Permittivity Definition and 135 Threads

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...

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...

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...

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...

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...

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...

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...

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...

[SIZE="4"]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...

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?

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...

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...

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...

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...

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...

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...

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...

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"...

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...

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...

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...

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...

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?

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...

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...

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...

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

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...

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??

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...

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...

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...

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...

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...

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

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?

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...

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...

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

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...

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...

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?

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.

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...

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...

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...

I read that in some ferroelectrics,such as Barium Titanate, dielectric permittivity approaches infinity near Curie point. For example,for Barium Titanate it`s closer to 120 centigrads. Do those effect allow as (in theory) create capacitor with almost unlimited energy density?Or there are...

What does negative electric permittivity mean?

I read from a paper that we can generate the permittivity variation by low-frequency electro-optic modulation. So, does anyone know, how this modulation changes the permittvity? or a link will be appreciated!

Hi, It is seen that noble metals (gold, silver) show a negative permittivity in optical frequencies. Can somebody explain the physical interpretation of this phenomena? How is the negative permittivity measured? Really appreciate if someone could point me in the correct direction. Thanks.