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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Solving poisson equation in a trivial case: electrostatic [closed]

Consider a dielectric with volume $\Omega$ and frontier $\partial \Omega$ at a potential $V_0$ given. The milieu is at dielectric constant $\epsilon_r(\mathbf{x})$ and contains free charges $\rho_{l}(\...
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Effect of dielectric on electric field outside the dielectric [duplicate]

I have the problem given in Irodov stated as follows Two positive charges $q_1$ and $q_2$ are placed a distance $r$ apart in air, now a dielectric slab of thickness $t$ $(t\lt r)$ with relative ...
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40 views

Why do some writers on EM theory call the displacement $\vec D$ a field? It's a hybrid quantity - a field ($\vec E$) plus a charge displacement vector

Gauss' equation for free space balances the number of charges in a volume with the amount of $\vec E$ field flux through the surface of the volume. When material is included in the volume, a new term ...
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Force by dielectric [closed]

Consider the following thought experiment: Suppose we have a setup with a dielectric medium of dielectric constant $\kappa$ on a horizontal floor extending from $-\infty$ to $+\infty$. And we have a ...
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My question is on electric field and charges [closed]

if the force of repulsion between 2 charges in vacuum and the distance between them is given, then what is the force of repulsion in a medium, with dielectric constant given?
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Why does the electric displacement vector $D$ have the same unit of charge density?

I was in doubt about electric displacement, after some time I tried to find the unit of $D$ which is $Cm^{-2}$. Why?
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1answer
31 views

When do we consider the dielectric constant while using Coulomb's law?

I am trying to solve this problem: The answer given is an option (D). I had learned that whenever there exists a medium whose dielectric constant is $K$ then the Coulomb force becomes $\frac{F}{K}$...
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32 views

What is the electric displacement $D$ in gauss's law for dielectric medium? [closed]

What is the physical significance of electric displacement? I am unable to imagine it what it is. if dielectric is linear then how Susceptibility of the dielectric medium effect electric field inside ...
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1answer
50 views

Eigenvectors in anisotropic media

I have several questions: 1) First, In the susceptibility tensor, when it's diagonalized, i don't understand the physical significance when the off diagonal terms are zero. $$P_x=\epsilon_0\chi_{11}...
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1answer
26 views

Why does the breakdown voltage increase when the separation between the electrodes is decreased beyond a particular value?

When I was learning about Paschen's law from Wikipedia, I came across the following statement: Paschen studied the breakdown voltage of various gases between parallel metal plates as the gas ...
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1answer
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$E$-field between dielectric and plate in parallel plate capacitor and Feynman's claim

Feynman says about $E_{0}$ below Note that the field $E_{0}$ between the metal plate and the surface of the dielectric is higher than the field $E$; it corresponds to $\sigma _{free}$ alone. $\...
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Proof that the static dielectric constant $\varepsilon_0$ is an intensive property

I am trying to prove (or disprove) my intuition that the dielectric constant, or equivalently the permittivity, is an intensive property. Does anybody have a proof or a suggestion for a method for ...
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Is the relationship $\vec{D} = \epsilon \vec{E}$ always valid?

In electromagnetism class we had a problem proposed which led me to some thoughts about the relationship between $\vec{D}$ and $\vec{E}$. I know it certainly $\textbf{is}$ a definition so it must be ...
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1answer
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Surface charge density from volume density in Feynman's treatment of dielectrics

In the second volume of the Feynman Lectures, chapter Dielectrics, section $10–3$ Polarization charges, which can be found here, Feynman says about the dielectric slab below If $A$ is the area of ...
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Enquries about capacitance of parallel plates with a dielectric slab between it while being connected to a constant voltage source

As the title suggests, it is a question about parallel capacitors. I believe that it would be hard to understand what my question is if I am going to directly type it out. Please take a look at below. ...
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Propagation of electromagnetic waves through dielectric with dispersion

My question is rather simple. Imagine a dielectric with dispersion such that $\frac{ε(ω)}{ε_0} = 1+ \frac{ω_p^2}{ω^2}$ and $\frac{μ(ω)}{μ_0}= 1 + \frac{Fω^2}{ω_0^2 - ω^2}$ $ω_0<ω_p$ and $F<...
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Is the plasma frequency independent from the relative dielectric constant of the solid crystal?

I have found many unclear explanations regarding plasma frequency in 3D condensed matter. Based on many textbooks and Wikipedia, the plasma frequency is $f_p=(\frac{e^2n}{m*\epsilon_0})^{0.5}/(2\pi)$...
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FInding Electric FIeld of a System Containing a Dielectric Shell At the Origin and a Charge At Any Location [closed]

So this problem would be (relatively) easy if the charge was only in the center, but because it can be at any distance from the origin, I am not sure how the electric field behaves. From what I have ...
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2answers
91 views

Electric field boundary conditions in the radiation regime

In electrostatics, one obtains the boundary conditions on the tangential components of $\vec E$ across two boundaries by using a small closed circuit so that \begin{align} \oint \vec E\cdot d\vec\ell =...
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Dielectric Material with Variable or Tunable Permittivity

Is there a material or some kind of instrumental setup which is able to change its permittivity significantly thorugh some external factors, like radiation, current or temperature? I am trying to ...
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1answer
24 views

Effect of a linear medium on a plane wave's electric and magnetic fields using wave impedance

A homework problem provides that a plane wave is traveling through a medium with a electric permittivity of 2.54 and has an electric field strength $E$ of $5V/m$. I am asked to find the magnetic field ...
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1answer
50 views

Is the capacitance of all types of capacitors increased by a factor of dielectric constant like parallel plate capacitors?

I've learnt that the capacitance $C$ of a parallel plate capacitor is given by: $$C=\frac{A\epsilon_0}{d}$$ where, $A$ is the area of cross section of the plates and $d$ is the separation between the ...
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1answer
27 views

Sphere, dielectrics and bound charge

I have this situation. A conducting metal sphere of radius $a$ and charge $Q$, surrounded by a dieletric shell with inner radius $a$ and outern radius $b$. If I try to evaluate the induced charge ...
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Permittivity and electric Susceptibility intuition

I have a question on the intuition behing the relation between relative permittivity $\epsilon(\omega)$ and electric susceptibility, $\chi_e$ of a of a material, more precise a dielectric medium. ...
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1answer
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Gauss's law and material dependency

Is Gauss's law $$\Phi_E = \oint \vec{E}\cdot{d}\vec{a}=\frac{Q_{int}}{\epsilon_0}$$ dependent on material properties? If yes, how should it change based on the material involved? Thanks in ...
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How does gravity affect the permitivity of a dielectric?

Intuitively, I would not expect gravity to significantly affect electric permitivity. But, Consider a neutral black hole with a plastic sphere outside the event horizon. The protons-electrons of the ...
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1answer
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Ionization of Dielectric Material

I'm reading Introduction to Electrodynamics by Griffiths and in chapter 4 when discussing induced dipoles and the effect of an electric field on an electrical insulator, it says the following: ...
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How London dispersion forces come into existence out of nowhere?

I was revisiting the chapter on states of matter and one thing that bothered me was a section on London dispersion forces. This is what the textbook says: Atoms and nonpolar molecules are ...
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Does a charge moving through a dielectric at any speed create radiation?

A moving charge has a corresponding electric field, which is time and position dependent. If the charge is moving through a dielectric, this electric field will induce a certain polarization in the ...
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1answer
29 views

Adding dielectric to a capacitor

When we introduce a dielectric of dielectric constant $K$ in the space between the conducting plates(slowly) of a capacitor connected to a battery with a voltage $V$ across it, we find that an extra $(...
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Gauss-Theorem on a solid dielectric sphere

We have an $Q=2\, \textrm{nC}$-load uniformly distributed on a solid dielectric sphere of $R=1\, \textrm{m}$-radius with center at the coordinate origin of an $Oxyz$ axis system. At the $O$ centre of ...
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Reason behind dependence of forces on the medium [duplicate]

I am a high school student and have covered basic concepts in electrostatics, magnetism and gravitation. It is clearly stated in my text book that the gravitational force experienced between two ...
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63 views

Fringe fields do not explain the origin of the force pushing dielectric slab inside a capacitor?

In the problem of a dielectric slab being inserted between the plates of a parallel plate capacitor, it is usually argued that the origin of the inward force acting on the slab is the fringing ...
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Calculate $\epsilon_1$ given geometry and capacitance

The space between two plates in a capacitor is filled with a material with permittivity that varies according to $$\epsilon(x)=\frac{\epsilon_0}{1+\frac{\epsilon_1}{3d^2}x^2}, \tag1$$ ...
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1answer
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Electric displacement vector $\mathbf{D}$: linear dielectrics

Excuse me for this simple question, but I have occurred of a clarity for this question. The Electric displacement vector $\mathbf{D}$ is defined, as: $$\mathbf{D}=\epsilon \mathbf{E}+\mathbf{P}$$ ...
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1answer
80 views

What happens when a dielectric-ball is placed in the uniform electric field?

Let the space filled with a dielectric having a dielectric constant $\varepsilon_1$, there are a uniform electric filed $\textbf{E}_1$ in the space. We set a dielectric-ball in this space. My text ...
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2answers
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Why is the energy density in dielectrics greater than that in vacuum for the same electric field?

The following text is from the book Concepts of Physics by Dr. H.C.Verma, from the chapter on "Capacitors", page 154, under the topic "Energy in the Electric Field in a Dielectric": Consider a ...
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1answer
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Dielectric constants of semiconductors

If a material has a high dielectric constant, is it a good semiconductor? I am asking this because from what I understand, the dielectric constant in a way measures the materials ability to hold ...
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1answer
101 views

What is the expression of electrostatic energy density in dielectric medium?

I read in my book electrostatic energy density is $ \frac{1}{2} \epsilon_0 E^2$, where $\epsilon_0$ is permittivity of vacuum and $E$ Is electric field in that region. But I want to know whether it is ...
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1answer
39 views

Are these forms for effective permittivity equivalent?

I was browsing through a book and noticed the following form for effective permittivity (Eq. 1.14.2 of this book): $$\epsilon(\omega) = \epsilon_d(\omega) + \frac{\sigma_c(\omega)}{j\omega}$$ ...
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33 views

Force on charge next to dielectric half space

Given the charge q placed at (0,0,d), next to an infinite half space filled with a dielectric with $\epsilon_1$ which extends to z<0. Calculate the Force on the Charge by Integrating the stress ...
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1answer
48 views

Capacitor problem: What's wrong with this?

The capacitor shown contains 3 different dielectric material $\epsilon_1,\epsilon_2,\epsilon_3$ between the top and bottom metallic plates on which lie teh points $A$ and $B$ as shown. The electric ...
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29 views

Dielectric between two like-charged plates

I have read that a dielectric can be inserted between two capacitor plates, thereby increasing capacitance of the capacitor. But what happens if we try to insert a dielectric between two like-charged ...
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34 views

Dielectric Slab: Force due to fringing field

A parallel plate capacitor whose plates are maintained at a constant potential difference has a partially inserted dielectric slab. The force on the dielectric slab is given in most of the books. (...
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1answer
38 views

What's the quantum origin of electric polarization?

In electrostatics, the polarization vector $\vec{P}$ is introduced as the sum of dipoles in materials. But from the viewpoint of microscopic, the dipole is ill-defined due to all materials are ...
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2answers
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Why does increasing capacitor dielectric allow it to store more charge under constant voltage?

Take two capacitors that are each connected to and charged from identical constant voltage sources. The capacitors are identical in every way (distance, area, etc) except that their dielectric ...
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9 views

Volume required to calculate D and H macroscopic variables

For a dielectric, we replace E, B by D, M realizing that the latter pair is a macroscopic property averaged out over a large number of molecules. What is the lower bound on number of molecules or ...
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2answers
38 views

Effects of Dielectric on the Electrostatic Potential Inside a Capacitor

Let's consider two identical capacitors (same geometry) with the same applied DC voltage, but with different dielectrics. Is the electrostatic potential function V (y) (with y = distance with ...
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1answer
24 views

Method of Images - Point Charge with Semi-infinite Dielectric

To calculate the electric field for the system where a point charge is placed at a distance d from a semi-infinite dielectric medium (eg. http://farside.ph.utexas.edu/teaching/jk1/lectures/node42.html)...
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1answer
37 views

Energy of a dielectric rod [closed]

Let a dielectric rod kept in an electric field (initially in equilibrium) be rotated by an angle, and then released. Is some energy stored in it (the rod)? Why? What is the value of this energy? How ...

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