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-...

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2answers
531 views

Gauss' law in differential form for a point charge

I'm trying to understand how the integral form is derived from the differential form of Gauss' law. I have several issues: 1) The law states that $ \nabla\cdot E=\frac{1}{\epsilon 0}\rho$, but when ...
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1answer
56 views

Effect of introducing an external charge beside a Gaussian surface

As far as I know, Gaussian surface's are surfaces that enclose a net charge and are shaped in such a way that the electric field vector's magnitude is the same over the entirety of the surface. My ...
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1answer
229 views

How charges can be at rest if there is a force on it?

Electrostatics deals with forces between charges at rest. But if there is a force on a charge, how can it be at rest? My guess is that charges is being kept at rest by some unspecified forces that ...
2
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2answers
453 views

What is Gauss's Law in two dimensions?

I am trying to figure out how the equation for the field if a Gaussian surface was applied to a 2D plane. I did see another question already asked on the subject, but I didn't get a particular ...
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0answers
97 views

Relationship between electric field and distance

I am working on a lab report that asks a conceptual question related to one of the labs we did on electrostatic fields. For the context of my question, here is how the experiment is set up. We have ...
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1answer
186 views

Why isn't energy stored in a capacitor equal to just $QV$ when it is fully charged? [duplicate]

I just learned that the energy stored in a capacitor is electrostatic potential energy. Also potential energy is a state function and is independent of the path. So, when the capacitor is fully ...
0
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1answer
66 views

Calculating the rate of electrostatic discharge via current density

After I asked this question, with the help of Floris' comment, I tried to learn more about the concept of current density and tried to calculate the current density in my scenerio which, it seems, is ...
3
votes
1answer
200 views

Calculation of long-range forces in Molecular Dynamics - Ewald summation

I am trying to write a code to calculate the potential and forces, for the same using ewald summation.For this purpose, the formula for potential and force I have used is : $$ U = U^{(r)} + U^{(k)} +...
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0answers
90 views

Derivation Electric force

I’m a physics of high school (SMAN 3 Bandar Lampung, Lampung, Indonesia 35116). I make the experimental apparatus in static electric field. Instrument arrangement in the image below: The theoretical ...
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2answers
387 views

When I take a Gaussian surface inside an insulating solid sphere, why does the outer volume have no effect on the electric field?

Say I try to find the magnitude of the electric field at any point within an insulating solid sphere. I know that in the case of a conductor, the electric field within it is 0. However, I have not ...
2
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1answer
67 views

EMF produced when a square wire is pulled from the corners [closed]

The shown diagram is of a square conducting frame being pulled from the corners. The velocity of A and B is given as $u$. Each side has length $a$. I was trying to find the induced emf at the instant ...
0
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0answers
29 views

How does air neutralize charged objects? [duplicate]

How exactly does air neutralize charged objects? For example, at what rate does air neutralize a copper sphere of radius R and net charge Q? I assume that the rate may vary depending on the surface ...
1
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1answer
57 views

In a Wimshurst machine, why are the Leyden jars connected?

I generally understand how Wimshurst machines and Leyden jars work, but I can't figure out why the outside of the two Leyden jars in a Wimshurst machine are connected to each other. The DIY guide I've ...
1
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1answer
101 views

Help me understand Gauss law

Suppose I have the following, the gaussian surface is the drawing in the middle. So charge enclosed is zero, and then eletric field must be zero since the area of the gaussian surface is not zero. But,...
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0answers
37 views

Eletric field on a slab, uniform volume charge density

These are the question and the solution in solutions manual. However, I don't understand the step in which he goes from $\rho V/A$ to $\rho \Delta x$.
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0answers
55 views

Can you calculate the charge after rubbing two objects

If there are two insulators and you rub them together for a long time, is there a way to calculate how much charge should have transferred between them. I'm sure there is some relation to the ...
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1answer
172 views

Electric field outside conductor with cavity

Recently I heard a lecturer claim that the electric field outside a solid conductor containing a cavity with a point charge $q$ at a point $\mathbf{r}$ is the same as the electric field due to the ...
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1answer
47 views

How to charge a conductor w.r.t ground

How to make a charged conductor ? (without using friction). Here is one of the suggestions... where a charged conductor is used for creating a field around a conductor, creating induced charge on it.....
2
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2answers
2k views

What makes Human a Conductor

Conductors, are those which have free electrons... and because of this have same electric potential all over. But considering our body, which has many electrical voltage, current signals passing by in ...
2
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3answers
341 views

Shielding of electric and gravitational force on particles inside a spherical shell

A cavity inside a conductor is shielded from outside electric influences. But, if you put charges inside the cavity, the exterior of the conductor is not shielded from the fields by the inside charges....
3
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0answers
31 views

Scale-covariant decomposition of capacitance

I'm wondering if there is any good insight of how to evaluate a given capacitive geometry in such a way that it would be expressed as a function that depends only on two components: as a geometric ...
1
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1answer
148 views

Charge distribution on a Gaussian surface

In the text, it is said that the skewed distribution of positive charge on the inner wall cannot produce an eletric field in the shell to affect the distribution of charge on the outer wall. Why? ...
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0answers
63 views

How to measure the static electricity voltage?

Some of the Wimshurst machine producers claim their machines produce about 70 000 volts. I wonder how to measure this value. How is it possible to measure the static electricity voltage?
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0answers
63 views

Potential of a point charge in dielectric

My configuration is a static point charge q embedded in a dielectric region (red area). Outside the dielectric region there is vacuum. The configuration is: Thus, the difference to the "classical ...
-1
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1answer
152 views

Eletric field on a semi circular ring, different charges on each quarter of a ring

In this image to calculate the net eletric field is used integration from 60 degrees to -60 degrees. Ok for me by now. But then I was doing this question, number 26: And he solves by doing that: ...
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2answers
64 views

Is the electrostatic field really static? Does thermal vibrations not affect it?

We know that if a conductor has any net charge, the charges reside on the surface. The electric field immediately outside the surface is perpendicular to the surface. But the charged particles, say ...
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2answers
432 views

Wimshurst machine - How does it work?

Look at this VIDEO to see what is supposedly happening: A Wimshurst machine is a seemingly simple device consisting of two plastic wheels with embedded metal plates on the rim. The wheels spin in ...
8
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1answer
514 views

Tesla coil arc in air - where is it going?

here is a picture of a Tesla coil with a discharge that seemingly terminates in the air. What completes the circuit at the end of the streamers?
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1answer
239 views

Electric field inside two parallel lines of charge

At what force will a particle be subjected to inside two parallel line charges with the same length and charge density. I get that in the middle the forces will cancel, but will they cancel if the ...
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1answer
74 views

Charges on a tree

Can anyone tell me why is the tree in this photo charged with a positive charge although I thought it must be neutral.
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1answer
105 views

What if electric force was independent of the distance?

The electric force between two charged particles becomes weaker with increasing distance. Suppose instead that the electric force were independent of distance. In this case, would a charged comb ...
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0answers
43 views

redistribution of charge between plates

How is charge redistributed when a charged conducting plate is placed between two identical wire-connected uncharged plates? For eg,
2
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1answer
125 views

Can a static electric field have a vector potential field?

We know very well that static electric fields have scalar potential fields, and magnetic fields can't have scalar fields, as $$\nabla\times \vec{B}=\mu_0\vec J$$ $$\Rightarrow \int\nabla\times \vec{...
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2answers
164 views

Why does electrostatic energy not obey superposition principle? What does the extra energy term account for?

Energy stored in an electrostatic field is given by $\frac{\epsilon_0}{2}\int\text{E}^2\text{d}\tau$ where the integration is over all space.If $\vec{\text{E}_0}=\vec{\text{E}_1}+\vec{\text{E}_2}$ and ...
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0answers
186 views

Question related to charged concentric conducting shells

There is a charged conducting spherical shell given a certain positive charge.Another larger spherical shell is given the same negative charge.The first shell is now placed inside the second shell so ...
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3answers
158 views

Is capacitance calculated over a finite volume or over all space?

Is the capacitance of a system of conductors calculated in a finite volume or over all space? My question is motivated by the following problem. A volume $V$ in vacuum is bounded by a surface $S$ ...
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1answer
35 views

Help with this question (Eletric Fields, Dipole) [closed]

The answer in the textbook in the solutions manual is the following: I didn't undestand the last step. He said he did a binomial expansion, I just can't figure out! Appreciate any help.
0
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1answer
57 views

Difference in resistance between two configurations

Given a spherical shell of a conducting material with radius $a$, surrounded by a poorly conducting material between it and another conducting shell with radius $b$, you can calculate the resistance ...
0
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1answer
75 views

RF disturbances produced by transmission power lines

I need a book or paper that contains "the effects of transmission lines on the radio frequency transmission and disturbances". Could you help me find a useful textbook? Thank you
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0answers
75 views

What is the maximum field strength of an electret?

What is the maximum practical (and available) field strength in modern electrets? Also, what, if any, are the theoretical limits? From wiki: An electret is a stable dielectric material with a ...
0
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1answer
33 views

Putting an Electron on a Conducting Sphere [closed]

What all might go on inside a conducting sphere if I (try to) dump an electron upon it?
2
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3answers
177 views

Laplacian of 1/r satisfies laplacian equation?

We know that $$ \nabla^2 \left( \frac{1}{r} \right) = -4 \pi \delta(r) \tag{1}$$ and that the general solution to the laplace equation $\nabla^2\Psi = 0$ may be expanded as $$\Psi=\sum_l \left(A_lr^l+...
0
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1answer
53 views

Dissolving photoconductor (TiOPc) from Laser Printer drum possible?

When I was thinking of a Lab-On-a Chip Application which combines a lensless microscope and an optical tweezers I saw the ODEP-concept:(http://pubs.rsc.org/en/content/articlelanding/2013/lc/c3lc50351h#...
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0answers
58 views

Charge distribution on uncharged conducting sphere

I am trying to solve the following problem: A charge $q$ is brought to a distance $d$ from the center of an uncharged, conducting sphere of radius R. What is the charge per unit area of the sphere ...
1
vote
1answer
71 views

How to divide areas in electric field lines based on field strength?

A negative charge is surrounded by four positive charges. They are all of the same strength. The electric field lines are plotted below. I am looking for the property of the drawn 'red lines' that ...
0
votes
1answer
684 views

(homework) finding location of third point charge [closed]

having trouble with the following There are three point charges along the x-axis: q1 is +3µC, located at the origin q2 is -5µC, located at x = +0.200m q3 is -8µC Where is q3 located if the net ...
4
votes
2answers
201 views

Why in electrostatics is $dV=-E.dr$ but in electromagnetic induction, $EMF=+E.dS$?

In electrostatics we learned that $$dV=-E.dr$$. I understood the derivation which was used to derive this. Now when I have come to Electromagnetic Induction,I see that when there is a time varying ...
3
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1answer
258 views

Basic electrostatics - Poisson's Equation

I would like to solve Poisson's Equation for a space charge region (fixed and free charges) that is located within a device of semiconductor material. Unfortunately I do not have any boundary ...
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2answers
210 views

Why does the superposition principle work in method of images?

Okay, let there be a conducting sphere having radius $a$ initially charged with $Q$ & insulated. Now, $q$ is brought in front of the conductor at $y$ from the center. Now, Jackson in his book ...
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1answer
140 views

Why do some charges of a charged spherical conductor feel no force from a point charge outside the conductor?

I was reading "point charge in the presence of a charged, insulated, conducting sphere" from Jackson's Classical Electrodynamics. Let initially the sphere had on its surface $Q$. When $q$ is brought ...