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2answers
50 views

Understanding parallel plate capacitors [closed]

I need help with understanding this assignment. I originally though of using the equation of Eo*A/D = Q/ΔV but I don't know how to answer this without actual numbers to plug in besides the epsilon-not ...
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0answers
16 views

Advantages of placing a solid dielectric [closed]

If a solid dielectric is placed between the plates of a capacitor, its capacitance increases. What ae the other advantages of placing a solid dielectric?
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0answers
17 views

Can I tell if a material has undergone dielectric breakdown? [closed]

Can I tell without specialist equipment if a material has undergone dielectric breakdown?
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1answer
30 views

Relation between dipole moment and polarisaton

In the Landau's book "Electrodynamics of Continuous Media" he derives the relation between the polarisation $\vec P$ and the dipole moment $\vec p$. Starting with the definition of the dipole moment: ...
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1answer
23 views

Confusion about the total bound charge of a sphere placed in dielectric

There is a solved exercise in which a charged sphere of radium $r=a$ is inside a dielectric material. The surface bound charge and the volume bound charge are respectively: $$p_{sp}=\vec{P}\cdot ...
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0answers
38 views

Can I safely heat stainless steel 1-2 inch ball bearings in a consumer microwave? [closed]

I am looking to heat 1 or 2 inch stainless steel spherical ball bearings in a microwave. I would like the bearings to get to about 140 degrees F but not hotter. I have read that this should be fine as ...
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0answers
19 views

Relation between displacement current, dielectric and time varying Electric field

I know that displacement current is produced in dielectric material due to dipole moment. I also know that displacement current is produced by time varying electric field (according to maxwell ...
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0answers
20 views

Can we lock electric charges in dielectric cells?

Suppose next. We using Wimshurst machine and gathering charges in dielectric cells such as mica .Before discharge we put whole machine in vacuum chamber.Question is next. Can we storage those charges ...
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0answers
11 views

Electric field in a sphere embedded in a medium

Consider a system where a sphere of conductivity $\sigma_i$ is embedded in a large medium of conductivity $\sigma_e$. An electric field $E_0$ is applied and the question is, what is the electric field ...
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2answers
107 views

Displacment field for linear dielectric

Consider the following statement: In the case of a linear dielectric of arbitrary shape, when no free charges are present, in an external applied electric field $\vec E_0$, then $\vec D=0$. Is ...
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1answer
29 views

How to find the polarization of a dielectric sphere with charged shell surrounding it?

A shell with negligible thickness has a given charge density as a function of theta, and is filled with a dielectric material with a given electric susceptibility. Using lovely legendre polynomials ...
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1answer
31 views

Uniformly charged disk

A uniformly charged disk is an isolant or a conductor? Or could it be both of them? I only know its radius and its surface charge density, which is uniform throughout the disk.
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0answers
9 views

Calculating pressure on a dielectric kept inside a capacitor

Firstly, the pressure is because of the opposing forces acting on both sides of the dielectric slab. On the left side of slab, the field due to the left plate is $\frac{\sigma}{2\epsilon_0}$ and ...
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0answers
32 views

Dielectric field in a homogenous electric field

I'm working through my workbook right now and currently am stuck on the chapter about dielectrics. The term $\vec{E}=\frac{3}{\epsilon_r +2}\vec{E_0}$ was introduced without a proper proof. Instead ...
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1answer
59 views

Why phase velocity of light is slower in a dielectric than vacuum?

Why does light speed suffer a reduction when it passes through a homogeneous dielectric medium? I know my math says so, i.e.- a highly polarizable ($\chi$) medium is associated with high $\epsilon$ ...
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0answers
59 views

dielectric polarization

Suppose a small solid sphere made of an isotropic dielectric is introduced in the field of some given system of remote charges. Assuming that the polarization in the dielectric does not affect the ...
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0answers
26 views

Direction of polarization in dielectrics

Our teacher just taught us polarization in dielectric materials. I have some doubts that he wasn't able to clear. Is the direction of polarization, for any non-linear dielectric, in the direction of ...
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1answer
31 views

Plane wave normal incidence on dielectric, direction of fields

I'm having an extremely hard time to figure out the direction of the $\vec E_R$ (reflected electric field) and $\vec H_R$ (reflected magnetic field) as well as the transmitted fields. I've been ...
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0answers
28 views

Buy thin film electret material [closed]

I know that electret could be fabricated by charging the dielectric material (such as corona dis-charger); however, I do not know how to set it up and whether my school facility is able to do that or ...
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1answer
64 views

Rotating dielectric cylinder in magnetic field?

In this example we find that the polarization in a rotating cylinder is given by an iterative method (see section 2.2 in the link) using an effective $E$-field of $\vec E_0=\omega B \vec r/c$. Why ...
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2answers
60 views

Parallel Connection of Capacitor

Assume Two Capacitor filled with different dielectrics with dielectric constant $K_1$ and $K_2$ respectively in Parallel connection. Then we have same voltage $V$ on both capacitors. Therefore, ...
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4answers
168 views

Energy density with complex permittivity?

Question What is the correct form of the energy density when we have a complex permittivity (such as in a dielectric)? Additional information A complex permittivity means that we have: $$\vec ...
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1answer
28 views

Work done when applying an electric field?

On these example questions from MIT in the solution to 4.1 they write the work done by applying the electric field to be: $$W=V_0 \int \vec E \cdot d \vec D$$ Where does this equation come from and ...
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1answer
194 views

Why is $\textbf{D}$ the response to $\textbf{E}$?

In the text Wooten, equation 2.69 shows $\textbf{D}$ being the response to $\textbf{E}$ with $\epsilon$ as the response function: $$ \textbf{D}(\textbf{r},t) = \int d\textbf{r}^{\prime} \int ...
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0answers
69 views

Effect of a dielectric medium on electric field and electric flux

What is the effect of dielectric medium in comparison to vacuum on electric field and electric flux. I read that higher dielectric constant means higher relative permittivity which means more ...
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3answers
120 views

How is complex permittivity measured?

Complex relative permittivity is defined as $$\epsilon_r = \frac{\epsilon(\omega)}{\epsilon_0}=\epsilon_r^{\prime}(\omega) + i\epsilon_r^{\prime\prime}(\omega) = \epsilon_r^{\prime}(\omega) + ...
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1answer
80 views

Force between two charges when the dielectric constant of the material varies?

If two point charges $q_{1}$ and $q_{2}$ are seperated by a distance $l$ apart, and the space between them is filled with a variable dielectric constant. Near $q_{1}$, the dielectric constant is ...
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4answers
151 views

Are insulators non-ohmic conductors?

Can insulators/ dielectrics be considered as non-ohmic conductors ? As they apparently breakdown when sufficiently large potential differences are applied across them.
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0answers
39 views

what can be the BG and dielectric constant of monolayer MoS2 in semiconducting state (2H) and in metallic state (1T)

Monolayer MoS2 is a semiconductor that can undergo an MIT (Metal to insulator) or semiconducting state to insulating state transition. The semiconducting state is referred as 2H State and the metallic ...
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1answer
432 views

What's the meaning of linear medium in electromagnetism?

I'm studying the book Polarimetric Radar Imaging: From Basics To Applications and on page 31, there's this sentence: In the following, we shall consider the propagation of an electromagnetic ...
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3answers
58 views

Nonlocal dielectric function - what does it mean?

I'm reading this* article and in the second sentence of introduction I encountered a term I haven't heard of before. Namely: nonlocal dielectric function. What does this nonlocality mean? And how does ...
2
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1answer
49 views

Why there are spikes in permittivity Vs. frequency curve?

When the frequency is increased the permittivity of a dielectric material decreases. But in the way of decrease there are some spikes which indicates sudden increase of permittivity for certain ...
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0answers
75 views

Quantitative understanding of excess heat capacity in ferroics

I'm looking to understand what an excess heat capacity in a ferroelectric (FE) can correspond to qualitatively. Typically one starts with a Landau expansion of the free energy if you want to study the ...
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1answer
94 views

Surface bound charge in the electric displacement

In Griffiths, the electric displacement is written with just volume charge density, and that is because, he says, 'we cannot apply gauss law precisely at the surface of a dielectric, for here volume ...
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1answer
313 views

How does a bulb light up when it's connected in a circuit with an uncharged capacitor and a cell?

Since there is a capacitor, isn't it an incomplete circuit? How does the current flow across the dielectric medium? If a bulb was connected to a cell alone and if there was a break in the wires of the ...
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1answer
338 views

The truest/most general Maxwell's equations in isotropic, linear, inhomogeneous media with sources

Sources use $\mu H=B$ and $\epsilon E= D$, assuming homogeneous media. Obviously if $\mu$ is space varying, $\nabla . (\mu H)$ need not be equal to $\nabla . B$ What is the most general form for ...
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0answers
57 views

Calculating rise in water surface due to a charged capacitor

Two metal plates separated by a distance d & initially charged with charge +Q & -Q are kept so that it just touches the surface of a very large water tank as shown in figure a. Thus water ...
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0answers
30 views

Does water absorb microwaves above of beneath its relaxation frequency

I am a bit confused about the concept of relaxation frequency. In my course text we derived a model with the help of Newton's law to describe the movement of polar molecules in an electromagnetic ...
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1answer
27 views

Does polarization take place in non polarized solid?

According to polar - non polar division polar substances like H2O have dipole moment but unpolarised matter like O2 doesn't have dipole moment I.e. Dipole moment = 0. But my question is does ...
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0answers
29 views

Calculate characteristic frequency from atomic polarizability

With Lorentz model, the plasma frequency can be calculated from electron density $$\omega_p=\sqrt\frac{4\pi N e^2}{3m}$$ But I also found in this paper that it could also be calculated from atomic ...
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0answers
52 views

Density of polarisation charge is zero always for linear isotropic homogeneous dielectrics?

It seems to me that the volumetric density of polarisation charge in a linear homogeneous isotropic dielectric in an external field is always zero, but I find this rather surprising. Consider such ...
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0answers
75 views

What is the origin of the “polarization catastophe”?

According to the Clausius-Mossotti relation, $$ \frac{\epsilon_r - 1}{\epsilon_r + 2}=\frac{n\alpha}{3\epsilon_0} $$ So when $n\alpha = 3\epsilon_0$, the relative permittivity $\epsilon_r$ ...
2
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2answers
605 views

What would be electric potential due to induced charge sphere?

We know that the potential at the center of the charged sphere (if it is conductor) would be $$V_o = \frac{1}{4\pi E_0}\frac{+q}{x}$$ If the distance between charges is x from their center of the ...
0
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3answers
179 views

In the electric field we have dielectrics.What about the magnetic field?

Do we have insulators in the magnetic field just like we have dielectrics in the electric field? How are they called and how do they work?
1
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1answer
162 views

The Faraday experiment about electric displacement field

I read the description and the explanation of the result of the experiment in my book but still I can't understand it. Here is the process of the experiment. A pair of concentric metallic spheres ...
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0answers
21 views

Inhomogeneous scattering from a dielectric box in 2D?

I wrote an E&M simulator and need to verify the accuracy. My simulator evaluates a 2D grid (which is what my camera measures), and would like to test an object that is minimally perturbed by ...
2
votes
1answer
54 views

Why does the medium affect the Coulomb's constant but not the gravitational constant?

Why does the medium affect the Coulomb's constant but not the gravitational constant? My friend said maybe the particles of the medium affect the electric field. But the net charge in the medium is 0 ...
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0answers
59 views

Speed of light in a medium as superposition of dipole radiation

Studying electromagnetism I know that the speed of light in a medium is $v = c/\eta$ and that it's possible to derive this from the Maxwell equations in the medium. But I wanted to find a microscopic ...
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1answer
747 views

What is the meaning of permittivity of free space?

We all know about the value of permittivity of free space but is this actually enough of for our knowledge? We should be taught that what actually does permittivity of free space means.
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0answers
16 views

Force between charges when there's a slab of dielectric between them [duplicate]

Consider the following arrangement - Blue and red are two opposite charges +q and -q separated by a distance R. A dielecric slab is placed between them. The thickness of the slab is t. What will ...