Stack Exchange Network

Stack Exchange network consists of 175 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers.

Visit Stack Exchange

Questions tagged [electrostatics]

Electrostatics is concerned with the electrical fields and scalar potentials of stationary electrical charges and charge distributions. Use this for questions about electromagnetic situations in which currents and magnetic fields are absent, otherwise use [tag:electromagnetism] and/or [tag:magnetic-fields]

0
votes
1answer
11 views

Method of Images conundrum

My lecturer and I have found separately valid solutions to Poisson's equation in the region of interest for the following problem: Here is my interpretation of the boundary conditions: $$V(x,y,z \to ...
0
votes
0answers
12 views

Relationship between polarization charge density and free charge density

I have concluded that in a uniform dielectric, volume free charge density $\rho_0$ and volume polarization charge density $\rho'$ satisfy $$ \rho' = \frac{-(\epsilon - \epsilon_0)}{\epsilon}\rho_0 $$ ...
1
vote
0answers
38 views

is possible to create a nuclear fusion using simple electric arc discharge?

If we have a simple discharge tube filled by deuterium gas or even heavy water, and put tungsten electrodes close to each other to create a huge electric field, then using a megavolt generator to ...
0
votes
0answers
23 views

Principle of superposition in spherical shells

If I have a spherical shell with a uniform positive charge desnity on its surface is near a positive point charge q (sitting in quadrant II area) In consideration of the electric field strength and ...
0
votes
2answers
49 views

Gauss divergence theorem (GDT) in physics

Some of the statements for $GDT$ which I find in modern textbooks (both electromagnetism and multivariable calculus textbooks) are: (1) Calculus: Several variables Adams Let $D$ be a regular, ...
1
vote
1answer
15 views

element of surface area versus vector element of surface area

In the context of calculating electric flux, is there a difference between element of surface area versus vector element of surface area? Thanks
0
votes
0answers
26 views

How to apply the Gauss law when charge density is a function of not only $r$? [on hold]

How to apply the gauss law when charge density is a function of not only r? Caution : I am not asking anyone to do the sum fully . I just wanna know how to apply gauss law in this problems only the ...
0
votes
0answers
13 views

Electric Potential and conservation of energy [on hold]

An infinitely long line of charge has linear charge density 5.00×10−12 C/m . A proton (mass 1.67×10−27 kg, charge +1.60×10−19 C) is 18.0 cm from the line and moving directly toward the line at 4.10×...
0
votes
0answers
12 views

Continuity of electric field and displacement at interface

Imagine having a conducting sphere with free charge $Q$ surrounded by a spherical shell filled with a dielectric and then a conducting spherical shell with no free net charge. The dielectric being ...
0
votes
0answers
31 views

Spherical capacitor with dielectrics [on hold]

Consider the following system: which consists of a conducting sphere with free charge 𝑄, a dielectric shell with permittivity $\epsilon_1$, another dielectric shell with permittivity $\epsilon_2$ ...
0
votes
0answers
20 views

Doubt in application of $GDT$ in electrostatics

Consider a volume charge distribution with continuous density $\rho({\bf r'})$. The electric field at ${\bf r}$ is: $${\bf E}({\bf r})=k\int_V \frac{\rho({\bf r'})}{R^2}\hat{\bf R}\, \mathrm dV$$ ...
0
votes
1answer
25 views

A Conducting Disc

A conducting disc is given a charge Q. As the disc is conducting it must be equipotential and hence the charge distribution will not be uniform. From what I know the charge will have a tendency to ...
-1
votes
0answers
29 views

“No stable equilibrium halfway between two equal point charges”

From my instructors notes. Obviously if we displace the negative charge(from the halfway point) in either horizontal direction then it will not return to its initial position. If we displace a ...
1
vote
2answers
25 views

Edge Effect in Parallel Plate Capacitors

I have a problem understanding the edge effect in parallel plate capacitors. The part of the fringe is clear to me, at least I think so. I know that the field fringes to the outside of the capacitor, ...
-1
votes
0answers
25 views

Condition for balance of rigid body

I'm learning this subject right now and I didn't understand this problem from the book, also for you, the reader I mark: $$\textbf{N} = momentum\;N = normal\;force$$ The problem is: A box with the ...
-2
votes
0answers
34 views

Problem in Electrostatics [closed]

Two point positive charges $q$ each are placed at $( - a,0 )$ and $(a, 0)$. A third charge $q_o$ is placed at $(0, y)$. For what value of $y$ is the force on $q_o$ maximum ?
0
votes
1answer
11 views

Electric potential inside a solid conducting sphere, next to other charges

The way I initially justified the potential inside a charged conductor to be $\frac{kQ}{R}\ for\ \ 0\le r\ <R$ was that from Gaus's law, you could determine that when you were a distance $r$ away ...
-1
votes
0answers
31 views

Electric field in the region of a spherical shell of inner radius A and outer radius B

Consider that we have a spherical of inner radius $A$ and outer radius $B$ where $B>A$. It is given the field in the three regions: $$E = \begin{cases} 0 & \text{at } R>a \\ K\frac{R^2-A^...
1
vote
2answers
67 views

Physical example of line charge

Electric field due to an infinite line charge, sheet of charge, point charge, etc are popular problems solved in most text on Gauss's law of electromagnetism. My question: does an (exact or ...
3
votes
3answers
78 views

Why are the two outer charge densities on a system of parallel charged plates identical?

One of the ways examiners torture students is by asking them to calculate charge distributions and potentials for systems of charged parallel plates like this: the ellipsis is meant to indicate any ...
-1
votes
0answers
14 views

Computing image charge and it's location for cylindrical conductor [closed]

I am dealing with the below question: A line charge $\rho_{l}$ C/m is located at a distance $d$ from the axis of a parallel conducting and grounded cylinder of radius $a$. Both the line charge and ...
2
votes
1answer
183 views

Is it possible that an electric field exists like $E=kx$?

Is it possible for an electric field $\vec{E}$ to exist such that its electric field intensity increases continuously, something like $E=kx$, while all the $\vec{E}$ pointing in the same direction?
1
vote
0answers
22 views

Energy Density Confusion [closed]

The energy density of an electromagnetic field with a linear dielectric is often expressed as $0.5 E \cdot D$. It is also known that energy can be found by $\int_{V} \rho V dV$. Using the latter, the ...
0
votes
1answer
32 views

Quantifying potential energy

As per the definition of potential energy we kept a fixed charge, and in the presence of an electric field of the fixed charge, we release another charge of the same sign moving towards the fixed ...
1
vote
2answers
62 views

Why does Jackson ignore the surface term in this integration by parts, in the electric potential of a polarized dielectric?

In Jackson's electrodynamics Page (153), it is given that the total potential is the sum of potential due to free charge and potential due to dipole. Therefore, \begin{align*} \phi(x) & = \frac{1}{...
6
votes
5answers
777 views

Doubts in understanding some concepts of potential energy

Let us consider a system of charges in space. The potential energy of the system of charges is determined by the amount of work done by the external force to assimilate the charges in that manner. But ...
-1
votes
0answers
59 views

Electric field intensity due to line charge, at a point [closed]

In my first approach to this problem I used Gauss's law to give me an answer in terms of cylindrical coordinates $\hat{E}=\hat{a}_rE_r=\hat{a}_r\frac{\rho_l}{2\pi\epsilon_0r}=\hat{a}_r192.929 (V/m)$ ...
0
votes
0answers
33 views

Problem finding the electric field at any point on an infinite straight thin (idealized in one dimension) wire with uniform charge distribution [closed]

We know that while calculating the electric field due to a point charge at that point itself using Coulomb's law directly gives us a singularity at that point where the electric field tends to ...
1
vote
2answers
37 views

Energy Density with a Linear Dielectric Inconsistency

The energy density of an electromagnetic field with a linear dielectric is often expressed as $0.5 E \cdot D$. It is also known that energy can be found by $ 0.5\int_{V} \rho V dV $. Using the latter, ...
0
votes
1answer
17 views

Force between two point charges separated entirely by a conductor

The relative permittivity and hence absolute permittivity of a conductor is infinity. Now coulomb force between two point charges is inversely proportional to the permittivity of the medium between ...
0
votes
0answers
9 views

Single atom in an ion trap [duplicate]

I have seen this photo in a lot of articles which is described as picture taken of a single atom in an ion traphere's the link to one of them. I find this very fascinating, but i still can't ...
1
vote
0answers
69 views

Why can we break up a capacitor?

I have a hard time understanding why we are allowed to break up one capacitor into multiple capacitors if the capacitor is filled with different dielectrics. For example, what justifies us to do what ...
0
votes
1answer
29 views

What is the difference between Closed and Bounded surface?

When I was going through "The Feynman's Lecture on physics" Volume-2 , I found the line "It is useful to speak of the flux not only through a completely closed surface, but through any bounded ...
0
votes
0answers
10 views

Azimuthal Symmetry is on a certain axes that is not simply the $z$-axes

let's say in a problem, the azimuthal symmetry is along the axis $\frac{1}{\sqrt6}(-1, -1, 2)$. If I create two new basis angles and get solved the LaPlace's equation with that, what should I do to ...
0
votes
1answer
20 views

Electric fields and electric potentials in semiconductors

The zener diode is heavilier doped than a normal diode , that is why its depletion region is smaller than the delpetion region of a normal diode and that is why the electric field is very strong.Zener ...
0
votes
0answers
24 views

tribo charge and work function - adiabatic vs vertical

I am interested in estimating relative tribo charging for different dielectric materials (insulators). I understand that I can use the work function difference between two materials to estimate ...
1
vote
3answers
43 views

How can Torque act on an electric dipole if an electric dipole is not a rigid body?

According to my knowledge of physics, torque can only exist on a rigid body and an electric dipole is defined as a "system of charges" (equal in magnitude, opposite in sign) separated by an ...
26
votes
8answers
6k views

How can neutral atoms have exactly zero electric field when there is a difference in the positions of the charges? [duplicate]

It is said that atoms with the same number of electrons as protons are electrically neutral, so they have no net charge or net electric field. A particle with charge cannot exist at the same position ...
1
vote
1answer
90 views

Induced charge in a conductor

My question here is based on the following question in Physics for Scientists and Engineers (3rd edition) by Randall Knight: An electroscope is positively charged by touching it with a positive ...
0
votes
1answer
42 views

Confusion with electric field in a capacitor circuit

I'm having a confusion involving a couple of laws for a capacitor: $C = \frac{Q}{V} \propto \frac{1}{d}$. The capacitance, the amount of charge the capacitor can hold for a certain voltage between ...
1
vote
1answer
40 views

What form does the electric field take in a voltage difference?

A laser of driving frequency $\omega$ emits a planar wave of the form $$\mathbf{E}(\mathbf{r},t) = Ae^{i(\mathbf{k} . \mathbf{r} - \omega t)}\hat{\mathbf{a}}$$ where $\mathbf{a}$ is the polarization ...
4
votes
2answers
475 views

Charged enclosed by the sphere

I'm reviewing the book "Conquering the Physics GRE" for my upcoming Physics GRE. I came across this problem which I'm having trouble with understanding. In particular, I understand the solution that ...
1
vote
1answer
57 views

Integrating Laplace's equation over a sphere

The Wikipedia page on Laplace's equation states that if the Laplacian of $u$ is integrated over any volume that encloses the source point, $$\iiint_V \nabla \cdot \nabla u \, d^3V =-1.$$ I can'...
4
votes
2answers
78 views

Why do I get static shock due to wool, but not due to cotton?

I have experienced electrostatic shock quite a lot of times due to woollen fiber, and as far as I can remember, never due to a cotton fiber. Any explanation as to why this happens? Edit I ...
0
votes
0answers
28 views

Dielectrics between charges

Why does inserting a dielectric of dielectric constant $k_e$ have an effect of increasing the distance from $r$ to $r+t(\sqrt{k} -1)$ in Coulomb's law of electrostatics (where $t$ is the thickness of ...
0
votes
1answer
48 views

Electrostatics and Gauss law [duplicate]

How can we prove that surface integral of the electric fieldfor a point charge that is outside a gaussian surface, $$\int\mathbf E\cdot\,\mathrm d\mathbf S,$$ without actually using the concept of ...
0
votes
0answers
8 views

Effect of dielectric on electrostatic force [duplicate]

does the electric force between 2 charges decrease if a thin(not negligible) dielectric is placed b/w them? If it does then why?
1
vote
2answers
58 views

Why don't the electric field vectors cancel each other out in a non-conducting infinite plane sheet?

Why do these vectors not cancel each other out in spite of their being in the opposite directions?
0
votes
0answers
12 views

Unstable equilibrium due to an arbitrary electrostatic configuration

Suppose n charges are put in an arbitrary electrostatic configuration and a small test is placed at a null point (i.e., where $\vec{E}=0$ ) of the configuration. The task is to show that the ...
1
vote
1answer
30 views

Supposed Uniqueness Theorem Corollary

Following my instructor's notes the statement of the Uniqueness Theorem(s) are as follows "If $\rho_{inside}$ and $\phi_{boundary}$ (OR $\frac{d \phi_{boundary}}{dn}$ ) are known then $\phi_{inside}$ ...