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Questions tagged [dielectric]

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Charges in different mediums [duplicate]

Generally we read or solve problems about charges in the same medium. I wonder what would happen if the two charges were placed in different mediums. eg.) One is placed in vaccum and other is placed ...
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Energy momentum tensor in polarizable media

I am trying to follow Soper's derivation of the energy-momentum tensor for polarizable media in his book 'Classical field theory'. Given a Lagrangian density $\mathcal{L} = \mathcal{L}(\phi_A, \...
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Change in temperature of dielectric when capacitor is charged and discharged

Suppose I have a capacitor with a dielectric between its plates. Intially the temperature of dielectric is $T_{-1}$. The capacitor is fully charged and the temperature of dielectric is noted.. say, $...
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Why does Jackson ignore the surface term in this integration by parts, in the electric potential of a polarized dielectric?

In Jackson's electrodynamics Page (153), it is given that the total potential is the sum of potential due to free charge and potential due to dipole. Therefore, \begin{align*} \phi(x) & = \frac{1}{...
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Energy Density with a Linear Dielectric Inconsistency

The energy density of an electromagnetic field with a linear dielectric is often expressed as $0.5 E \cdot D$. It is also known that energy can be found by $ 0.5\int_{V} \rho V dV $. Using the latter, ...
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Is the electrical permittivity of perfect conductor infinite or negative or both? What about a good conductor, is its permittivity large negative?

I have read that metals are very good conductors and thus their electrical permittivity is infinite. But I have also read that the permittivity of metals is negative. So is a perfect metal (conductor)...
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Maxwell's equations, nonlinear media, and dynamic response

Maxwell's equations in the vacuum with electric permittivity $\epsilon_0$ and magnetic permeability $\mu_0$ are given as: $$\nabla \cdot \vec E = \frac{\rho}{ \epsilon_0}$$ $$\nabla \cdot \vec B = 0$...
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tribo charge and work function - adiabatic vs vertical

I am interested in estimating relative tribo charging for different dielectric materials (insulators). I understand that I can use the work function difference between two materials to estimate ...
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Dielectrics between charges

Why does inserting a dielectric of dielectric constant $k_e$ have an effect of increasing the distance from $r$ to $r+t(\sqrt{k} -1)$ in Coulomb's law of electrostatics (where $t$ is the thickness of ...
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Effect of dielectric on electrostatic force [duplicate]

does the electric force between 2 charges decrease if a thin(not negligible) dielectric is placed b/w them? If it does then why?
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4answers
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Why do we use dielectric materials in a capacitor?

Okey first of I know dielectric materials used in capacitors to insulate and polarize due to electrical field created by two metal plates and then when you connect this stored energy to a system you ...
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Dielectric vs. Ferrite

I am currently taking electricity and magnetism. And I do not understand something, what is the difference between ferrite and dielectric materials. I understand that they each correspond to one of ...
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Is it absolutely insulating in its interior of topological insulator?

If putting a 3D topological insulator (TI) into a sandwich testing structure (electrode-TI-electrode), can we detect any leakage current in its interior like the ordinary insulator? Is it absolutely ...
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Sphere half-submerged on a dielectric

This is a classic problem in electrostatics with a twist, so I thought it could be useful for others here. I did have a problem with the integration at the end, but on general I think the idea can ...
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1answer
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Why is charge proportional to capacitance? [closed]

I'm having trouble understanding why the charge is multiplied by the dielectric constant in the following question: A parallel-plate capacitor has capacitance C0 = 5.00 pF when there is air between ...
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5answers
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Why is capacitance increased with a dielectric rather than reduced?

So conceptually, if a capacitor is connected to a voltage source, and if you decrease the distance between two plates, the electric field in between the plates increases. This means that you can hold ...
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1answer
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How do you calculate the capacitance of a parallel plate capacitor with multiple dielectrics? [closed]

My question is how would you go about calculating the capacitance of a parallel plate capacitor which has two mediums in between the parallel plates. I am aware that for a regular parallel plate ...
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1answer
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Influence of an external electric field on an uncharged capacitor

Influence of an external electric field on an uncharged capacitor. Fig A shows an uncharged capacitor with no external electrical field. There is no net charge on each of the plates. Since the ...
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2answers
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What happens to a system of capacitors when a dielectric is inserted into one of them?

sorry for my English. While doing some homework I've stumbled upon this "circuit": the system is connected to the same potential difference through a generator that is connected to points A and B. ...
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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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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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1answer
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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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1answer
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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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1answer
31 views

Electric Field & Polarization

Does everytime the electric-field $E$ & the electric displacement vector $D$ are parallel for every material?
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2answers
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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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1answer
67 views

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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2answers
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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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1answer
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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
52 views

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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1answer
39 views

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
64 views

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
64 views

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 ...