Dielectric Definition and 731 Threads

In electromagnetism, a dielectric (or dielectric material) is an electrical insulator that can be polarized by an applied electric field. When a dielectric material is placed in an electric field, electric charges do not flow through the material as they do in an electrical conductor, but instead only slightly shift from their average equilibrium positions, causing dielectric polarization. Because of dielectric polarization, positive charges are displaced in the direction of the field and negative charges shift in the direction opposite to the field (for example, if the field is moving parallel to the positive x axis, the negative charges will shift in the negative x direction). This creates an internal electric field that reduces the overall field within the dielectric itself. If a dielectric is composed of weakly bonded molecules, those molecules not only become polarized, but also reorient so that their symmetry axes align to the field.The study of dielectric properties concerns storage and dissipation of electric and magnetic energy in materials. Dielectrics are important for explaining various phenomena in electronics, optics, solid-state physics, and cell biophysics.

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  1. G

    Capacitance of a spherical capacitor

    When I try to do Gauss, the permeability is not always that of the free space, but it varies: up to a certain radius it is that of the void and then it is the relative one. How can I relate them? I'm trying to calculate the capacity of a spherical capacitor. The scheme looks like this: inside I...
  2. HelloCthulhu

    Arcing during water bridge, which dielectric breaks down first?

    I've been interested in the effects of electric fields on water for a while and came across this impressive demonstration of the water bridge experiment: The thing that fascinates me the most is how much the electricity arcs out of the water. For example at timestamp 8:43 the arc clearly goes...
  3. K

    Electron path in the presence of a dielectric

    Hello! Assume that I have a parallel plate capacitor. If i place an electron close to the negative plate, it will move in a straight line (and accelerate) towards the positive plate. Now, assume that I place a neutral dielectric close to the electron trajectory (parallel to it), say at 1 mm away...
  4. G

    Gauss-Theorem on a solid dielectric sphere

    The load system formed by the point load and the load distribution generates two regions in space corresponding to r<1m and r>1m, i.e. inside and outside the sphere. Given the symmetry of the distribution, by means of the Gaussian theorem we can find the modulus of the field at a distance r from...
  5. B

    Does stacking mylar dielectric film reduce it's breakdown voltage?

    According to the attached image, the dielectric strength of Mylar film decreases with increasing film thickness. My question is if this trend is also present for when films are stacked or if the film can be stacked arbitrarily high with the same breakdown voltage as a single layer.
  6. danush_S

    Interfacing Garfield++ with COMSOL

    I am trying to simulate a Thick-GEM detector in Garfield++. In order to do so, I need information of the field maps which I generate using COMSOL. I've already extracted the mesh data and the potential data. For the initialise function, I need another file that gives dielectric information of...
  7. Saptarshi Sarkar

    Electric field inside a polarized dielectric sphere

    My attempt: I know from Gauss' law in dielectric ##\nabla .D = ρ_f## where ##D = ε_0E + P##, so as ##ρ_f = 0## (as there is no free charge in the sphere) => ##\nabla .D = 0## => ##ε_0\nabla .E = \nabla .P## from this I get ##E = \frac {-kr^2 \hat r} {ε_0}## But, I know that for a uniformly...
  8. M

    Find the charge on the plates of a parallel-plate capacitor w/ dielectric

    This is an online HW question so maybe my digits are just off from rounding or something, but I don't know why I am not finding the correct answer. I got Q = 6.9e-8 as the magnitude of charge on each plate. I basically just needed to calculate the original capacitance of this capacitor using c...
  9. L

    Dielectric interface plate capacitor at angle alpha

    Consider a plate capacitor with a dielectric interface (\epsilon = \epsilon_0*\epsilon_r, thickness=d) tilted at the angle \alpha . Outside the interface \epsilon = \epsilon_0. Without dielectric interface is the field \vec{E}=E_0*\vec{e_z}. Determine the E-field inside and outside the...
  10. adamaero

    Electric energy density in the dielectric of a coaxial cable

    V(ρ) = V_o*ln(ρ/0.0018)/ln(45/180) (Attached picture is where the unit vector of r is really ρ.) In cylindrical coordinates ∇V = ρ*dV/dρ + 0 + 0 ∇V =derivative[V_o*ln(ρ/0.0018)/1.386]dρ ∇V = V_o*0.0018/(1.386*ρ) E = V_o*0.0012987/ρ Work = 0.5∫∫∫εE•E dv Bounds: 0.0018 to 0.00045 m D = εE =...
  11. Amartansh

    Simulating forward electromagnetic scattering for a dielectric

    I want to simulate 2D TM scattered fields (microwave range) for austria profile. Austria profile has 2 circles beside each other of certain dielectric and one ring below the circles. So basically I have three dielectric objects in the domain of interest and also positions of Tx and Rx are known...
  12. I

    Inserting a dielectric material between two plates of a capacitor

    1. new capacity: ##C = K\cdot C_{0}##. 2. initial potential energy: ##U_{i} = \frac 1 2 \cdot C_{0}V_{0}^2##. 3. final potential energy: ##U_{f} = \frac 1 2 \cdot KC_{0}V_{0}^2##. 4. total work done: ##W_{tot} =\Delta U = U_{f} - U_{i} = \frac 1 2 \cdot (K-1)C_{0}V_{0}^2 > 0##. 5. also total...
  13. Hawkingo

    What is the effect of the dielectric material on Gauss' law?

    [PAGE 1] [PAGE 2] [PAGE 3] so in the 2nd page,when the dielectric material is introduced the gauss's law becomes $$\oint _ { S } \vec { E } \cdot \vec { d S } = \frac { ( q - q _ { i } ) } { \epsilon _ { 0 } }$$.But my question is why the ##{ \epsilon _ { 0 } }## is in the equation.Shouldn't...
  14. L

    Capacitance with dielectric permittivity that depends on r

    The first part (which I believe I've done correctly) asks us to find the electric displacement everywhere. For this: $$\int D \cdot da = Q_{f,enc}$$ For a < r < b: $$D = \frac{Q}{4\pi r^2} \hat{r}$$ Otherwise, D = 0 When finding the capacitance, I'm unsure how to handle the r dependence. I...
  15. A

    Core shell nanoparticle based liquids/ferrofluid dielectric properties

    I found a few research papers with regards to a special type of microsized/nano particles mixed within an oil creating a special sort of ferrofluid or liquid which among other things has the property of extremely (gigantic) high dielectric constant. Now such a fluid would be ideal for a variable...
  16. rofldude188

    Solving Dielectric Problem: Electric Field & Charge Density

    a) Find the electric field in space For r < R (where R is the radius of the gold ball), E = 0 because the gold ball is a conductor. For r > R, let us make a Gaussian surface. $$\int \vec{D} \cdot \vec{dS} = Q_{free} \implies \vec{D} = \frac{Q}{4 \pi r^2}$$ Now this is a bit hand wavy but the...
  17. maxipoblete

    Capacitance of a circular capacitor with two parallel dielectrics

    Hello, the problem is better illustrated at the picture below. The capacitor is isolated, with an initial charge Q0. I understand that Q0 does not distribute along the plates homogeneously. How could it be solved with the equivalent parallel circuit?
  18. Pushoam

    The electric field inside and outside of a dielectric

    I bring a dielectric in a region with electric field ##\vec E_0##. Net electric field ## \vec E_{net} = \vec E_0 + \vec E_p ## , where ## \vec E_p ## is electric field due to polarization of dielectric. For linear dielectric, ## \vec E_p ## is 0 outside the dielectric. So, ## \vec E_{net} =...
  19. R

    A dielectric plate and a point charge: the problem with series

    The problem of the interaction of a point charge with a dielectric plate of finite thickness implies the existence of an infinite series of image charges (see http://www.lorentzcenter.nl/lc/web/2011/466/problems/2/Sometani00.pdf). I introduce notations identical to those used in this work. The...
  20. Kaguro

    Induced charge density at the interface of dielectric slabs

    E0=V/d = 100/0.1 =1000v/m In slab 1, E1=E0/k1=500v/m In slab 2, E2=E0/k2=250v/m Applying Gauss' Law to a box surface surrounding the interface with area equal to the plates we have (-E1+E2)*A = Q/epsilon_naught So charge density sigma = -250 epsilon_naught But answer given is...
  21. T

    Capacitance and induced charge of a spherical Capacitor + dielectric

    I) For the first part I used: ##V = - \int E ds = \int_a^c \frac{1}{4\pi\epsilon_0} Q /r^2 dr+ \int_c^{c+d} \frac{1}{k} \frac{1}{4\pi\epsilon_0} Q /r^2 dr + \int_{c+d}^b \frac{1}{4\pi\epsilon_0} Q /r^2 dr ## And by using ##C = Q/V## We get an answer which is somehow large for writing here...
  22. E

    Difference between polarization and the dielectric constant?

    Hi everyone, When an electromagnetic wave passes through a material, then depending upon the atomic structure of that material it polarizes that material. There is another definition of polarization in physics which says that polarization is the direction of oscillating electric field in EM...
  23. 1

    High dielectric strength, vacuum compatible glue

    Hi all, I would need an high dielectric strenght glue to fix PTFE or Hostaphan to the vacuum chamber wall in stainless steel, so the glue should be vacuum compatible. Force against the bonding direction would be 50N, so if the glue has already 100N it would be good but I don't think it is an...
  24. John Greger

    A Imaginary part of the dielectric function

    Hi everyone, I was thinking about the complex part of the dielectric function. To my understanding there's good physical explanation of it. is a superimposed description of dispersion phenomena occurring at multiple frequencies. Say I only have the real part such as the one below, and would...
  25. 1

    High dielectric strength insulator

    Hello! I would need advice on insulator material I can use for an ion Thomson Parabola spectrometer. I would need to use an insulating sheet of 225x600x1,5mm and a smaller sheet of 100x100x1,5mm I found PBN having an incredible dielctric strength, but seems like it cannot be manufactured in...
  26. CharlieCW

    Conductor sphere floating on a dielectric fluid

    Homework Statement A conductor sphere of radius R without charge is floating half-submerged in a liquid with dielectric constant ##\epsilon_{liquid}=\epsilon## and density ##\rho_l##. The upper air can be considered to have a dielectric constant ##\epsilon_{air}=1##. Now an infinitesimal...
  27. S

    A change in the dielectric constant changes the current or voltage?

    hi everyone! i am not into physics, but need it now,i am a programmer workin on an IOT project...so kinda need help. i want to use a capacitor to see what passed between two plates...knowing, it is the change in dielectric after certain intervals...how do i measure the change at the other...
  28. laurieke

    Wavelength of light in a dielectric material

    Homework Statement In a physics lab, light with a wavelength λ0 travels in vacuum from a laser to a photocell in a time t1. When a slab of glass with a thickness d is placed in the light beam, with the beam incident along the normal to the parallel faces of the slab, it takes the light a time...
  29. N

    A Symmetry of the permittivity tensor of lossless media

    I read in various sources (such as page 8 of these notes) that the dielectric permittivity tensor of a lossless medium is always symmetric. I am wondering how this can be the case, when: Phase accumulation in the medium could in theory depend on direction Coordinate system may be rotated to...
  30. T

    Confused by capacitors and potential energy

    HiI was reading about capacitors and potential energy. But the equation seems counter to how i thought. For potential energy you have: U = Q^2 / 2C or U = CV^2 / 2 But doesn't this suggest you lose potential energy the more capacitance you have? Since in the first equation as C increases U...
  31. Raihan amin

    How does a dielectric interact with a laser beam?

    Homework Statement A laser tweezer is a laboratory instrument, which uses highly focused laser beams to ‘trap’, hold or move small sized objects. The principle of the operation is that in the focal spot, the light intensity is inhomogeneous, and acts on the particle with a force that points...
  32. D

    Bound surface charge on a linear dielectric half-cylinder

    Homework Statement Problem statement in attached photo. This is an ungraded assigned problem which I am using to study for an exam, so I don't need the whole solution just help with a couple of points I am confused about. One: Part d) is really important to how I will answer part b). If we can...
  33. tworitdash

    Relation between conductance and dielectric relaxation time

    I am studying about dielectric materials and their relaxation properties. There are several ranges of electromagnetic frequencies where different material show different kinds of resonance starting from molecular to atomic motions. Based on the frequency dependence of the imaginary part of the...
  34. P

    Wire surrounded by a linear dielectric in a uniform E field

    Homework Statement We have an uncharged, conducting wire with radius a. We surround it by a linear dielectric material, εr, which goes out to radius b. We place this in an external electric field, Eo. Homework Equations We have electric potential inside (a < s < b) Vinbetween=Acosφ +...
  35. F

    Understanding Dielectric Materials: E Field and Coulomb Force Explained

    My basic understanding of a dielectric material is that the coulomb force between charges in a dielectric must be reduced by some factor since some of the electric field energy gets stored in the medium. The following thought experiment is confusing me and I am wondering where my mistake lies...
  36. B

    Calculating the Electric Field outside a dielectric

    In the textbook (Introduction to Electrodynamics by Griffiths), the problem in the attached image asks to find the electric field ##E## outside a dielectric. The problem consists of dividing the electric field into the one produced by the negative charges in the dielectric and another by the...
  37. L

    Work done when Inserting a Dielectric between Capacitor Plates

    Hi, today in lecture, we discussed the work done on inserting a dielectric between a capacitor. Two cases of this example: One case, where the battery is disconnected so that the charge stays constant. Other case where the battery stays connected so voltage is constant. I am confused on...
  38. A

    Force between the plates of a capacitor when a dielectric slab is added

    Say there are two parallel plates separated by a small fixed distance d and charged +q, -q. The force attracting the plates is F. If a solid block of dielectric (dielectric constant k) is introduced between the plates, will the force of attraction be different from F. My answer: The electric...
  39. K

    The height of a dielectric material between two coaxial pipes

    Homework Statement This is the exercise 10.6 from Feynman lectures on Physics 2. Two coaxial pipes of radii a and b(a<b) are lowered vertically into an oil bath. If a voltage V is applied between the pipes, show that the oil rises a height H. Show that H=(V^2)(κ-1)ε_0/[ln(b/a)ρ(b^2-a^2)g] where...
  40. TenJuu

    Capacitor with Irregular size dielectric

    Is it possible to make a capacitor with a dielectric not of the same size with its conducting plates?
  41. Krushnaraj Pandya

    Changes in capacitor after dielectric inserted

    Homework Statement A parallel plate capacitor (capacitance C) is charged with a battery of emf V volts. A dielectric slab of dielectric constant K is placed between the plates to fully occupy the space. The battery remains connected. What are the changes in-1)C 2)Q (charge on capacitor) 3)E(E...
  42. Krushnaraj Pandya

    What Is the Direction of Force on a Dielectric Slab in a Capacitor?

    Homework Statement A constant potential is maintained across a parallel plate capacitor. A dielectric slab is slowly inserted between the plates (width of slab=distance between the plates). What will the direction of force applied by capacitor on dielectric be? Homework Equations All relevant...
  43. F

    Increase in internal energy due to polarization of a dielectric

    I have a plate capacitor with a given charge. It is then dipped in a dielectric fluid and I must determine which height the fluid reaches(all the necessary parameters are given). I can solve this problem if I make the following assumption: the polarization of the dielectric does not( or...
  44. Muhammad Usman

    Capacitor Electric Field in a Dielectric?

    Hi, I was reading the capacitor and its operation and it is written there that when the DC is applied to the capacitor it becomes open circuit. The main mechanism behind this phenomena is explained as below:- "When DC voltage is applied the charge started accumulating on the plates of the...
  45. A

    Capacitors: find the dielectric constant

    Homework Statement A parallel plate capacitor has a capacitance of 7.8 μF when filled with a dielectric. The area of each plate is 1.5 m^2 and the separation between the plates is 1.3 x 10-5 m. What is the dielectric constant of the dielectric? Homework Equations C= (K(8.85E-12)A)/d The...
  46. S

    Dielectric Rod Antenna: Can It Radiate?

    I have a fundamental question about the antennas made by using dielectric materials that I have not found a satisfied answer online. According to Wikipedia, antennas are described as, "In radio, an antenna is the interface between radio waves propagating through space and electric currents...
  47. A

    Dielectric constant of air with temperature change

    I'm looking to see how much the dielectric constant of air will change mostly as a function or air temperature. Is there a formula that outputs air dielectric as a function of temperature or atmospheric pressure?
  48. A

    Calculating permittivity in a constant field

    Homework Statement Having a conducting sphere with radius ##R## and charge ##Q##, dielectric is put on it so that a spherical shell with inner radius ##R## and outer radius ##3R## is formed. Calculate: 1. Electric permitivitty ##\epsilon## such that ##E(r), R<r<3R## is constant and there's...
  49. A

    Confusion with constant voltage and dielectric

    Homework Statement Consider a conducting sphere with radius ##R## connected to a voltage source of ##V_0## volts. If the sphere is then covered by a dielectric spherical layer of radius ##9R## calculated the relative permitivitty ##\varepsilon_0## needed so that the field in the empty zone...
  50. N

    Dielectric Constant: Does Positive Matter?

    Does the dielectric constant of a material have to be positive?
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