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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Principle of superposition and QED

For finding a net force on a charge when it is in influence of many charges we simply do vectorical addition of all individual interaction of that charge with others. That's what is principle of ...
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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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Finding Electric Field outside a Charged Cylinder

I'm trying to solve a problem that involves finding the electric field due to a uniformly cylinder of radius $r$, length $L$ and total charge $Q$. Well, my thought was: if I am to use Gauss' Law, I'll ...
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Can spheres leaking charge be assumed to be in equilibrium?

I am struggling with the following problem (Irodov 3.3): Two small equally charged spheres, each of mass $m$, are suspended from the same point by silk threads of length $l$. The distance between ...
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Uniformly charged sheet and metal rods

A friend of mine asked me a question. Suppose there are two metal rods which are placed in front of a uniformly charged non-conducting plane one after other with their length perpendicular to the ...
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7 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?
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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 ...
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18 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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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 ...
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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 ...
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100 views

Electric Potential Energy

When work is done on a positive test charge by an external force to move it from one location to another, does the potential energy increases or decreases, and does the electric potential increases or ...
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1answer
46 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 ...
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467 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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47 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
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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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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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 ...
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25 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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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 ...
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1answer
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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 ...
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redistribution of charge between plates

How is charge redistributed when a charged conducting plate is placed between two identical wire-connected uncharged plates?
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150 views

Static electricty and fields inside of the conductor?

I have a few related questions about static electricity and conductors. 1. when we say static electric field inside a conductor is zero, let us take an example of two concentric conductors, outer one ...
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2answers
33 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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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 ...
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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
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23 views

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

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.
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4answers
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A problem of missing energy when charging a second capacitor

A capacitor is charged. It is then connected to an identical uncharged capacitor using superconducting wires. Each capacitor has 1/2 the charge as the original, so 1/4 the energy - so we only have 1/2 ...
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3answers
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Polarization vector of dielectric electrostatics

I know two laws for Polarization vector of a dielectric material $$\vec P = N q \vec{\Delta L}$$ Where $N$ is the number of dipoles per meter cube, $\vec{\Delta L}$ is the vector that represents the ...
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The electric field of a conductive sphere containing a charge - grounded vs not grounded

Let's suppose we have a sphere but unlike theoretical ones it'll have some thickness say $\Delta r$ and inner radius $R$. What I was wondering about is how will it behave if we place some charge $q$ ...
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28 views

Putting an Electron on a Conducting Sphere [on hold]

What all might go on inside a conducting sphere if I (try to) dump an electron upon it?
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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 ...
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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 ...
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Charge distribution on conductors?

You have seen that the excess charge on an isolated conductor moves entirely to the conductor’s surface. However, unless the conductor is spherical, the charge does not distribute itself uniformly. ...
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68 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 ...
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1answer
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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 ...
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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
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 ...
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1answer
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(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 ...
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3answers
99 views

Electrostatics and two electric charges

How can two identical metallic objects have the same but opposite charges (one loses electrons and one gains electrons) when we know that metals have the ability to lose electrons only?
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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 ...
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802 views

Electric field from conductive to dielectric media

I am interested in the main difference between transitions from electric fields from Conductive to Conductive/ Dielectric to Dielectric and Dielectric/Conductive media. What are the boundary ...
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670 views

Proof of charge existence on a grounded conductor

A question regarding the existence of charge on grounded conductors is confusing me. Could there be charge on a grounded conductor? How does this not contradict Gauss' Law? Since every conductor ...
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1answer
40 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 ...
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3answers
887 views

How can I find the potential created by spherical capacitor with dielectric material?

If we have a spherical capacitor with inner radius or r1 and outer radius of r2, with charges (+/-)q on them and there is a dielectric material (with constant e) in between them with. What kind of a ...
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2answers
3k views

How can a conductor be grounded yet there are induced charges on it?

A classic example for the method of images is the following, quoted from Griffiths's Introduction to Electrodynamics, page 121: Suppose a point charge $q$ is held a distance $d$ above an infinite ...
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4answers
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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 ...
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105 views

Two charged spheres connected with a conductor

I have a problem with a electrostatics problem: there are two spheres, each one of the same size carrying the same amount of charge, but of different sign. They are connected by a conducting wire, ...
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2answers
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Dirichlet and Neumann Boundary condition: physical example

Can anybody tell me some practical/physical example where we use Dirichlet and Neumann Boundary condition. Is it possible to use both conditions together at the same region? If we have a cylindrical ...
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1answer
42 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 ...
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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 ...