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. HelloCthulhu

    Water as a dielectric. Is this video a good demonstration?

    I found, at least in my uneducated opinion, a very good demonstration of water as a dielectric. I understand that putting water in a bag will change the dielectric constant of the water in it somewhat, but I think the capacitance meter at least makes water's value as a dielectric visually...
  2. R

    Polarization charge density of homogeneous dielectric

    Hi everyone, there's something that I can't comprehend: when a homogeneous is in a conservative and non-uniform in module electric field polarization expression is given by P=ε0χE. Supposing the most general situation there's: divP=ρp where ρp is the polarization charge density in the...
  3. V

    Dielectric inserted into a parallel plate capacitor

    Homework Statement The capacitor (of thickness d) is disconnected from a potential source of V and a dielectric of thickness t is inserted and it has relative permitivity Er. Find the new potential between the plates Homework Equations [/B] This is the answer : Vf = V/d(d - t + t/Er) The...
  4. S

    How an electric field is absorbed by a dielectric

    when a em waves strikes a dielectric the atoms vibrate in response to the electric field and if the frequency matches the resonant frequency the Lorentz oscillator the electric field is absorbed how a field can be absorbed we know the em field contain energy how is the em field destroyed is some...
  5. H

    Does the charge of a capacitor change during immersion?

    If given a capacitor with stored charge, would its charge remain constant before and after it is immersed in a liquid (i.e. distilled water)? Why? I know that before immersion, the capacitance would be = (ɛAV/d), but would that be the same if immerged in distilled water?
  6. T

    What is the difference between PP(polypropylene) and CPP?

    To my knowledge, CPP means cast-polypropylene, which I've seen used in a coaxial cable. Some cables use CPP as dielectric material. My question is: 1. what is the difference between PP(polypropylene) and CPP? 2. How is CPP made? 3. Is the permittivity and loss tangent of CPP different from that...
  7. S

    How do I get this interface condition?

    Homework Statement I have an infinitely long cylinder of a dielectric material, surrounded by another dielectric material and coated with graphene which has surface conductivity \sigma, implying it has a superficial current. The sheet of graphene is very thin, and the dielectrics are asumed to...
  8. R

    Plasma Generation using Dielectric Barrier Discharge

    I am having trouble in making a power source for the DBD. I can't seem to find any calculations to get the required voltage and frequency of AC to generate plasma. I want to know the circuit/method/equipment needed to generate that voltage from a normal 220 V/50 Hz AC socket in my lab.I am doing...
  9. S

    Interface conditions on a graphene interface

    Homework Statement I'm trying to do all the calculations for the attached paper, and I'm having trouble with the boundary conditions for P polarization. My question is, how can I arrive to those conditions? The problem is 2D, an infinite dielectric cylinder coated with a layer of graphene...
  10. DoobleD

    Direction of reflected E field on a dielectric surface?

    When studying Fresnel equations in EM, I very often came across the following type of picture for a s-polarized incident wave on a dielectric interface (http://iqst.ca/quantech/pubs/2013/fresnel-eoe.pdf) : Many similar diagrams can be found on the internet, for instance...
  11. P

    Dielectric problem -- two line charges inside a dielectric cylinder

    Homework Statement Consider a cylindrical hole of radius a and infinite length cut into a dielectric medium with relative electric permittivity ε (the interior can be treated as a vacuum). Inside the hole there are two line charges of infinite length with line charge densities λ and −λ...
  12. S

    Liquid crystals: dielectric torque and electric torque

    Dear Members, I was reading a tutorial on ferroelectricity of liquid crystals, underneath is the excrept: "For ferroelectric materials, in addition to the dielectric torque, the electric torque will have a term due to the linear coupling between the spontaneous polarization" Could someone...
  13. HelloCthulhu

    The relationship btw dielectric strength and temperature

    Wiki suggests dielectric strength is temperature dependent, but I've yet to find any math supporting this. I found some math corroborating a relationship between conductivity and temperature, but whether or not there's any causality between conductivity and dielectric strength has eluded me. Any...
  14. Pushoam

    How Is the Dielectric Constant Determined for a Rod to Prevent Light Absorption?

    Homework Statement Homework EquationsThe Attempt at a Solution ## n_1 = \sqrt{ \epsilon _1} ## ...(1) , ## n_2 = 1 ## ...(2) ## \frac { \sin {\theta_i}}{ \sin {\theta_l} } = \frac { n_1}{n_2} = n_1 ## ...(3) ## \cos{\theta_1} = \frac { n_2}{n_1} = \frac1{ n_1} ## ...(4)...
  15. HelloCthulhu

    Floating Water Bridge and Dielectric Strength per Volume

    I recently watched a great video demonstrating the floating water bridge experiment: At around 34 sec, you can see an electrostatic discharge before the water bridge forms. I've read that this is due to the electrostatic breakdown of air between the two beakers.This made me curious about the...
  16. A

    Fully filled capacitors with parallel dielectrics problem

    consider that we have two dielectrics inside a capacitor as shown in the picture, let0s consider also that Q is the charge of the capacitor and d the distance between the two plates , the first dielectric occupy a surface of S/3 with a dielectric constant of er1 and the second a surface of 2S/3...
  17. C

    Force acting on a dielectric placed between parallel plates

    Homework Statement A parallel plate capacitor of length l and width w and separation d, has a dielectric of dielectric constant k inserted to a distance x, if the capacitor has a charge q, find force acting on the dielectric when its near the edge Homework EquationsThe Attempt at a Solution ...
  18. C

    I Stream inside paraffin oil when exposed to high volage

    Here is the experience: I put two electrodes inside paraffin oil (separated by at least 3cm), and submitted the electrodes to high voltage. At 20000 V - 30000 V, strong streams can be observed inside the paraffin oil. Since paraffin oil is a good dielectric, I just would like to understand the...
  19. f95toli

    A Surface excitons on dielectric surfaces/interfaces

    Does anyone have a good reference for work on surface excitons? I am in particular interested in excitons on surfaces of metal oxides (TiO2, Al2O3 etc) I've spent a fair amount of time trying to find information using Google Scholar etc. My (old) undergraduate surface science textbook does have...
  20. G

    Coaxial cable conductors with dielectric: polarization of charge

    Homework Statement Consider a coaxial cable which consists of an inner cylindrical conductor of radius R1, and a shell cylindrical conductor of radii R2 and R3. The 2 conductors are separated with a dielectric material of permittivity ε. Consider the length of the cable, ℓ, much larger than R3...
  21. G

    Is the Total Charge of Polarization in a Non-Homogeneous Dielectric Zero?

    Homework Statement Consider an infinite environment with electrical permittivity non-homogeneous $$\epsilon=\epsilon_0(1+a/r)$$ a being a positive constant. A conducting sphere of radius R and charge Q is put on that environment, centered at r=0. Determine the electric field $$E$$, the...
  22. G

    Electric field in a capacitor with a dielectric

    Homework Statement A parallel plate capacitor has 2 square plates of side l, separated by a distance d (l is a lot bigger than d). Between the plates, there is a linear and non-homogeneous dielectric with constant $$\epsilon_R=1+ay$$ with $$a$$a positive constant. Calculate the electric field...
  23. J

    Surface bound charge on the outer surface of a dielectric

    Homework Statement With regards to a one dimensional conducting wire with a homogeneous charge density λ surrounded by a cylindrical glass dielectric of radius R, find: (a). The displacement vector inside the dielectric (b). The surface bound charges on the surface of the dielectric Sorry...
  24. L

    Capacitance with smoothly varying dielectric in 1D

    Dear all, I am trying to find the capacitance of a parallel plate structure that comprises a spatially varying (linear) dielectric in one dimension. I have two methods of solving this which give different answers, and I am not sure which is correct. I consider the dielectric region to be...
  25. G

    Energy changes upon insertion of a solid dielectric in a capacitor

    Consider a simple circuit consisting of a battery and a parallel plate capacitor .During the process of charging of capacitors, we come to learn that half of the work done by the battery is stored in the form of potential energy and half of it is lost as heat or electromagnetic radiation...
  26. G

    Dielectrics and standing waves

    How do dielectrics affect the number of modes for standing electromagnetic waves in a box?
  27. Experience111

    How does dielectric heating actually work?

    Hi everyone, I'm currently working on a research project about dielectric heating of some materials and I'm trying to understand the physics of this phenomenon before going any further. I'm especially trying to understand the concept of complex dielectric constant and loss factor. I'm...
  28. mnb96

    Capacitance with changes in dielectric material

    Hello, Let's consider a capacitor simply made of two conductors with arbitrary shape in the vacuum (http://www.kshitij-iitjee.com/Study/Physics/Part4/Chapter26/3.jpg). Now, if I place a small piece of dielectric material (for example a tiny sphere of glass) between the two conductors, the...
  29. Eclair_de_XII

    I got bored and did something with the dielectric constant

    Homework Statement I want to prove or disprove that the dielectric constant ##K## is the projection of ##\vec E_0## onto ##\vec E## using linear algebra. Homework Equations ##\vec E = \frac{\vec E_0}{K}## The Attempt at a Solution ##(\vec E)⋅\vec E = (\vec E)⋅\frac{\vec E_0}{K}## ##K(\vec...
  30. Muthumanimaran

    Capacitor with dielectric as spring

    Homework Statement Two parallel plates of metal sandwich a dielectric pad of thickness d, forming an ideal capacitor of capacitance C. The dielectric pad is elastic, having a spring constant k. If an ideal battery of voltage V across its terminals is connected to the two plates of this...
  31. J

    Dielectric inserted in parallel plate capacitor

    Homework Statement Homework EquationsThe Attempt at a Solution The force between the plates is given by (1/2)QE ,where Q is the charge on the plates and E is the electric field between the plates . Now Q = CV and E = V/d , where C is the capacitance , V is the potential difference and d is...
  32. Pushoam

    Electric field inside a cavity in a dielectric

    Homework EquationsThe Attempt at a Solution A)[/B] In the spherical cavity, let me have a Gaussian Spherical Surface around the center. Applying Gauss' s Law for dielectrics, ##\oint _S\vec D⋅ d \vec a = Q_{f_{en}} ## Due to the symmetry of the problem and ## Q_{f_{en}} =0## , ## \vec D = 0...
  33. Leonardo Machado

    Cavity in a dielectric material

    Hello friends. If i have a dieletric material ( w/ a hole) and apply an uniform eletric field on it, the eletric field in the hole will stay null ? Peace.
  34. R

    Boundary conditions in dielectric problems

    Q) A conducting sphere of radius R floats half submerged in a liquid dielectric medium of permittivity e1. The region above the liquid is a gas of permittivity e2. The total free charge on the sphere is Q. Find a radial inverse-square electric field satisfying all boundary conditions and...
  35. A

    Why is the electric field inside the dielectric cancelling?

    So, I was studying force between the plates of a capacitor when a dielectric is inserted. Here is my question https://ibb.co/cenvXk Shouldn't it be like this picture below https://ibb.co/kOUsCk So, why is my teacher saying that the electric field inside the dielectric cancelling. So, what...
  36. O

    Alternative to Mie Theory for Analysis of Homogenous Sphere

    I know that mie theory is used to analyze the absorption/scattering/extinction of a homogeneous sphere within a homogeneous dielectric medium. However, if I wanted to perform the same analysis on a sphere enclosed by two different media, is there an analytic solution to this?
  37. G

    Dielectric or Piezoelectric: What's the Difference?

    Hi, What is the difference between dielectric material and piezoelectric material ? Even Wikipedia use exactly the same figure for illustration. I googled, Both of them is - material between plates - polarization, dipole of molecule As far as I understood from google, When material is...
  38. Q

    Dielectric tensor in an isotropic media

    In the lecture notes http://top.electricalandcomputerengineering.dal.ca/PDFs/Web%20Page%20PDFs/ECED6400%20Lecture%20Notes.pdf at page 15 eq. (2.46) it says that the dielectric tensor in an isotropic media can be represented by: δi j A(k,ω) + ki kj B(k,ω) I understood that in the case of I. M...
  39. A

    Capacitance capacitor parallel plate with dielectric (Gauss)

    Homework Statement I have an elementary doubt with the calculation of the capacitance of a capacitor of parallel plates that has a dielectric in the middle. https://ibb.co/b0W4BQ Homework Equations ∫D⋅ds=Q D=E+γP C=Q/V The Attempt at a Solution Suppose the top plate has a positive charge...
  40. Emmanuel_Euler

    Dielectric Constant Vs Temperature Vs Polarity

    please explain the concept of dielectric constant in the simplest CHEMICAL terms possible. why does it decrease when the temperature increases? and why does it increase when the polarity increases? please keep it simple and brief.
  41. Atacan

    Capacitance of the capacitor after inserting the dielectric

    Homework Statement Homework Equations V=Ed Q = CV W = 1/2 QV The Attempt at a Solution Hi. My instructor gave me this problem as a homework. Actually he didnt teach us this subject. So what should i know to solve this question or from where can i study to this subject? Of course it would be...
  42. pallab

    The dielectric constant of water is 80, but refractive index

    The dielectric constant of water is 80, however its refractive index is 1 ·33 invalidating the expression n*n=ε. why?
  43. Arman777

    How Does Inserting a Dielectric Affect Capacitance and Potential?

    Homework Statement Homework EquationsThe Attempt at a Solution I couldn't find the V(x).I don't know ho to write the equation.I think that it will be constant cause potential betwwen two plates should be constant... ?
  44. S

    Dielectric Charges: Explaining Why They Don't Attract

    can someone in detail explain to me why can't a dielectric attract charges?
  45. J

    Dielectric Constant & Electric Field: How It Works

    The higher the dielectric constant, in a sense the more mobile the charges are in side the material. So a higher dielectric constant will cancel more of the field inside of itself, and a metal will ideally cancel out all of it. But what happens on the other side of the material? Does it re...
  46. rodv92

    Decreasing gas breakdown distance in a spark gap with UV

    Hello ! I am currently investigating a technique that would allow several spark gaps to breakdown synchronously in an enclosed but not hermetical cavity, flushed with N2 at 1atm and ~25°C My idea was to use "indirect" photoionization (basically a synthetic fused quartz UV flash discharge inside...
  47. E

    Potential of dielectric cylinder with constant polarization

    Homework Statement The dielectric cylinder is radius R and thickness d. Origin is at the center of the cylinder, which is oriented along the z-axis. It has polarization P=pz∧I need to calculate the potential V(0,0,h) at h>d/2. Homework Equations σb=P⋅n∧...
  48. qnach

    Where Can I Find Books on Shell Dielectric Resonance Antennas?

    WiKi indicate Millimetre Wave Antennas for Gigabit Wireless Communications: A Practical Guide to Design and Analysis in a System Context Huang, Kao‐Cheng ; Edwards, David J. Chichester, UK: John Wiley & Sons, Ltd But our library do not have this book. Has anyone know other book on this...
  49. qnach

    Dielectric Antennae: Energy Feed-In/Take-Out Explained

    There are many webpage about dielectric antenna For instance, https://en.wikipedia.org/wiki/Dielectric_resonator_antenna But I cannot figure out where does the energy feed-in or take-out from the antenna?
  50. A

    Heat produced when a dielectric is inserted into a capacitor slowly

    if a capacitor is connected to a battery and then it is fully charged . then a dielectric slab of k is inserted in the capacitor while the battery is still connected SLOWLY my question is will there be any heat produced?? my approach -- after insertion of dielectric , the charge on the...
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