Dielectrics Definition and 141 Threads

Homework Statement You are building a parallel plate capacitor out of two square metal plates with side lengths of L and a thin piece of dielectric of thickness d and dielectric strength of Eb. The piece of dielectric will act as a means of separating the two metal plates. In terms of l...

Hi all, I am wondering how is it possible that the polarization effects of a dielectric material remain confined inside the material itself. That is: for a LIH dielectric, the equations state that the electric field inside the material is reduced by \epsilon_r. But outside the material, no...

My question is simple; yet, I can not find the answer. In the picture below, all variables are identical; the plate separations, surface area, etc. The only difference is the fact that example 1 has 2 different dielectrics. Better yet, it has a dielectric that doesn't extend the entire distance...

Dear all: The boundary condition of electric field is well know for us which illustrates that the normal component of the electric field will not be continuous across the interface between 2 dielectric material with different dielectric functions. (There is no extra fixed charge on the...

Homework Statement My question is: If we have a parallel plate capacitor with 2 parallel dielectrics both taking A/2 of the complete surface, is the total electric charge equal to sum of the electrical charges in the first dielectric and the second dielectric, i.e is qtotal=q1+q2=σ1*A/2+σ2*A/2...

Hello all. I have a doubt about the derivation of energy in dielectrics formula (Griffiths pages 191 - 192). In a certain step of the formula derivation, we encounter the following operation: (view formula below). I do not undertand that operation. Can someone help me?

Consider a parallel plate capacitor with layers of dielectric between its plates somehow that the interfaces between them are parallel to the plates of the capacitor. If the surface charge density on the plates of the capacitors be \sigma , gauss's law gives D=\sigma which is the same inside...

Homework Statement A ##240 nF## capacitor and a ##4.0 \mu F## capacitor are connected in series with a ##240 V## potential difference. The ##4.0 \mu F## capacitor has a parallel plate configuration, with a surface area of ##110 cm^2## and a dielectric material between the plates. The...

Hi all, I'm stuck on this incompatibility within the differential form of Gauss' thearem (or Maxwell's first equation) with dielectrics. \vec{\nabla}\cdot\vec{E}=\frac{\rho_{free}+\rho_{bound}}{\epsilon_{0}} \rho_{bound}=-\vec{\nabla}\cdot\vec{P} But with a linear, homogeneous...

How come an insulator is put in between two capacitors? I realize it is to polarize the atoms and create a smaller electric field and hence smaller electric pressure/voltage and increase the capacitance. But why not use a conductor? Pretty much all the charge would cancel. OR am I missing a...

Homework Statement A unit sphere at the origin contains no free charge or conductors in its interior or on its boundary. It is, however, embedded in a dielectric medium. The dielectric is linear, but the permitivity varies by angle about the origin. It is constant along any radial direction...

So I was thinking about similarities in the nature between these two which could justify similarity in the nomenclature. So, diamagnetic materials are those whose atoms do not have permanent magnetic dipols, so when you apply magnetic force on them, they create local dipole oriented...

Find that capacitance of the system consisting of 3 dielectrics w/ length, l=1.0m, width, w= 1.0m and depth, d= 1.0 CM. ##k_1=1.5, k_2=2, k_3=2.5## *dimensions of conducting plates not given* Equations: Capacitance, ##C= Q/{\delta}V## Field in the dielectrics...

Homework Statement Electromagnetics, Kraus, 4th edition problem 4.7.3 The y-z plane is the boundary between 2 dielectrics of relative permittivities εr = 2 and εr = 5. For negative values of x, E = (3,0,2) V/m. Find D (magnitude and direction) for positive values of x. Homework Equations...

Hi, I need help with this. A non-conducting slab of thickness t, area A and dielectric constant κe is inserted into the space between the plates of a parallel-plate capacitor with spacing d, charge Q and area A, as shown in Figure 7.7.5(a). The slab is not necessarily halfway between the...

Homework Statement A parallel-plate capacitor is constructed by filling the space between two square plates with blocks of three dielectric materials, as in Figure P26.61. You may assume that l >> d. (a) Find an expression for the capacitance of the device in terms of the plate area A and...

Homework Statement I'm asked to find 1)The capacitance 2)The electric field 3)The surface charge density 4)The polarization charge at the interface between the dielectrics. Of 2 set ups. The first one is a parallel plate capacitor which is half filled with a dielectric ##\varepsilon _1## and...

Homework Statement A parallel plate capacitor with plate area A and plate separation d=5mm is connected to a 120 Volt power supply and allowed to fully charge. A) Calculate the capacitance, stored charge, electric field midway between the plates and potential energy stored. The...

Homework Statement A dielectric slab with a susceptibility ##\chi_e## rests on a conducting plate whose upper surface carries a free surface charge density ##\sigma##. Show that the polarization surface charge density ##\sigma_{pol}## on the lower face of the dialectic slab is: ##\sigma_{pol}...

I have two questions: 1) Is it in general assumed that the parallel plates of a capacitor are fixed to some surface or is there a force that counteracts the attractive force between the plates whenever one considers a typical problem involving capacitors? 2) Consider a dielectric of length L...

Homework Statement A capacitor is formed by 2 square metal plates of edge a and separated by distance d. Dielectrics of dielectrics constants K1 and K2 are filled in the gap as shown. 2. The attempt at a solution This was my initial approach: I integrated the parallel combination of...

Hi, So I am learning about parallel-plate capacitors. The way my book puts it is that it is basically two parallel plates of opposite polarities, separated by a distance d. In order to establish that distance, work must be done and the energy is stored as electric potential energy. From...

Hi all, I'm doing what should be a pretty simple problem, but some theory is giving me trouble. Basically, in this problem I have a conducting sphere, surrounded by a thick insulating layer, and then vacuum outside that. I'm attempting to solve for the potential in the insulating layer by...

Homework Statement http://img209.imageshack.us/img209/1508/problemhd.jpg Homework Equations The Ampere law: \oint_C \vec{B} \cdot d\vec{l} = \mu_0 I_{enc} The field and flux is proportional to the current: \Phi = LI The Attempt at a Solution (a) \oint_C \vec{B} \cdot d\vec{l} = \vec{B}...

Say we have a linear dielectric with electric susceptibility χe a certain free charge density ρ. By using the fact that ∫D\cdotda = Qfree-enclosed you can find the resulting electric field, because D = εE , where ε = ε0(1+χe). The above is very weird for me. It seems to me that you are...

Inside a dielectric we have: ∇\cdotε0E = ρbound + ρfree , where ρbound refers to the fact that these charges come from polarization. We can write this as: ∇\cdotε0E = -∇\cdotP + ρfree where P is the polarization of the material. And combing the two divergence terms...

I have a project about High Frequency Dielectrics and I am searching everywhere but nothing found. Please I need your help to find some information that would help me in my project.

Homework Statement When a dielectric is inserted in a capacitor, why does the charge remain unchanged while the potential decreases and capacitance increase? Homework Equations The Attempt at a Solution i'm not really about this one, but is it because the charges accumulate on the surface area...

Homework Statement So my question is conceptual. I am trying to figure out in what direction an electron will move if it starts between two plates of a parallel plate capacitator. One of the plates is at 0V and the other is at 50V. Also, would placing a dielectric in a charged, isolated...

Homework Statement A parallel plate capacitor of area 2 cm^2 is filled with three dielectrics with constants k1=3.5, k2=1.7 and k3=8.5. The dielectrics are placed as shown in the figure, each occupying half the total area, while the volume of the first double of the other two. If the...

just kidding

http://imageupload.org/getfile.php?id=171120&a=a955b8cf905480ad89ee96abfea140da&t=4f27421f&o=36BBD6199C49C981F6CC7562A37DC69B664D4F14FBA06DFCF24E9B24875233233B2BA7CB1980&n=%E6%9C%AA%E5%91%BD%E5%90%8D.png&i=1 I have just been given the question without much support so I can't even get a...

Homework Statement The two media are lossless dielectrics with n1>n2. If θ exceeds thtee critical angle, state how b affects the amplitude and phase of the reflected wave, and give a physical reason for your statement θ:angle between incident wave and normal line b:distance between...

Hi I have some comments/questions about the terminology used for dielectrics in physics textbooks. Linear dielectric means that components of \vec{P} are linear combination of the components of \vec{E}. Homogeneous dielectric means that dielectric constant is not the function of...

Homework Statement 1. A parallel plate capacitor, with plates of area A, and spacing d, is filled with a non-uniform dielectric, with a permitivity that varies as ε = ε0 + ax where a is a constant, and x is the distance from one plate Homework Equations C = Q/V I'm...

Homework Statement The problem is on page 40 of this PDF: http://web.mit.edu/8.02t/www/802TEAL3D/visualizations/coursenotes/modules/guide05.pdf Find the capacitance of a spherical capacitor with 2 different homogeneous dielectrics arranged concentrically.The Attempt at a Solution In that...

here is the thing, I have understood this in dielectrics, and I know that we have a new vector field instead of E, the displacement that is not neccessarily conservative. what I was thinking is that all these books, when they want to drag this law out of the info we already had, just try to make...

I have been studying polarization in dielectrics recently. I got stuck after coming to Claussius Mossoti equation. I can't understand it's importance. I read that it is used to determine molecular structure but how exactly? I've just joined this forum, hope someone can help. :) TIA P.S: Sorry...

I am very curious as to why dielectrics such as water have a varying level of reflectivity depending on what angle they are viewed at. For a lake of water, what angle yields 100% (or near 100%) reflectivity? Is this angle the same as the Brewster angle? Also, why exactly is it that metals do...

Homework Statement Does placing a dielectric rod between two electric charges increase or decrease the total force exerted on any of the charges? Homework Equations Not really algebraic, only conceptual. The Attempt at a Solution

A coaxial cable used in a transmission line has an inner radius of 0.10 mm and an outer radius of 0.60 mm. Calculate the capacitance per meter for the cable. Assume that the space between the conductors is filled with polystyrene. Kappa for polystyrene is 2.6 I have no clue how to start or...

Homework Statement A 25pF parallel plate capacitor with an air gap b/w the plates is connected to a 100v battery. A Teflon slab is then inserted b/w the plates and completely fills the gap. What is the change in charge on the positive plate when the Teflon is inserted? Homework Equations...

So suppose we have two dielectrics in contact and we want to know how \mathbf{D} varies across them, then we can use the fact that since \nabla \cdot \mathbf{D} = \rho_f and we have no "free" charges at the boundary then \mathbf{D} is continuous across it. So my question is, in Grant & Philips...

Homework Statement Two coaxial metal tubes (placed vertically) have an inner radius a and outer radius b. They are placed vertically between a dielectric oil (with susceptibility X and mass density p). The inner tube has potential V and the outer one is grounded (V=0). How high will the oil...

Homework Statement A point charge Q is at the boundary plane of two infinite, homogeneous dielectrics with dielectric constants \epsilon_1 and \epsilon_2. Calculate the electric potential, the electric field and the displacement vector at any point in space. Homework Equations...

So, I know what happens with the first two cases, but what if the dielectrics are on a diagonal?

Homework Statement We have two infinite conductor plates, with two dielectrics (with permitivities K1 and K2) put together between them so that the capacitor may be taken as two capacitors connected in series. We know that the maximum electric field for the first dielectric is Er1, and we also...

what is the difference between insulators and dielectrics?::confused:

Homework Statement Єr = 3.0, atomic density = 1028 atoms/m3. The mag. of the E-field is 10,000 [V/m]. Two electrons in outer orbital shell will distort with an applied E-field. If both both electrons follow some orbital path as a pair, find spacing between center of nucleus and average...

question: so here is what my problem is. there are two dielectrics between a parallel plate capacitor. distance between the two plates is '2s' and each dielectric is 's' long. each plate has a charge of \itshape \sigma (top being pos. and bottom being neg. and doesn't give an area) how would i...