously into my experiments, conclusions and mistakes... as usual, finding in everything that was happening even more unclear. My problem was that I could do or create “unusual” very easily, but the whole problem was that I also wanted to understand how I create it all... And this is precisely what I have not been very successful in yet ...
From many years of technical practice, we know that the inductance of a coil strongly depends on the characteristics of the environment where the coil is located. If a ferromagnetic core is added to a coil of copper wire with a known inductance L0, then, under other previous circumstances, the self-induction currents (extra currents of closure and opening) in this coil will increase many times, experiment will confirm this, which will mean increased several times, which now will become equal to L.
Experimental observation
Let us assume that the environment, the substance filling the space inside and around the described coil, is homogeneous, and generated by the current flowing through its wire, is localized only in this designated area, without going beyond its boundaries.
If the coil has a toroidal shape, the shape of a closed ring, then this medium together with the field will be concentrated only inside the volume of the coil, because outside the toroid there is almost completely no magnetic field. This position is also true for a long coil - a solenoid, in which all the magnetic lines are also concentrated inside - along the axis.
For example, let us assume that the inductance of a certain circuit or coil without a core in a vacuum is equal to L0. Then for the same coil, but in a homogeneous substance that fills the space where magnetic fields are present power lines of a given coil, let the inductance be equal to L. In this case, it turns out that the ratio L/L0 is nothing more than the relative magnetic permeability of the named substance (sometimes they simply say “magnetic permeability”).
It becomes obvious: magnetic permeability is a quantity that characterizes the magnetic properties of a given substance. It often depends on the state of the substance (and on the conditions environment, such as temperature and pressure) and its type.
Understanding the term
The introduction of the term “magnetic permeability” in relation to a substance placed in a magnetic field is similar to the introduction of the term “dielectric constant” for a substance located in an electric field.
The value of magnetic permeability, determined by the above formula L/L0, can also be expressed as the ratio of the absolute magnetic permeability of a given substance and absolute emptiness (vacuum).
It is easy to notice: relative magnetic permeability (also known as magnetic permeability) is a dimensionless quantity. But the absolute magnetic permeability has the dimension H/m, the same as that of the magnetic permeability (absolute!) of vacuum (it is also the magnetic constant).
In fact, we see that the medium (magnet) affects the inductance of the circuit, and this clearly indicates that a change in the medium leads to a change in the magnetic flux F penetrating the circuit, and therefore to a change in induction B, applied to any point in the magnetic field.
The physical meaning of this observation is that with the same coil current (at the same magnetic intensity H), the induction of its magnetic field will be a certain number of times greater (in some cases less) in a substance with magnetic permeability mu than in a complete vacuum.
This happens because , and itself begins to have a magnetic field. Substances that can be magnetized in this way are called magnets.
The unit of measurement for absolute magnetic permeability is 1 GN/m (Henry per meter or Newton per ampere squared), that is, it is the magnetic permeability of a medium where, at a magnetic field strength H equal to 1 A/m, a magnetic induction of 1 T occurs.
Physical picture of the phenomenon
From the above it becomes clear that various substances(magnets) under the influence of a magnetic field, the circuits with current are magnetized, and the result is a magnetic field, which is the sum of magnetic fields - the magnetic field from the magnetized medium plus from the circuit with current, therefore it differs in magnitude from the field of only the circuit with current without the medium. The reason for the magnetization of magnets lies in the existence of tiny currents inside each of their atoms.
According to the value of magnetic permeability, substances are classified into diamagnetic (less than unity - magnetized against the applied field), paramagnetic (greater than unity - magnetized in the direction of the applied field) and ferromagnetic (strongly greater than unity - magnetized, and possess magnetization after turning off the applied magnetic field).
It is characteristic of ferromagnets, therefore the concept of “magnetic permeability” in its pure form is not applicable to ferromagnets, but in a certain magnetization range, to some approximation, it is possible to identify a linear section of the magnetization curve for which it will be possible to estimate the magnetic permeability.
Superconductors have a magnetic permeability of 0 (since the magnetic field is completely displaced from their volume), and the absolute magnetic permeability of air is almost equal to mu of vacuum (read magnetic constant). For air, the relative mu is slightly greater than 1.
Magnetic permeability is different for different media and depends on its properties, therefore it is customary to talk about the magnetic permeability of a specific medium (meaning its composition, state, temperature, etc.).
In the case of a homogeneous isotropic medium, magnetic permeability μ:
μ = V/(μ o N),
In anisotropic crystals, magnetic permeability is a tensor.
Most substances are divided into three classes according to their magnetic permeability:
- diamagnetic materials ( μ < 1 ),
- paramagnets ( μ > 1 )
- ferromagnets (possessing more pronounced magnetic properties, such as iron).
The magnetic permeability of superconductors is zero.
The absolute magnetic permeability of air is approximately equal to the magnetic permeability of vacuum and in technical calculations is taken equal to 4π 10 -7 Gn/m
μ = 1 + χ (in SI units);
μ = 1 + 4πχ (in GHS units).
Magnetic permeability of physical vacuum μ =1, since χ=0.
Magnetic permeability shows how many times the absolute magnetic permeability of this material greater than the magnetic constant, i.e., how many times the magnetic field of macrocurrents N is enhanced by the field of microcurrents in the environment. Magnetic permeability of air and most substances, with the exception of ferro magnetic materials, is close to unity.
Several types of magnetic permeability are used in technology, depending on the specific applications of the magnetic material. Relative magnetic permeability shows how many times in a given medium the force of interaction between wires with current changes compared to vacuum. Numerically equal to the ratio of absolute magnetic permeability to magnetic constant. Absolute magnetic permeability is equal to the product of magnetic permeability and magnetic constant.
Diamagnets have χμχ>0 and μ > 1. Depending on whether μ of ferromagnets is measured in a static or alternating magnetic field, it is called static or dynamic magnetic permeability, respectively.
The magnetic permeability of ferromagnets depends in a complex way on N . From the magnetization curve of a ferromagnet, one can construct the dependence of magnetic permeability on N.
Magnetic permeability, determined by the formula:
μ = V/(μ o N),
called static magnetic permeability.
It is proportional to the tangent of the secant angle drawn from the origin through the corresponding point on the main magnetization curve. The limiting value of magnetic permeability μ n when the magnetic field strength tends to zero is called the initial magnetic permeability. This characteristic is of utmost importance in the technical use of many magnetic materials. It is determined experimentally in weak magnetic fields with a voltage of the order of 0.1 A/m.
Magnetic permeability is different for different media and depends on its properties, therefore it is customary to talk about the magnetic permeability of a specific medium (meaning its composition, state, temperature, etc.).
In the case of a homogeneous isotropic medium, magnetic permeability μ:
μ = V/(μ o N),
In anisotropic crystals, magnetic permeability is a tensor.
Most substances are divided into three classes according to their magnetic permeability:
- diamagnetic materials ( μ < 1 ),
- paramagnets ( μ > 1 )
- ferromagnets (possessing more pronounced magnetic properties, such as iron).
The magnetic permeability of superconductors is zero.
The absolute magnetic permeability of air is approximately equal to the magnetic permeability of vacuum and in technical calculations is taken equal to 4π 10 -7 Gn/m
μ = 1 + χ (in SI units);
μ = 1 + 4πχ (in GHS units).
Magnetic permeability of physical vacuum μ =1, since χ=0.
Magnetic permeability shows how many times the absolute magnetic permeability of a given material is greater than the magnetic constant, i.e., how many times the magnetic field of macrocurrents N is enhanced by the field of microcurrents in the environment. The magnetic permeability of air and most substances, with the exception of ferromagnetic materials, is close to unity.
Several types of magnetic permeability are used in technology, depending on the specific applications of the magnetic material. Relative magnetic permeability shows how many times in a given medium the force of interaction between wires with current changes compared to vacuum. Numerically equal to the ratio of absolute magnetic permeability to magnetic constant. Absolute magnetic permeability is equal to the product of magnetic permeability and magnetic constant.
Diamagnets have χμχ>0 and μ > 1. Depending on whether μ of ferromagnets is measured in a static or alternating magnetic field, it is called static or dynamic magnetic permeability, respectively.
The magnetic permeability of ferromagnets depends in a complex way on N . From the magnetization curve of a ferromagnet, one can construct the dependence of magnetic permeability on N.
Magnetic permeability, determined by the formula:
μ = V/(μ o N),
called static magnetic permeability.
It is proportional to the tangent of the secant angle drawn from the origin through the corresponding point on the main magnetization curve. The limiting value of magnetic permeability μ n when the magnetic field strength tends to zero is called the initial magnetic permeability. This characteristic is of utmost importance in the technical use of many magnetic materials. It is determined experimentally in weak magnetic fields with a strength of the order of 0.1 A/m.
Dielectric constant of substances
Substance |
Substance |
||
Gases and water vapor |
Liquids |
||
| Nitrogen | 1,0058 | Glycerol | 43 |
| Hydrogen | 1,00026 | Liquid oxygen (at t = -192.4 o C) | 1,5 |
| Air | 1,00057 | Transformer oil | 2,2 |
| Vacuum | 1,00000 | Alcohol | 26 |
| Water vapor (at t=100 o C) | 1,006 | Ether | 4,3 |
| Helium | 1,00007 | Solids |
|
| Oxygen | 1,00055 | Diamond | 5,7 |
| Carbon dioxide | 1,00099 | Waxed paper | 2,2 |
Liquids |
Dry wood | 2,2-3,7 | |
| Liquid nitrogen (at t = -198.4 o C) | 1,4 | Ice (at t = -10 o C) | 70 |
| Petrol | 1,9-2,0 | Paraffin | 1,9-2,2 |
| Water | 81 | Rubber | 3,0-6,0 |
| Hydrogen (at t= - 252.9 o C) | 1,2 | Mica | 5,7-7,2 |
| Liquid helium (at t = - 269 o C) | 1,05 | Glass | 6,0-10,0 |
| Barium titanate | 1200 | ||
| Porcelain | 4,4-6,8 | ||
| Amber | 2,8 | ||
Note. Electric constant ԑ o (dielectric constant of vacuum) equal to: ԑ o = 1\4πс 2 * 10 7 F/m ≈ 8.85 * 10 -12 F/m
Magnetic permeability of a substance
Note. Magnetic constant μ o (magnetic permeability of vacuum) is equal to: μ o = 4π * 10 -7 H/m ≈ 1.257 * 10 -6 H/m
Magnetic permeability of ferromagnets
The table shows the values of magnetic permeability for some ferromagnets (substances with μ > 1). Magnetic permeability for ferromagnetic materials (iron, cast iron, steel, nickel, etc.) is not constant. The table shows the maximum values.
1 Permalloy-68- alloy of 68% nickel and 325 iron; This alloy is used to make transformer cores.
Curie temperature
Electrical resistivity of materials
High resistance alloys
Alloy name |
Electrical resistivity µOhm m |
Alloy composition, % |
|||
Manganese |
Other elements |
||||
| Constantan | 0,50 | 54 | 45 | 1 | - |
| Kopel | 0,47 | 56,5 | 43 | 0,05 | - |
| Manganin | 0,43 | > 85 | 2-4 | 12 | - |
| Nickel silver | 0,3 | 65 | 15 | - | 20 Zn |
| Nikelin | 0,4 | 68,5 | 30 | 1,5 | - |
| Nichrome | 1,1 | - | > 60 | < 4 | 30 < Cr ост. Fe |
| Fechral | 1,3 | - | - | - | 12-15 Cr 3-4 Al 80< Fe |
Temperature coefficients of electrical resistance of conductors
Conductor |
Conductor |
||
| Aluminum | Nickel | ||
| Tungsten | Nichrome | ||
| Iron | Tin | ||
| Gold | Platinum | ||
| Constantan | Mercury | ||
| Brass | Lead | ||
| Magnesium | Silver | ||
| Manganin | Steel | ||
| Copper | Fechral | ||
| Nickel silver | Zinc | ||
| Nikelin | Cast iron |
Superconductivity of conductors
- Notes
- Superconductivity found in more than 25 metal elements and in large number alloys and compounds.
- Until recently, the superconductor with the highest transition temperature to the superconducting state -23.2 K (-250.0 o C) - was niobium germanide (Nb 3 Ge). At the end of 1986, a superconductor with a transition temperature of ≈ 30 K (≈ -243 o C) was obtained. The synthesis of new high-temperature superconductors is reported: ceramics (manufactured by sintering oxides of barium, copper and lanthanum) with a transition temperature of ≈ 90-120 K.
Electrical resistivity of some semiconductors and dielectrics
| Substance | GlassTemperature, o C | Resistivity | |
| Ohm m | Ohm mm2/m | ||
Semiconductors |
|||
| Indium antimonide | 17 | 5.8 x 10 -5 | 58 |
| Bor | 27 | 1.7 x 10 4 | 1.7 x 10 10 |
| Germanium | 27 | 0,47 | 4.7 x 10 5 |
| Silicon | 27 | 2.3 x 10 3 | 2.3 x 10 9 |
| Lead(II) selenide (PbSe) | 20 | 9.1 x 10 -6 | 9,1 |
| Lead(II) sulfide (PbS) | 20 | 1.7 x 10 -5 | 0,17 |
Dielectrics |
|||
| Distilled water | 20 | 10 3 -10 4 | 10 9 -10 10 |
| Air | 0 | 10 15 -10 18 | 10 21 -10 24 |
| Beeswax | 20 | 10 13 | 10 19 |
| Dry wood | 20 | 10 9 -10 10 | 10 15 -10 16 |
| Quartz | 230 | 10 9 | 10 15 |
| Transformer oil | 20 | 10 11 -10 13 | 10 16 -10 19 |
| Paraffin | 20 | 10 14 | 10 20 |
| Rubber | 20 | 10 11 -10 12 | 10 17 -10 18 |
| Mica | 20 | 10 11 -10 15 | 10 17 -10 21 |
| Glass | 20 | 10 9 -10 13 | 10 15 -10 19 |
Electrical properties of plastics
| Name of plastic | The dielectric constant | |
| Getinax | 4,5-8,0 | 10 9 -10 12 |
| Capron | 3,6-5,0 | 10 10 -10 11 |
| Lavsan | 3,0-3,5 | 10 14 -10 16 |
| Organic glass | 3,5-3,9 | 10 11 -10 13 |
| Styrofoam | 1,0-1,3 | ≈ 10 11 |
| Polystyrene | 2,4-2,6 | 10 13 -10 15 |
| Polyvinyl chloride | 3,2-4,0 | 10 10 -10 12 |
| Polyethylene | 2,2-2,4 | ≈ 10 15 |
| Fiberglass | 4,0-5,5 | 10 11 -10 12 |
| Textolite | 6,0-8,0 | 10 7 -10 19 |
| Celluloid | 4,1 | 10 9 |
| Ebonite | 2,7-3,5 | 10 12 -10 14 |
Specific electrical resistance of electrolytes (at t=18 o C and 10% solution concentration)
Rushing. The resistivity of electrolytes depends on temperature and concentration, i.e. from the ratio of the mass of dissolved acid, alkali or salt to the mass of dissolving water. At the specified concentration of solutions, an increase in temperature by 1 o C reduces the resistivity of a solution taken at 18 o C by 0.012 for sodium hydroxide, by 0.022 for copper sulfate, by 0.021 for sodium chloride, by 0.013 for sulfuric acid and by 0.003 - for 100 percent sulfuric acid.
Specific electrical resistance of liquids
Liquid |
Electrical resistivity, Ohm m |
Liquid |
Electrical resistivity, Ohm m |
| Acetone | 8.3 x 10 4 | Molten Salts: | |
| Distilled water | 10 3 - 10 4 | potassium hydroxide (KOH; at t = 450 o C) | 3.6 x 10 -3 |
| Sea water | 0,3 | sodium hydroxide (NaOH; at t = 320 o C) | 4.8 x 10 -3 |
| River water | 10-100 | sodium chloride (NaCl; at t = 900 o C) | 2.6 x 10 -3 |
| Air is liquid (at t = -196 o C) | 10 16 | soda (Na 2 CO 3 x10H 2 O; at t = 900 o C) | 4.5 x 10 -3 |
| Glycerol | 1.6 x 10 5 | Alcohol | 1.5 x 10 5 |
| Kerosene | 10 10 | ||
| Melted naphthalene (at (at t = 82 o C) | 2.5 x 10 7 | ||