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.

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

    Could we use flowing air as a capacitor dielectric?

    I wanted to use air as the dielectric for a capacitor for energy storage for aircraft. My thinking was that we could charge the capacitor on the ground and leave the capicitor open to the flowing air in flight. As long as the density of the flowing air remained the same, the capacitance would...
  2. S

    Dipole in a Dielectric: Analysis of r→0

    We have a dipole in a vacuum cavity inside an otherwise infinite LIH dielectric. We assume form Vin = Arcos(theta) + B/(r^2) * cos(theta) Vout = C/(r^2) * cos(theta) We are told that "as r tends to 0 the field must approach the dipole field". I'm not sure if they are talking about the...
  3. M

    Capacitance W/ Dielectric Problem

    A parallel-plate capacitor has rectangular plates of length L = 19 cm and width W = 3 cm . The region between the plates is filled with a dielectric slab of dielectric constant K= 4 which can slide along the length of the capacitor. Initially, the slab completely fills the rectangular region...
  4. K

    Is My Calculation of the Radius in a Dielectric Strength Problem Correct?

    Dielectric Strength problem. Please Help! :( If anyone can let me know if I went about this right, I'd appreciate it, as well as any advice. The dielectric strength of an insulating material is the maximum electric field strength to which the material can be subjected without electrical...
  5. I

    Optics: refractive index and dielectric constant

    Dear all, i am a bit confused with a very simple equation connecting refractive index of water and its dielectric constant for visible range of wavelengths and room temperature. i hope, You can help me as we know, the refractive index 'n' can be defined as n=sqrt(epsilon*mu)...
  6. S

    How Does Inserting a Copper Slab Affect a Capacitor's Performance?

    A slab of copper is thrust into parallel plate capacitor as shown in the figure. a) What is the capacitance after the slab is introduced? This is like two capacitors in series so C_{1} = \frac{\epsilon_{0} A}{d-b-x} C_{2} = \frac{\epsilon_{0} A}{x} when added it yields...
  7. I

    Minimum Thickness of Dielectric

    1. Basically, we have coaxial cable with an inner wire of radius a, perfectly conducting, straight and infinitely long, with radius a, surrounded by an outer hollow cylinder, also made from perfectly conducting material, having inner radius b and outer radius c. The hollow cylinder functions...
  8. S

    Measuring Dielectric Constants of Materials in a Parallel Plate Capacitor

    I wanted to find the dielectric constant of different materials placed in a parallel plate capacitor using the equation: K = \frac{E_{dielectric}}{E_{original}} Where E = \frac{V}{d} I would use sensors connected to a computer to measure the voltage and i could easily measure the...
  9. S

    Finding The Dielectric Constant?

    Hi, I'm currently an A2 student and was wondering is it possible to find dielectric values for different materials placed within parallel plate systems. I have an idea but i think doing this is more complicated than i expect. I found the equation: k=Cd/epsilonzero*A d = distance between...
  10. S

    Electric polarization involves the defect centers in the dielectric

    I konw that the defect centers in a dielectric contribute to the electric polarization and thus affect the permittivity.If there is any microscopic theory can derivate the relationship between the defect centers and the permittivity?
  11. H

    Electric energy of a dielectric sphere

    Electric energy of a dielectric sphere! Hi there, I have attempted a question, I was just seeing if some one can go over it and check if it is ok! Q. The Electric field E inside a dielectric sphere placed between the plates of a large parallel-plate capacitor is uniform. Given that the...
  12. H

    Total energy of a dielectric sphere

    Total energy of a dielectric sphere please help! I have a problem that I can not do after searching the net and looking through my notes and textbook. I think it is a basic electomagnetic field question but i just can't get my head around it. The question is: The electric field E inside...
  13. N

    Dielectric in an electrostatic field

    Hi all, I am sorry this could sound like heard many times before, but I am trying to understand this problem and found nothing in my physics books. If I put a small dielectric (bit of paper) into an electrostatic field (for example generated by a rubbed plastic rod), the paper will be...
  14. R

    Finding Electric & Magnetic Field Energy Densities in a Dielectric Medium

    If current densities are given in a perfect dielectric medium having \epsilon , \mu I have to find the power dissipated per unit volume, the electric field energy density, and the magnetic field energy density everywhere. Can I get help with equations?
  15. D

    Capacator with moving dielectric

    suppose you had a capacator and a free to move dialetric, which was outside of it, and you attatch a voltage to the capacator. the dialetric will move in. however, does anybody know what force and where the force is that causes the dialetric to move in?
  16. maverick280857

    Simple Harmonic Motion of a Dielectric Slab in a Parallel Plate Capacitor

    Hello Here's a situation I would like to discuss... Suppose we have an ideal parallel plate capacitor which is filled with air (or vacuum) with permittivity = 1. Now if a dielectric slab of width equal to the space (d) between the plates is inserted into the space between the plates, it...
  17. S

    Dielectric constant and index of refraction

    I'm a little confused. My source says the dielectric constant for water is 80. Then I have the equation that gives the index of refraction as n=\sqrt{\epsilon_r} (since it isn't very magnetic). But the index of refraction for water is 1.33. What am I missing?
  18. G

    Spherical capicator w/ dielectric

    I am not sure if I have done the following problem correctly. To start, I do not know how to prove the electric field must be directed radially. Assuming this is true, then the magnitude of the field must be uniform along any spherical boundary (otherwise we could form a nonconservative loop...
  19. X

    How Does Capacitance Change with Multiple Dielectric Materials in a Capacitor

    Hey Guys, I was just doing a question on capacitance and i was wondering since capacitance is usually determined by a fixed formula which is dependent on the di electric material that is contained within a capacitor.. However it struck me that a capacitor does not neccesarily contain...
  20. H

    Induced Magnetic Field in Dielectric

    I need a little help on an E&M problem I'm working on. A dielectric slab suspended in free space has a time dependant, non-uniform electric field inside of it (it was given in the problem, but I don't have it with me right now). For the material \mu=\mu_0 and \epsilon=2.56\epsilon_0. I need...
  21. Gokul43201

    How Does Helium's Dielectric Constant Vary with Temperature?

    I'm having trouble finding reliable data on the dielectric constant of helium(4) gas as a function of temperature, from 4K up. Grateful for any help
  22. C

    Power transmission and dielectric constant

    How do I find the reflectivity of a combination of ice on top of water(infinite half-space) as a function of the thickness of ice? I know how to find it for each material, it's just rho = ((root(dielectric constant)-1)/(root(dielectric constant)+1) )^2. I'm given dielectric constants for both...
  23. J

    Capacitor with partially inserted Dielectric

    This is one of my homework problems that I am stumped with: A parallel-plate capacitor with only air between the plates is charged by connecting it to a battery. The capacitor is then disconnected from the battery, without any of the charge leaving the plates. A) A voltmeter reads V_1...
  24. Cyrus

    What is the point in using a dielectric

    Hi tide. question. What is the point in using a dielectric. I was doing a problem in the physics book and it showed that when you use a dielectric, the amount of energy stored in your capictor decreases. Wouldent you want to store the MOST amount of energy in your capacitor? So why bother...
  25. M

    Do Dielectric Properties of Materials Change with Frequency of RF Waves?

    Help Plz... Dielectric Properties Hii.. I am a new member of this forum. I wish to know about dielectric properties of materials. Do they change with the variation of frequency of RF wave, if the materials are exposed to RF waves? Please assist. Thanks in anticipation, Mahfuz
  26. A

    Exploring Phonons in Dielectrics: A Beginner's Guide

    Hi everybody. I know a little about phonons in a lattice such as semiconductors, which are energy quanta of the vibrational states of the crystal, but I can't figure out how a phonon can exist in a dielectric or even in a non monocristalline material. Can somenone help me or advise me a book on...
  27. S

    Confused on this dielectric capacitance problem

    The electric field between the plates of a paper-separated (K=3.75) capacitor is 9.41E4 V/m. The plates are 1.75mm apart and the charge on each plate is 0.775E-6C. Determine the capacitance of the capacitor and the area of each plate? I got the voltage by V=Ed. and that came out to 164.675...
  28. C

    Material Dielectric Properties: Charging 4th Grader Science Fair

    Where should I go to identify some very basic dielectric properties of the following materials: PVC, polyethylene, polystyrene, glass, acrylic, nylon, polyester?? I'm trying to determine whether these materials have negative or positive charges and how the charge is determined. My son, a 4th...
  29. A

    Dielectric constant for a plastic kitchen bag?

    Hello! I'm making some home-made capacitors for an up-coming lab, and I was thinking of using Market Basket/DeMoulas' plastic kitchen bags as a dielectric. I'm really hoping to use it because the packaging info includes the thickness of the bag (19 micrometers), which should increase the...
  30. D

    Discovering the Material with the Highest Dielectric Constant

    I would dearly like to know what material has the highest relative dielectric constant and how much is it?
  31. M

    Dielectric boundaries and symmetry

    I have been reviewing the method of images for electrostatic problems and noticed the following: Textbooks point out that to use Gauss' Law successfully there must be geometric symmetry that makes the Efield constant over some reasonable surface. I thought this was just to make the math...
Back
Top