What is Permittivity: Definition and 142 Discussions
In electromagnetism, the absolute permittivity, often simply called permittivity and denoted by the Greek letter ε (epsilon), is a measure of the electric polarizability of a dielectric. A material with high permittivity polarizes more in response to an applied electric field than a material with low permittivity, thereby storing more energy in the material. In electrostatics, the permittivity plays an important role in determining the capacitance of a capacitor.
In the simplest case, the electric displacement field D resulting from an applied electric field E is
D
=
ε
E
.
{\displaystyle \mathbf {D} =\varepsilon \mathbf {E} .}
More generally, the permittivity is a thermodynamic function of state. It can depend on the frequency, magnitude, and direction of the applied field. The SI unit for permittivity is farad per meter (F/m).
The permittivity is often represented by the relative permittivity εr which is the ratio of the absolute permittivity ε and the vacuum permittivity ε0
κ
=
ε
r
=
ε
ε
0
{\displaystyle \kappa =\varepsilon _{\mathrm {r} }={\frac {\varepsilon }{\varepsilon _{0}}}}
.This dimensionless quantity is also often and ambiguously referred to as the permittivity. Another common term encountered for both absolute and relative permittivity is the dielectric constant which has been deprecated in physics and engineering as well as in chemistry.By definition, a perfect vacuum has a relative permittivity of exactly 1 whereas at STP, air has a relative permittivity of κair ≈ 1.0006.
Relative permittivity is directly related to electric susceptibility (χ) by
χ
=
κ
−
1
{\displaystyle \chi =\kappa -1}
otherwise written as
From the second equation I get that,
##\vec D =\frac{q}{4\pi \vec r^2}\hat r##
From first equation I get that
##\vec E = \frac{q}{4\pi \vec r^2 \epsilon}=\frac{q}{4\pi \vec r^2 K \epsilon_0}##
But I saw that the answer is ##\vec E=\frac{\vec E_0}{K}##
While writing the comment my mind said...
If I have an anisotropic material with permittivity:
$$\epsilon=
\begin{pmatrix}
\epsilon_{ii} & \epsilon_{ij} & \epsilon_{ik} \\
\epsilon_{ji} & \epsilon_{jj} & \epsilon_{jk} \\
\epsilon_{ki} & \epsilon_{kj} & \epsilon_{kk} \\
\end{pmatrix}
$$
What exactly does each element represent in this...
The Vacuum Permittivity of the classical vacuum seems to be for just conversion of units in Coulomb's Law, like Coulomb's Constant in disguise.
Does the Electrical Permittivity of the Vacuum in classical electromagnetism have any real physical significance other than in the above context...
Coulomb's Law $$ \vec{F} = \frac{1}{4 \pi \epsilon} \frac{q_1 q_2}{r^2} \hat{r} $$
$$ \vec{E} = \frac{1}{4 \pi \epsilon} \frac{Q}{r^2} \hat{r} $$
Let's say we want to find electric field with a distance r from charge Q. How does permittivity effects the magnitude? Will I choose the permittivity...
This is a second grade high school problem, translated from my native language.
I don't have a problem with calculating, but with understanding the concept. There is an instruction with the assignment that says: The capacitor can be viewed as a combination of two capacitors in series with...
What happens if we make a dimensional analysis of permeability and permittivity ?
Will we get a minimum possible amount of electric and magnetic values?
Summary:: How can Schrodinger's Equation be written relative to vacuum permittivity
I am wondering why a particular problem uses this equation:
It is stated to be Schrodinger's equation. Where does the potential come in, as well as the e^2/r ?
An explanation would be greatly appreciated. Thanks.
The first part (which I believe I've done correctly) asks us to find the electric displacement everywhere. For this:
$$\int D \cdot da = Q_{f,enc}$$
For a < r < b: $$D = \frac{Q}{4\pi r^2} \hat{r}$$
Otherwise, D = 0
When finding the capacitance, I'm unsure how to handle the r dependence. I...
Hi
When I read the following article:
http://nopr.niscair.res.in/bitstream/123456789/14183/1/IJPAP%2050%286%29%20405-410.pdf
I tried to convert the value of the conductivity for saline in 500 MHz.
At the article, they present the conductivity as ε'' = 70. Which ε'' is the imaginary part of...
i'm working on a project about the surface plasmon in graphene.
i found on some articles that we don't use Drude model to calculate permitivity on graphene but they didn't mention what's the right model !
can you help me please and give me the relation that link links between permitivity and...
I read in various sources (such as page 8 of these notes) that the dielectric permittivity tensor of a lossless medium is always symmetric. I am wondering how this can be the case, when:
Phase accumulation in the medium could in theory depend on direction
Coordinate system may be rotated to...
I am studying about dielectric materials and their relaxation properties. There are several ranges of electromagnetic frequencies where different material show different kinds of resonance starting from molecular to atomic motions. Based on the frequency dependence of the imaginary part of the...
Say the space is divided into two parts: one has permittivity e1 and other e2. A charge q1 is placed at a distance d1 from the interface of two media in region in permittivity e1 and another charge q2 is placed at a distance d2 in region of permittivity e2. What is the force experienced by a...
The permittivity of free space, ε0, is usually given without any derivation or historical context as to how it was experimentally determined.
Could you explain to me how the value of ε0 was first determined experimentally or provide a resource that gives such a derivation?
Thanks!
I've been having a sign problem while deriving the permittivity formula using Drude model,
and I found out that the problem came from the fact that complex field vectors are expressed with e-iwt, not eiwt, thus producing (-iwt) term when differentiated...
Homework Statement
Given that the relative magnetic permeability and relative electric permeability of water are respectively, ##\mu_{rel}=1## and ##\epsilon=1.769## calculate the following 6 parameters.
1. Index of refraction of water ## n ##
2. speed of electromagnetic waves in water ## c...
Homework Statement
Having a conducting sphere with radius ##R## and charge ##Q##, dielectric is put on it so that a spherical shell with inner radius ##R## and outer radius ##3R## is formed. Calculate:
1. Electric permitivitty ##\epsilon## such that ##E(r), R<r<3R## is constant and there's...
Homework Statement
Distance between plates of a parallel-plate vacuum capacitor is d. The capacitor is attached to a battery that keeps it at a voltage V. The space between plates is now filled dielectric relative permittivity epsilon. How will charge density of the plates change?
Homework...
In the derivation of the electric field inside a non conducting sphere, We still use the permittivity of free space even though we are in a medium.
The same applies for ampere's law in a solid wire.
http://physics.bu.edu/~duffy/semester2/c15_inside.html...
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...
I have a doubt about coulomb's force equation in free space..ie 1/4πε0... Actually coulomb found that force exerted b/w charges are directly proportional to the product of charges and inversely proportional to the sqr of the distance bw them.we can measure force exerted and distance of...
Consider a metal such as Al.
How do we look up or determine the relative permittivity of the metal?
Suppose we have some known incident frequency, say about c/500nm for visible light.
We can look up the bulk plasma frequency (3.7 PHz for Al), can it be calculated from that?
For context, what I...
Why does an increased electrical permittivity reduce the phase velocity of light in a medium? Furthermore, what interactions do we see on an atomic level?
I am aware of the equation that defines the speed of light in terms of the electrical permittivity and magnetic permeability, but I do not...
Muggo
Thread
Electrical
Light
Permittivity
Speed
Speed of light
Why does an increased electrical permittivity reduce the phase velocity of light in a medium? Furthermore, what interactions do we see on an atomic level?
I am aware of the equation that defines the speed of light in terms of the electrical permittivity and magnetic permeability, but I do not...
I have a question about permeability and permittivity of free space. Theoretically speaking. If either one or both were to increase in value would that make the speed of light be faster or slower. I know they are constants. I am just curious if they did change what would happen.
Negative permittivity of metals – The effect of light-trapping via plasmonics
I’m trying to understand the effect of light-trapping by plasmonics (for example - Localized Surface Plasmon Resonance, Surface Plasmon Polariton, Scattered Plasmons), and how negative permittivity related to that...
I analyzed uncertainty analysis of 2 port measurement. I referenced 2 book
"Transmission Reflection and Short Circuit Line Methods for Measuring Permittivity and Permeability"
at pages 31 equation(2.83)
"Transmission and Reflection and SCL Permittivity Measurements" at pages 44 equation(2.67)...
Where can I found values of the relative permittivity of air at different temperatures, frequencies, pressure, humidity, etc. or its dependence?
I'm particularly interested in data around 1.4 GHz, 25ºC, 1 atm. 50% hum.
Thanks in advance.
For example if you send a light beam towards a massive object the propagation speed will reduce if μ and ε are increasing, but the spacetime curvature will compensate for that reduction.
I just have a few conceptual questions:
Is it as difficult to remove electrons from an insulator as it is to add to it?
I understand insulators have a lower permittivity than conductors, and that they still allow charges to build upon the surface. However, I read that when you rub an insulator...
First of all I will being with I'm not an electric engineer so I might be out of my wits, but I will give it a try.
So I have an instrument which reads relative permittivity using a transmitter and two receiver placed at different distances. The instrument is calibrated to read either in a...
Many textbooks and online sources give the relative permittivity of water as about 80 and the refractive index as 1.33. If you use the definition of refractive index to find the speed of light in water, you will find v = c/n ~ 2.56e8 m/s. However, if you use the equation to find the speed of...
In a dielectric material, permittivity makes sense, because it's easy enough to interpret the polarization density as the number density of molecules times their induced dipole moment. I'm basing this description off chapter 4 of Griffith's E&M textbook. In this model, the charges are all...
Homework Statement
A harmonic EM-wave is propagating in glass in the +x-direction. The refractive index of the glass ##n = 1.4##. The wave number of the wave ##k = 30 \ rad/m##. The magnetic portion of the wave is parallel to the y-axis and its amplitude ##H_0 = 0.10A/m##. At ##t=0## and ##x =...
Homework Statement
- A point charge is placed at the origin of the medium.
- The relative permittivity of the medium, \varepsilon_r = a / r, a is a constant, r is the radius from origin to any point around the charge.
- Objective of this question is to find the expression for voltage.at any...
What actually is permittivity of free space I know it is εo and I know it's value but I want to know it's physical meaning,what does it actually do ?I have referred this
https://www.physicsforums.com/threads/what-is-permittivity.763156/#post-4804922
but did not get the answer.
I have also...
Homework Statement
Spherical capacitor with two linear and uniform dielectrics with relative permitivitty Ɛr1 and Ɛr2 is connected to constant voltage U. When second dielectric is removed, intensity of electric field by inner electrode is reduced by 1/3, and electric field by outer electrode...
I originally posted the following question on physics.stackexchange, but no one was able to answer it. I did find this answer on PhysicsForums, but I was already aware of the oscillation of electrons in response to an external electric field.
What is the physical cause behind a material having...
According to Maxwell's Equations, the classical vacuum permittivity and permeability have a very important role: They determine the speed of light. But it seems like these two important concepts are not as precisely defined in the quantum world. Are there rigorous analogs of these two...
Homework Statement
I've been given a question where I have to find the electric field strength at a point between two charges. Now I understand the mathematics but the question I'm trying to solve says two point charges of value 2C and 3C are position within a medium of relative permittivity...
Good evening,
So... I am looking for the Tungsten permettivity and i don't find this feature...
I have searched on Wikipedia, some material data but i don't find...
Do you know what is the Tungsten permettivity?
Thanks.
I'm currently working with some materials that have a high permittivity in order to improve image quality of MRI scanners but finding it hard to find a good book that explains the various effects that contribute to a material's permittivity/dielectric constant. Can anybody point me in a good...