Questions tagged [dielectric]

This tag is for questions relating to a non-conducting material called *dielectric* (or dielectric material). Dielectrics are very much important to explain various phenomena in various field of physics like solid-state physics, optics, electronics, cell biophysics etc.

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Gauss law for an arbitrary dielectric with a dielectric constant that varies accross its volume

someone knows what is the form for the Gauss law or Poisson equation for an arbitrary dielectric with a dielectric constant that varies accross its volume?
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Difference between $E$ and $D$ in conservative fields

I am having a tough time visualizing the derivation of boundary conditions in Electrostatics. My main problem lies with the fact $\oint \mathbf E\cdot \text d\mathbf l = 0$ is used instead of $\oint \...
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Minimum Electric Field for Ionisation - Griffiths

Here's a problem from Electrodynamics by Griffiths, which I've solved but need more clarification in: A hydrogen atom (with the Bohr radius of half an angstrom) is situated between two metal ...
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10 views

Polarizability Tensor and Choice of Axes

An extract from Griffiths Electrodynamics: The set of nine constants $\alpha_{ij}$ constitute the polarizability tensor for the molecule. Their values depend on the orientation of the axes you use, ...
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Oscillating Electric Field and Dielectric Constant

Here's an extract from Purcell's Electricity and Magnetism: Every dielectric constant in the table is larger than 1. We should expect that if our explanation is correct. The presence of a ...
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Dielectric Constant Relation With Polarizability

Suppose a Dielectric is placed between the plates of a capacitor. If the Dielectric is easily polarized (high Polarizability ($p$)) , then the capacitance increases, if the dielectric constant ($k$) ...
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71 views

Derivation of Hamiltonian in non-linear optics

Update 2: one half of the answer to this question can be found here and the other half in the second half of this post. I asked this question a few hours ago, but decided to re-post it because I ...
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48 views

Gauss law use not in free space

Gauss' law specifies permitivity for free space. what happens if electric field is not in free space. does the law apply?
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24 views

Dielectric constant change in the atmosphere?

I'm curious about the refractive index changing in the atmosphere. As I understand it (and I may very well be wrong/naive) when a ray of light enters from one medium into another, the electric field ...
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3answers
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What prevents ice from being an electret?

My question is apparently simple: if we put water in a electrostatic field and leave it to freeze, while still in the strong electrostatic field, to make ice, why wouldn't this ice exhibit electret ...
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1answer
41 views

Doubt in the derivation of Gauss's law in dielectrics

so in the 2nd page,when the dielectric material is introduced the gauss's law becomes $$\oint _ { S } \vec { E } \cdot \vec { d S } = \frac { ( q - q _ { i } ) } { \epsilon _ { 0 } }$$.But my ...
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57 views

Force in an isolated capacitor when a dielectric slab is introduced [closed]

my question is about capacitance: a dielectric slab is inserted between the plates of an isolated capacitor. The force between the plates will remain unchanged. how? I mean the knowledge I had gained ...
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1answer
23 views

Does an induced dipole experience a toruqe in an electric field?

In Griffiths' Electrodynamics, it is shown that if a neutral atom is placed in an electric field, it will become polarized with a dipole moment given by $\mathbf{p}=\alpha \mathbf{E}$, where $\alpha$ ...
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Non-uniform Polarization Vector in dielectrics

In Feynman's Lectures on Physics Volume 2, Chapter 10; Dielectrics, we calculate the Capacitance of a condenser when a dielectric is placed in-between, whose polarization vector is non-uniform. ...
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How to derive the macroscopic dielectric function?

I'm following Matteo Gatti's slides to repeat the derivation of macroscopic dielectric function $\epsilon_M$: $$\epsilon_M=\dfrac{1}{\epsilon^{-1}_{\vec{G}=0,\vec{G}'=0}(\vec{q},\omega)}.$$ On page ...
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50 views

What happens if permanent magnets are placed under electric field?

I understand that ferromagnets have domains that align parallel to the applied magnetic field, in which the spin of the unpaired electrons line up. But I am curious as to what happens to such magnets ...
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Why do bound charges not appear in boundary conditions on a surface between two dielectrics?

I'm studying electromagnetism, more specifically dielectrics. However, the concepts of bound charge and free charge have been somewhat confusing for me yet. The Griffiths' book deduces one of the ...
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Difference between permittivities eps-opt and eps-inf?

Very often in materials physics we are interested in the relative permittivity at optical frequencies, which is usually denoted by $\varepsilon_\text{opt}$ or $\varepsilon_\infty$. But I'm confused ...
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Charge in the middle of a flat dielectric

We know that due to external uniform fields, the dielectric atoms get polarized in the direction of the field, but what if the charge is inside the dielectric, the electric field of the charge is ...
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1answer
196 views

Dielectric above and below the xy plane

This is problem 4.25 from Griffiths' electrodynamics, it says: Suppose the region above the $xy$ plane is filled with linear dielectric of susceptibility $\chi_e{}'$ , and the region below the $xy$ ...
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Transformation of dielctric constant tensor

I have a dielectric tensor $$K = \begin{pmatrix} 2000 & 0 & 0 \\ 0 & 2000 & 0 \\ 0 & 0 & 50 \end{pmatrix};$$ which I want to transform to a new coordinate system given by ...
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1answer
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Anodizing Process as Dielectric

I want to use anodizing process as dielectric coating I just want to know , if I do the process by low voltage, like 48 volts , for long time , will that coating become resistant to 1000 volts ...
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List of complex refractive indices for various frequencies and various materials

I want a list of refractive index values for various materials (or even a single material) for various frequencies / wavelengths (I need this specifically for the micro wave - radio wave regions of ...
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How to calculate how far radio light goes in the ocean [closed]

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
60 views

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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1answer
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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
37 views

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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3answers
79 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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1answer
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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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31 views

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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31 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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32 views

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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130 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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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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1answer
25 views

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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42 views

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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1answer
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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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1answer
47 views

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 ...