Questions tagged [dielectric]

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How to calculate how far radio light goes in the ocean

Radio light is not a practically useful way of communicating underwater over large distances. My question is how does one calculate how far a radio wave at a given frequency will propaagate in the ...
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1answer
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Change in potential energy of a parallel plate capacitor as a dielectric slab is moved in the space between plates

I was doing this question: If a parallel plate capacitor made of square plates of side L and separation D is connected to voltage source V. And then a dielectric slab of width D is introduced ...
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Dielectric properties of polarizing beam splitter

Are all polarizing beam splitters made up of dielectric materials?If so, what kind of dielectric materials are actually used to make them?
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Force on Dielectric on pulling it out from capacitor

This is the text from Griffiths Electrodynamics for calculating force on dielectric on pulling it out from capacitor when the capacitor is connected to Battery so that voltage of capacitor is fixed: ...
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Characteristic matrix for thin dielectric stack at arbitrary angle

So I have this exercise in my nanophotonics class that I do not know how to solve or begin with. Exercise Derive the “characteristic matrix” for a thin layer of dielectric material for arbitrary ...
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Polarizing Beam splitter

What could be the effect of aging in Polarizing Beam Splitters? Is it possible that the Axes for s-polarization and p-polarization change due to some environmental effects on a polarizing beam ...
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1answer
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How flux density increases in the dielectric medium?

The above figure shows a polar dielectric medium in an external electric field which is normal to it's surface. From the equation of D(electric flux density) we see that flux density increases but ...
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62 views

Direction of electric field in the following cases?

In the above figure if applied electric field is at angle(but not normal) to the surface and is limited only to a specific region as shown, I believe the Electric field due to the induced charges ...
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Why total positive bound charges of polar dielectric exist only on surface and negative charges in volume when exposed to external electric field?

The above image describes the potential due to Polar dielectric material when placed in an external electric field. In that I don't understand why only total bound positive charge exists on the ...
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Electric field in capacitor arrangement with different dielectric media

Please consider the following arrangement of infinitely extended charged plates. In z-direction the system also extends to infinity. The charged plate in the middle of the figure is 2x negatively ...
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Concentric cylinder cell constant

For a concentric cylinder cell (with liquid dielectric), mathematically the equation for the cell constant will always yield a lower value than for the parallel plate case for the same volume of fluid....
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29 views

Thermal energy produced by electric polarisation?

Does DC polarisation of a dielectric liquid (stretching & rotation) cause heat to be produced and if so what is this heat production process termed scientifically?
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Uniform Polarized Sphere - are there free charges? How to use Electric Displacement?

I'm studying EM for the first time, using Griffiths as the majority of undergraduates. So, in studying electric fields in matter, we derived equations for the volume and surface density charge of the ...
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For the high-frequency permittivity of a material, do I need to look beyond its value in the optical energies region?

I was trying to find $\varepsilon_\infty$ for InSb, and the value I found on Kittel p. 416 was 15.6. But in the literature, even at 6 eV, $\varepsilon (\omega )$ is still in the negative (at -3.835) ...
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Dielectric constant in terms of fundamental forces [duplicate]

How can one explain the slowing down of electromagnetic waves travelling in a medium using fundamental forces of nature like electromagnetism?
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1answer
53 views

Why cant a polar dielectrics molecules ever completely align with an applied electric field?

In my electro statics course my professor said that the molecules in a polar dielectric cant ever fully align with an external electric field as they will want to then 'turn back on one another', so ...
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23 views

Induced charges in Electrostatics

How to find the distribution of induced charge on conductor kept in a uniform electric field? Is there a particular method to do the same?
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Is it possible to create and control a magnetic field in a dielectric material?

A capacitor is usually formed by an insulater between two conductive plates. By applying voltage difference between the plates we create an electric field within the insulator in one direction. If you ...
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Potential of a polarized hollow spherical shell due to uniform electric field

A hollow spherical shell has inner radius $a$, outer radius $b$ and is made with a material with dielectric constant $\epsilon_r = \epsilon / \epsilon_0$. It is placed in a uniform electric field $\...
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Polarizability of Jellium model (Bruus's many-body textbook)

I am currently reading Bruus's "Many-body quantum theory in condensed matter physics". In Chapter 9, Fourier transform of the polarizability $$\chi_e^R(\mathbf rt, \mathbf r't')=-i\theta(t-t')<[\...
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Dynamics of dielectric dipole during polarization?

When a dielectric material is placed in an exterior electric field, a process of polarization would occur. During the stretching phase, does that happen uniformly(stretch evenly)or only in a specific ...
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Dielcetric Tensor Transforms under Product Representation

How do I show that the Dielectric tensor in 2D transforms as a product of representations? I am told that the electric displacement and electric field transforms with the representation $D^v(g)$, and ...
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27 views

Dielectric equivalents of diamagnetics

Is there a dielectric material that would oppose an electric field such that field lines never enter in the material? An electric analog of diamagnetism
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Net bound current with uniform magnetization

My confusion stems from the following: Can I reason the answer being (D) analogous to... for instance: If this was instead a solid cylinder with uniform polarization $\mathbf P$ pointing in the z-...
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Directional differences between $\mathbf E$ and $\mathbf D$

My confusion stems from the following exercise: Since $\mathbf E$ and $\mathbf D$ (electric displacement) are parallel (assuming we are dealing with a linear dielectric), and that given the picture ...
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1answer
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CombinationsDielectrics in parallel

I was reading about dielectrics and wondered why there was no formula for their parallel connection between two parallel plate capacitors. So I thought of deriving it myself. Let $k_1$ and $k_2$ be ...
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I'm confused about charge density and complex conductivity, complex permitivity!

I'm confused about some notations in electromagnetism. Please help me to solve these questions. I first studied electromagnetism with David cheng's book, but From the book : Lukas Novotny, Bert ...
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If an electric field passing through a dielectric medium, back into the original medium, is it “back to normal”?

Suppose there is an electric point charge causing an electric field E in a medium with a dielectric constant $\epsilon_1$. You can calculate the scalar potential $\phi$ at a given distance $r$, as ...
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Location of free charge in insulators

I'm going through the introductory section to Electrostatics in Materials in Griffiths, and I have a question that I can't seem to find a satisfactory answer to. If I have an insulator with free ...
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How to calculate Average Electric Field for a microscopic filed in dielectric?

In Griffith's book in The chapter of Electric Fields in Matter (The field inside dielectric) , He has considered the Sphere of Radius R and for the inner dielectric element He used the field as $$\...
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1answer
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Why does potential decrease when a dielectric is introduced?

Here is a problem that I have encountered: A parallel-plate capacitor has the space between the plates filled with a slab of dielectric with constant $K_1$ and one with constant $K_2$, each of ...
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2answers
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Is polarization matrix always diagonalizable?

In chapter 31 of Feynman lectures Vol 2, he covers polarization , polarization tensor and its diagonalisation, he proves that for a crystal, the tensor matrix is symmetric hermitian and hence ...
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Why is this method of solving this capacitor problem wrong? [closed]

The problem was to solve for the capacitance of this system if initial capacitance was C. I solved it using the method which has been given as wrong.My question is that why is potential difference ...
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1answer
104 views

Why can't $ε_r<1$ (at low frequencies)?

I've heard it said that the vacuum permittivity is the lowest possible permittivity for any substance, that no substance can have $ε_r<1$. Is this true? If so, why is this different from ...
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Resistivity of dielectric liquids

I was wondering if anyone here knows how the resistivity values of highly resistive dielectric liquids have been determined since the best commercial conductivity sensor I can find online only ...
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1answer
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Finding electric displacement $\mathbf D$ for a parallel-plate capacitor filled with two slabs of linear dielectric material

This problem refers to Griffiths Problem 4.18: According to my solutions, my lecturer wrote: Only free charge is on plates. $$\mathbf D = -\sigma \hat z \ \text{between the plates and $0$ ...
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1answer
33 views

What does the curve branch for $\omega > \omega_p$ mean for surface plasmon dispersion?

Consider a half-infinite metal (the other half is vacuum with $\varepsilon=1$). By solving Maxwell's equations and using boundary conditions at the interface, we get the dispersion: $$ \frac{\...
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2answers
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Why the phases of incident, transmitted and reflected waves are the same at planar dielectric boundary?

From "Fundamentals Of Photonics", Saleh: 1) Why k1 = k3? 2) Why condition 2.4-2 holds? or "differ by constants"? How do we get it from invariance to x, y? I have tried to write the continuity ...
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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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31 views

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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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 ...