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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207 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 ...
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1answer
229 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
271 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
214 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
372 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
750 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
803 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
132 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
127 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
61 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
383 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
3k 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
98 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 ...
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3answers
451 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 ...
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1answer
160 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
296 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
175 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
180 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 ...
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0answers
126 views

mathematical model of one electrostatic problem

I am trying to find direct-current electric field in a specific domain: it is a brick made from a low-conductive material with a number of more conductive inclusions of different shapes - spheres, ...
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1answer
342 views

Do inner shell electrons feel the electric field/force from an outer shell electron in an atom?

We just finished studying Gauss’ law and were puzzled by this thought. If I look at a copper atom and focus on the 29th electron in the 4th shell, according to Gauss’ law, I can draw a Gaussian ...
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1answer
216 views

Gauss's / Divergence theorem in Classical electrodynamics for the Electric field [duplicate]

Can somebody explain the proof of Gauss's theorem / divergence theorem taking the vector as electric field $$\iiint(\nabla\cdot\vec E)\mbox{ d} V=\iint \vec E \cdot\hat{n} \mbox{ d} ...
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2answers
515 views

Gauss's (Divergence) theorem in Classical Electrodynamics

How does divergence theorem holds good for electric field. How does this hold true- $$\iiint\limits_{\mathcal{V}} (\vec{\nabla}\cdot\vec{E})\ \mbox{d}V=\mathop{{\int\!\!\!\!\!\int}\mkern-21mu ...
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1answer
145 views

Physical interpretation of $\iiint (∇\cdot\vec E)\mbox{d} V$ [duplicate]

Can anybody explain the physical interpretation of Gauss's law $$\iiint (\nabla\cdot \vec E)~\mbox{d}V~=~\frac{Q}{\epsilon_0}? $$ Also, how is the differential form of Gauss's law obtained from ...
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2answers
3k views

Flux through side of a cube

I am looking at Griffiths introduction to Electrodynamics 3rd ED. Problem 2.10 asks for the flux of $E$ through the right face of the cube, when a charge $q$ is in the back left corner of the cube. ...
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1answer
452 views

Where to place my second image charge? (Spherical ungrounded conductor)

I am trying to find the potential $V$ inside a sphere using the method of image charges. I have a conducting spherical shell. The charge $q$ is inside the sphere. The sphere is ungrounded and is an ...
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2answers
2k views

Why potential energy of a dipole in an electric field has a negative sign?

In the following equation $$V = -\mathbf{P}\cdot \mathbf{E}$$ why I have to take Potential Energy as negative. Is there any simple reason behind this ? I am preparing for my high school ...
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1answer
191 views

Volume charge density of H-atom

I have a problem where I am supposed to calculate the volume charge density of a neutral hydrogen atom. The potential is given to be $$ \Phi = k \frac{e^{-ar}}{r} \left(1 + \frac{ar}{2}\right) $$ Now ...
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1answer
93 views

Cylindrical charge distribution [closed]

I'll just list the problem first and then explain what I need help with. Consider a cylindrical charge distribution extending from $r = 0$ to $r = 8.2 $cm of charge density $\rho = r/a_0$, where ...
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1answer
32 views

What does it mean for a $2$ dimensional object to be charged with a charge distribution which is $1$ dimensional $\lambda$?

I saw an example, in a tutorial of my Physics $2$ course that there was a hollow cylinder (which is $2$ dimensional) charged with uniform charge distribution $\lambda>0$ per unit length. What does ...
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1answer
341 views

Does the electric field change only inside the dielectric, or even after exiting the dielectric?

I know that the field inside a dielectric is changed and is $\epsilon$ times less the original field (some books use $K$ for this constant). This is because the induced field inside the dielectric is ...
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2answers
196 views

Charge and conducting thick slab

I have thought over this problem but I haven't found the solution: There is an electric charge $q$ at a distance $d$ from a conducting slab with thickness $t$, the problem is to find the potential ...
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1answer
199 views

(Exercise review) Find the moment of the electric dipole

I have solved an exercise, but the result I have obtined is wrong and I can't understand why. If you can help me, I'll be so grateful. Let's consider a charged cylinder, its radius is equal to R and ...
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1answer
229 views

A question from a Physics 2 exam: About electron cloud an a constant external field:

I am trying to prepare for my exam in Physics $2$, the following is a question from an old exam (the question also have a detailed answer to it, but I don't really understand it). An acceptable ...
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0answers
62 views

Point charge in a five-dielectric medium [closed]

What is the electrostatic potential due to a point charge in a five-dielectric medium with planar interfaces? Specifically, consider a system with planar interfaces, and the dielectric constants: $$ ...
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0answers
94 views

How did Jackson get the exact solution to potential in polar coordinates

On page 45 of Jackson's Classical Electrodynamics (3ed), He solved a polar potential problem with known source distribution. $$ \frac{1}{\rho}\frac{\partial}{\partial \rho}\left( \rho\frac{\partial ...
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2answers
825 views

Electric field. Linear charge density [closed]

I was wondering if anyone could help me out in this exercise I've been struggling to solve. A straight, nonconducting plastic wire $ 8.50 cm $ long carries a charge density of 175 $ nC/m$ ...
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1answer
90 views

Electron inside a conducting shell

Suppose I keep a single electron inside a hollow metallic/conducting shell,what will the charge distribution on the surfaces of the shell? Now in principle from Maxwell's equations,it simply should ...
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0answers
175 views

Where can I find a database for dielectric constants in the visible range?

I am looking for a database of dielectric constants in the visible range and I could not find them by Googling, so I was wondering whether anybody here knows where I can find those parameters for some ...
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3answers
804 views

Can someone give an intuitive way of understanding why Gauss's law holds?

Gauss' Law of electrostatics is an amazing law. It is extremely useful (as far as problems framed for it are concerned :D. I do not have a real world-problem solving experience of using Gauss' Law). ...
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2answers
2k views

Using the image charges method to find the electric field

The following is a question from a tutorial in my Physics 2 course about conductors and the Method of image charges. We are given two infinite perpendicular and grounded plains. The first ...
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1answer
947 views

Electric field outside a hollow cylindrical conducting shell [closed]

Imagine that a point charge $+Q$ is located at radius $R$ and height $z=0$ inside of an infinitely long conducting cylinder shell of inner radius $a>R$ and outer radius $b$. From what we know of ...
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1answer
1k views

Difference between parallel and series capacitors

Basically, I can't figure out that whether a capacitor is connected in series or parallel. The same problem occurs while solving for resistors. Can someone help me understand this difference ...
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0answers
87 views

Consistency of equation with special relativity?

The following is the equation which, I want to know, if it is valid in relativistic domain. Consider two equal charges moving in same direction with velocity $v$ and charge $q$ at a separation of ...
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2answers
3k views

Why does the electric field perpendicular to every point on the surface of a conductor?

I am reading Berkeley Physics Course, Volume 2 (Electricity and Magnetism by Edward M. Purcell). I am in chapter $3$ pg $92$, and the book discusses conductors. The following is from the book: ...
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1answer
79 views

About electrostatic induction

when we approach a charged rod (+) to a neutral metal rod ( not touching) a number of electrons to that side ( lets call it side B) negating the effect of the introduced electric field, reaching ...
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1answer
626 views

Equation for the equipotential lines? [closed]

What is the equation for the equipotential lines in $x$-$y$ plane for a dipole oriented along the $x$ axis?
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7answers
1k views

Why is there a factor of $4\pi$ in certain force equations?

I mean to ask why there is $4\pi$ present in force equations governing electricity? Though all objects in universe are not spherical and circular, the constant of proportionality in both equations ...
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0answers
56 views

What is the relationship between strain and electric current?

Strain or stress can be caused by different sources. I categorized theses sources as mechanical, thermal and electrical loads and formulated the total stress as follows: $$ \epsilon_{total} = ...
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1answer
170 views

Do we need infinite energy to make 2 similar charges touch only in theory?

By Coulomb's law, say if we have 2 point particles each having a charge of +1C then by the formula, F = k/(d)^2 if we need to make the distance between them zero, clearly y the formula, we need to ...