Electrostatics is concerned with the field and potential of stationary electrical charges and electric charge distributions. Problems are this type are almost exclusively concerned with mathematics of geometries using the inverse-square law.

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Can protons in the nucleus of an atom be aligned by electromagnetic fields?

Can protons in the nucleus of an atom be aligned by electromagnetic fields? If so can it be done around $-135°C$ zero?
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1answer
99 views

Slight variation to method of images

Suppose a point charge $q$ is located at $(x=0,y=0,z=d)$, and that along the $x$-$y$ plane is a infinite plate of potential $V = 0$. Then the method of images solves Laplace's equation for the ...
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3answers
200 views

Homework question about electric field between two spheres

I was helping a friend of mine with the following question from Knight's book and I was not able to answer part (c). Here is what I think I know: (a) I expect $V_1 = V_2$; the two spheres are in ...
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2answers
79 views

Charged spheres - help with method to work these out? [closed]

Can anyone demonstrate how to get the answers to these questions? I'm just interested in the method I need to use in order to obtain the correct answer no matter what the values are. Three small ...
2
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2answers
784 views

When can a surface charge density exist?

In my syllabus about electromagnetism, they state: "This surface charge density will not always be present, e.g. when considering two non-conducting dielectrics such surface charge density remains ...
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1answer
83 views

Analytic solution of particle in electric field [closed]

This is homework and I need some guidance. The question I struggle with is: Place a particle with $m=2$ , $q=3$ in a constant electric field $\vec{E}=(5,0,0)$ Choose $\vec{r}(0)=(0,0,0)$ and ...
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1answer
119 views

If Electricity and magnetism are the same viewed from a different reference frame then is electricity medium dependant?

If Electricity and magnetism are the same viewed from a different reference frame (they are the same force as unified by maxwell) then is electricity medium dependant? I came to this question when ...
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3answers
740 views

2 dimensional Coulomb's law equation

We can notice that in the Coulomb's law equation, $$\begin{equation}\tag{1}F=\frac{1}{4\pi\epsilon}\cdot\frac{q_1q_2}{r^2}\end{equation} $$ $4\pi r^2$ factor in the denominator expresses directly ...
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2answers
62 views

Measurements from inside conductors

We have known for some time now that when electric field is applied across any conducting shell, then electric field inside it would be zero. It also has some fantastic applications such as ...
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5answers
565 views

electric field inside a conductor?

We have studied so far that electric field inside a conductor if no charge is placed inside is zero. But we know that every conductor has only a limited number of electrons. What happens when ALL the ...
4
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2answers
229 views

Why do clouds appear black?

I have noticed clouds appearing black during rain. But I don't know what makes clouds to acquire that colour. This phenomenon doesn't appear every rainfall. There has to be distinction to white ...
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2answers
287 views

What happened to potential energy?

I was learning how charge can be virtue of a body's potential energy.Meanwhile,I was hung by this question. [gravitational and other forces except coulombic,are assumed to be not acting on the ...
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2answers
430 views

How do I express the interaction energy between two charged spheres?

Consider two identical insulating spheres each with radius $R$ and uniform charge $Q$ through their volume. They are separated from their centers by a distance of $d>2R$. Here is my general ...
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1answer
146 views

Is there any metal having the properties of rubber? [closed]

I have seen tires of vehicles to be made of rubber with air filled tube inside.Why can't we have whole tire to be made of rubber? I hope there would be some use of the air filled tube.Then What is ...
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1answer
399 views

Why the electric bulb turns on almost instantly when the switch is closed? [duplicate]

The electron drift speed is estimated to be very low.How could there is current almost the instant a circuit is closed?? By the discussions it is known that The information about beginning of the ...
2
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2answers
921 views

Do electric and magnetic lines of force physically exist?

As per my imagination any thing can't impose force on the other by not giving even a touch(i,e action at a distance). So I thought there must be some physical existence of lines of force. Although ...
26
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4answers
8k views

Why do same/opposite electric charges repel/attract each other, respectively?

I know plus pushes another plus away, but why, really, do they do that? On the other hand, molecules of the same type are attracted to each other. I find that weird. I do know some stuff about four ...
2
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0answers
228 views

Calculating Electric Field from a Potential Difference w/o Charge

So here is my homework question: Two long cylindrical shells of metal (radii $r_1$ and $r_2$, $r_2 > r_1$) are arranged coaxially. The plates are maintained at the potential difference ...
4
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2answers
247 views

Will there be any force of attraction or repulsion between an electrified body and a non-electrified body?

Up to my knowledge an electrified (charged) body can attract a non-electrified (neutral) body. I thought this because, when we bring a charged (suppose negatively charged) body near a neutral one. ...
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2answers
94 views

Why is charge $q$ symmetrically distributed?

Simple question: Why is charge $q$ outside symmetrically distributed? The material is a conductor.
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0answers
64 views

why boundary condition in steady electric current?

when we electric field between two conductors in certain direction the current density should pass in its direction why current density direction change at boundary although the direction of electric ...
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1answer
63 views

Uniqueness of equilibria in electrostatics

I have the following problem. Suppose we place some continuous charge distribution (with total charge $Q$)on some conducting domain. The charge will redistribute itself on the domain until it's in ...
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2answers
175 views

Why 3 dipole terms in a multipole expansion?

As can be seen on this page http://en.wikipedia.org/wiki/Multipole_expansion when we take a multipole expansion without assuming azimuthal symmetry we end up with $2l+1$ coefficients for the $l^{th}$ ...
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0answers
113 views

Variation of electric field and current flowing

Theoretically, a change in either electric or magnetic field will cause a current to flow , I am already familiar to Faraday's law of electromagnetic induction, so I tried to search about producing a ...
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2answers
507 views

Meaning of boundary condition for steady current density?

Although I understand the derivation of boundary condition in case of steady electric current but I did not understand, that the electric field which is in direction of $J$ current density that is ...
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2answers
187 views

My conundrum with Gauss’ law in electrostatics

If I use Gauss’ law to calculate the electric field outside of a charged (conducting or insulating) sphere or a point charge, the fields are the same. However, as a test approaches a point charge, the ...
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1answer
228 views

Coulomb interaction as virtual particles exchange?

I've been reading about virtual particle exchanges in physics books and in Physics SA posts, where a particle interpretation of gravity and Coulomb interaction is established. The Feynman Diagram ...
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2answers
80 views

What happen if we put permanent potential across conductor?

why if we put conductors under permanent potential like a battery ,it will not be equi-potential ?? and why if we just put it under electric field it is equi-potential although there is a surface ...
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3answers
471 views

How would charge be distributed in charged conductors if the Coulomb law was not ${1}/{r^2}$?

Would the excess charge on a conductor move to surface until the electric field inside become zero if the Coulomb law was for example $\frac{1}{r^3}$? If yes, would the distribution $\sigma(x,y)$ be ...
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2answers
325 views

Is Ohm's law obeyed in power transmission?

We learnt in high school that according to OHM'S law V/I=R.. i.e.V proportional to I.. We also learnt that during power transmission in an electric line P=VI and that inorder to minimise loss voltage ...
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2answers
3k views

Electric Field Between Two Parallel Infinite Plates of Positive Charge and a Gaussian Cylinder

Is the electric field between two positively charged parallel infinite plates one with a charge density twice the other effect the electric field on the outside of the plates? I am thinking no, ...
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1answer
164 views

Coulomb force on the center of a hexagon?

Six point charges $q$ are at the corners of a regular hexagon that has sides of length $a$. What is the force on another charge $Q$ which is located in the center of the hexagon? What is the force on ...
2
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1answer
145 views

How can electrostatic forces provide lift to the gossamer spider?

I was reading this article entitled "“Ballooning” Spiders Use Electrostatic Forces To Generate Lift". What I would like to know is how can a electrostatically charged object generate lift within the ...
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2answers
71 views

Capacitor's voltage

Imagine I have two plates that form a capacitor, so the magnitude of the charge in each plate is, let's say, $Q$. So, the force, in respect to the distance $d$, is gonna be: $$F(d) = ...
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1answer
228 views

Information content of the electrostatic Maxwell equations vs Coulomb's Law vs Poisson's Equation

In electrostatics, we have Maxwell's equations: $\nabla \cdot E = \rho$ $\nabla \times E = 0$ These four equations (the second line standing for three equations) can also be written in terms of the ...
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1answer
203 views

Density of repulsive particles on a disk?

NB: the external circle (where particle or water is in it) is fixed ! It's a 2D theoretical problem (just for understand something in particular). Here, no gravity, no temperature. I put in a disk a ...
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4answers
329 views

Distribution of point charges on a line of finite length

How will $N$ freely moving charges confined to a line with length $L$ be distributed? What are their equilibrium positions?
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2answers
515 views

Prove a dielectric with infinite dielectric constant behaves as a conductor for static fields

I read the following problem: Prove that a dielectric medium for which $\varepsilon \to \infty$ behaves as a perfect conductor in the presence of static electric fields. So, the easy part is that the ...
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3answers
472 views

when we rub objects together, what determines which material will pick up electrons?

For example We know glass when rubbed by silk will become positively charged while the silk will be charged negative. What exactly makes glass appropriate for losing electrons in that experiment? (
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1answer
98 views

Where do electrical charges go, on a nonconductor dielectric when we make it charged?

My question is about electrically nonconductor dielectrics. We know such materials don't possess free charges.They have atoms bound together and every atom has specific numbers of electrons turning ...
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1answer
125 views

what is in the electrostatic field that makes the word done independent of path taken?

I am trying to understand how is it possible for electric force to behave like this (path independence)? I am repeatedly failing to get an intuitive meaning behind its (electric field) nature of ...
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1answer
59 views

Need a more efficient way to find where the $E$ field is zero

So this is a problem I already know how to solve, but I feel like my method is really inefficient and I'm wondering if there's a more intuitive, less tedious way to arrive at this conclusion. If we ...
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1answer
309 views

Electrostatics:2 concentric spheres

An external charge when brought close to a conductor induces bound charges on the nearer side and free charges on the further side so that the field induced in the conductor can counterbalance the ...
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1answer
1k views

Net flux calculation through a cube [closed]

Ans: Applying Gauss’s law the net flux can be calculated. And for option (B), I guess the flux will be 0. But not sure. Can anyone explain all the 3 options? For left and rignt face, EA = ...
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0answers
83 views

Understanding unit vectors

Trying to understand how the unit vector ${\mathcal{\hat{r}}}$ defined as $\frac{r' - r}{|r' - r|} $ (where $r'$ is the source point) works in this problem: Work out the electric field, $E$, at point ...
2
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3answers
330 views

Electrostatic energy integral for point charges

The electric energy stored in a system of two point charges $Q_1$ and $Q_2$ is simply $$W = \frac{1}{4\pi\epsilon_0}\frac{Q_1Q_2}{a}$$ where $a$ is the distance between them. However, the total ...
4
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1answer
117 views

Experimental relationship between linear dependence and superposition

From Griffith's Introduction to Electrodynamics The principle of superposition may seem obvious to you, but it did not have to be so simple: if the electromagnetic force were proportional to the ...
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1answer
236 views

Electric field of an infinitely long (thin) metal cylinder [closed]

An infinitely long thin metal cylinder of radius $a$ coaxial with the $z$ axis carries a uniform surface charge density $\sigma=\frac{\lambda}{2\pi a}$, where $\lambda$ is a constant. A thick ...
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1answer
149 views

Does proton make neutron charged by the process of induction/friction/conduction?

If two bodies undergo friction, the one of the bodies which has electrons less tightly bound than the other loses them. Here the protons do also have charged quarks which they could exchange with ...
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2answers
163 views

Moving the plates of a charged capacitor to calculate energy density - where's the flaw in my argument?

For a charged air-dielectric capacitor, let the plates be parallel to the $xy$ plane, with the top carrying a positive charge $+Q$, the bottom a charge $-Q$. The force on an infinitesimal charge ...