What is Dielectric: Definition and 729 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. cseil

    Capacitors with dielectric in series

    I would like to know if everything is good in my reasoning. I've never done exercises like that and I don't have the results. Homework Statement A generator which mantains a constant potential difference of 400V is connected to two capacitors in series C1 = 500pF and C2=1000pF. A dielectric is...
  2. W

    Quantization of EM field in dielectric?

    hi , what is the equation for the hamiltonian of EM field in dielectric and how can we say we have quantized the hamiltonian?
  3. CopyOfA

    Spherical Capacitor with Frequency Dependent Dielectric

    This is a long post. Sorry... 1. Homework Statement We are given a spherical capacitor with an inner conductor of radius ##a## and outer conductor of radius ##c##. The space between the conductors is half filled (##a<r<b##) with a dielectric with permittivity...
  4. P

    Can Different Electrodes Affect Air's Dielectric Strength Values?

    Hi, Am I correct in thinking that for a medium such as air, the dielectric strength is a property of the material and as such has a single value for that material? The reason I ask is because I have been testing the breakdown of air between different types of electrodes and because the...
  5. N

    Can a spinning dielectric sphere induce a magnetic field?

    Homework Statement http://web.phys.ntnu.no/~ingves/Teaching/TFY4240/Exam/Exam_tfy4240_Dec_2013.pdf http://web.phys.ntnu.no/~ingves/Teaching/TFY4240/Exam/Solution_tfy4240_Dec_2013.pdf problem 2g Homework EquationsThe Attempt at a Solution Hi, this is taken from problem 2g in the problem set...
  6. R

    Prove E field does not depend on dielectric (capacitors)

    Homework Statement "Show that the variation of the potential between the plates of a large parallel plate capacitor remains the same if the air between the plates is replaced by a conductive medium." Homework Equations E = σ/ϵ0 ; C = ϵ0A/d ' C = Q/V ; E = -dV/dx ; R = ρl/A The Attempt at a...
  7. P

    Convention for the symbol of Dielectric Constant

    I have come across the dielectric constant represented by two variants of epsilon. Is there any convention behind the two variants such that: \varepsilon is the SI Dielectric Constant \epsilon is the CGS Dielectric Constant or does it really depend on the writer and how frisky they feel?
  8. G

    A sphere of linear dielectric material surrounded by another dieletric material

    Homework Statement A sphere of linear dielectric material with permittivity ##\epsilon_1## and radius ##a## is surrounded by an infinite region of linear permittivity ##\epsilon_2##. In the spherical region, there is free charge embedded given by ##\rho_{free}=\beta r^2##, ##0<r<a##, where...
  9. deedsy

    How Do You Calculate Charge and Potential in a Polarized Dielectric Sphere?

    Homework Statement A dielectric sphere radius R is injected with free charge so that the resultant polarization can be described by ## \vec P = \frac{K}{r} \hat r_1## where ##\hat r_1## is the unit radial vector. a) Calculate the volume and the surface density of bound charge b) Calculate the...
  10. M

    Dielectric resonator - microwaves

    Hi, recently there was an article in one scientific journal where they claimed that when microwaves are shined on a mixture of dielectric solid (powdered or crystalline) of high dielectric constant with some liquid, the EM field is much higher, both in the dielectric and in the liquid, as...
  11. P

    How much the dielectric loss tangent of 10 nm thick SiO2 ?

    How much the dielectric loss tangent of 10 nm thick SiO2 at 1Ghz ? I am studying the MOSFETs i want to know the the dielectric loss tangent of SiO2 dielectric at such manometer thickness, So if anybody know any reference about it Please let me know..
  12. Jasonlwe

    Help please -- Model of the capacitance and dielectric

    Hi everyone, I'm new in physics forum and this is my first post. So basically, our lecturer grouped us and gave each group a project to carry out. And the only information that we got is the name ( The one we got is "Model of the capacitance and dielectric" ). With only this information, me...
  13. F

    Electrostatic Potential in Dielectric Medium

    Homework Statement I need to find the green function for a dielectric sphere (\epsilon_1) inside another dielectric medium (\epsilon_2) using the method of images. Homework Equations In gaussian units I have: \phi=\frac{q}{\epsilon|r-r1|} The Attempt at a Solution Due to the symmetry of the...
  14. W

    Torque acting on a movable dielectric

    Homework Statement parallel-plate capacitor consists of two fixed metal semicircles of radius R and a dielectric plate (susceptibility \varepsilon). The plate is able to rotate without friction around the axis centered at the point O (axis O is perpendicular to the picture). Plate's thickness...
  15. R

    Proving Gradient of Electric Field in Coaxial Line Dielectric is 0

    Homework Statement Show that (Grad dot E) =0 in the dielectric of a coaxial line. (Hint: apply the divergence theorem to a portion of the dielectric.) Homework Equations Divergence theorem The Attempt at a Solution I think I need to show that grad dot E = p/epsilon = 0 I don't know - I'm...
  16. N

    How Are Electrons Introduced into Dielectrics Beyond Particle Accelerators?

    So I have seen some people doing making lichtenberg figures using a particle accelerator to blast electrons into a dielectric where they get stuck until the dielectric breaks down. Here is an example http://www.capturedlightning.com/ Are there other ways to get electrons into a dielectric other...
  17. almarpa

    Understanding the Derivation of Energy in Dielectric Systems

    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?
  18. deep838

    Gauss' Law in a dielectric material

    This is what we have in text-books and in Wikipedia: ρ=ρb+ρf and from there we get ∇.D=ρf. But I am unable to understand why we are not considering the bound surface charge in deriving this equation. Can anyone explain this to me.
  19. P

    Dielectric slab with a uniform field

    Homework Statement An example I am reading has the following setup: a dielectric slab of dielectric constant εr exists between z=0 and z=d, whilst an external electric field E0=E0k is applied with k a unit vector in the z direction. This setup exists for all x and y. The rest of space is a...
  20. A

    Why Does a Dielectric Slab Experience Force When Fully Inserted in a Capacitor?

    ...partially inserted between the plates of a parallel plate capacitor. I have a few questions about this - it is section 4.4.4 of Griffiths, 3rd edition. Imagine a parallel plate capacitor, of plate area l*d, separation d, filled with a linear dielectric of susceptibility X. Now imagine...
  21. X

    Dielectric Polarization Components in Ideal RC and C circuits

    Hi, I would like to know what the theoretical implication is, as it pertains to RC circuits of the following hypothetical situation(s): If one were to connected an ideal discharged capacitor in parallel with an ideal voltage source with zero resistance in the loop, the calculated RC time...
  22. N

    How does a dielectric increase maximum electric field strength?

    Homework Statement How does a dielectric increase maximum electric field strength? From the two cases where a dielectric is inserted into a charged capacitor after it is disconnected and after it is remained connected it seems that E will either decrease or stay the same. But I read in...
  23. kartikwat

    Does the dielectric constant affect the capacitance of a capacitor?

    Why do the capacitance increase with increase in dielectric constant(K) of the medium between the capacitor?
  24. O

    Why Dielectric Constant is Constant ?

    What I meant to ask is; When we double the electrical field passing through the insulator, the opposite electrical field that caused by the insulator is doubled too. How can this happen, what happens to the molecules in that time to increase the opposite electrical field? In my opinion, the...
  25. f95toli

    DOS for impurities in a dielectric

    I have a question regarind how to calculate the DOS for ferromagnetic impurities in a dielectric We have samples with ferromagnetic rare-earth ions implanted in a dielectric material. The concentration known and is quite high but the ions are probably only interacting weakly (they are on...
  26. L

    What is the dielectric function of PTFE (Teflon)?

    Hi, Does anyone know where I can find the dielectric function of PTFE (Teflon) ? Thank's
  27. Salvador

    Quartz Dielectric in Capacitors: What Happens?

    Hi everyone. I have been reading on capacitors and dielectrics , before that i was reading up on piezoelectric materials like quartz crystal. My question is , what would happen if we put a layer of quartz crystal between two parallel plates of a capacitor ? I think quartz is a dielectric...
  28. J

    Capacitor Energy with a Dielectric

    Homework Statement A dielectric-filled parallel-plate capacitor has plate area A = 15.0cm2 , plate separation d = 5.00mm and dielectric constant k = 3.00. The capacitor is connected to a battery that creates a constant voltage V = 5.00V . Throughout the problem, use ϵ0 = 8.85×10−12C2/N⋅m2 ...
  29. J

    Charged wire inside a linear dielectric

    Homework Statement see attachment 2 Homework Equations a. The Attempt at a Solution see atachment 1 i am stuck at problem a. the question is to write down the boundary conditions for that the E field has to satisfy infinetly far away from the wire and at the boundary of...
  30. U

    Boundary Conditions - Cylinder in dielectric

    Homework Statement Part (a): List the boundary conditions Part (b): Show the relation for potential is: Part (c): Find Potential everywhere. Part (d): With a surface charge, where does the Electric field disappear? Homework Equations The Attempt at a Solution Part (a) Boundary conditions...
  31. U

    Bound volume and surface charges in dielectric

    Homework Statement Find surface and volume charge densities. Deduce electric field. Homework Equations The Attempt at a Solution Volume charge density: \epsilon_0 \epsilon_r \nabla . \vec E = \rho_f Using ##\vec P = \chi \epsilon_0 \vec E = (\epsilon_r -1)\epsilon_0 \vec E##...
  32. U

    How Does a Dielectric Material Affect Electric Field and Surface Charge Density?

    Homework Statement Find the electric field inside dielectric and surface charge density on plates. Homework Equations The Attempt at a Solution \rho_b = -\vec {\nabla} . \vec{P} = -\vec {\nabla} . \epsilon_0 \chi \vec E = -\vec {\nabla} . (\epsilon_r - 1)\epsilon_0 \vec E \int \rho_b dV...
  33. lonewolf219

    Are current-carrying wires made of dielectric material?

    Here is an excerpt from my textbook: "Ordinarily, this charge would simultaneously generate so large an electric force as to swamp the magnetic one. But if we arrange to keep the wire neutral, by embedding in it equal amount of opposite charge at rest, the electric field cancels out, leaving...
  34. E

    A point charge inside a dielectric sphere

    Hello again I seen in this forum about this problem but not in the special case when the point charge is at the center of the sphere how do I solve the series legendre polynomials?
  35. baby_1

    The electric field in the dielectric is wasted?

    Hello as you see the problem and solution (see the attachment)the input electric filed is 2K v/m but in the glass the electric filed decrease approximately to 705.9 v/m.i want to know 1- The electric field in the dielectric is wasted? 2-why electric field decrease? Thanks
  36. K

    Effect of dielectric on charges

    What happens To the force between 2 charges if a metal sheet or a dielectric sheet is kept in between the two charges ..(the charges are in vacuum)
  37. I

    Capacitors don't require a dielectric material they?

    capacitors don't require a "dielectric" material they? whenever i hear about capacitors, i hear about the 'dielectric' material, but a dielectric material as opposed to a non-dielectric insulator just means that the material is polarizable. but polarizability only affects the field strength...
  38. C

    Electric field with dielectric

    Homework Statement There's a ring of radius R with linear uniform charge density \lambda=constant (which includes both free charges and polarization charges). The ring is in a dielectric region with \varepsilon_r. I have to find the electric field on any point of the axis of the ring Homework...
  39. D

    Effect of a dielectric cylinder parallel to an external field

    Homework Statement If a dielectric cylinder, say radius R, is placed with its axis parallel to a uniform electric field. What effect will it have on the field? Picture is included which makes it a bit clearer Homework Equations The Attempt at a Solution I know that the D-field...
  40. H

    Dielectric test as per IEC for Low voltage panels

    Hello guys, I was searching for what voltage does IEC standard call for Di electric test that should be done to low voltage panels? is it 2.5 KV for 1 minutes? If yes how how low voltage cable rated 600/1000 V can withstand 2.5KV without insulation failure?
  41. T

    Dielectric polarization and capacitance

    Hello all! My friend and I are having a bit of a discussion. We did an experiment on liquid crystals as dielectrics with changing voltage, and we came across some weird conclusions (capacitance decreased with increasing voltage? odd. Our theory is that liquid crystals don't act as normal...
  42. M

    Can the Dielectric Permittivity of a Material Be Altered?

    Hi , I would like to know if there is any material , a dielectric like the one used in a capacitor , whose dielectric permittivity could be altered , like increased or decreases , I'm not talking about older type capacitors which had plates on a rotor that could be adjusted so that one could...
  43. U

    Dielectric half-filled parallel plate capacitor

    Question taken from Griffiths Pg 185, Problem 4.19: For part (b): -Why are the electric fields the same whether in dielectric or in air? In part (a), they are clearly different! -Why is σ_{tot} = ε_{0}E = ε_{0}\frac{V}{d} -In calculation of capacitance, why is the total charge (\frac...
  44. U

    Field inside Dielectric (Griffiths)

    Hi guys, I do not really understand the explanation bit where he describes the "term left out" of the integration. Why is there any term left out? I thought it's rather straight forward that E = E(inside) + E(outside)?
  45. R

    Calculating Capacitance: A Derivation

    Homework Statement A parallel plate capacitor consists of two plates, each of area A, separated by a small distance d. in this gap, a dielectric of relative permittivity εr and thickness d/2 is fitted tight against one of the plates, leaving an air gap of thickness d/2 between it and the other...
  46. R

    Capacitance & Inductance in Diff. Dielectric Mediums

    Hello! How do I calculate the capacitance of a twisted wire pair in 3D? The pair of wire would have two different dielectric(air and insulation) mediums and hence I am not able to figure out how to calculate it by hand. My plan was to create a 3D Model, mesh it and put it up in...
  47. B

    [Electromagnetism,optics]How to attack a problem of dielectric tensor?

    Hi, I am currently making an effort to solve a boundary value problem of electromagnetic field. The problem is as follows: The region ##y<0## is vacuum. The region ##y \geq 0## is filled with material with ##\mu=\mu_0## and dielectric tensor ## \left( \begin{array}{ccc} \alpha & i\beta &...
  48. T

    Breakdown in parallel plate capacitor with dielectric

    Homework Statement Two related questions (from Electromagnetics by Notaros) The dielectric of a parallel-plate capacitor has two homogeneous parts, referred to as dielectric 1 and dielectric 2. The boundary surface between the parts is flat and parallel to the capacitor plates. The dielectric...
  49. S

    Are P and E fields in LIH dielectric in dynamic equilibrium

    If we know that the Polarization P in LIH dielectrics is proportional to the net field inside the dielectric according to: P = ε0χeE...(1) And we know that D = εE...(2) Does it not follow that we can ascertain the polarization directly from the applied (free charge) field, since we...
  50. X

    Finding the bound charge in a dielectric ATTEMPT 2

    Homework Statement The space between the plates of a parallel plate capacitor is filled with a dielectric material whose dielectric constant ϵr varies linearly from 1 at the bottom plate (x=0) to 2 at the top plate (x=d). The capacitor is connected to a battery of voltage V. Find all the bound...
Back
Top