# What is Dielectric constant: Definition and 96 Discussions

The relative permittivity, or dielectric constant, of a material is its (absolute) permittivity expressed as a ratio relative to the vacuum permittivity.
Permittivity is a material's property that affects the Coulomb force between two point charges in the material. Relative permittivity is the factor by which the electric field between the charges is decreased relative to vacuum.
Likewise, relative permittivity is the ratio of the capacitance of a capacitor using that material as a dielectric, compared with a similar capacitor that has vacuum as its dielectric. Relative permittivity is also commonly known as the dielectric constant, a term still used but deprecated by standards organizations in engineering as well as in chemistry.

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1. ### 2D electric field distribution in electrolyte solution

Hi there, How can I determine the electric field distribution from a planar electrode? The known parameters are potential applied to the electrode, ionic strength and dielectric constant of the medium. (E.g. for the most simple case 0.5 mM NaCl in water) I'm having difficulty finding a...
2. ### I Dielectric constant, dispersion and response of the medium

Hello, for my PhD, I've been studying an influence of a gain medium on spectral linewidth of light inside a fiber cavity. I've encountered a formula in one paper to which I don't how to get to (see screenshot), it's the formula (A3). On the left hand side there is electric flux density, the...
3. ### Optical vs Static Dielectric Constant for E-field Simulation

I am just learning about e-field simulations and I came across two different types of dielectric constants: optical and static. I'm unsure which to use and in which cases. I would like to simulate e-field intensity to help ensure I'm always below the dielectrics breakdown strength.
4. ### The Net Electric Field Inside a Dielectric

The net Electric field(inside the dielectric): $$E_{net} = \frac{1}{4\pi \varepsilon_0 \varepsilon_r} \frac{q}{r^2}$$ $$\vec E_{net} = \vec E_{applied} - \vec p$$ where p is the polarization vector. let charge ##q_{-}## be present on the inner surface of dielectric and ##q_{+}## on the outer...
5. ### Wavelength in relation to the Dielectric Constant Dk

Hi, On slide 9 of this presentation: http://www.globalcommhost.com/rogers/acs/techsupporthub/en/docs/MWJ_webinar_June20_2017_JC_microstrip_coplanar_stripline_final.pdf it states the signal wavelength can be changed with dielectric constant Dk. As far as I understand the wavelength and the...
6. ### Phase lag of light in materials

There are 5 fantastic videos in this website: http://www.alfredleitner.com/ He is a very good educator and it is also very good to see those authentic experiments and aparatus. Anyway, in the following one at exacly 8:00 minutes he says that the phase lag induced by the dipole is always 90...
7. ### Difference between polarization and the dielectric constant?

Hi everyone, When an electromagnetic wave passes through a material, then depending upon the atomic structure of that material it polarizes that material. There is another definition of polarization in physics which says that polarization is the direction of oscillating electric field in EM...
8. ### A change in the dielectric constant changes the current or voltage?

hi everyone! i am not into physics, but need it now,i am a programmer workin on an IOT project...so kinda need help. i want to use a capacitor to see what passed between two plates...knowing, it is the change in dielectric after certain intervals...how do i measure the change at the other...
9. ### Modeling the Driven Damped Oscillations in a Material

Homework Statement [/B] Let us assume that neutral atoms or molecules can be modeled as harmonic oscillators in some cases. Then, the equation of the displacement between nucleus and electron cloud can be written as $$\mu\left(\frac{d^x}{dt^2}+\gamma\frac{dx}{dt}+\omega_0^2x\right)=qE.$$ where...
10. ### Capacitors: find the dielectric constant

Homework Statement A parallel plate capacitor has a capacitance of 7.8 μF when filled with a dielectric. The area of each plate is 1.5 m^2 and the separation between the plates is 1.3 x 10-5 m. What is the dielectric constant of the dielectric? Homework Equations C= (K(8.85E-12)A)/d The...
11. ### Dielectric constant of air with temperature change

I'm looking to see how much the dielectric constant of air will change mostly as a function or air temperature. Is there a formula that outputs air dielectric as a function of temperature or atmospheric pressure?
12. ### Theoretical ξr of a molecule from the absolute configuration

I am wondering if anybody knows how to calculate the theoretical relative permittivity of a molecule (1) using the theoretical configuration and values that are easily accessible (2). I am also wondering what the technique would be. In my pharmaceutical reaction class and also O-chem 2 we have...
13. ### Confusion with constant voltage and dielectric

Homework Statement Consider a conducting sphere with radius ##R## connected to a voltage source of ##V_0## volts. If the sphere is then covered by a dielectric spherical layer of radius ##9R## calculated the relative permitivitty ##\varepsilon_0## needed so that the field in the empty zone...
14. ### Dielectric Constant: Does Positive Matter?

Does the dielectric constant of a material have to be positive?
15. ### I EM Radiation of "Permanent" Molecular Electric Dipoles

Suppose I were to subject a polar molecule to a high-frequency electric field. The polar molecule responds to the high-frequency electric field and thus it has a time-varying electric dipole moment vector. If we treated this as a classical electric dipole, it would be expected to radiate some of...
16. ### Dielectric constant of a rod

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)...
17. ### 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...
18. ### 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...
19. ### 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...
20. ### Coupling capacitance between interconnects in VLSI

Hello all, I'm trying to measure the effect of adding charges in the silicon dioxide separating two interconnects in VLSI circuits and how it will effect the coupling capacitance between these two wires. How can I measure this effect ? The VLSI circuit I'm working on has frequency of 500...
21. ### 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.
22. ### A How to start my reading for 2D screening models

Hi All, I needed some help or guidance starting my MSc reading, as there is tonnes of literature out there and it's difficult to understand what is necessary. I am beginning to look at applying screening models to a 2D system, such as the Thomas-Fermi continuum screening model, to a 2D system...
23. ### 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?
24. ### Electric Potential at Center of Sphere

Homework Statement A solid conducting sphere of radius R and carrying charge +q is embedded in an electrically neutral nonconducting spherical shell of inner radius R and outer radius 9 R . The material of which the shell is made has a dielectric constant of 2.0. Relative to a potential of zero...
25. ### Layering different dielectric materials to increase breakdown voltage

This is a general question, not a homework question, and @berkeman said I should post it in the EE forum... I'm trying to get a better understanding of the relationship of dielectric constant (relative permitivity) to dielectric strength (breakdown voltage).I want to know what happens when you...
26. ### Complex dielectric constant -- metals, insulators and Reflections

Hi everyone Can anyone help me understanding the physical meaning for the complex dielectric constant? Assuming a electromagnetic wave from air to a conductor, the following equation is valid R= ((n-1)2+k2)/((n+1)2+k2) where K is the extinction coefficient (the complex part of the complex...
27. ### Sample smaller than parallel plates in capacitance setup

Hi, My setup for measuring parallel plate capacitance consists of an LCR meter and a parallel plate test fixture. The area of the parallel plates is much larger than the area of the samples I am measuring. From what I've seen in literature, and my physics classes, the sample area should be...
28. ### Build a Capacitor in 30 minutes

Hi! I have to build a capacitor out of the following materials: 10 square feet of aluminum foil, 10 square feet of saran wrap (polyvinyl chloride), several sheets of paper, and tape to put it all together. I will only have about 30 minutes to manufacture my design. I have been researching...
29. ### Find Dielectric Constant from Parallel Plate Capacitor Problem

Homework Statement A parallel plate capacitor has a capacitance of 1.5µF with air between the plates. The capacitor is connected a 12V battery and charged. The battery is then removed. When a dielectric is placed between the plates, a potential difference of 5.0V is measured across the plates...
30. ### Investigating the water-ice electret

Hello all, I'm going to investigate the properties water when frozen in a strong electric field for a product I'm designing. A strong field will align the polar water molecules, and then they will freeze. I'm planning to create this strong field with a car battery attached to two parallel...
31. ### Building a capacitor to find the dielectric constant

Homework Statement I have a lab where I have to use two methods to find the capacitance of printer paper. Homework Equations C = kAeo / d The Attempt at a Solution From these slopes, I got k = .897 for the first type (using changing distance between the plates of the capacitor) for the...
32. ### Dielectric constant in few-layer and in bulk materials

Why is the dielectric constant smaller in few-layer materials than in bulk materials?
33. ### Electric field using dielectric constant

Homework Statement What is the magnitude of the electric field due to a 6.0 x 10-9 C charge at a point located 0.025m from the charge? The charge and the point in question are located underwater (κ(water) = 80). Homework Equations I know that E = magnitude of electric field = kq/r2, where k =...
34. ### Plates of capacitors and dielectric constant

In my textbook it is written that Electric charge on plates of capacitors (without dielectric ) is Q=CV And when dielectric is inserted in the space between plates of capacitors .charge Q remains the same whereas values of C and V change. i.e Q=C'V' is it correct?
35. ### Dielectric Constant Chart of Gases

Is there a creditable chart out there - on the dielectric constant of gases? What is the dielectric constant of Sulfur hexafluoride (SF6) compared to other gases or other gases in a vacuum? Thank You
36. ### 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?
37. ### 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...
38. ### Dielectric Constant of Food in microwave

I made the experiment up myself so my errors may be a result of this, but I heated up marshmallows, eggs and cheese in the microwave and measured the distance between the hotspots in order to get the wavelengths. For the marshmallows I got 0.13cm, for the eggs I got 0.16cm and for the cheese I...
39. ### Calculate the dielectric constant of the material

Homework Statement two point charges in free space are separated by distance d and exert a force 2.6 nN on each other. The force becomes 1.5 nN when the free space is replaced by a homogeneous dielectric material. Calculate the dielectric constant of the material. Homework Equations I...
40. ### Capacitors: why is the dielectric constant defined the way it is?

usually when we have some initial variable U(0), and we have some factor K that changes this initial variable, we usually express the new variable U(f) like so.. U(f)=KU(0) and NOT the other way around... so why is the dielectric constant expressed in the following way? Eκ=E0 this...
41. ### Relationship Between Conductance and the Dielectric Constant

Hello all, I'm new to the forum so I hope I'm posting this in the correct section. I'm currently conducting an experiment in which I'm examining how the dielectric constant of a binary mixture changes with concentration and temperature using a parallel plate capacitor for measurements. The...
42. ### Why is the index of refraction dependent on the dielectric constant

and frequency? Could someone point me in a direction where this is explained in depth? I understand polarization and the dielectric constant as I've taken E&M 1
43. ### Find the dielectric constant of the medium?

Homework Statement Two point charges a distance d apart in free space exert a force of 1.4∗10^−4 [N]. When the free space is replaced by a homogeneous dielectric medium, the force become .9∗10^−4 [N]. What is the dielectric constant ϵr of the medium? Homework Equations E=F/Q The...
44. ### Finding The Dielectric Constant

Homework Statement The voltage across an air-filled parallel-plate capacitor is measured to be 181.0 V. When a dielectric is inserted and completely fills the space between the plates as in the figure below, the voltage drops to 27.0 V. What is the dielectric constant of the inserted...
45. ### How to determine the dielectric constant of egg tray?

Hi, can i know how to get the dielectric constant of the egg tray (the one with the paper) beside using dielectric probe technique? is it have same dielectric constant of paper? or it is different? i hope someone can help me. if the egg tray mix with the carbon or graphite, as i know the...
46. ### Which dielectric constant in media?

Hi, In deriving a complex wave vector for waves in media, an equation D = ε E is typically used. Later though, it is common to relate D and E through a complex ε which is generally written as εcomplex = ε + 4 pi i σ / ω. It seems a contradiction to insert one relationship into the Maxwell...
47. ### Dielectric constant is throwing me off

A spherical capacitor is formed from two concentric, spherical, conducting shells separated by vacuum. The inner sphere has radius 0.39 m and the capacitance is 108 pF. What is the radius of the outer sphere? Give your answer in meters to the third decimal place. C-->Capacitance...
48. ### Dielectric Resonators, Resonant Frequency, and Dielectric Constant?

Hello, I have been trying to better understand the effects of dielectrics in resonant cavities. I read that the addition of a dielectric in a resonant cavity will reduce the resonant frequency of the cavity. My questions: Is there any relation to the reduction of the resonant...
49. ### Conducting sphere surrounded by insulator with dielectric constant

Homework Statement A conducting sphere of radius A has a charge +Q on it and is surrounded by an insulating material whose dielectric constant varies with radius according to εr = 2exp[-(r/a-1)]2. The dielectric has a spherical outer boundary B. Find the values of D, E, P, ρ as a function of...
50. ### Dielectric constant refractive index relationship

hi, i have seen on another topic here that the refractive index equals the square root of the dielectric constant. from datasheet values we have... water refractive index = 1.333 dielectric constant = 80.1 Without even doing the calculation its obvious that the square root of 80.1 is not...