Dielectric Definition and 731 Threads

If a capacitor's dielectric partially breaks down, as in some of the material has ionized and acted as a conductor, will there still be a capacitance to the component? Say its a high frequency AC signal on a capacitor with a small part of its dielectric material in a breakdown state. My...

Hi everyone, From what I understand if you had a time varying magnetic field inside a dielectric it will induce a time varying electric field according to Faraday's Law: \nabla\times\mathbf{E}=-\frac{\partial \mathbf{B}}{\partial t} My question is will the dipoles in the dielectric then...

Homework Statement http://img99.imageshack.us/img99/763/prob45.gif Fig. 1 and 2 show a dielectric slab being inserted between the plates of one of two identical capacitors, capacitor 2. Select the correct answer to each of the statements below (enter I for `increases', D for `decreases', or...

Homework Statement A slab of width d and dielectric constant K is inserted a distance x into square parallel capacitor plates of side L. Determine the magnitude and direction of the force on the slab (Assume V0 is constant. Homework Equations F= d/dx(U) U=1/2CV2 The Attempt at a...

If you have a simple circuit with only a battery and a parallel plate capacitor with a dielectric, what exactly happens when the battery is turned on? Also, if the voltage of a capacitor with a dielectric is less than the EMF of the battery, what happens to the rest of the voltage? One...

Homework Statement How large proportion of wavefront's power penetrates dielectric material's surface in a perpendicular collision from air. The only parameter that I have is \varepsilon_r = 16 where \varepsilon_r is the relative permittivity.Homework Equations \varepsilon = \varepsilon_r...

Homework Statement A 6.8-nF parallel plate capacitor with a sheet of Mylar (κ = 3.1) filling the space between the plates is charged to a potential difference of 160 V and is then disconnected. (The initial capacitance including the dielectric is 6.8 nF.) (a) How much work is required to...

I have seen some examples where a system has a resonance frequency, and, when the system changes, its Q factor also changes, and so the resonance frequency shifts, and this shift can be measured to detect the change in the system. An example I can think of is very sensitive mass measurement...

Homework Statement Two parallel plates, each having area A = 3118cm2 are connected to the terminals of a battery of voltage Vb = 6 V as shown. The plates are separated by a distance d = 0.35cm. You may assume (contrary to the drawing) that the separation between the plates is small compared...

Hello, I have been trying to better understand the effects of dielectrics in resonant cavities. I read that the addition of a dielectric in a resonant cavity will reduce the resonant frequency of the cavity. My questions: Is there any relation to the reduction of the resonant...

Homework Statement A conducting sphere of radius A has a charge +Q on it and is surrounded by an insulating material whose dielectric constant varies with radius according to εr = 2exp[-(r/a-1)]2. The dielectric has a spherical outer boundary B. Find the values of D, E, P, ρ as a function of...

Homework Statement Given a dielectric sphere with relative permittivity = ε in a homogeneous E-field: \vec{E_{0}} = E \vec{e_{z}}. The E-field causes a homogeneous polarisation (dipole density) of \vec{p} = \frac{vec{P}}{V} with big P the dipole moment vector. The total electric field...

So for just vacuum in between one could say F=q*E = (σA)*(σ/2ε0) = A*σ^2 / (2ε0) Alternatively, F = dU/dx, where x is the separation. U = 1/2 CV^2 = 1/2 QV = x*A*σ^2 / (2ε0). To get V, we just add up pieces of E-field*distance. But now let's say part of x is a dielectric of thickness t...

Homework Statement consider a long cylindrical dielectric shell of inner cross-sectional radius a , outer radius b, and constant volume charge density raw zero . THe potenials of the ineer and outer surfaces of the cylindrical shell are held at potentials 0 and V respectively as shown in the...

I know that I should do my homework, but I lost all my notes because of the flood brought by "Sendong" a storm in the Philippines. I just need the equations to be used to solve the problem that was given to us. So here it is: A parallel plate capacitor has a capacitance of 7MF when filled...

i was reading Random Phase Approximation and encouter with dielectric function ε(q,ω)= 1- v(q) ∏(q,ω) where v(q) is coulumb potential and ∏(q,ω) is density-density correlation function without coulumb interaction now i do not understand this dielctric...

A capacitor is connected to a HVDC power supply which provides a minimal current. When the volage reaches the capacitor plates the dielectric material in the capacitor polarizes. Now, if there existed a barrier between the dielectric and the capacitor plate the capacitor could theoretically...

hi, i have seen on another topic here that the refractive index equals the square root of the dielectric constant. from datasheet values we have... water refractive index = 1.333 dielectric constant = 80.1 Without even doing the calculation its obvious that the square root of 80.1 is not...

Hello! Electric force is inversely proportional to the dielectric constant. In a textbook, this is said to be forty-fold greater for water than the phospholipid membrane. As such, ions are unlikely to cross the plasmamembrane. I assume this has something to do with preferring to stay in...

Hi all, An electrolytic capacitor has 2 AC sources connected to it, 1 at each plate. The AC sources are 180 degrees out of phase and have a high impedance which limits current in the nA range. Even though each plate should have AC on it which is 180 out of phase the voltage at each plate...

When the dielectric in a capacitor polarizes does it effect the leakage current through the dielectric? Just wondering, if you had a capacitor with a lossy dielectric and you were able to polarize the dielectric would the leakage current drop? Can anyone give me any links for further...

Why are optical traps constructed using beads that are made of dielectric materials? What property of dielectrics is being employed here? Would a non-dielectric material still experience radiation force from photons? Thanks!

Here is the problem from I.E.Irodov's Basic laws of electromagnetism. An infinitely large plate made of homogeneous linear isotropic dielectric with dielectric constant \epsilon is uniformly charged by an extraneous charge (see footnote) with volume density \rho > 0.The thickness of the...

The problem is as follows: Two long coaxial cylindrical metal tubes (inner radius a, outer radius b) stand vertically in a tank of dielectric oil (susceptibility χe, density ρ). The inner one is maintained a potential V, and the outer one is grounded. To what height (h) does the oil rise in the...

Homework Statement This was done on my Physics II class, ans the Professor has'nt want to explain it to usA 2 Circular Metallic Plate Capacitor, maybe of a diameter of 15cm, was connected to a constant sourch of DC voltage until it was charge to 10Volt, after this the source was DISCONNECTED...

Homework Statement Dual plate capacitor with two dielectric slabs placed between the capacitors and a battery supply's a voltage across the capacitors. The slabs are not equal in dielectric permeability. What is the charge at the interface of the two slabs? Homework Equations The...

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

Calculation of plasma frequency and static dielectric constant (urgent) Hello: Can anyone tell me how to measure the plasa frequency of a metal and wherher energy band gap of a metal is equal to the plasma energy of that material which is equal to (plank constant * plasma angular...

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}...

Hey, I was going over my electromagnetics course material and I realized we didn't learn much about anisotropic mediums (and still we had some homework questions about them). I'm trying to find some information about transition between anisotropic mediums, or even to be more specific -...

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...

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...

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...