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Questions tagged [dielectric]

This tag is for questions relating to a non-conducting material called dielectric (or dielectric material). Dielectrics are very much important to explain various phenomena in various fields of physics like solid-state physics, optics, electronics, cell biophysics, etc.

Dielectrics are insulating materials that exhibit the property of electrical polarization, thereby they modify the dielectric function of the vacuum. All the charges in a dielectric are bound and thus they cannot support an electric current. In spite of this, the electric field is changed greatly by the presence of a dielectric material.

References:

https://en.wikipedia.org/wiki/Dielectric

https://web.archive.org/web/20190429182422/http://www.pas.rochester.edu/~cline/P114/chapter6.pdf

http://web.mit.edu/8.02t/www/802TEAL3D/visualizations/coursenotes/modules/guide05.pdf

926 questions
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Difference between electric field $\mathbf E$ and electric displacement field $\mathbf D$

$$\mathbf D = \varepsilon \mathbf E$$ I don't understand the difference between $\mathbf D$ and $\mathbf E$. When I have a plate capacitor, a different medium inside will change $\mathbf D$, right? $\mathbf E$ is only dependent from the charges…
kame
  • 949
25
votes
4 answers

What is the force between two charged objects when the space between them is partially filled by a dielectric medium?

I am given two charged particles of same charge at a distance of $r$. They initially apply force $F$. Now an infinite dielectric (of dielectric constant $4$) of width $\frac{r}{2}$ is introduced between the particles. What will be the new force? I…
Sigma
  • 604
23
votes
3 answers

Why is there no permittivity-type constant for gravitation?

When I look at electric or magnetic fields, each of them has a constant that defines how a field affects or is affected by a medium. For example, electric fields in vacuum have a permittivity constant $ϵ_0$ embedded in the electric field expression…
Jesus
  • 655
19
votes
1 answer

How can the refractive index be below 1 in a dielectric?

Upon checking the optical properties of different dielectrics, I found the interesting case of $Al_2O_3$. It seems to be reported with a refractive index below 1 in the infrared range of $10 - 12~\mu m$, for example by Kischkat, Boidin and Querry.…
DK2AX
  • 4,860
19
votes
2 answers

Why aren't all dielectrics transparent?

Conductors are opaque because, when hit by a Maxwellian wave, the free charges on their surface create another wave which destructively interferes with the former in the region of space beyond said surface. This doesn't happen in dielectrics; why…
user115153
18
votes
7 answers

How does current flow in a circuit with a capacitor?

When a capacitor is connected to a battery, current starts flowing in a circuit which charges the capacitor until the voltage between plates becomes equal to the voltage of the battery. Since between plates of a capacitor there is an…
Dario Mirić
  • 635
15
votes
2 answers

What is the intuition behind Kramers-Kronig relations?

I have heard that Kramers-Kronig relations constrains the real and imaginary parts of complex permittivity $\varepsilon= \varepsilon^{'} + j\varepsilon^{''}$. What is the intuition behind this relation? Coming from an electrical engineering…
praveen kr
  • 495
15
votes
2 answers

Charge distribution on a plate of Capacitor with Dielectrics .

I had this Homework Problem with a capacitor (parallel plate) that has a group of 3 dielectrics between it like so : Now We were asked to find the equivalent capacitance and the distance of separation between the plates was $d$ and its area was…
The-Ever-Kid
  • 1,000
14
votes
1 answer

How does $\epsilon \mu = 1/c_m^2$ change when $\mu$ or $\epsilon$ (permeability or permittivity) is a tensor?

I've read that in some materials, $\mu$ can be a tensor, not a mere scalar. (I haven't actually dealt with tensors before, but I'm assuming for my purposes here, it is synonymous with "matrix".) I'm not sure if the same holds for $\epsilon$, but…
user541686
  • 4,311
13
votes
3 answers

Why does electromagnetism attenuate so much faster than gravity?

Electromagnetism and gravity are both inverse distance-squared laws, so why is gravity affected so much less by distance? Is it that electrical charges tend to pretty much completely balance out beyond a micro scale? Is it that matter interferes…
Jim Clay
  • 537
11
votes
1 answer

Why do oxides form amorphous films instead of crystalline films?

If I oxidize a metal at room temperature, say aluminum, why does it form an amorphous material instead of crystalline $\rm Al_2O_3$?
Frank
  • 135
10
votes
6 answers

How is bound charge and free charge possible?

I am studying Introduction to Electrodynamics by Griffiths and I came along a concept I cannot seem to understand properly. The concept of free charge AND bound charge. I do not understand how we can have both. I understand bound is created by the…
user1198778
  • 215
10
votes
0 answers

Sphere half-submerged on a dielectric

This is a classic problem in electrostatics with a twist, so I thought it could be useful for others here. I did have a problem with the integration at the end, but on general I think the idea can help others. The idea is that a conductor,…
Charlie
  • 1,222
10
votes
2 answers

What exactly is breakdown voltage of air?

Most of the online sources say that the breakdown voltage of air is 30kV/cm. I've made a Cockcroft Walton multiplier and I can see the air breaking in between 17-18kV/cm. Only in a discussion at one online forum : , someone claimed it to be 17kV/cm.…
Sardar_Usama
  • 201
9
votes
4 answers

What happens when you heat vodka in a microwave?

Since ethanol has a lower dielectric constant than water would the water heat up and boil before the ethanol? Would the water transfer heat to the ethanol and, since ethanol has a lower boiling point, bring it to a boil before the water?
user18684
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