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Topic: Dielectric


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In the News (Sat 25 May 19)

  
  Dielectrics   (Site not responding. Last check: 2007-10-15)
The dielectric is characterized by a dielectric constant k, and the capacitance is multiplied by that factor.
When a dielectric is placed between charged plates, the polarization of the medium produces an electric field opposing the field of the charges on the plate.
The permittivity is a characteristic of space, and the relative permittivity or "dielectric constant" is a way to characterize the reduction in effective field because of the polarization of the dielectric.
hyperphysics.phy-astr.gsu.edu /hbase/electric/dielec.html   (219 words)

  
 Dielectric Summary
Electrically, the dielectric constant is a measure of the extent to which a substance concentrates the electrostatic lines of flux.
Layers of dielectric are commonly incorporated in manufactured capacitors to provide higher capacitance in a smaller space than capacitors using only air or a vacuum between their plates, and the term dielectric refers to this application as well as the insulation used in power and RF cables.
Dielectric fluids with higher dielectric constants, such as electrical grade castor oil, are often used in high voltage capacitors to help prevent corona discharge and increase capacitance.
www.bookrags.com /Dielectric   (2314 words)

  
 Dielectric - Wikipedia, the free encyclopedia
As the dielectric interacts with the applied electric field, charges are redistributed within the atoms or molecules of the dielectric.
When a dielectric material is placed between two electric charges it decreases the effective force between them and, when an electromagnetic wave travels through a dielectric, the velocity of the wave will be reduced and it will behave as if it had a shorter wavelength.
The dielectric constant is also known as the static permittivity.
en.wikipedia.org /wiki/Dielectric   (1246 words)

  
 dielectric - HighBeam Encyclopedia
One important application of dielectrics is as the material separating the plates of a capacitor.
Generally, the dielectric constant of air is defined as 1 and other dielectric constants are determined with reference to it.
Other properties of interest in a dielectric are dielectric strength, a measure of the maximum voltage it can sustain without significant conduction, and the degree to which it is free from power losses.
www.encyclopedia.com /doc/1E1-dielectr.html   (425 words)

  
 Dielectric Constant   (Site not responding. Last check: 2007-10-15)
The dielectric constant of snow (es) is comprised of an imaginary part, which is directly related to wetness (W), and a real part which is a function of the density (r) as well as the wetness.
The dielectric constant of a water molecule is dominated by the reorientation of the molecule due to its large dipole moment.
The dielectric constant, e, is equal to the sum of the real (e') and imaginary (e'') permittivity of a material and is the square of the refractive index, or e = m2.
snobear.colorado.edu /Markw/SnowHydro/dielectric_const.html   (433 words)

  
 Microwave dielectric porcelain composition - Patent 5939344   (Site not responding. Last check: 2007-10-15)
The dielectric porcelain composition according to the present invention can be used as microwave circuit board, impedance matching member for various microwave circuits or the like besides as dielectric resonator in microwave range.
In the dielectric porcelain composition according to the present invention, the composition of the main component preferably satisfies the relationships 0.820.ltoreq.x.ltoreq.0.900, 0.010.ltoreq.y.ltoreq.0.070, and 0.090.ltoreq.z.ltoreq.0.130, as claimed in the second aspect of the present invention, more preferably 0.840.ltoreq.x.ltoreq.0.900, 0.010.ltoreq.y.ltoreq.0.050, and 0.090.ltoreq.z.ltoreq.0.130, as claimed in the third aspect of the present invention.
The form of the dielectric porcelain composition according to the present invention is not limited to the foregoing specific embodiments and may be varied within the scope of the present invention depending on the purpose.
www.freepatentsonline.com /5939344.html   (2198 words)

  
 Dielectric Strength ASTM D 149 IEC 80243
Dielectric Strength is a measure of the electrical strength of a material as an insulator.
Dielectric strength is defined as the maximum voltage required to produce a dielectric breakdown through the material and is expressed as Volts per unit thickness.
Dielectric strength is calculated by dividing the breakdown voltage by the thickness of the sample.
www.ptli.com /testlopedia/tests/DielStr-d149.asp   (384 words)

  
 Converting Magazine - Choosing the correct dielectric in corona treating   (Site not responding. Last check: 2007-10-15)
Dielectric constant: Material that is able to concentrate an electric charge is expressed as a "dielectric constant." Deficient treatment levels can usually be overcome by using a material with a higher dielectric constant.
Therefore, to maximize the voltage storage capacity of the dielectric, it is desirable to have a high dielectric constant.
Dielectric strength: The ability to withstand excessive voltages that sometimes cause pinholing in dielectric coverings is a major concern when higher treatment levels are used.
www.convertingmagazine.com /cgi-bin/current.cgi?view=12_99_88.htm   (1586 words)

  
 Dielectric Properties of Polymers - The Zeus Polymer Minute
The dielectric constant is a measure of the influence of a particular dielectric on the capacitance of a condenser.
The dielectric strength is the direct current voltage between two electrodes at which dielectric breakdown occurs and is an indicator of how good an insulator the material is. The voltage is increased until the material breaks down, there is an arc across the electrodes and substantial current flows.
The dielectric properties of polymers are largely predictable from the chemical structure of the polymer.
www.zeusinc.com /newsletter/dielectric.asp   (2077 words)

  
 Dielectric Responses of Living Organisms
We observe enormous linear dielectric constants at very low frequencies (with relative dielectric constants of over a hundred million at 10 Hz) attributed to the high polarizability of live cells resulting from their finite membrane potential.
The dielectric responses of the living cell suspensions are seen to be enormous at low frequencies and to decrease with frequency.
Nonlinear dielectric spectroscopy is an extremely sensitive probe in which the spectra depend on the type of organism and its metabolic state.
www.isso.uh.edu /publications/A2002/miller2.htm   (2434 words)

  
 On Capacitor Dielectric Materials   (Site not responding. Last check: 2007-10-15)
Where dielectrics with larger constants are employed, their larger dipole moments/polarizabilities interact more strongly with the inter-plate field, resulting in a stronger induced opposing field on the dielectric.
The residual charge from dielectric relaxation is known as the "dielectric absorption." When an audio signal is passed through a capacitor the dielectric absorption prevents full charging and discharging of the capacitor at the frequency of the alternating current signal.
Dielectric materials can be classified based on their relative polarity/polarizability properties, which the dielectric constants and dielectric absorptivities parallel.
www.audience-av.com /on_capacitor_dielectric_material.htm   (1551 words)

  
 Water dielectric and microwave radiation   (Site not responding. Last check: 2007-10-15)
Dielectric permittivity and dielectric loss of water between 0°C and 100°C, the arrows showing the effect of increasing temperature (data is indicative only but based on [64, 135]; exact data is plotted below) or increasing water activity.
This (1) lowers both the static and optical dielectric permittivities, (2) lessens the difficulty for the movement dipole and so allows the water molecule to oscillate at higher frequencies, and (3) reduces the drag to the rotation of the water molecules, so reducing the friction and hence the dielectric loss.
Dielectric and dielectric loss of a dilute salt solution between 0°C and 100°C (dashed lines; the solid lines shows the pure water curves as Figure 1 above), the arrows showing the effect of increasing temperature.
www.lsbu.ac.uk /water/microwave.html   (1431 words)

  
 The Dielectric Properties of Body Tissues   (Site not responding. Last check: 2007-10-15)
The application of such models require that dielectric properties be allocated to the various tissues at all the frequencies to which the model is exposed.
The dielectric properties of tissues have been extracted from the literature of the past five decades and compared to the corresponding data from the current study.
The basis of the analysis is well known dispersions in the dielectric spectrum of biological materials and their expression as a summation of terms corresponding to the main polarisation mechanisms.
www.brooks.af.mil /AFRL/HED/hedr/reports/dielectric/Report/Report.html   (3135 words)

  
 Dielectric Loss Tangents
The dielectric loss tangent is about 0.01 (although it isn't constant with frequency so manufacturers typically specify a worst-case value of 0.02), and the dielectric constant deteriorates from about 4.7 at 1KHz, to 4.5 at 1 MHz, to 4.3 at 1 GHz.
Because, for good dielectrics, the dielectric constant is such a slowly moving function of frequency we generally assume it's just constant over the band of interest.
Dielectric losses are discussed in a general way on page 159 of "High-Speed Digital Design", but not incorporated into any of the models in the back of the book.
www.sigcon.com /Pubs/news/4_5.htm   (972 words)

  
 Process Characterization: Dielectric Materials
Additional technical information on the dielectric materials project is included in the 2000 Yellowbook.
Dielectric materials have many applications throughout the electronics, microwave, communication, and aerospace inductries.
NIST is developing new measurement methods for characterizing permittivity and loss tangent of dielectric materials for the purpose of producing Standard Reference Materials.
www.itl.nist.gov /div898/charact/dielectric.htm   (592 words)

  
 What is dielectric material? - a definition from Whatis.com - see also: dielectric
A dielectric material is a substance that is a poor conductor of electricity, but an efficient supporter of electrostatic fields.
An important property of a dielectric is its ability to support an electrostatic field while dissipating minimal energy in the form of heat.
Another consideration is the dielectric constant, the extent to which a substance concentrates the electrostatic lines of flux.
whatis.techtarget.com /definition/0,,sid9_gci211945,00.html   (392 words)

  
 Dielectric constant - Wikipedia, the free encyclopedia
The relative dielectric constant of a material under given conditions is a measure of the extent to which it concentrates electrostatic lines of flux.
The dielectric constant is an essential piece of information when designing capacitors, and in other circumstances where a material might be expected to introduce capacitance into a circuit.
The dielectric constant of a solvent is a relative measure of its polarity.
en.wikipedia.org /wiki/Dielectric_constant   (412 words)

  
 Dielectric Constant
A collection of different dielectrics was assembled; the dielectric constants were determined at low frequencies (10kHz) by measuring the capacitance of parallel-plate dielectric sandwiches.
The greatest effect of dielectric loading was produced by the first two sheets (lambda/32), which reduced the resonant frequency by 17%.
Other measurements made included varying the position of the dielectric loading sheets within and around the antenna structure, investigating the effect of encasing the antenna in a graded dielectric constant by assembling sheets of different dielectric into a matrix, and investigating the effect on the azimuth radiation pattern (essentially there was no detectable effect).
www.ee.surrey.ac.uk /Personal/D.Jefferies/antennexarticles/diecon.htm   (1284 words)

  
 Broadband Dielectric Spectroscopy   (Site not responding. Last check: 2007-10-15)
Broadband Dielectric Spectroscopy provides a powerful tool for investigating a variety of dielectric processes for both electrical and non-electrical applications.
The sensing electrodes are measured not with a continuous frequency wave, but with a rapid voltage pulse containing a broad range of frequencies at once.
An arc in the complex impedance plane demonstrates that material behaves as an electrolyte resistance in parallel with an interelectrode capacitance, allowing the bulk resistance to be quantified independent of electrochemical effects at the electrodes.
www.msi-sensing.com /broadband_dielectrics.htm   (1000 words)

  
 Mauritz - Dielectric Spectroscopy
Dielectric spectroscopy can provide information about the segmental mobility of a polymer by probing its dielectric properties.
The complex dielectric properties, the loss factor(e") and the relative permittivity(e'), are determined by performing several isothermal scans as a function of frequency.
Dielectric relaxation is the result of a movement of dipoles or electric charges due to a changing electric field in the frequency range of 10^2-10^10 Hz.
www.psrc.usm.edu /mauritz/dilect.html   (594 words)

  
 [No title]
The dielectric loss angle, ð, is the difference between (theta) and 90o and is generally noted as tan o.
Dielectric absorption will not be discussed in any depth here: those wanting technical details should refer to Richard Marsh's previous groundbreaking work.
Film dielectric type capacitors, particularly polystyrene, have very low dielectric absorption and for this reason are preferred in audio circuits.
www.lycos.com /info/capacitor--dielectric.html   (321 words)

  
 Dielectric Spectroscopy.
In dielectric spectroscopy the current flowing through a sample cell containing a colloidal suspension and the voltage across this cell are measured as a function of frequency.
High polarization is manifested as a relative dielectric permittivity that may be much greater than that of the suspending medium.
Dielectric spectroscopy characterizes the dynamics of double layer relaxation and yields more information per measurement than static methods such as electrophoresis.
www.unisa.edu.au /laser/Research/Dielec.asp   (306 words)

  
 Dielectric microwave resonator probe - Patent 5105158
A dielectric resonator is mounted near to but spaced from a conductive plate and is positioned in contact with a test material.
The dielectric resonator is spaced from the conductive plate, preferably by a dielectric spacer and is substantially in contact with the test material.
The dielectric spacer 66 preferably is in the form of a cylinder and has a hole 68 extending therethrough for accommodating the bolt 58.
www.freepatentsonline.com /5105158.html   (3924 words)

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