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 ...

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2
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3answers
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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 ...
2
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0answers
24 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
votes
0answers
31 views

Why do electrical charges given to a conductor come to the surface? [duplicate]

It is said that any charge given to a conductor comes to its surface. Should all the protons come to the surface? Should all the electrons come to the surface, or should all the free electrons come ...
0
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0answers
23 views

Solving Poisson's Equation in 1-D for a point charge? [migrated]

Ok so I was trying to solve the Poisson's equation for a point charge with a Fourier transform to get the familiar equation. This is what I did so far: So ultimately I am trying to solve this in 3 ...
0
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1answer
31 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? ...
0
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0answers
13 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
10 views

Potential of a point charge in dielectric

My configuration is a point charge embedded in a finite dielectric geometry. I have to calculate the potential of the point charge only within the dielectric device. How should I do this?
0
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0answers
48 views

Solving Laplace's Equation for a point charge at orgin with Fourier transform? [on hold]

Ok So I have Laplaces equation: $\nabla^{2} \phi(\vec{r}) = \frac{q}{\epsilon_{o}} \delta(\vec{r})$ And I want to solve by using Fourier transforms. So I take the Fourier transform of the right ...
0
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0answers
8 views

What is the total energy stored in lattice of point charges?

I am wondering if there is an equation that describes the the total energy stored in lattice of point charges? I know I calculate it by summing up the energies of all the individual charges but I am ...
-1
votes
1answer
20 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: ...
1
vote
2answers
49 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 ...
1
vote
2answers
59 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
votes
1answer
471 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?
0
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1answer
52 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 ...
1
vote
1answer
25 views

Charges on a tree

![charges on a tree][1] [1]: http://i.stack.imgur.com/NhRsL.jpgemphasized text 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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votes
1answer
27 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 ...
0
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0answers
10 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
votes
1answer
58 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 ...
0
votes
2answers
35 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
12 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 ...
2
votes
3answers
115 views
+50

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 $S$ ...
0
votes
1answer
24 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
30 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
votes
1answer
28 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
0
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0answers
11 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
28 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?
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2answers
72 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 ...
0
votes
1answer
10 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 ...
0
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0answers
35 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
34 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
54 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 ...
1
vote
1answer
47 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 ...
2
votes
1answer
79 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 ...
1
vote
2answers
96 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 ...
0
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1answer
27 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 ...
0
votes
1answer
41 views

What is the reason behind the charge residing on the surface of the conductor having the same magnitude as that of image charge?

Lately, I'm studying the method of images especially to mention the renowned example of "A point charge near a conducting sphere". So, we have a grounded conducting sphere & a point charge ...
5
votes
1answer
47 views

Levitating capacitor

As the title already says, I would like to make a large capacitor levitate. Before you dismiss this question please hear me out: In essence, this is intended to be a way to avoid the constrains of a ...
0
votes
0answers
26 views

Are muscle cells electric dipoles?

I'm wondering how we can detect the electrical activity of a muscle cell. My initial thought on this question was that the membrane potential, around $\Delta V_{\text{membrane}} = -80mV$ across the ...
0
votes
4answers
94 views

What really happens with the charges on the surface of the conductor that let them to create equipotential surface?

Everyone does know that the surface of a conductor is at equipotential during equilibrium. I was reading Feynman's lectures where I found this (bold)line: Suppose that we have a situation in ...
1
vote
2answers
39 views

Why do we get electric shocks when most structures are insulators?

Suppose I was standing in the sea, and touched an electric fence; I would receive an electric shock, because both my body and the sea are conductors, and create a path for the electricity to flow. The ...
0
votes
0answers
25 views

Using the dipole moment to calculate the electric potential

I have the following defintion of dipole moment given: $$ \vec{p} := \int\vec{r}'\rho(\vec{r}')dV $$ Where $\rho$ is a charge density function and $\vec{r}'$ traces out the body of charge. I am ...
0
votes
0answers
17 views

Will charge transfer without friction

I know rubbing two objects of different materials together will result in a negative charge on whichever material has a higher electron affinity. However, I was wondering if a negatively charged ...
0
votes
3answers
36 views

Nonlocal dielectric function - what does it mean?

I'm reading this* article and in the second sentence of introduction I encountered a term I haven't heard of before. Namely: nonlocal dielectric function. What does this nonlocality mean? And how does ...
10
votes
1answer
528 views

Confused medical student needs explanation of the electrocardiogram

From what I understand, as the heart depolarizes it turns into a lot of electric dipoles , the resultant of which can (somehow) be measured in the extremities. But how does this actually happen? How ...
0
votes
2answers
41 views

An IE IRODOV Electrodynamics problem

A ring (radius R) is given a negative charge -q and at the centre a positive charge +q is kept. We have to calculate the electric field on the axis of the ring at a distance X from the centre. Take ...
0
votes
1answer
24 views

a point charge is kept at the centre of a metallic inducted spherical shell.then why the net induced charge on the sphere is zero?

Why the net induced charge is 0 in a inducted spherical shell when a point charge is kept in the centre of that sphere?
1
vote
4answers
69 views

How to calculate the work of the electrostatic forces in a parallel-plate capacitor?

The expression of the energy stored in a parallel-plate capacitor is: $$U = \frac{e_0\cdot A \cdot V^2}{2d}$$ with $e_0$ the vacuum permittivity, $A$ the surface of the capacitor, $V$ the applied ...
0
votes
1answer
48 views

Simple question regarding Gauss's electric law

I just read that electric flux=enclosed charge/permittivity. Considering the charge in an enclosed surface is always 0, what is the point in even having this equation? Or is the equation actually ...
1
vote
1answer
48 views

In the case of two equally charged particles, is the electric field between them incompressible?

When approach two electrons (or two protons or ...), the electric fields do not merge and stay isolated from each other. Which I borrowed from here. Is it right to conclude that in the case of ...
0
votes
1answer
34 views

Electric potential of a sphere at a point on its surface

I'm struggling to figure out how to determine the infinitesimal area of the sphere given in the question. More specifically, in part (b) of the question. For part (a) it's the volume so $$V = ...