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14 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 that ...
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0answers
42 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
96 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
93 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
47 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
36 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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1answer
110 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
71 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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5answers
247 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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2answers
498 views

Capacitors in a series circuit with dielectric

When a dielectric slab is inserted between the plates of one of the two identical capacitors in Fig. 25-23, do the following properties of that capacitor increase, decrease, or remain the same: (a) ...
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1answer
32 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
244 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 dt^{\...
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1answer
249 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
163 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) + \frac{i\...
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1answer
440 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 $K_{1}...
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4answers
217 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
54 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
901 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
83 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 ...
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1answer
63 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
89 views

Qualitative 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
166 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
758 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
530 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
92 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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1answer
33 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
33 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
83 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
79 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 $\epsilon_r$ ...
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2answers
1k 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 ...
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3answers
251 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?
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1answer
236 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 ...
2
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1answer
80 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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1answer
969 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 ...
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1answer
186 views

Dielectric constant of Transition Metal Dichalcogenides (TMD)

Why is the in-plane dielectric constant of transition metal dichalcogenides larger than the out-of-plane dielectric constant? Is this because of the spacing between monolayers of the TMD? Why do these ...
3
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1answer
729 views

Dielectric slab inserted into a constant voltage capacitor

I was told that a dielectric slab inserted into a capacitor connected to a battery (constant voltage) will be repelled, because the energy stored in the capacitor increases when the dielectric is ...
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3answers
272 views

How to find dielectric constants of ferroelectric materials experimentally?

What is the procedure to find out dielectric constant of barium titanate at different temperatures ?
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1answer
77 views

Dielectric heating - does EM field transfer energy to polar molecules?

In AC field, polar molecule are trying to align with external field. At high freguencies, changes of field are so quict, that molecules cannot align with it. This leads to increasing kinetic energy of ...
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0answers
28 views

Why breakdown voltage decreases with increasing FWHM of an asperity?

I am running a simulation for a dielectric breakdown. I am getting breakdown voltage decreases with FWHM, which does not make sense as field enhancement is higher for a small width. Simulations solve ...
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1answer
1k views

The advantages of a dielectric in a capacitor

In a capacitor a dielectric can be placed in between the two plates. I have trouble understanding the points / advantages of a dielectric from what I have read in a text book. The points written there ...
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3answers
411 views

Electromagnetism boundary condition

The dielectric slab surrounded by air as shown in diagram has permittivity $\epsilon$ different from air and permeability almost same as air. Electric field everywhere within the slab is given to be $$...
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1answer
131 views

Charged dieletric/conductor in capacitor

It is a standard problem to consider a dielectric or a conductor between the parallel plates of a capacitor. But what happens to capacity, voltage, charge, inserting between the plates of an ideal ...
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0answers
1k views

How are band gap energy, dielectric constant (permittivity) and resistance related to each other?

The following three properties are related to current flow: Band gap energy Dielectric constant Resistance I would expect them all to have the same trend (i.e. higher band gap energy would cause ...
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3answers
1k views

Why is signal bad in a tunnel?

Consider this: you are driving through a tunnel listening to your AM radio and a GPS, all of the sudden AM radio has nothing but statics and your GPS says "reconnecting - please hold". You say to ...
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1answer
733 views

Force per unit length between two long parallel wires, one of which is insulated

Suppose we have two very long parallel wires of radius $a$ and distance between their axes $d$ ($d>>a$). The first wire if is carrying charge of linear charge density $\alpha$ and is insulated ...
2
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0answers
75 views

Validity of the static limit of a dielectric function

In general, the dielectric function $\epsilon(q,\omega)$ reflects the spatial and temporal response of a condensed matter system to an applied potential. If we put an electron into an electron sea, ...
2
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1answer
64 views

Question about wavelength of EM wave in dielectric

Many websites (http://maxwells-equations.com/materials/permittivity.php) lists out the following formula as to how you can compute the wavelength of an EM wave in a dielectric $$\lambda_d = \lambda_o/...
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1answer
331 views

Dependence of capacitance on its build material

We know that the capacitance of a capacitor depends on the dielectric material in between the plates as $$C=\dfrac{K\epsilon_0 A}{d}\,.$$ But what if the electrode material is changed? For example ...
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0answers
88 views

Dielectric constant of gases - constant?

A number of questions related to the topic: Is the dielectric constant actually constant as a function of temperature and frequency (when used in a capacitor)? Is it constant as a function of field ...