What is Dielectric: Definition and 729 Discussions
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.
We have recently developed a motion sensor that introduces charge into an electric field. From the 200V (containment field) we derive a modulation of 100mV. Although the sensor has passed pre-production tests we are struggling to come up with a simple formula to describe the operation. Can...
Homework Statement
A point dipole p is embedded at the center of a sphere of linear dielectric material (with radius R and dielectric constant \epsilon_{r} ). Find the electric potential inside and outside the sphere.Homework Equations
Well I'm guessing that using the method of separation of...
Hi,
Does anyone know which insulator will have very high dielectric strength at room temperature?
The dielectric strength is the electric filed strength of a material can resist before it breakdown.
Homework Statement
[PLAIN]http://img408.imageshack.us/img408/1685/wergp.png
Homework Equations
H\psi = E\psi
The Attempt at a Solution
For part a) I used H\psi = E\psi to get:
E = \frac{\widehat{p}}{2m} + \frac{Kx^2}{2} + \frac{e\Phi_o}{a}x
and assuming E = Q? and rearranging for K...
1. What plate area is required if an air-filled, parallel-plate capacitor with a plate separation of 2.3 mm is to have a capacitance of 24 pF?
Which I found correctly to be 6.2 x 10^-3 m^2 by using the formula C= k(8.85x10^-12)A/d
What is the maximum voltage that can be applied to this...
Homework Statement
A parallel plane capacitor with conducting plates area \Sigma= 400cm2, distant d=5mm, is half filled of mica (k1=5) and half filled of paraffin (k2=2). Calculate:
a) C (Capacitance of the capacitor)
...othersHomework Equations
None
The Attempt at a Solution
I haven't...
Homework Statement
Hello there:
In electrodynamics where there is a two parallel plane capacitor filled partially with air and partially with a dielectric \epsilon > 1 connected to a voltage V, The question is to calculate the force on the dielectric.. ¿¿Does anybody...
Homework Statement
The plates of a parallel plate capacitor measure 15cm x 15cm, and they are separated by 6cm. The capacitor is charged with a potential difference of 18V, then removed from the voltage source and kept isolated. A 15cm x 15cm x 3cm slab of dielectric material (k = 2.5) is...
Homework Statement
You have 2 square metal plates of side length L, separated by a very small distance d. The two plates are held at fixed potential difference ΔV by a battery. A thin slab with dielectric constant κ and thickness d is inserted a distance x into the gap between the plates...
http://www.screencast.com/users/trinhn812/folders/Jing/media/9527c4fa-05b4-4baa-98ee-2a3ad47e7e5a
I need an explanation for question 6. Why would voltage stay the same across capacitor 3?
The dielectric increases capacitance which is inversely related to voltage correct? The equation...
Hello everyone,
I am a little reluctant to post this question because it is a common problem type assigned for introductory electrodynamics courses, so I understand any level of vagueness that should be practiced with regards to answering the question so as to not make it too obvious how to do...
Homework Statement
A planar waveguide is formed from a 10mircometer thick film of material of refractive index 1.46 sandwiched in material of refractive index 1.45. Calculate the number of modes of propagation that guide support at the wavelength 1.3mircometer, and estimate the propagation...
Hi there,
Do we know which material has the highest dielectric constant (exact figures would be nice),and what is the highest break down voltage achievable for that particular material.
We have the equations available for computing the reflected and transmitted electric fields in the case when a plane wave is incident on a dielectric surface.
Now what I wish to do is compute similar reflected and transmitted components of the electric field due to an oscillating electric...
Homework Statement
This is not a problem from any book or any kind of source. I was just thinking on this. Suppose u have a capacitor attached to a battery. And then u insert the dielectric slab. Then do the electric field between the plates changes?
Homework Equations
The Attempt...
I read that in some ferroelectrics,such as Barium Titanate,
dielectric permittivity approaches infinity near Curie point.
For example,for Barium Titanate it`s closer to 120 centigrads.
Do those effect allow as (in theory) create capacitor with
almost unlimited energy density?Or there are...
I have another question. Let us assume we have some dielectric oil and two electrodes (submerged into dielectric oil) connected to positive and negative of a voltage source.
The system shall have some breakdown voltage , how can I calculate that? Any link available to get the formula...
Dear All,
I am trying to calculate the dielectric function of a thin silicon film from the real and imaginary values of the refractive index, which I have for wavelengths between 300 and 900 nm. If I have the n and k values (real and imaginary components of the refractive index), could anyone...
Hi Everyone,
I am trying to find the real and imaginary dielectric constants for TiO2 (rutile) as a function of wavelength. Could anyone suggest a good place to find something like this? Palik has a nice book but it is incomplete, so I'm not sure if there is something newer. Also, could...
in ac fields permittivity becomes complex quantity and has real and imaginary parts. in metals (may be few exceptions but i don't know) imaginary part is always positive and represents loss factor or energy absorbed. why the plot of imaginary part of dielectric constant as function of energy is...
Homework Statement
Two capacitors, identical except for the dielectric material between their plates, are connected in parallel. One has a material with a material with a dielectric constant of 2, while the other has a material with a dielectric constant of 3. What is the dielectric constant...
Homework Statement
A slab of dielectric is now inserted between the plates, the battery still being connected. 7.5μC of additional charge flows from one plate, through the battery and onto the other plate. What is the dielectric constant of the dielectric material?Homework Equations
A 1.0μF...
I am currently in a research lab working with various polymers. I have been searching for a while, with no luck, to locate the dielectric constant of PAH poly(allylamine hydrochloride). Can anyone provide me with this constant? Thanks.
How do you work out the transmittance across two boundaries (i.e. a wall)?
Do you multiply the transmittance for one boundary by the transmittance across the other boundary?
I'm interested if it's possible to compute potential inside and outside
dielectric sphere (with permittivity \varepsilon_1 ) which is
placed in field of point charge q lying outside the sphere where
permittivity is \varepsilon_2 . I've tried to solve it
using Legendre polynomilas but I...
[PLAIN]http://img340.imageshack.us/img340/4058/15244008.jpg
so
C = epysilon A / d
C= (8.85x10^-12 x 5.0x10^-3)/0.002 = 2.2125x10^-11
so the capacitance of the capacitors is ^
then with a dielectric where k = 3
can i use this equation
C = epysilon A k/ d, just putting the k next to...
In general the electronic susceptibility, χ, is a function of frequency and is complex for a dielectric medium.
So what are the implications of this for the propagation of EM signals in a dielectric medium?
Since the electronic susceptibility varies with refractive index, and the refractive...
A dielectric cylinder of radius 'a' and permittivity 'e' is placed in a uniform field Eo with the direction of field perpendicular to the axis of the cylinder, find the E field (Ei) inside the cylinder. I CAN DO THIS PART OF THE QUESTION FINE. It turns out that:
Ein=2Eo/(1+e)
Next...
Does anyone know what the relation between frequency and dielectric strength is? I'm mainly concerned with the dielectric strength of air in the High Frequency and Very High Frequency Ranges (3MHz - 300MHz). Thanks.
Hey, all.
If we partially introduce a linear, isotropic and homogeneous dielectric slab in a charged, isolated, parallel plate capacitor, we know that it experiences a forces pulling it into the dielectric, and we can obtain the expression of this force using energy considerations. However...
Homework Statement
If I have two co axial conductors at V = 0 and the dielectric has a free charge density. Is that physically possible?
Homework Equations
No relevant equations
The Attempt at a Solution
I am not sure if you can have free charge density in a dielelctric when both conductors...
This isn't a homework problem, just something to explore my understanding so correct me if any of my assumptions are wrong.
I have given myself the situation where I have a capacitor of area "A" and separation "d"
Between them is a non-uniform but continuous dielectric, so that the...
What are the dielectric constants of metals and i have heard that some materials have dielectric constants that are complex numbers. Please tell me which materials have complex Dielectric constants?
The longitudinal dielectric function of a gas of free electrons (+ homogeneous positive background) is often described in the Lindhard- or Random Phase Approximation (RPA).
The dielectric function depends on both frequency omega and wavevector k. However, it is non-analytic at the point...
A point charge q is a distance d from a dielectric half-space (z < 0). We will
solve for the potential outside of the dielectric, in the region z > 0.
(a) Away from the point charge, what equation does V satisfy? Find the boundary conditions at the dielectric surface.
(b) Find an image...
If anyone can help with this problem it would be greatly appreciated. I think I know what I'm doing, but am not sure of a couple things.
An isolated spherical capacitor has charge +Q on its inner conductor of radius r1 and charge -Q on its outer conductor of radius r2. half of the volume...
Homework Statement
A point charge q is a distance d from a dielectric half-space (z < 0). We will
solve for the potential outside of the dielectric, in the region z > 0.
(a) Away from the point charge, what equation does V satisfy? Find the bound-
ary conditions at the dielectric...
When a dielectric is inserted between the plates of a parallel plate capacitor , what would happen to its charge , Q and electric potential , V as compared to when there is no dielectric ?
My thoughts are the presence of dielectric cause the resultant electric field to decrease , and from...
A derivation of the capacitance for a parallel plate capacitor is as follows:
[ assume uniform field, plate area is infinite in relation to the separation, the conductors are perfect conductors ]
So, V=Ed
where
V=voltage difference between plates
E= electric field (uniform)...
Homework Statement
A coaxial cable of circular cross section has a compound dielectric. The inner conductor has an outside radius a , which is surrounded by a dielectric sheath of dielectric constant K_1 and of outer radius b . Next comes another dielectric sheath of dielectric constant...
Homework Statement
Fig. 1 and 2 show a dielectric slab being inserted between the plates of one of two identical capacitors, capacitor 2. Select the correct answer to each of the statements below (enter I for `increases', D for `decreases', or S for `stays the same').
1. In Fig. 2...
Hi guys,
If you have a parallel plate capacitor and then u insert two insulaters in such a way that it is diagonal( as shown in the attachment) how would we find the potential difference and field inside the capacitor?
Attempt: I was thinking that the area would be the area of two...
Homework Statement
Say, i have a setup as shown on the photo below
http://www.flickr.com/photos/47719498@N07/4375079183/
* setup also seen as attachment
how can i be able to compute for the dielectric constant provided it is not parallel plate and considering two different area is...
A parallel plate capacitor of capacitance 10microfarads has the space between filled with material with
(dielectric constant k)= 4.0. The capacitor is charged to a potential difference of 2.0V . With the capacitor connected
to the battery the dielectric is removed.
1. The capacitance is F...
Homework Statement
You are an intern at an engineering company that makes capacitors used for energy storage in pulsed lasers. Your manager asks your team to construct a parallel-plate, air-gap capacitor that will store 120 kJ of energy.
(a) What minimum volume is required between the...
Hello,
I am looking to purchase Dielectric couplings. I am located in the east coast (NY/NJ).
I am having trouble finding these, any help is appreciated.
Does anyone know any businesses who sold these during the mid 1990's ?
Homework Statement
A medium is described by the response functions \varepsilon (\omega ) and {\mu ^{ - 1}}(\omega ) in
\textbf{D} = \varepsilon (\omega )\textbf{E}, \textbf{H} = {\mu ^{ - 1}}(\omega )\textbf{B}.
Construct the equivalent dielectric tensor {K_{ij}}(\omega ,\textbf{k}) in...