Dielectric Definition and 676 Threads

usually when we have some initial variable U(0), and we have some factor K that changes this initial variable, we usually express the new variable U(f) like so.. U(f)=KU(0) and NOT the other way around... so why is the dielectric constant expressed in the following way? Eκ=E0 this...

Hello everyone here! See i got my hands on this paper: Optical properties of metallic films for vertical-cavity optoelectronic devices by Rakic et al. A simple google search of the title will give you access to the paper. Now, i am writing the function in MATLAB to calculate the...

Hello. I am not sure if I must post here. The problem is not for homework, it derived from a classmate's question. Homework Statement We have a large quantity of liquid dielectric with relative permittivity \varepsilon and a charge Q immersed in the liquid in depth h. We bring another...

Hi everyone, I have a question about electric potentials and dielelectrics: 1. when I have a dielectri in the half space x<0 and air in x>0 is the potential steady at x=0? 2. does a potential depend on the relative permittivity ? I know that the electric field gets weaker in a...

Hi everyone I have an understanding problem concerning the method of images method Homework Statement Jackson uses this kind of problem in his textbook but I don't understand it. We have a charge q on the z axis at distance d. the dielectric constant is e1 when z>=0 and e2 when z<0. Now...

Assume that there is a dielectric material with a mass density of ρ0 observed in the dielectric-rest frame. And further, it is assumed that observed in the lab frame, v(x,y,z,t) is the velocity distribution, β=v/c is the normalized velocity, and γ=(1-β2)-1/2 is the relativistic factor, with c...

Homework Statement the separation of a parallel plate capacitor is 2mm with a potential difference between them of 45V. (i) Find the electric field between the plates. (ii)Find the charge per unit area of the plates if the permittivity of the dielectric medium is 20 \epsilon_0 (iii) Find...

(My last https://www.physicsforums.com/showthread.php?p=4424810#post4424810 post did not get much attention so I try again without all these formulae. Think this will be more clear...) To derive the local field in a non-polar dielectric you assume a very small spherical cavity in which (since...

Can someone help me in understanding where I am wrong when thinking about the derivation of the Lorentz field in a dielectric. I give the derivation in italics (although the familiar reader should not need to read it) and after that I present the paradox. The basic idea is to consider a...

Hi, I have a question regarding the boundary condition present for a dielectric immersed in a static field. I hope one of you physics guru's can shed some light on this. Suppose we have a dielectric in space subjected to some external static electric field. I have read (without explanation)...

Hi, One of the boundary conditions when solving for the potential, \Phi, outside a dielectric sphere placed within a uniform electric field is \lim_{r→0}\Phi(r,θ)<\infty Can anyone explain/prove why this so. Thanks,

Hello all, I'm new to the forum so I hope I'm posting this in the correct section. I'm currently conducting an experiment in which I'm examining how the dielectric constant of a binary mixture changes with concentration and temperature using a parallel plate capacitor for measurements. The...

Homework Statement A conducting sphere of radius ##a## carries an initial charge ##q_o##. It is surrounded by another concentric sphere of radius ##b##. The space between the two spheres is filled with a dielectric of permittivity ##\epsilon## and conductivity ##\sigma##. Find the electrostatic...

Dielectric break down... i understand that there is current passing through the insulator but why is this damaging to the insulator? please go as deep as you can. thankyou

Homework Statement A point charge Q is placed at a perpendicular distance a from an infinite planar LIH (linear, isotropic, homogeneous) dielectric of relative permittivity ε. By considering the normal component of the electric field at an arbitrary point just inside the dielectric to be the...

Homework Statement Calculate the capacitance of a spherical capacitor of inner radius A and outer radius B which is filled with a di-electric varying as e=c+dcos^2θ . c and d are constants and θ is the angle made with the z axis.(also known as the polar angle) Homework Equations $C=εA/d$The...

and frequency? Could someone point me in a direction where this is explained in depth? I understand polarization and the dielectric constant as I've taken E&M 1

Homework Statement If the max E-field in the capacitor is E=1.2(103) N/C and the space between the plates is filled with a dielectric of constant 100,000, what is the separation between the plates? Homework Equations I know C=kεoA/d where k is the dielectric constant, A is the area of...

can negative dielectric constant be possible?if yes then for which one.

Homework Statement Two point charges of magnitude q and 3q are located at a distance of 'a' from each other within an infinite dielectric medium of dielectric constant k. The force by the larger charge 3q, on the dielectric equals A)zero B)##\frac{1}{4\pi \epsilon_o}...

Hi! I have a high school physics question. I know the concept of induction, and I also know what happens when a dielectric slab is placed between 2 plates of a capacitor. 2 charged particles are kept at a distance r. The mutual force of attraction/repulsion is F. What happens to the force...

Homework Statement A large block of dielectric contains small cavities of various shapes whose sizes are much smaller than the block. The dielectric has uniform polarization P except those cavities which are assumed not to disturb the polarization of dielectric. (a) Show that, inside a...

Homework Statement Draw the equivalent circuit for a lumped capacitance with dielectric losses that would be appropriate at RF frequencies. Homework Equations Possibly Xc=-j/ωC The Attempt at a Solution I do not really know what the question is asking. I know that a lumped capacitance...

Homework Statement An arbitrarily-shaped object is given a charge q and is then surrounded by a dielectric of permittivity ε as shown in the figure below Find the charges induced in the inner and outer surface of the dielectric. Homework Equations I'm not sure but Gauss's law may...

Would a magnetic field have any effect on the dielectric breakdown of insulators? For example, the dielectric breakdown of air is 3 Mega volts per meter at a gap of one meter; if you applied a magnetic field to that breakdown, would it help guide the electrons along the path and therefore reduce...

Homework Statement Two point charges a distance d apart in free space exert a force of 1.4∗10^−4 [N]. When the free space is replaced by a homogeneous dielectric medium, the force become .9∗10^−4 [N]. What is the dielectric constant ϵr of the medium? Homework Equations E=F/Q The...

What's the difference between Corona Discharge and Dielectric Breakdown? For me both stand for the same process, but wikipedia (as many other sites) says they are different. Actually they say corona discharge occurs when the electric gradient is high but not enough to create an electrical...

Homework Statement 2 parallel plate capacitors of distance separation d between the plates are connected in parallel of capacitance C_1 and C_2 respectively and charged with a voltage V after that the Voltage is disconnected and a dielectric of κ is inserted into C_2 I) Express the charge on...

Homework Statement The voltage across an air-filled parallel-plate capacitor is measured to be 181.0 V. When a dielectric is inserted and completely fills the space between the plates as in the figure below, the voltage drops to 27.0 V. What is the dielectric constant of the inserted...

Is there some material that could withstand relatively high voltages before it starts to conduct electrons,but in the same time a good hole conductor? Could such material be obtained by doping some dielectric similar to SiO2?

This is polarization density. Can somebody explain to me why exactly this is so? My book just says that's how polarization is defined.. Can you guys give me an intuitive understanding of why? Only thing I know is that χ is related to κ, the dielectric constant, and κ is related to how well a...

Hello! In the study of electric and magnetic fields, two equations are called the constitutive relations of the medium (the vacuum, for example): \mathbf{D} = \mathbf{\epsilon} \cdot \mathbf{E}\\ \mathbf{B} = \mathbf{\mu} \cdot \mathbf{H} But in a generic medium (non linear, non...

I'm studying the dispersive properties of metals using Lorentz-Drude model, but I'm confused about the equation set-up. What is LD model different from the classical dielectric function using for other dielectrics? Namely: ε(w) = ε’ + iε’' where the imaginary part is the attenuation. In...

Homework Statement Two concentric conducting spheres of inner and outer radii a and b, respectively, carry charges +/-Q. The empty space between the spheres is half-filled by a hemispherical shell of dielectric (of dielectric constant ##\varepsilon / \varepsilon _0## ). a)Find the electric...

Suppose a (parallel plate) capacitor of capacitance C is charged to a potential difference V and then disconnected and isolated. Energy stored E1= Q2/2C. Now if a material of appropriate dimensions and dielectric constant K is fully inserted between the plates, energy stored E2= Q2/2KC. E2...

It is usually written that the speed of light in a dielectric medium is ##v=\frac{c}{\sqrt{\epsilon_r}}##, where ##c## is the speed of light in vacuum and ##\epsilon_r## is the relative permittivity. But, how can it be calculated for lossy and not necessarily low-loss dielectrics, i.e. those...

Hi, can i know how to get the dielectric constant of the egg tray (the one with the paper) beside using dielectric probe technique? is it have same dielectric constant of paper? or it is different? i hope someone can help me. if the egg tray mix with the carbon or graphite, as i know the...

In Griffiths, for deriving the bound charges for a given polarization P , the formula used is the general formula for dipoles .i.e ( equation 4.9) {Here the potential at r is calculated due to the dipole at r' ) V(r) = ∫\frac{x.P(r')}{X^2}d\tau' Here X = r - r' , and x = unit vector in...

Hi, In deriving a complex wave vector for waves in media, an equation D = ε E is typically used. Later though, it is common to relate D and E through a complex ε which is generally written as εcomplex = ε + 4 pi i σ / ω. It seems a contradiction to insert one relationship into the Maxwell...

hello, I am learning electromagnetism and read the polarization in dielectric. The textbook tell me that in linear dielectric exists a simple relation: P=\chi*ε0*E where \chi is the susceptibility, ε0 is the permittivity of vacuum and E is total electric...

A spherical capacitor is formed from two concentric, spherical, conducting shells separated by vacuum. The inner sphere has radius 0.39 m and the capacitance is 108 pF. What is the radius of the outer sphere? Give your answer in meters to the third decimal place. C-->Capacitance...

Hi, I'm interested in how a dielectric sphere effects a (spatially) uniform time varying field. I'm sure I'm not the first to inquire about this very topic. Could anyone direct me to a resource? Thanks,

Hi, Do material posses both dielectric as well as resistance properties? I imagine that when there is a difference in potential across a volume of some material, some current will flow (I=V/R <-- the material's resistance), but also the material may become polarized to a certain degree...

I've examined and re-examined the proof that the energy density of a linear dielectric is u=\frac{1}{2}\mathbf{D}\cdot\mathbf{E}, but I still don't understand it. I'll rewrite it here and try to explain what I'm having trouble grasping. We first imagine that the free charge (as a function of...

Given the following statement: "A plane wave is incident (from the free space) upon a semi-infinite medium made of N=100 different lossless dielectric slabs." Visually/spatially, what does this look like? I can see two possibilities 1) the slabs are stacked on top of each other...

1)What exactly is meant by the 'static limit' where the frequency is taken to zero, but the wavenumber is finite? I am getting confused because if the frequency is zero, then surely the probing electrons/photons/whatever have no wavelength, so how can the wavenumber be finite and non-zero? 2)...

Homework Statement Suppose the field inside a large piece of dielectric is \vec{E}_{0}, so that the electric displacement is \vec{D}_{0}=\epsilon_{0}\vec{E}+\vec{P}. a. Now a small spherical cavity is hollowed out of the material. Find the field at the center of the cavity in terms of...

Hi, so I'm having a little trouble understanding why... you would put a dielectric in between a parallel plate capacitor? I know it increases the capacitance but it does so by lowering the potential difference sooo... The charge is still the same, I believe the potential energy also decreases as...

Homework Statement A point charge q is located at the center of a dielectric sphere of radius a. Find D, E, and P everywhere and plot your results. What is the total bound charge on the surface of the sphere? (I assume by "everywhere" my professor meant inside and outside the sphere.) (D is...

Sometimes the dielectric function is defined as the connection between the total electric field in a material and the external field, \mathbf{E}(\mathbf{r},\omega) = \int \epsilon^{-1}(\mathbf{r},\mathbf{r'},\omega) \mathbf{E}_{\text{ext}}(\mathbf{r'},\omega) d \mathbf{r'}, and sometimes...