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Questions tagged [dielectric]

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Electric field produced by a moving charged particle above a planar dielectric interface

The electrostatic field of a single charged particle above a planar dielectric interface is a standard example given in many books (see example 4.4 in Griffiths or https://en.wikipedia.org/wiki/...
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Electric field in dielectric sphere surrounded by conductive shell connected to ground? [on hold]

Electric field in dielectric sphere surrounded by conductive shell connected to ground? The radius of the dielectric sphere is $a$, while the radius of the conductive shell is $a$ (internal surface) ...
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Find force between the 2 charges? [on hold]

There are 2 charges q1 and q2. The distance between them is divided into 2 parts: one has a medium with dielectric constant K1 and the other has a medium with dielectric constant K2. The length of the ...
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What is permittivity at infinite frequency in cole-cole equation?

I am working with estimating the dielectric constant as a function of frequency. I did calculate the S-Parameters from Agilent VNA. The study is similar to this paper When working this, i came across ...
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Experiment interpretation. Dielectric polarization/triboelectricity/other?

My aim was to create a relatively strong electrostatic field to experiment with biological systems. So, I built a kind of "sandwich" made of a plate of aluminium surrounded by two 4mm plates of ...
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How can I beforehand determine whether a material is a good candidate for a microwave sensor?

Is there a table of some sort or formula where I can determine before I test the material under a microwave sensor whether it will allow the microwaves to pass through and if so at what depth. for ...
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Electrodynamics of inhomogeneous media

I'm interested in electromagnetic scattering and for that purpose I would like to write out Maxwell's equations for space-dependent permittivity (and permeability). Actually I only need them for ...
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Spectrum of Dielectric Function along Energy

What do the peaks and troughs in the spectrum of the dielectric function (real and imaginary parts) along energy indicate? I understand that the real part represents the polarization and the imaginary ...
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Dielectric polarization - should not the dimensions of the polarised dielectric increase in the direction of the field?

In the classical model for polarization, if a dielectric is placed in a an electrical field (assumed to be static for the sake of simplicity), the trajectory of the electrons inside the atoms of the ...
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High frequency limit of permitivity function

I am taking a course in solid state physics, and I have a question about the behavior of the (relative) permitivity function $\epsilon_r (\omega) $ for dielectric materials. In the Drude model, we ...
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Is the permittivity of a dielectric medium measured by application of radio frequency of 1 KHz and a resonant circuit of 1KHz are same?

I am working on a procedure in which I assess the dielectric constant of a medium by subjecting the dielectric medium to electromagnetic radiation of certain frequency (or the medium is subjected to a ...
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Electric Field & Polarization

Does everytime the electric-field $E$ & the electric displacement vector $D$ are parallel for every material?
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What is meant by a longitudinal electromagnetic wave?

I reckon this is most likely a rather obtuse question, but I was wondering what would be meant by a longitudinal electromagnetic wave? Questions such as this one refer to there being 'no longitudinal ...
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Could one calculate relative permittivity from tight-binding model

For an insulator, we could built up a tb model to describe the microscopic behavior. Could one starts from it to get the electromagnetic features, like relative permittivity.
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Can electric potential be discontinuous?

I am studying the following problem, which is 9.11 of "Modern Electrodynamics" by Zangwill. The idea is that you have a wire attached to a perfectly conducting sphere (radius $a$) buried into the ...
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1answer
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Partially Filled Capacitors

I know that, for partially filled capacitors, one treats the space between the capacitor plates as two or more capacitors either in series or parallel. However, I don't fully understand why the ...
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When is the permittivity tensor not Hermitian?

I understand that a permittivity tensor is symmetric if there is no absorption. On the other hand is it always Hermitian? Under what cases would that not be the case?
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What is the difference between a dielectric and a semiconductor?

It would be very nice if you could give an equation to discern the two material classes. Please do not provide an answer which is based on the band gap size, since in the last years also diamond (...
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1answer
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Symmetry of the permittivity tensor of lossless media

I read in various sources that the electric permittivity tensor of a lossless medium is always symmetric. I am wondering how this can be the case, when: Phase accumulation in the medium could in ...
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How to mathematically express permittivity as a function of frequency

I am a amateur physics student. I am modelling the wave propagation of an EM wave at different frequencies through water placed between two acrylic rectangular materials using COMSOL. But since the ...
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Liquid dielectrics, having polar molecules(such as water), always have dielectric constants that decreases with increasing temperature. why?

liquid dielectrics having polar molecules (such as water) always have dielectric constants that decreases with increasing temperature. what will be the explanation for that scenario? why is that ...
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Why are there outward forces on the ends of a flat plate capacitor?

I'm working my way through some formulas for electrical forces on the dielectric in a flat plate capacitor. In particular, I have formulas for forces that operate on the interface between the ...
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1answer
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How does a dielectric interact with a laser beam? [closed]

A nano-ball made of latex, which is insulating, has no net electrical charge, and is much smaller than the wavelength of the light. The ball is compact, homogeneous with spherical shape. It has ...
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The potential difference when neutral dielectric ($\varepsilon_r$) flows with speed $v$ through capacitor in magnetic field $B$

The distance between the two parallel plates of the initally discharged capacitor is $d$. Parallel to the plates there is a magnetic field $B$, as the image shows: So we want to know the potential ...
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Dielectrics and capacitors

Does the electric field after passing through the dielectric reduce. What I mean is If there is a dielectric which is in between the plates ( but NOT IN contact with them ) Suppose field begins from ...
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1answer
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Nature of force between two identical dielectric bodies carrying the same charge when kept in a dielectric medium

Let's say that I have two identical glass spheres with $\kappa_{\text{body}}=5$ charged negatively with a charge $-q$ on both of them. I then place them in glycerin which has $\kappa_\text{medium}=40$....
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1answer
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Electromagnetic field propagation in any medium at high frequency

I am trying to understand an important concept regarding the propagation of EM fields in materials at high frequencies, which is: "At high frequencies any material behaves as a dielectric material. ...
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1answer
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Polarization vector for linear dielectrics

I'm confused about the relations between electric field vector $\bar{E}$, polarization vector $\bar{P}$ and induction vector $\bar{D}$. In a parallel plate capacitor filled with a dielectric I find ...
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1answer
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Complex permittivity of mixture

I have been reading a few papers regarding the estimation of the permittivity $\epsilon_{mix}$ of a mixture of materials of permittivities $\epsilon_1$ and $\epsilon_2$ (I am not a phisicist or a ...
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1answer
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How do I experimentally measure the resistance from using dielectric grease on battery posts?

The internet gives lots of contradicting advise about greasing or not greasing car battery posts to prevent corrosion. So rather than rely on the internet, I want to perform an experiment so that I ...
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1answer
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Dielectrics in series, electric field strength

I am trying to apply a strong electric field to a porous material by applying a strong voltage across two conductive parallel plates that are sandwiching the material. Goal is to align dipoles in the ...
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2answers
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Question about $E$ field in Dielectric Medium

My basic understanding of a dielectric material is that the coulomb force between charges in a dielectric must be reduced by some factor since some of the electric field energy gets stored in the ...
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2answers
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Dielectrics in Capacitors [duplicate]

Is dielectric capable of storing charge? I mean if a dielectric is removed out of a charged capacitor will it still have charges stored into it??
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1answer
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Electric field for a partially inserted dielectric slab in a parallel plate capacitor [closed]

I’m working on a problem that I think I solved incorrectly yet I don’t know where my mistake is. Suppose we partially insert a dielectric slab (with constant $\kappa$) inside a parallel plate ...
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How can the refractive index be below 1 in a dielectric?

Upon checking the optical properties of different dielectrics, I found the interesting case of $Al_2O_3$. It seems to be reported with a refractive index below 1 in the infrared range of $10 - 12~\mu ...
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Total charge in an insulated dielectric

Is it trivial that the total charge in an insulated polarized dielectric is zero?? My T.A. mentioned it in class but I didn't quite got how the "insulated" part of the affirmation could lead to this ...
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Derivation of the formula for the electrostatic force with a dielectric in the middle

In the answer by user JohnRennie on the post "What is the force in the presence of a dielectric?", it says: If the dielectric constant is $K$ and the thickness of the dielectric is $t$, then for ...
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1answer
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Coaxial cable with compound dielectric

I'm trying to solve a problem from Reitz and Milford's Foundations of Electromagnetic Theory (3rd ed, problem 4-8), and don't know how to start: A coaxial cable of circular cross section has a ...
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1answer
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E field within parallel plate capacitor with dielectric

I know that for an air-filled parallel plate capacitor with applied voltage, there exist the relation $E=V/d$, where d is the separation distance. Does this relation still hold when the parallel ...
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Electrostatics: Charge Distribution and Energy - Confusion

Consider the following situation: Between two metallic plates, are two dielectrics of dielectric constants $K$1 and $K$2. The surface charge density on the upper metallic plate is $\sigma$, and that ...
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Electric field inside a uniformly charged dielectric sphere

Every basic course and book on electrostatics has this problem, to find out the electric field inside a uniformly charged sphere. The result always is $\frac{\rho r}{3 \epsilon_0}$, obtained using ...
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Charging a parallel plate capacitor if a dielectric is already present inside

A parallele plate capacitor is placed in a dielectric liquid such that one of the plates is inside the liquid and the other is outside. Then the plates are connected to a battery which supplies the ...
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1answer
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What is the physical significance of polarization vector? [closed]

What is the physical significance of the polarization vector in studying dielectric materials? Why do we need that term, what information does it give about the property of the dielectric?
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Velocity factor in coax cables

I mainly see the term "velocity factor" used when referring to the velocity of propagation of an electromagnetic wave front in coax cables. This velocity seems strongly dependent on the properties of ...
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Why does current from a grounded electrical outlet flow through me if I stay on the floor made out of a dielectric material?

Why does current from a grounded electrical outlet flow through me when I touch a "hot" terminal, if stay on the floor made of a dielectric material? Consider an AC voltage source, such as a wall ...
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1answer
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Two dielectric with resistivity. What is the charge distribution?

Consider two metal plates (very large). The distance between the two plates is $2a$. For the first half, the space between plates is filled by a material with dielectric constant $\varepsilon_1$ and ...
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Symmetry of the dielectric tensor

In the book Principles of Optics by Max Born, in chapter XIV, the rate of change in the electric energy density $w_{e}$ is generalised to \begin{equation} \frac{dw_{e}}{dt} = \frac{1}{4\pi}\sum_{kl}\,...
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Negative electric polarization on dielectric material

I've been solving the first problem set in my E&M course, and have come across something I think is unphysical. The problem consists of a parallel plate capacitor in which an inhomogeneous ...
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1answer
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Is Feynman wrong about the principle of virtual work to find forces in a dielectric?

In The Feynman Lectures on Physics, Vol II, 10–5 Fields and forces with dielectrics describes a method for finding the force between two charged conductors in a dielectric. I accept the first part of ...
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Feynman Lectures on Physics: Vol II Eq. 10.6: (How) could this be stated better?

So far as I know, the Feynman Lectures on Physics are still maintained. That is, corrections are still made when errors are reported. It appears to me there is a minor error in the wording leading ...