Permittivity Definition and 143 Threads

  1. T

    Classical Looking for a book on the causes of permittivity

    I'm currently working with some materials that have a high permittivity in order to improve image quality of MRI scanners but finding it hard to find a good book that explains the various effects that contribute to a material's permittivity/dielectric constant. Can anybody point me in a good...
  2. R

    Relative permittivity of a semiconductor material

    http://physics.stackexchange.com/questions/156708/can-the-relative-permittivity-of-a-semiconductor-material-be-lower-than-1 To measure the relative permittivity of a p-type semiconductor material (a metal phthalocyanine ) , a M-S-M structure was made by thermal evaporation method. The...
  3. E

    Do Material Properties Follow a Linear Response Pattern?

    Hi all, I have a general question about material properties. We know that the material property value depends on the input level. For example, the permittivity in a dielectric material changes depending on the applied electric field. That being said, when we apply an alternating electric...
  4. H

    Faraday rotation and permittivity tensor

    Dear all, In textbooks about optics in magneto-optic materials, we often come across a Hermitian permittivity tensor with off-diagonal imaginary components. These components are relevant to the Faraday rotation of plane of polarization of light through the material. Now my question is: Is the...
  5. F

    How Can Relative Permittivity Be Measured in the Stratosphere?

    So I am a 17 years old student who is interested in electronics and programming them (I am expirienced with Arduino). I and my friends decided that we will join a competition for all technical schools in my country. The goal of the competition is to make a project that will do something while it...
  6. P

    The complex refractive index vs. permittivity

    I have a process of thought and would like to run past some other minds to point out if I am incorrect in my thinking. I am looking into conductivity in high frequencies and a lot of papers I am looking up list a complex refractive index. They list something as in nAg = 0.1453 + j11.3587...
  7. T

    What Is the Relative Permittivity of the Dielectric in This Capacitor?

    Consider a commonly-used capacitor made from two circular parallel plates with a ceramic dielectric between them. The plates have 12.5 mm diameter and the whole thing is 3 mm thick with a capacitance of 10 nF. Neglecting the finite thickness and extent of the plates, what relative permittivity...
  8. F

    Why isn't the frequency dependence of permittivity monotonic?

    I naively thought that most materials were transparent to radiation of frequencies above their plasma frequency, and opaque to radiation below it. The most intuitive (and analyzed lightly in Griffiths' E&M book) reason I've heard is that opaqueness is caused by electrons in the material...
  9. C

    How to calculate complex permittivity from complex conductivity

    Hi, I got the complex conductivity vs. frequency table of a metamaterial. Its first lines are like this: f conductivity 1GHz 0.004+0.00297i 1.1GHz 0.004+0.00295i 1.2GHz 0.003+0.00294i the table goes up to 10GHz. Now the problem is that I need to enter...
  10. 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...
  11. Greg Bernhardt

    What is Permittivity? Definition & Explanation

    Definition/Summary Permittivity, \varepsilon, of a material is its ability to separate charge when a voltage difference is applied. It equals the ratio of the electric displacement field to the total electric field in the material: \boldsymbol{D}\,=\,\varepsilon\boldsymbol{E} It is...
  12. D

    Calculating microscopic permittivity

    It has been quite some years since I last used quantum chemistry software. Now I would like to use some program which allows the calculation of the microscopic omega and k-dependent dielectric function (tensor) for periodic crystals. Any proposals?
  13. PhysicoRaj

    Electrostatic force in a medium of non uniform permittivity

    Homework Statement Two point charges, +4 μC and -10 μC are placed 10 cm apart in air. A dielectric slab of large area and thickness 5 cm is placed between the charges. Find the force of attraction between the charges, if the dielectric has a dielectric constant of 9. Homework Equations...
  14. S

    Mechanical analogue of permittivity

    I refer to the velocity of propagation of an EM wave in a medium. I have been wondering about what plays the role, in this context, of inertia and elasticity. Here the formula has nothing in the numerator and the denominator is the product of the electric permittivity by the magnetic...
  15. M

    Can the Dielectric Permittivity of a Material Be Altered?

    Hi , I would like to know if there is any material , a dielectric like the one used in a capacitor , whose dielectric permittivity could be altered , like increased or decreases , I'm not talking about older type capacitors which had plates on a rotor that could be adjusted so that one could...
  16. A

    Relative Permittivity: Exploring Static Charge & Capacitance

    Hello forum members, I am trying to wrap my head around the concept of relative permittivity. I have read the Wikipedia article on the subject, but I don't feel quite satisfied. As far as I understand it, RP is essentially a measure of how well a given material holds a static charge relative to...
  17. S

    [MATLAB] complex permittivity for earth ionosphere syntax

    Homework Statement I have these equations: ga = exp(-σ^{R}Δt/ε_{0}*ε^{R}_{r}) Homework Equations σ^{R}=(ε_{0}*ω^{2}_{p}*v)/(ω^{2}+v^{2}) The Attempt at a Solution %ionospheric profile for earth-ionosphere waveguide as coefficients e = 1.602e-19; % electron charge...
  18. C

    Electron Doping and Permittivity

    I've read that electron doping in certain materials can lead to higher permittivity (for example, Nb in TiO2). This is a little confusing to me, as permittivity decreases with conductivity (see http://en.wikipedia.org/wiki/Permittivity#Lossy_medium). Can anyone explain this to me? P.S...
  19. F

    Understanding complex permittivity

    I'm not sure if this is the appropriate forum for my question as I actually am studying this as part of electrical engineering and I don't actually study physics. Nonetheless, I shall ask and if need be, move my question to another venue. My question is with regard to how complex...
  20. J

    Gauss's Law and the permittivity of free space

    Hi, could anyone help me understand the permittivity of free space in Gauss's Law: \Phi = q/\epsilon0 If you consider a point charge in a box then I think it tells you how easy it is to establish an electric field in free space. But what happens if the medium is not free space - say you...
  21. 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"...
  22. V

    How could one theoretically predict a material's permittivity?

    I know experimentally, the permittivity of a material is ##\vec D = \epsilon \vec E##, and you can also relate the Polarization to it. So it's basically a response of the material to an applied E field. But that seems like it would be a fairly complex thing to figure out theoretically. I...
  23. zrek

    Electric field direction and permittivity

    The electric field direction can be measured by the force affected on a test charge. Let's put a point-like charge not far from a material, that is polarized by it. See the figure: The test force on the test charge A points exactly to the charge. I think that because the surface is...
  24. S

    What exactly does negative permittivity mean?

    Hi, this is my first time posting on these forums but I've been reading them for a while. I was having a look at metamaterials and it mentioned that metamaterials had negative permittivity and negative permeability. I also found that metals naturally had negative permittivity; though I am...
  25. 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...
  26. K

    Notation of permittivity in farads per meter question

    I am using an old textbook as a reference, and the equation given for the electrical permittivity of free space ε0 is given in terms of: (Fm-1) where this measurement notation represents farads per meter. Why the superscript of -1 in the notation?
  27. M

    Change of relative permittivity of liquid and solid water

    Dear Physics Forum Users Commonly, the relative permittivity of liquid water is reported to be \epsilon_r = 78.0\epsilon_0, \epsilon_0 being the dielectric constant of the vacuum. For ice (solid water), \epsilon_r = 4 \epsilon_0 (heard it in a talk once). Is it correct to interpret the...
  28. C

    How do I measure/calculate the permittivity constant of materials?

    Hi, I am trying to figure out how to calculate the permeability constant of a lot of plastics by making solenoid (because that seemed to be the best method of doing so). I am currently using: μ=Ll/((N^2)A) to calculate that constant. Using this method I will only need an induction meter...
  29. D

    Determining electric permittivity from time constant decay

    Homework Statement a slab of some insulator with an unknown permittivity ε. To determine ε experimentally I go to the lab and insert the slab in between the plates of a capacitor whose plate spacing exactly matches the width of the slab. I observe that the time constant of exponential...
  30. H

    What Is the Permittivity of Al2O3 Over 95% Polished?

    Hi I was wondering if anyone could tell me the permittivity of Al2O3 >95% polished, or how to calculate it? Any useful electrical properties websites or books would be much appreciated. Also I was wondering if the the permittivity was frequency dependent? Thanks in advance
  31. 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...
  32. A

    How permittivity arises in vacuum?

    I've read that permittivity is resistance offered to flow of field lines,But vacuum does not have anything in it to resist or alternatively to get polarized.but we've seen that vacuum has permittivity constant..How's this possible??
  33. A

    Membrane Potential and Permittivity

    Hi, Was wondering if I could get some help with part b of this question? I've attached the question and my attempt in the pictures as there was a lot of data and writing, so thought this would be the easiest way. With my attempt I think I'm missing something pretty obvious, but I'm drawing...
  34. S

    Is Permittivity Equivalent to EM Conductivity?

    I was wondering whether, making a comparison between the propagation of electric current through a conductor and the propagation of an electromagnetic wave through a dielectric, one could establish the following correspondences: Ability of a material to facilitate the propagation of the...
  35. K

    Permittivity values in conductors

    Hello All, I am a masters student in electronics engg and reading technical electrodynamics. Please let me know when the electric current density becomes more than the displacement current (for a conductor ) why is the value of ε≈-jσ/ω Quick replies will be highly appreciated! Thanks...
  36. Chronos

    Permittivity, permeabiltiy and gravity

    The speed of light is theoretically constrained by the pemittivity and permeability of the medium through which it travels. It seems counterintuitive that pemittivity and permeabilty also constrain the speed of gravity since neither electric or magnetic fields appear to have any influence on...
  37. P

    Complex Permittivity: Solving Debye's Equation

    Homework Statement The problem statement is shown on the picture [PLAIN]http://img252.imageshack.us/img252/1184/graphsq.jpg Homework Equations Debye's equation? The Attempt at a Solution Hey guys, I am trying to figure out how to obtain the equation for the graphs, but from...
  38. V

    Help on vacuum permittivity related question

    Is it possible to derive the value for vacuum permittivity(εo) without using the speed of light.?
  39. Phrak

    Vacuum permittivity as a fundemental dimensioned unit

    As the usual argument goes, as I understand it, everything can be expressed in units of G, h and c. (though this argument exclude the particle masses from consideration.) The permittivity of the vacuum seems to be independent of G,h,c. Am I wrong?
  40. G

    Does Medium Polarization Decrease Electric Field Intensity?

    When a point charge is put in a medium, it polarizes the medium and thus reduces the total electric field inside the medium... I don't understand why does the electric field reduce when the medium gets polarized... My question in other words is that, when we look at the coulomb's law, we see...
  41. 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...
  42. C

    Measuring Air Permittivity: Change in Density

    Does anyone have a method of measuring the change in permittivity due to air density.
  43. W

    Permittivity versus conductivity

    Would it be fair to say that permittivity corresponds to the opposition of a material to an electric field, whereas conductivity corresponds to the opposition of a material to the first time derivative of the field? It seems like these two concepts should have some sort of quantitative link, as...
  44. X

    Can there be a material with relative permittivity < 1?

    Just a thought experiment... Cover a metal plate with a material of relative permittivity 0 on one side. Then place a charge on the metal plate. The system as a whole will accelerate towards the metal side since there is no flux on the covered side and so the charge is accelerated in the...
  45. G

    Polarizability and permittivity

    hi i am looking for a method to calculate the polarizability and permittivity of arbitrary compounds like e.g. oxygen. does anybody know an effective method for at least one of the two constants?
  46. J

    Permittivity of free space in physics

    Hi, In my physics book I have two values for the permittivity of free space: 8.854x10^-12 c^2 N^-1 m^-2 and 8.988x10^9 N m^2 C^-2 What is the difference between these two? When would I use one or the other? Thanks.
  47. R

    Find Electric Field between Two Plates with Varying Permittivity

    We have a problem for our Electromagnetics class. It is the following "A parallel-plat capacitor of cross-sectional area A an thickness d is filled with a dielectric material whose relative permittivity varies linearly from \epsilon_{r}=1 at one plate to \epsilon_{r}=10 at the other plate...
  48. S

    Explain the term permittivity and how this affects force

    Hey everyone I just started an engineering course and have been given a few questions but I am struggling with this one as i feel that i have not included all the info that should be there. Can someone tell me briefly what they would explain the term permittivity as and how they think it would...
  49. W

    Electric Field and Coulombic Force: Effect of Halving Electrical Permittivity

    Hi, I was just wondering if you had an electric field which had the coulombic force acting on the two charges as: F1= (1/4πε)*(q1q2/d2) Then what would happen to the force if you placed the charges in a medium of half the electrical permittivity? I tried to solve this using ratios and got...
  50. E

    Permittivity Constant and Coulomb's Law

    This is more of a general question than a homework problem. We haven't gotten too far into e&m so maybe there is a different use for this later on that I just haven't seen yet. Even skipping 7-8 chapters ahead, it is still used in the same way. What is the point of using...
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