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 fields of physics like solid-state physics, optics, electronics, cell biophysics, etc.

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Does complex permittivity account for dielectric damping attenuation, or only for conductivity related attenuation?

In many sources like wikipedia they describe two sources of atenuation in lossy dielectrics: the related to the conductivity and the related to the dielectric damping $\nabla \times \mathbf{H}=j \...
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Doubt regarding free volumetric charge density and bound volumetric charge density in Linear, homogeneous, isotropic dielectrics

In Example 4.8 of Griffith's Introduction to Electrodynamics (page 194 of the 4th edition) the bound volumetric charge density inside a homogeneous, isotropic, linear dielectric filling the $z<0$ ...
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What is the relationship between emissivity $\varepsilon$ and the imaginary part of relative permittivity constant $\epsilon^{''}_{\rm r}$ if any?

In terms of the Stefan-Boltzmann law a body that does not absorb all incident radiation emits less total energy than a black body and is characterized by an emissivity $0<\varepsilon <1$ such ...
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Calculate steady state temperature of an object heated by electromagnetic radiation

I would like to calculate the steady state temperature of a small cube of any material heated by electromagnetic radiation. Suppose the cube floats in air and doesn't touch anything. The air is at 20 °...
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Drude model - frequency dependent dielectric constant of the metal

This is from the slide used in class and I have a few questions to ask. First question: In the first line of equations of the phasor form, why is there a negative sign? Is this a sign error? How is ...
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Conductor instead of dielectric in between the capacitor

What happens to capacitance if we put conductor between the two plates of capacitor? What's important though is that we (some how) made the conductor between two plates immobile and remain detached ...
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What is the formula for expressing the complex permittivity due to space charge polarization in terms of frequency?

The complex permittivity depends on the frequency. I want to express the complex permittivity due to space charge polarization by the frequency equation. Simple Debye relaxation and Cole-Cole ...
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38 views

Potential of a dielectric sphere with radially dependent variable permittivity [closed]

Consider a dielectric sphere of radius $R$ in a constant external $E$-field, $\mathbf{E}=E_0\mathbf{\hat{z}}$, with a radially dependent variable permittivity $\epsilon=\epsilon_0 (R/r)^2$ for $r<R$...
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Does continuously moving dielectric changes capacitance?

Let's assume we have a standard two-plate capacitor and the space between its plates is filled with dielectric that has permittivity >> 1 . Will its capacitance change if we move such a ...
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Inserting a conductor that touches a parallel-plate capacitor

I understand that if a conductor of thickness $t$ is inserted between a parallel plate capacitor having a distance $d$ between its plates, the capacitance becomes $C' = \frac{\varepsilon_0 A}{d-t}$. ...
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Non-local connection Between $D$ and $E$ (Kramers-Kronig relations)

I'm trying to solve next exercise from Jackson's Electrodynamics, Chapter 7, page 348, 3th edition: Consider the non-local (in time) connection between $D$ and $E$, $$\vec{D}(\vec{x},t)=\epsilon_0 \...
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Approximately calculating structure of modes in a waveguide

I know this a super open-ended question, but I hope I can get something out of it anyway. Here is a crude diagram of the cross section of a waveguide I am simulating on COMSOL: and here is the output ...
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Planck radiation law of a dielectric layer

Suppose we have a rectangular slab of thickness $h$, width $a$ and length $b$. The upper surface of the slab is put at constant temperature $T$ while all the rest is at initial temperature $T_0$. ...
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Why we use $E$ field for the EM-Wave and not the electric displacement field or electric induction?

Why we use E field for the EM-Wave when is propatating on vacuum and not the electric displacement field or electric induction?
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Free, bound and total charge density

If in a medium we have: $\rho(\vec r)_{total} = \rho(\vec r)_{free} + \rho(\vec r)_{bound} $. Now we know: $-\nabla\vec P = \rho(\vec r)_{bound}$ $\nabla\vec D = \rho(\vec r)_{free}$. Since $\vec D=\...
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Can Lorentz force polarize a neutral dielectric atom?

Is it possible to electrically polarize an atom (typically a dielectric) with magnetic field? For example, if dielectric fluid flows near magnetic field, does it shift each atom's positive charge down ...
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Hollow Sphere inside a dielectric material

In our book it is said that : If we investigate a positive polarization charge on the boundary of the waveguide (I assume this is another word for the hollow sphere), which creates an electric field ...
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Relationship between Polarisation field and electric dipols (for a discreet distribution of ele. dipols in a volume)

I know that the Polarisation is a field. If we are having a discreet distribution of electric dipoles in an arbitrary volume, then for the polarisation we have: $\vec P(\vec r) = \Sigma_i \vec p_i \...
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Max Voltage of a Coaxial Cable

I have a coaxial cable with an inner radius a and an outer cylindrical conducting sheath of radius b. The space between them is filled with insulating material with dielectric constant $(1+\chi_e)=\...
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Clausius-Mossotti factor for ellipsoides

The dielectrophoresis (DEP) force acting on a sphere involves the calculation of the real part of the complex Clausius-Mossoti factor, which is nothing but a relationship between the dielectric ...
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Relationship between $\vec E$,$\vec P$,$\vec D$ inside a dielectric material

If we put a dielectric material in region where an electric field $\vec E_0$ is present then, the fields that are present within the dielectric are: $\vec E$,$\vec P$,$\vec D$ . $\vec E$ is the ...
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Polarization charges in a dielectric

I am reading currently feynman's notes on dielectric material under the influence of electric field. And there is a part that is not very clear to me. Here's the link to the lecture: https://www....
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To what direction will a compass in a magnetic medium points? The direction of $B$-field or that of the $H$-field?

Question in title. To avoid "same direction" answers, let's assume the B and H are pointing in different direction, i.e., the magnetic permeability is not a diagonal matrix. What direction ...
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25 views

Problem With Regards to Change of Parameters after Insertion of a Di-Electric in a Capacitor

I came across this problem where we had to calculate the maximum charge that can be accumulated on the plates of a capacitor (containing a di-electric) before the di-electric breaks down due to the ...
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Plasmonic - Dielectric function

Regarding the electrical permittivity of the metal in a high frequency regime, I cannot find research material related to the lead dielectric function (PD). I can't get the matatrial as values, I'll ...
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42 views

The difference between the equation of Permittivity and Permeability in a medium

I notice that the equations of Permittivity and Permeability in a linear medium are exactly opposite of each other. One is $$\mathbf{D} \equiv \varepsilon \mathbf{E}$$ while the other one is $$\mathbf{...
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Sphere boundary at different potentials and filled with different dielectrics

I am trying to solve for the potential inside the sphere whose northern hemisphere's boundary is at $V_{0}$ and filled with dielectric permittivity $\epsilon_{1}$. Similarly, the lower half is filled ...
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Dielectric material between two plates

I wonder if the capacitance is the same if we have two plates with a dielectric material between. I mean, is it the same when the dielectric material only touches one of the plates, compared with when ...
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Shouldn't we take square of the electric field induced inside the dielectric due to electric field applied (as opposed to how it's solved in image)?

Formula used: $ \textrm{Energy} = \frac{1}{2}\epsilon \int E^2dV$ in the image here. If my assumption of finding induced electric field is correct; then will the amount stored energy depend upon ...
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What is the electric field at point P due to the charged dielectric and +Q?

$+Q$ is $D$" /> We are given a a uniformly charged dielectric sphere of radius $R$. The dielectric contains a cavity of radius $r$. The distance between the centre of the sphere and that of the cavity ...
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Why can we consider a capacitor with mixed dielectrics equivalent to two series or parallel capacitors?

When a parallel-plate capacitor has two different dielectrics as shown below, it can be considered equivalent to two capacitors in series, one taking the value of one of the dielectrics and the other ...
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Relationship between work done to insert dielectric into parallel-plate capacitor and work done by battery during/after process?

As a dielectric material starts to be inserted into the uniform electric field between a capacitor's parallel plates, the electric field does work to polarise the molecules within it, and so there is ...
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Why is the dielectric function related only to the longitudinal component of the permittivity tensor?

I have been working through Fundamentals of Physics of Solids, Vol. 3 by Jeno Solyom. When talking about how linear dielectrics respond to external perturbations, he decomposes the (Fourier ...
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Charge of capacitor

Consider a slab of dielectric material sandwiched between the metallic plates of a capacitor. Call $l$ the thickness of the slab and $A$ its surface area parallel to the plates. Can you explain me why ...
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443 views

Why is wood opaque?

Glass does not allow the flow of electrons through it, is transparent, and has higher skin depth. Similarly, wood has no free electrons and higher skin depth, but still it is opaque. Why?
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Is an electrical capacitor ever possible to exist in a perfect vacuum space?

Fig.1 Magnetic field outside the plates of a charging capacitor This question could be rephrased as: Does a non-ideal capacitor have a magnetic field outside its plates after it is fully charged? It ...
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How to determine the peak of the dielectric function represent an exciton?

I am reading a paper about exciton-induced dielectric function peak, but I am not sure how could I determine the peak of dielectric function represent an exciton? The original paper is on Nature ...
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Discontinuity of potential due to point charge at dielectric boundary

Suppose we have point charge $q$ enclosed in a uniform spherical dielectric medium of dielectric constant $\epsilon$ with radius $R$. The electric field due to that would be: $$ \vec{E}(r) = \begin{...
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Equilibrium of electrostatic potential

we often talk about the similarities between the temperature and the electrostatic potential. However, we do not know of exact analogue of the Heat diffusion equation $\nabla^2{T}=\alpha\frac{\partial ...
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37 views

How do I determine the polarizability of a material?

Is there a simple and elegant way to determine the polarizability of a material? If so, how? Experimentally, one can easily measure the electric and polarization fields, but measuring polarizability ...
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36 views

High frequency limit of dielectric permittivity

The electric susceptibility $\chi_e(t)$ of a material is defined via a convolution relation between the polarization field $P$ and the electric field $E$: $$P(t) = \epsilon_0 (\chi_e * E)(t) = \...
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EM-wave equation in matter from Lagrangian

Setup Let's suppose a homogeneous dielectric with a (spatially) local dielectric response function $\underline{\underline{\epsilon}} (\omega)$ (in general a tensor), such that we have the linear ...
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Dielectric displacement tensor indexes

I am confused on how to express the dielctric displacemnt tensor. In textbooks, I found the following equation: $\boldsymbol{D} = \varepsilon_{0} \boldsymbol{E} + \boldsymbol{P}$ which relates to ...
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Dielectric permittivity and Kronecker symbol

I tried to express the dielectric permittivity tensor $\varepsilon_{ij}$ as: \begin{equation} \varepsilon_{ij} = \varepsilon_{r} \varepsilon_{0} = \left(\chi_{ij} +1\right) \varepsilon_{0}\text{,} \...
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53 views

What does complex permittivity mean?

I have been trying to solve the following question: $U(t)$ has the frequency $\omega$. Without an electric, the Voltage drop around the resistance is $U_R$. When half of the capacitor is filled with ...
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For capacitors, why does the dielectric need to be inserted at a small constant speed?

Likely a very silly question. I am aware that there is an attractive force from a charged parallel-plate capacitor in an open circuit without battery pulling the dielectric in, and that a decrease in ...
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Electric displacement - why are field lines continuous?

I recently attempted problem 4.17 in Griffiths's "Introduction to Electrodynamics" 3rd edition in which you are asked to make a sketch of the electric displacement vector D in and around a ...
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Concentric conducting spheres with dielectric

In the following image, there are 2 concentric conducting spheres. Initially, both are uncharged, outer one is earthed and the space between them is filled with air. After sometime, I somehow put some ...
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208 views

Direction of electric field at points on boundary between two dieletrics

I am ripping my hairs trying to understand this answer, it is written that, for the following set up of two capacitor plates separated by distance $d$ and area $A$ with three dielectrics insert with ...
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Does Electric Flux Density due to an external Electric field increase in a dielectric medium as compared to free space?

There is exactly the same question on StackExchange but I don't find it rigorous or even right per se. How flux density increases in the dielectric medium? In the 7th edition of the book "...

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