The tag has no usage guidance.

learn more… | top users | synonyms

0
votes
0answers
16 views

Lightning, Electrical breakdown, and Current

Recently a discussion came up about this gif: http://i.imgur.com/r9Q8M4G.gifv This lead to a few questions about electrical breakdown of insulators. The disagreement we're having is whether or not a ...
0
votes
1answer
24 views

Numerical calculation of electric field in dielectric medium

I want to numerically calculate the electric field between two parallel plates with finite length. Where parallel plates are connected to source of constant potential difference: I have boundary ...
0
votes
0answers
25 views

Black body emission by a dielectric slab [on hold]

I need to calculate the radiation emitted by a rectangular dielectric slab (glass) at temperature $T_0$. The slab has a thickness $t$, sides $a,b$ and a dielectric constant $n(\lambda)$. How can I do ...
0
votes
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 ...
5
votes
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 ...
1
vote
0answers
44 views

Refraction of the electric field lines, at the interface of separation between two conductive media

Suppose we have 2 media with electrical parameters ${\varepsilon _1},\,{\sigma _1}$, respectively ${\varepsilon _2},\,{\sigma _2}$, separated by the plane surface $\Sigma $; electrical charge surface ...
0
votes
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 ...
1
vote
1answer
297 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?
4
votes
3answers
7k views

Electric field intensity in a dielectric inside a capacitor

In the question A parallel plate capacitor is charged from a cell and then isolated from it. A dielectric slab of dielectric constant $K$ is now introduced in the left half region between the ...
0
votes
0answers
44 views

Why does the polarization vector P depend on the net electric field and not the original one?

P= χε0E, where E is the net electric field from the effects of both free and bound charges. But E=(σfree-P)/ε0 So E itself depends on P. My concern is, isn't this circular? ...
1
vote
0answers
66 views

Work to assemble charge distributions in the presence of a dielectric

I am asked by a problem to: Find the potential energy of a point charge in vacuum a distance $x$ away from a semi-infinite dielectric medium whose dielectric constant is $K$. I wish to approach ...
0
votes
3answers
247 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
votes
1answer
250 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
votes
0answers
193 views

Electric Honeycomb [duplicate]

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 ...
2
votes
3answers
916 views

Dielectric slab counter-intuitive formula?

For the calculation of force on one of the two equal(in magnitude, opposite in sign) point charges separated by $r$ with a dielectric slab of dielectric constant $K$ and width $d$ in between, the ...
-1
votes
1answer
55 views

what is the physical significance of dielectric constant and loss tangent?

I want to know that the significance of dielectric constant and loss tangent behaviour. How it characterises the materials. and possible relation between the dielectric constant and polarisation ?
0
votes
1answer
27 views

Does the sign of imaginary part of complex permittivity have any physical meaning?

I have noticed some papers having written complex permittivity as $e' + je'' $ and others as $e' - je''$. The data in literature does not specify the sign. What should I use and does the sign of $e''$ ...
14
votes
2answers
866 views

Why is there no permittivity-type constant for gravitation?

When I look at electric or magnetic fields, each of them has a constant that defines how a field affects or is affected by a medium. For example, electric fields in vacuum have a permittivity constant ...
0
votes
2answers
52 views

Why doesn't the gravitational force have a permittivity in its formula? [duplicate]

We know that the electrostatic force between two charges depends on the medium between the charges and its permittivity. Why, then, doesn't the gravitational force depend on the medium?
0
votes
0answers
17 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
votes
1answer
33 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
votes
1answer
23 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 ...
4
votes
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 $$...
4
votes
2answers
109 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 ...
0
votes
0answers
12 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?
0
votes
1answer
29 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
votes
1answer
44 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 ...
1
vote
0answers
15 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 ...
1
vote
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 ...
3
votes
2answers
55 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
votes
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) ...
0
votes
2answers
46 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 this ...
2
votes
1answer
42 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 ...
0
votes
0answers
24 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 ...
1
vote
0answers
37 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 ...
0
votes
1answer
46 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 ...
0
votes
2answers
53 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
votes
1answer
27 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 E(t)=E($\omega$)*exp(...
0
votes
1answer
79 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 ...
-1
votes
1answer
63 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
votes
1answer
74 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 $\...
0
votes
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 ...
4
votes
2answers
97 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 ...
0
votes
0answers
26 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
56 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 ...
1
vote
1answer
53 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.
0
votes
1answer
40 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 medium?...
0
votes
0answers
30 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 ...
0
votes
0answers
27 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 ...
1
vote
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 (...