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1answer
287 views

Dielectric sphere placed in another dielectric medium with uniform external field: is there a surface charge density?

Consider a dielectric sphere placed within a dielctric medium. There is a uniform electric field $E_0$ present throughout in the medium. Would there be surface charge on the sphere?
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0answers
15 views

capacitance inside dielectric [on hold]

two parallel plate capacitor separated by 2 mm,are at a potential difference of 20 v.A dielectric sheet of dielectric constant 2 and thickness 1 mm is inserted between the plates.How does the ...
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0answers
12 views

How can I know the induced charge density in a dielectric?

There's an infinite conduciting plane lying over the XY plane, conected to a battery that keeps it at a constant potential $\phi_0$. At a distance $D$ from the plane there is a point charge $q$ that ...
0
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1answer
161 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 ...
0
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1answer
21 views

Charging capacity and capacitance of a conductor

I know that charging capacity of a conductor is the maximum charge a conductor can hold And capacitance is the ability of a conductor to hold charge in a given potential . But how are these two ...
0
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2answers
231 views

Dielectric boundary

I am trying to determine why electric field may be confined to a certain region if there is a large difference in the permitivity for example if electric field flows through water and then reaches a ...
0
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1answer
15 views

Dielectric permittivity tensor of rank 2

In special relativity, one knows the Euclidean and Minkowski metric to raise or lower the index of a covector or vector. The Euclidean metric is a (1,1) tensor and is represented by a 3x3 identity ...
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3answers
401 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 ...
4
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4answers
216 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 ...
4
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2answers
93 views

What happens to the electric field at the boundary of a dielectric?

The question in the title is a broader one, but for now, I want to confine myself to the following problem. I have the task to find the potential difference between points A and B shown in the ...
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0answers
10 views

Electric displacement and Field

Given a problem with dielectric constant value in a region and asked me to find Electric Field and Electric Displacement inside the medium, Should I calculate E first or D first?
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1answer
142 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 ...
0
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1answer
19 views

The effect of an electric field on capacitance

Decreasing the distance between the two parallel plates of a capacitor increases the amount of charge that can be held on each plate. If this is because the charges are attracted to each other and ...
2
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1answer
34 views

Difference between dielectric and insulators

AS per my knowledge - dielectric are insulators which can be polarized in presence of external electric field. Does that mean all Insulators are not dielectrics ? If yes then kindly share example of ...
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0answers
13 views

Constructing a chriped dielectric mirror for negative dispersion for ultrashort laser pulses resulting in group velocity delays

I'm currently looking at designing a chirped mirror for a project but I am confused over several aspects. I understand the principle of a chirped mirror in terms of how a laser pulse has a broad set ...
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3answers
5k views

How is bound charge and free charge possible?

I am studying Introduction to Electrodynamics by Griffiths and I came along a concept I cannot seem to understand properly. The concept of free charge AND bound charge. I do not understand how we can ...
0
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1answer
123 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 ...
3
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2answers
52 views

Electric field inside a material

I was thinking about the polarisation, and how the electric field behaves inside the material of permittivity greater than one. I think to have understood what happens to D and P, but is not clear ...
0
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2answers
444 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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2answers
45 views

Electric Field Vector on an insulating solid ball

An insulating solid ball with radius $R$ has a uniform charge density $ρ$. Find the electric field vector inside and outside of the ball if it has dielectric constant $K$. Normally, I'd treat ...
2
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1answer
38 views

Gauss law in dielectrics

How shall we apply Gauss's law for a space such that the volume enclosed by the Gaussian surface have 2 or more mediums with different dielectric constants, such that equal or more than two ...
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0answers
23 views

Why is the direction of E field inside a Linear Dielectric same as an external field?

If an uncharged linear dielectric is exposed in a uniform external field, an e field inside is induced that points in the same direction as the External field, Why is this so? Isnt the field be ...
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0answers
29 views

What exactly is Breakdown Voltage of Air?

Most of the online sources say that the breakdown voltage of air is 30kV/cm. I've made a Cockcroft Walton multiplier and I can see the air breaking in between 17-18kV/cm. Only in a discussion at one ...
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1answer
41 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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2answers
40 views

Capacitor and Dielectric [closed]

Here's a homework problem: A $12 \mu F$ capacitor $C_{1}$ consists of plates $A$ and $B$. An $18 \mu F$ capacitor $C_{2}$ consists of plates $C$ and $D$. (a) Each are charged up by a $10 V$ battery ...
0
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1answer
26 views

I want to use the complex susceptibility to prove that E dot J is independent of the real part

As stated above, I want to use $\chi$=$\chi'$-i$\chi''$ to prove that E$\cdot$J is related to $\chi''$ and independent of $\chi'$. I need to do this using a monochromatic field ...
0
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1answer
42 views

Inserting dielectric slab into a capacitor

I studied that inserting the slab into a capacitor which is connected to a battery is difficult and we have to do the work, and inserting the slab into a disconnected capacitor is easy and we don't ...
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1answer
27 views

Things that must be considered when mass producing a capacitor [closed]

The question is to list four things that must be considered when a capacitor is chosen for inclusion in a circuit which is to be mass produced. Are there a specific set of four things? I've come up ...
2
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1answer
73 views

When exactly do we substitute $\epsilon_0 \rightarrow \epsilon$ and $\mu_o \rightarrow \mu $?

If everything is embedded into vacuum, why aren't Maxwells Equations always with $\mu_o$ and $\epsilon_o$? When exactly do we have to make the substitution $\epsilon_0 \rightarrow \epsilon$ and ...
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0answers
86 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 ...
4
votes
2answers
85 views

What is the meaning of the zero point of the real part of the dielectric function for a semiconductor?

I basically understand the zero point of the real part of the dielectric function for a metal. It generally corresponds to plasmon. For a metal, if the frequency is lower, the real part is negative ...
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0answers
24 views

Calculating potential differences: why integrate E- and not D-field?

So here's my problem. I was thinking about the following. Let's say we have a parallel plate capacitor, filled completely with a dielectric medium. If we want to find the potential difference between ...
0
votes
1answer
50 views

Variation of electric field with volume of dielectric in space

Suppose there are 2 spheres which have charges $+q$ and $-q$ and separated by a distance d. Let the field be $\vec{E_0}$. Now I bring a dielectric rod which is eqal in length to the separation ...
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1answer
46 views

Is Gauss law still true in dielectric material?

In vacuum we have $$\nabla \cdot \mathbf{E} = \frac {\rho}{\varepsilon_0}.$$ Can we still use this formula when there's dielectric material in space? Where $\rho$ is total charge density.
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1answer
37 views

Applicability of coulombs law for objects in different dielectric media

Is the Coulombs law applicable for inter-medium interaction? Consider the example image shown below How can one deduce the angles the bobs might make if they are in different dielectric ...
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0answers
26 views

How can a metal and an insulator have high dielectrics yet one is conducting and one is insulating?

I don't get it: insulators are referred to as dielectrics. The higher the dielectric the higher the insulation(?). But the dielectric constant of metals is considered infinite. Aren't they supposed to ...
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0answers
25 views

Physics of the capacitance of an electrolytic capacitor

In explanations about the electrolytic capacitor one often cites the formula $$ C = \epsilon_r \epsilon_0 \frac{A}{d} $$ for the capacitance $C$. Then one says that by enlarging the area $A$ via ...
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1answer
17 views

Absorptance in multilayer dielectric [closed]

I have a simple question regarding absorptance in the 2nd of two back to back dielectric slabs: If I know the total reflectance R, transmittance through the first slab t1, and total transmittance T ...
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0answers
156 views

Electric Honeycomb

Set a vertically oriented steel needle over a horizontal metallic plate. Place some oil onto the plate. If you apply constant high voltage between the needle and the plate, a cell structure appears on ...
1
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1answer
1k views

What is the force between two charged objects when the space between them is partially filled by a dielectric medium?

I am given two charged particles of same charge at a distance of $r$. They initially apply force $F$. Now an infinite dielectric (of dielectric constant $4$) of width $\frac{r}{2}$ is introduced ...
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0answers
44 views

Detect ions in water using impedance spectroscopy

I would like to check the presence of Na, Ca or other ions dissolved in water using impedance spectroscopy. I was thinking that because the ions have different masses they will have different ...
2
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1answer
494 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 ...
6
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1answer
242 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
15 views

Are diodes (or FETs) electrets?

The explanations I see of diodes and FETs seem to involve various depletion regions, migration of electrons and holes, and the such. My (perhaps naive) interpretation of these explanations implies ...
1
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2answers
136 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 ...
2
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0answers
20 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
18 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?
1
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1answer
34 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: ...
0
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1answer
28 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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3answers
147 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) + ...