Dielectric Definition and 676 Threads

Hi I read in text for calculation dielectric constant in Lorentz model, we only regard electric field that coupled with each oscillator. So the magnetic field of input wave has no effect in calculation of dielectric constant in this model?

It is Example 4.5 in Griffiths intro to Electrodynamics. A metal sphere of radius a carries a charge Q. It is surrounded, out to radius b, by linear dielectric material of permittivity epsilon ... He goes on to say that E = P = D = 0 inside the sphere. I understand that D = 0 inside, but...

Homework Statement REFER TO ATTACHED SCREEN SHOT Homework Equations The Attempt at a Solution My discrepancy is with the last question labeled "Exercise" (What is the maximum energy that can be stored in the capacitor?). Since the max voltage is 16000V = 16000 J/C, why is...

Hi. I have this problem, which I must solve. It says: two concentric conducting spherical shells, of radius a and b (a<b), are charged at Q and -Q respectively. The space between the spheres is filled at its half by an hemisphere of dielectric with dielectric constante ε. a)Find the field for...

Good day All: How can I prove that a linear relationship exist between the displacement (d) and the capacitance(C) of a Variable dielectric capacitor? I know that the equation for a capacitor's capacitance is: C= εA/d

Hello: I want to calculate the plasma frequency of Au, Ag, Cu and Al. But wondering what is the most precise way to calculate the plasma frequency.If anyone can help me with that it will be really appreciated. I know that Plasma Energy = √(n*e^2/(m*ε°)) = plank constant * ωp Here...

What is origin of magnetism in dielectric crystals?

Hi everybody, I am getting confused by a very simple problem: let's take an infinite sheet electrically charged with a surface density σ. Because the sheet is infinite, we can first determine that the electrical field on both side contains only components normal to the sheet. If the plate is...

There is a parallel plate capacitor having capacity C. It initially has got no charge on it. Now we insert a dielectric material of dielectric constant K between its plates (it still has no charge). Now we connect this capacitor (with dielectric) to a d.c source of potential difference V. Now...

Homework Statement See figure attached. Homework Equations The Attempt at a Solution I'm confused as to how they got their D(r) Using Gauss' Law, For r < or = a \oint_{S} \vec{D} \cdot \hat{n} dS = \int_{v} \rho dv D(4 \pi r^{2}) = \frac{\rho 4 \pi r^{3}}{3}...

At a certain distance from a point charge q there is small, dielectric ball. How would change the value of electrostatic force acting on the ball, if the value of a point charge would be doubled? According to F=k[(q1*q1)/r^2] there would be no force on the dielectric ball, because his resultant...

Homework Statement There is a charged dielectric sphere of radius R. I center it at the origin of an x,y,z cartesian system. It has a charge density rho=3Qcos(theta)/4*Pi*R^3. Q and R are given. I need to find the Electric field at a point that is outside the sphere. Homework...

Hello! First time poster. I hope this is not a wrong sub-forum for this kind of question. Can anyone tell me where can I find values for dielectric constants of neurons and nerve fibers for frequencies in the range of 1e12 - 1e14 Hz (optical and RF part of the spectrum)? I have found data...

I have a parallel plate capacitor with a dielectric inside whose relative permittivity varies as εr = βexp(\alphax) [a theoretical calculation, I have not measured this directly] Eventually I want to calculate the capacitance of the system. First I need to calculate the \overline{D}...

Homework Statement Homework Equations \int\vec{E}\cdot\vec{dA}=\frac{Q_{enc}}{\epsilon_{0}} \int\vec{E}\cdot\vec{dA}=\frac{Q_{enc}}{k\epsilon_{0}} V=\int\vec{E}\cdot\vec{dS} C=\frac{q}{V} C_{eq}=C_{1}+C_{2}+... \frac{1}{C_{eq}}=\frac{1}{C_{1}}+\frac{1}{C_{2}}+... The Attempt at...

I just got this question on a classical mechanics assignment... and unfortunately I know NOTHING about dielectric materials (never been introduced to me for some reason >.<). I don't even know why this is on my classical mechanics assignment but it is anyway. And btw there is a disclaimer on the...

Hi, Is there any way to analytically calculate the perturbation of a uniform electrostatic field by a dielectric cube. I know a solution exists for dielectric spheres but I haven't been able to come across the solution, when dealing with a cube. Ohh.. and I'm assuming the simplest case...

Hi, I have deposited a film of dielectric on SiO2 substrate. Then, deposited metal dots on the top of dielectric film to measure electrical properties. I want to measure capacitance using metal dots on the top of dielectric. Since I have SiO2 as a substrate, I can not make a parallel plate...

Greetings, Could anyone help to tell me how to estimate the dielectric constant of cobalt oxide? Cause I have looked for the database, and couldn't find the data. Very thanks, jovis

Why is it that a dielectric sphere containing free charges, uniformly distributed throughout, has a net electric field? If the sphere is electrically neutral, then all the charges should cancel out, and since the free charges are uniformly distributed, I don't understand why there should be an...

Hello, This is simple question, but I didnt find the clear answer e.g. on the web pages: How Faraday cage works in electric field is clear. 1. The metal blown sphere = faraday cage in electric field - inside the sphere is not electric field. 2. But how is it when the blown sphere is...

Homework Statement A dipole p is situated at thecentre of a spherical cavity of radius a in an infiite medium of relative permitivity \epsilon_r . show that the potential in the dielectric medium is the same as would be produced by a dipole p' immersed in a continuous dielectric, where...

I am self-studying "Physics" (Volume 3) by Halliday, Resnick and Krane, and would like to ask some questions regarding the following example given in the book (with solution). I will copy the entire example here, with solution (translated from Portuguese, because I am using a Portuguese...

Homework Statement The polarization charge in the surface of a spherical cavity is -\sigma_e \cos\theta ,at a point whose radius from the centre makes and angle \theta with a give axis Oz. Prove that the field strength at the centre is \frac{ \sigma_e}{3 \sigma_e} parallel to Oz. If the...

Dear All, I have a question that is afflicting me and I would be glad if you can give me an answer. I have a dipole in vacuum put at a certain distance from the surface of a dielectric material. I know the entity of the dipole, I know the distance from the surface and I know the interaction...

Homework Statement a dielectric of dielectric constant 3 fills three fourth of the space between the plates of a parallel plate capacitor. What percentage of the energy is stored in the dielectric. Homework Equations U=CV2/2 = epsilon0AV2/d.2 The Attempt at a Solution When...

I thought capacitance was a function of geometry. So how come when we put in a dielectric in between a parallel plate capacitor it increases the capacitance. Is this because we can increase the E field in between without worrying about dielectric breakdown. Or does it have something to do with...

Homework Statement You have a co-axial cylindrical capacitor placed in vacuum. The two co-axial cylinder tubes are made of copper. The outside tube radius a1 and inside tube radius a2, with overlapping length L; both tubes have a thickness of t. Say, the capacitor was designed to withstand 5...

say you vaporized salt and threw it in the air. Would that be enough to turn that volume of air dielectric or would the minute pockets of fresh air in among the salt molecules still block low-med voltage

Why do materials like aluminum cut down the value of the B field? Like suppose we had an infinite current carrying wire wrapped with a cylinder of aluminum. To find the B field we would use amperes law and the magnetic susceptibility of aluminum. For example, when a superconductor is...

Say we have an electromagnetic wave propagating inside a dielectric material. Of course physically this material will radiate, due to the little electrons being excited by the wave (their wiggling is also the physical cause of the \epsilon \neq \epsilon_0), and oscillating dipoles radiate. And...

what is the difference between permeability and dielectric constant? advanced thanks.

Homework Statement ______|______ ... ... ... ... ...... _____________ | ^ y | |_ _ > x This is supposed to be a capacitor with a dielectric in a form of a wedge in it. Known data: area A of the plates, permitivity \epsilon_r The...

Homework Statement A long round dielectric cylinder is polarized so that the vector P = ar, where 'a' is a +ve constant & 'r' is the distance from the axis.find the space density rho` of bound charge as a function of distance r from the axis. Homework Equations Gauss Law. The...

This may seem like a dumb question, but is a dielectric constant calculated from a measured capacitance normalized to thickness and electrode area, I’m having a brain fart.

Hey, I have a question in how one can calculate the static dielectric constant, f, of NaCl. NaCl has density of 2170kg/m3, a lattice constant a= 5.6 A and a Young's modulus Y = 40GPa. the optical dielctric costant is 2.34. I couldn't find any formulas which connect these values together. We...

I'm trying to marry the concepts from my EM course with what I've been doing in my lab course. Correct me if I'm wrong, in a plain RC circuit, when closed with a DC source, the capacitor initially acts as a short (voltage is zero across the terminals, while I is max), until after a few...

Homework Statement The dielectric permitivity need not be a constant. Typically one can find problems where the permitivity varies, but always does so in the direction of the field. I came up with a problem that may (or may not) be solvable without the use of numerical methods. Consider a...

Homework Statement Consider a horizontal square plate capacitor of area 1*1 m2, capacitance in vacuum 2 uF, which contains a dielectric material with dielectric constant K=5. The dielectric slides frictionlessly and is attached via a massless string and a massless pulley to a block of mass 2.5...

Homework Statement When a certain air-filled parallel-plate capacitor is connected cross a battery, it acquires a charge (on each plate) of 130 μC. While the battery connection is maintained, a dielectric slab is inserted into and fills the region between the plates. This results in the...

Homework Statement A prallel plate capacitor placed in air has a plate area A and a plate separation d. It is cahred to charge Q by connecting a constant foltage source across the plates. The voltage source is then disconnected and a slab of dielectric constant K and thickness h is inserted...

if in a capacitor ,the dielectric medium is replace by higher dielectric constant material the how does the capacitance of capacitor vary and why? thanks.

Hi everyone, first time poster, long time reader (only because you're all so clever and I feel my contribution wouldn't be all that helpful haha). Homework Statement A dielectric (homogeneous, isotropic, with relative permativity \epsilon_{r}) is located in the region x<0. An infinite line...

Can renormalization of QED really be interpreted as a dielectric shielding of the vacuum by electron/positron pairs that appear and disappear out of the vacuum? I understand that's what the Feynman diagram for the QED vertex suggests, since it's the internal fermion lines that interact with a...

The energy density function for the electric field in vacuum is u=\dfrac{\epsilon_0}{2}E^2 And the cited textbook result for the energy density inside a dielectric is: u=\dfrac{\epsilon_0 \epsilon_r}{2}E^2 Now, one way to reach the upper formula is to look at the energy as...

I am having trouble with a homework problem assigned by my physics professor. An infinitely long cylinder of radius a and relative dielectric constant Er is immersed in a static electric field E=Eox where x is supposed to denote a unit vector in the x direction. The cylinder is alligned on the...

\\minerfiles.mst.edu\dfs\users\bjdphb\Desktop I'm trying to use the liftgarbagez equation to compute the Casimir-Liftgarbagez force between two different surfaces immersed in ethanol at a certain distance apart. I've never used or studied this equation before, and there are some things I...

Homework Statement A typical AAA battery has stored energy of about 3400 J. (Battery capacity is typically listed as 625 mA h, meaning that much charge can be delivered at approximately 1.5 V.) Suppose you want to build a parallel plate capacitor to store this amount of energy, using a plate...

While designing a microstrip, how do I calculate the effective dielectric constant if the microstrip is laid on FR4 PCB(er=4). Whats the formula for calculating effective er?

Homework Statement A cylindrical distribution of charge [tex]\rho=\frac{\alpha}{\sqrt{r}}[\tex] where [ tex ]\alpha = \frac{2\muC}{m^\frac{5}{2}} [ \tex ] extends from 0 cm to 8.2 cm. Concentric with this is a dielectric shell with 4.08 of inner radius 16 cm and other radius 26 cm. What is...