What is Dielectric: Definition and 730 Discussions

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.

View More On Wikipedia.org
Recent contents Top users
  1. B

    Construction of an equivalent dielectric tensor

    Homework Statement A medium is described by the response functions \varepsilon (\omega ) and {\mu ^{ - 1}}(\omega ) in \textbf{D} = \varepsilon (\omega )\textbf{E}, \textbf{H} = {\mu ^{ - 1}}(\omega )\textbf{B}. Construct the equivalent dielectric tensor {K_{ij}}(\omega ,\textbf{k}) in...
  2. A

    Large Static E Field, Dielectric Break Down, Quantum View

    Hi Got a question, hoping someone can give a good explanation for. We all know that large static uniform electric fields have the potential to ionize. (Dielectric breakdown of Air - Static Electricity Shock). In the Quantum picture, why does this occur. Take for instance the photo...
  3. R

    The potential difference in a capacitor with dielectric

    Homework Statement Two identical capacitors are connected in parallel, charged by a battery ov Voltage V, and then isolated from the battery. One of the capacitors is then filled with a material of relative permittivety E. Homework Equations What is the final potential difference...
  4. K

    Discharge of a non-ideal capacitor having a ‘leaky’ dielectric

    1. A non-ideal capacitor having a ‘leaky’ dielectric where RL =1.5 x1015 which is the leakage resistance measured across the dielectric. A100 pF parallel-plate capacitor has a mica dielectric of relative permittivity år = 12 and resistivity of ñ = 1014 Ù m. The capacitor holds a charge of 10...
  5. H

    Energy Stored leading to Dielectric breakdown

    Homework Statement A cavity can only store 1J of EM energy as it reaches dielectric breakdown at 3kV/mm. What dielectric strength would a new gas filling the cavity have if the energy stored was to be 4J. Homework Equations U=\frac{1}{2}(epsilon)E2The Attempt at a Solution I would use the...
  6. E

    Dielectric permittivity of 1 and polarization

    Homework Statement in a homework problem we have a spherical dielectric shell with permittivity of 1 [like a vacuum. inside are charges that are released and we have to say what the charge distribution will look like later. if the dielectric can be polarized, i know what the charges will do...
  7. T

    Calculate Dielectric Strength Breakdown Voltage

    I know it has to do something with the Breakdown voltage but I've looked everywhere on my book and i have no idea how to calculate it.
  8. T

    Dielectric Strength Formula: Find it Here!

    What's the formula to calculate it, I've looked everywhere.
  9. C

    Light, dielectric medium, c, wavelength

    What is happening to a ray of light of a certain wavelength that passes through a transparent dielectric medium? Ex: Green light enters in a Bose–Einstein condensate, and slows down some. Than the light is coming out of the medium in free space. What will be the speed of the ray light and...
  10. J

    Could crystalline GeSbTe be considered a dielectric?

    I am interested in the recent theoretical prediction that a shocked crystal can be a source of coherent THz radiation. The computational study was done for a crystal of NaCl, but the authors say that basically any dielectric crystal would work, as the radiation is emitted due to polarization...
  11. H

    Understanding Dielectric Spheres in Optical Tweezers

    im confused about what a dielectric sphere is. I have tried googleing it but i couldn't find anything that useful, please help
  12. F

    Dielectric Strength: Safe to Use Across 240v/415v Terminals?

    I understand that Dielectric Strength relates to the point where a compound breaks down under electrical load. Please correct me if I have it wrong. I want to now if an RTV compound (with Dielectric Strength of approx 500 volts/mm) is safe to use across 240v or 415v terminals that are 3-5mm...
  13. P

    Dielectric constant of a conductor

    i am reposting this question , earlier it had been deleted assuming it to be a "HOMEWORK QUESTION" , well my question is , can we define a dielectric constant for a conductor ?? is it conceptually meaningful?? if yes then why and what is it?
  14. B

    Find Flux Density On One Side of Dielectric Boundary Given Boundary Conditions

    Homework Statement A dielectric interface is defined as 4x + 3y = 10 m. The region including the origin is free space, where D1 = 2ax - 4ay + 6.5az nC/m2. In the other region, εr2 = 2.5. Find D2 given the previous conditions. Homework Equations an12 = ± grad(f)/|grad(f)| D2n = D1n =...
  15. A

    Parallel plate capacitor with dielectric in a gravitational field.

    Homework Statement A square parallel plate capacitor with vertical plates of area A and distance d, charged with a constant charge Q and is completely filled with a dielectric material the same dimension as the gap between the plates, with dielectric constant k and mass m. Assuming the...
  16. fluidistic

    Cylindrical capacitor with a dielectric

    Homework Statement I must calculate the capacitance of the following capacitor : A cylindrical capacitor made of 2 shells (not sure if shell is the right word in English. Made of 2 cylinders maybe), one of radius a and the other of radius b>a. It has a length of L. We introduce entirely...
  17. M

    Electric Field of a Dielectric Sphere

    Homework Statement A uniform charge q is distributed along a sphere of radius R. a) What is the Electric Potential in the center of the sphere? Homework Equations V(r1)-V(r0) = - \int \stackrel{\rightarrow}{E} * \stackrel{\rightarrow}{dl} The Attempt at a Solution
  18. T

    Linear dielectric material. susceptibility

    Homework Statement I have a linear dielectric material. The electric field in the material is 38% less than a vacuum field with the same external sources. I need to find the susceptibility of the material? Homework Equations P= \chi(vacuum) E P= \chi(material) .62E...
  19. J

    Susceptibility dielectric material

    Homework Statement I have a linear dielectric material. The electric field in the material is 38% less than a vacuum field with the same external sources. I need to find the susceptibility of the material? Homework Equations I used P=\epsilon\chi(vacuum)E P=\epsilon\chi(material).62EThe...
  20. R

    A point charge inside infinite medium of dielectric

    A point charge inside infinite dielectric material 1. The problem statement, all variables and given known data A point charge is an infinite medium of dielectric material having a relative permittivity \epsilonr. <--- epsilon(sub r). Find the electric field vector and the potential function...
  21. N

    Electric field in a dielectric material

    Homework Statement A very long cylinder of liner dielectric materil is placed in an otherwise uniform electric field E_0 . Find the resulting field within the cylinder. (the radius is a , the susceptibililty \chi_e and the axis is perpendicular to E_0) Homework Equations The Attempt at a...
  22. J

    Dielectric between Grounded Plates

    Homework Statement "When a block of insulating material such as Lucite is bombarded with high-energy electrons, the electrons penetrate into the material and remain trapped inside. In one particular instance a 0.1 mA beam bombarded an area of 25cm^{2} of Lucite (Class A: \epsilon_r=3.2) for 1...
  23. J

    Comparing Bound Charges on Cylindrical Dielectric Surfaces

    Homework Statement A conducting wire carrying a charge \lambda per unit length is embedded along the axis of the cylinder of Class-A dielectric. The radius of the wire is a; the radius of the cylinder is b. Show that the bound charge on the outer surface of the dielectric is equal to the...
  24. C

    Conducting Sphere Covered By Spherical Dielectric

    Homework Statement An isolated metal sphere of radius a has a free charge Q on its surface. The sphere is covered with a dielectric layer with inner radius a and outer radius b Calculate the polarization charge density on the inside and outside of the dielectric. Homework Equations...
  25. J

    Inside Needle-Like Cavity: E Field in Dielectric Using Gauss's Law

    Holy Dielectric! Homework Statement A large block of dielectric contains small cavities of various shapes that may be assumed not to disturb appreciably the polarization. Show that, inside a needle-like cavity parallel to P, E is the same as in the dielectric Homework Equations...
  26. B

    Max Voltage Cylindrical Capacitor w/Dielectric

    Homework Statement Hello: I am asked to find the maximum voltage in a cylindrical capacitor. The capacitor consists of an inner wire and an outer cylindrical shell. The wire has radius r_{1} and the cylinder has inner radius r_{2}. The space between the wires is filled with a dielectric...
  27. L

    Electrostatic energy of a dielectric sphere

    1. Find the electrostatic energy of a neoprene sphere or ratio R, charged with Q if: a) Q is uniformly distributed in surface The Attempt at a Solution So, I can calculate the displacement field (so that I can use the expresion U= \int \vec{D}.\vec{E} dV), but only for those points in...
  28. O

    Point charge inside Dielectric Sphere embedded in Dielectric Slab

    I've been working on this for a little while now (in CGS units), and am not really sure where I've gone wrong at in calculating the potential, so I've come here! Here is the problem: What is the potential caused by placing a point charge Q at the center of a dielectric sphere (\epsilon2)...
  29. L

    Dielectric and potencial

    Homework Statement I have the following problem regarding to dielectric and potencial Problem: Consider 2 conductive bars parallel with a distance “d” between them (smal distance compared to the size of the bars), connected to diference of potencial Vo.The space between the bars is...
  30. M

    Capacitance of two plates written in terms of height of liquid dielectric

    Homework Statement A liquid-level transducer consists of two parallel plates of conductor immersed in an insulating liquid. When the tank is empty the capacitance of the plates is 200pF. The relative dielectric constant of the liquid is 25. Determine an expression for the capacitance C as a...
  31. O

    Dielectric w/out knowing kappa

    Homework Statement A slab of copper of thickness b = 1.85 mm is thrust into a parallel-plate capacitor of plate area A = 2.25 cm2 and plate separation d = 5.00 mm, as shown in the figure; the slab is exactly halfway between the plates. What is the capacitance after the slab is introduced...
  32. W

    Field due to charge on surface of dielectric

    We have an infinite half-space filled with a dielectric. The other half-space is vacuum. We take a sheet of charge of density \sigma and place it on the surface of the dielectric. What are the D & E fields everywhere? We clearly have D_1 + D_2 = \sigma. But what other equation do we have? Can...
  33. O

    Electric Field inside uniformly charged dielectric sphere

    Homework Statement Either Coulomb's Law or Gauss' Law and r>R, I get \textbf{E}=k\frac{Q}{r^{2}}\textbf{r}. Q is the total charge. If R is the radius of the sphere, shouldn't the field at a point a<R simply be k\frac{Qa}{R^{3}}? Inother words, the field is proportional to the enclosed...
  34. H

    Calculating Potential Distribution of a Dielectric Cylinder in Electric Field

    How to calculation the potential distribution for a dielectric cylinder placed in electric field of point charge? The height of the dielectric cylinder is H, while its section radius is R. The dielectric constant of the cylinder is ε1...
  35. A

    Complex dielectric constant implies absorption?

    Hi everyone, My very first post after simply using physicsforums as a (very) handy FAQ resource. Okay, so my question is probably pretty simple, but I've been unable to find anything on here already. How does a complex dielectric constant imply the absorption of EM radiation? I...
  36. R

    Effect of electric field on a dielectric

    friends, can anyone explain me the effect of electric field on a dielectric(non- conducting) medium
  37. E

    Dielectric Strength Of Liquids: looking for data

    Hello all of you! I'm looking for reliable data about the dielectric strength (=breakdown field) of liquid insulators with a high permittivity and a low viscosity and not too dangerous. Examples of such liquids: - Ethylene glycol carbonate. Propylene glycol carbonate. Maybe the oxalates...
  38. E

    E field profile in a capacitor with two different dielectric material

    Hi everyone, this is not a homework, I'm actually dealing with the case in real life here. If this turns out to be standard textbook stuff then I'm sorry as I haven't studied this before. Suppose a plate capacitor has two different dielectric material layer sandwiched in it. Then a fixed...
  39. A

    Calculating Desired Length for Capacitor with Specific Capacitance

    A capacitor is constructed commercial wrap two sheets of aluminum separated by two sheets of paper coated with paraffin. Each aluminum foil and paper has width of 7cm. A sheet of aluminum has 4x10^{-6}m and thickness of paper is thick 25x10^{-6}m and a dielectric constant of 3,70. What is the...
  40. M

    What is the dielectric constant of the slab on a parallel plate capacitor ?

    Homework Statement When a certain air-filled parallel-plate ca- pacitor is connected across a battery, it ac- quires a charge (on each plate) of magnitude 214 μC. While the battery connection is maintained, a dielectric slab is inserted into the space between the capacitor plates and...
  41. J

    Determine the dielectric constant

    Homework Statement Two flat metal circles of radius r=15 mm are brought a distance d=8.0 mm apart to form a parallel plate capacitor. The surface charge density of one plate is measured to be +1.0*10^-3 microCouloubs/mm^2. The potential difference across the capacitor is measured to be .12...
  42. D

    Dielectric Constant K & Plate Charge Density

    Let me know if the following reasoning is correct : If the surface charge density on the internal surface of one of the plates in a parallel plate capacitor is Sigma, which becomes Sigma/K, when a dielectric material is inserted between the plates with dielectric constant...
  43. D

    Higher dielectric constant : better insulator

    Higher dielectric constant means better insulator. Water has a dielectric constant of 8, which is enormous(according to Walter Lewin), but it still is a very good conductor of electricity, why?
  44. P

    Measyrement of Conductivity and Dielectric constant

    can you please tell me, how do we measures the conductivity and dielectric constant of silicone oil and castor oil, because resistivity of silicone oil is very high so that's why it is difficult to mesure with conductivity meter,
  45. S

    Varied Electrical Potential Difference with Dielectric.

    Hello All, I am wondering why the presence of a dielectric reduces the potential difference of a capacitor (after having been separated from its energy supply). I understand how it works, based around maintaining the same charge, I just don't see why. Thank you for the Help.
  46. W

    Calculating the Dielectric Constant of Cold Dilute Rubidium Gas

    assume that i have a cloud of cold dilute Rubidium atoms i know the atomic levels of the Rubidium atom How to calculate the dielectric constant of this gas? Which book can i consult?
  47. S

    Energy of a Capacitor System with partially inserted Dielectric

    Homework Statement The above is a capacitor system. A dielectric is inserted into capacitor C3 and I need to find the total energy of the system. The dielectric is not fully in, only partially (lets say a length x). The Attempt at a Solution I first found the capacitance of C3 with...
  48. M

    Percentage of energy in a dielectric placed between a parallel plate conductor

    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? E(r) = 3, distance between plates = d, thickness (t) = (3/4) * d, C=capacitance of the...
  49. D

    Dielectric constants of polymeric materials

    I have done a series of tests on the dielectric constant of polymeric materials using Impedance measurements in a four electrode configuration. When varying the thickness of my polymeric materials, the dielectric constant remains relatively "constant". When the thickness of the material is...
  50. R

    Dielectric interface in a waveguide

    Homework Statement Consider a wave guide with a square cross section of dimensions a x a. Let the z axis be the axis of the wave guide. Suppose the region z < 0 is vacuum, and the region z >0 is a dielectric with permittivity \epsilon . Write a solution of the wave equations and boundary...
Back
Top