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Questions tagged [coulombs-law]

A fundamental and empirical law quantifying the electrostatic force between two charges.

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Do real electrons solve the Thomson Problem?

The question of how $N$ electrons (seen as point charges) on a conducting sphere will arrange themselves in the electrostatic final state was first posed by J.J. Thomson in 1904--hence, aka the ...
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1answer
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Electric field of two equal charges of the same sign [closed]

Two equal positive charges are at distance d, -d from the origin on the y axis. What is the distance on the x axis beyond which a small perturbation in y will move a particle away from the x axis? ...
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2answers
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Is the zero distance limit of Coulomb's law something to worry about?

Coulomb's law fails when the distance $r$ between to point charges vanishes. As $r\to 0$, the electric field between two point changes increases without limit. I should be bothered about the limit $r\...
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1answer
48 views

Gauss theorem and inverse square law [duplicate]

I know that the gauss law states that the Flux of the electric field through a closed surface is Q/ε , but does the gauss theorem works also for non inverse square law Fields?
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How to find electric field at a point on an arbitrary surface charge $(\sigma)$ due to it?

Electric field at any point due to any volume charge $(\rho)$ Electric field at a point outside a volume charge is given by Coulomb's law: $$\vec{E}=k \iiint_V \dfrac{\rho}{r^2} (\hat{r})dV \tag1$$ ...
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Coulomb's Law modified in general relativity?

It seems difficult to track down a clear explanation of this statement: So although the Coulomb law was discovered in a supporting frame, general relativity tells us that the field of such a charge ...
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When and why does the superposition principle of Coulomb's law fail to hold?

In this lecture, Professor Shankar Ramamurthi says that the superposition principle for force vectors of Coulomb's Law is experimentally observed and is not a product of logical analysis. In fact, the ...
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Can radio waves be detected using a coulomb torsion balance?

Radio waves are almost everywhere. shouldn't the coulomb torsion balance be sensitive to any passing through the device?
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(Two fixed charges add in a third), why does it matter which side I put the third charge if I change signs accordingly?

So the question is "Two charges, 1.0 micro-Coulombs and -3.0 micro-Coulombs, are 10 cm apart. Where can a third charge be located so that no net electrostatic force acts on it?". Now the instructor ...
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Electrostatics fundamentals

Suppose a charge is kept at the centre of a square frame and the vertices of the frame have four more charges fixed to the frame which are identical to each other but not necessary that these four are ...
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1answer
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Electric force is stronger than gravitational force yet gravitational forces holds the Sun and planets in their orbits around the Sun [closed]

The electric force between an electron and a proton, between two electrons, or between two protons is much stronger than the gravitational force between any of these pairs of particles. Yet even ...
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Functions unbounded at a point on the domain: How to show electric field exists for any continuous volume charge density?

My understanding after reading Mike Stone's answer: \begin{align} \vec{E} &= k \iiint_{V} \dfrac{\rho(x',y',z')[x-x'\hat{(i)}+y-y'\hat{(j)}+z-z'\hat{(k)}]}{[(x-x')^{2}+(y-y')^{2}+(z-z')^{2}]^{...
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Does Coulomb's law hold as long as $\dot{\rho} = 0$?

Does Coulomb's law, $$\textbf{E}\left(\textbf{r}\right) = \frac{1}{4\pi\epsilon_0}\int \rho\left(\textbf{r}'\right)\frac{\textbf{r} - \textbf{r}'}{\left|\textbf{r} - \textbf{r}'\right|^3}dV',$$ hold ...
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1answer
38 views

Earnshaw's theorem and stability of charge inside a hollowed cavity of conductor

When a positive charge q is placed in the center of a spherical cavity of a spherical neutral conductor, it induces a negative charge $q$ to line the inner wall of the conductor, and a positive charge ...
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1answer
100 views

What is the mathematical reasoning behind the inverse square law of two charges?

The Hon. Henry Cavendish performed an experiment with two spheres, by which he proved that no electric force is produced inside a hollow charged sphere. In other words, proving that no electric field ...
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0answers
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An alternative version to solve a electrostatic problem without definition of flux

I have this problem: The figure shows the electric field lines around a system of three charges $q_1$, $q_2$ and $q_3$. The central charge have a value of $q_2=-10.0\,\mu\mathrm C$. Find the value of ...
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2answers
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What is the fundamental explanation for the existence of Electrostatic force?

To explain my question in a better way I will first talk about gravitation! Gravity is not a force and the effects of gravity are ascribed to spacetime curvature My comments: Gravity was explained ...
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1answer
67 views

Is there a higher-level reason why $\nabla\cdot(\hat{\bf r}/r^2) = 0$ in three dimensions but not two? [duplicate]

I am working through Griffiths, Introduction to Electrodynamics, and finding the divergence of the electric field generated by a single charge sitting at the origin. $$\mathbf{E}(\mathbf{r}) = \frac{\...
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1answer
88 views

Fourier tranform of Coulomb-like potential $1/|r-r'|$

I've found that Fourier transform of Coulomb potential $V= q/r$ is $F[V]= 4\pi q/k^2$. Now I need to calculate fourier transform of function $1/|r-r'|$. And I exactly don't know how to operate with ...
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1answer
28 views

Force of electric charges

For the image below, lets say the top charge is 5C and the bottom 1C. And consider this observation frozen at $t=0$, consider an imaginary horizontal line between the 2 charges denoting the centre of ...
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2answers
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Why is the divergence of electric field equal to $\rho \over \epsilon_0$ in electrodynamics?

These two equations are true in electrostatics/magnetostatics: $$\nabla \cdot \vec{E}= {\rho \over \epsilon_0},$$ $$\nabla \cdot \vec{B}=0.$$ I have learned that they are also true in electrodynamics....
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2answers
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Can $E=\frac{q}{4\pi\epsilon_0 r^2}$ be directly derived from differential form of Maxwell equations?

The electric field of a point charge $q$ is well known to be $$\mathbf E=\frac{q}{4\pi\epsilon_0 |\mathbf r|^3}\hat{\mathbf r}$$ This can be derived easily from integral form of Gauss’s law. Taking $...
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1answer
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Solving dynamics of two oppositely charged particles without using energy conservation

Two charges, each $+q$, are separated by distance $d$. One of the charges is fixed, and the other is free to move under the influence of the force from the first. The second particle is initially at ...
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1answer
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Can the Earth's negative charge make negatively charged objects levitate?

Since the earth's surface has a negative charge, could it repel a large highly negatively charged body? An example is an object on stilts carrying a negative charge that is heavier than air, maybe ...
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Interaction of charges [duplicate]

As it is known in Physics, two point-size charges (say two electrons) interact with each other through em forces. How this is happening? do they exchange photons? And if so, then do they exchange ...
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2answers
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Why does Coulomb's law hold only for two point charges? [closed]

What is the condition for validation of Coulomb's Law?
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1answer
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Are two charges attracting each other constantly accelerating?

Using Coulomb's Law: $\frac{k_eq_1q_2}{r^2}$, say we have $2$ charges of $1\ \rm C$ each, separated by a distance of $1\ \rm m$. The force would be $8,987,551,787.3681767\ \rm N$, considering $k_e = ...
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1answer
62 views

Can I trap mosquitos with Coulomb's force? [closed]

Can I fill a metallic conductor with a very large positive charge, attach it with a insulator to a wall, put it near a window under the sun (visible light and UV in order to cause it to expell ...
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0answers
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Deducting from a special case that the electric field transforms as a 2nd rank tensor: Vanishing divergence concludes vanishing vector field?

I'm (as in the previous question) still working with Kobe's Paper. I try to understand his reasoning (given in Appendix A) why the electric field components should be components of a 2nd rank tensor. ...
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2answers
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What is the physical meaning of the Fourier transformed Coulomb potential $1/q^2$?

$V(r)=\frac{1}{r}$ means for any two electrons at position $r_1$ and $r_2$, the electric potential is given by $\frac{1}{|r_1-r_2|}$ The Fourier transform of $\frac{1}{r}$ is $\frac{1}{q^2}$. How ...
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4answers
486 views

Does a point charge inside a conducting shell cause redistribution of charge in the shell?

A point charge Q is placed inside a conducting spherical shell at a random place (non-centre). I have read that there is no force on Q from the shell no matter where Q is inside the shell ('there ...
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1answer
70 views

Cavendish's experiment on concentric conducting shells

In a paper were there was a section addressing Cavendish's experiment on concentric conducting shells which was basically the following : Two conducting spherical shells were put together (like the ...
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4answers
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Can Newton’s law of gravitation be derived from Coulomb’s law? [duplicate]

I’m casually learning physics and have noticed that Newton’s law of gravitation and the electrostatic force formulas look similar. I’ve asked this question before but would really appreciate another ...
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According to Coulomb law, why do fixed charges interact, if they don't emit the photons?

Why does it happens, if fixed charges don't oscillate the em field?
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Why there is a distance dependence in Coulomb's law if photons can travel to infinity?

Why there is a distance dependence in coulombs law if photons can travel to infinity? Why there is distance dependence at all?
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how the energy values of different landau levels depend on B field (quantum dot)

I came across a remark that "states in the first landau level fall in energy with increasing B, while those in the second landau level rise here. The book seems to be getting this from this paper. (...
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1answer
52 views

Intuitive understanding of 90° scattering

It can be shown that an electron of velocity $v$ colliding with an ion of charge $Ze$ will be scattered through 90° if its kinetic energy is equal to half the potential energy at a distance equal to ...
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1answer
117 views

Field inside a hollow sphere uniformly charged [duplicate]

How to prove that field inside a hollow sphere is zero anywhere inside that sphere using solid angle concept?
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1answer
82 views

How gaussian surface and continous charge distribution overlap in 2D?

It is well known that Gauss's Law & Coulomb's Law are inter-dependent. Any violation of Gauss's Law will indicate departure from inverse square law and vice versa. Then how gaussian surface and ...
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Why is electrostatic force a function of the product of charges, not the sum?

When you have two forces , you ADD them to get the total. If both of us push on a car, the total force on the car is the sum of our forces. But, If we have an electron approaching another electron, ...
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703 views

Why do we use cylindrical coordinates for infinite line charge?

Why do we use cylindrical coordinates for infinite line charge? And why can't we use rectangular or spherical coordinates?
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3answers
59 views

What is the use of vectors for forces? [duplicate]

i am studying the coulomb's law.then i encounter the formula for force between charges i.e $F=k q1q2/r^2$. They represent it with its vector form. now my question what is the use of that vector form. ...
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Charge distribution on Spherical conducting shells

For example we have very thin conducting spherical shells of radius R and 2R. Initially the smaller shell has Q and other shell has q charge of their own, now there will be charge induction in them ...
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0answers
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Coulomb force between two electrons with medium (compared to vaccum)

Im trying to understand why the Coulomb force decrease if the two electrons are in, for example, water, compared to if they were in vaccum. because the epsilon is in the denominator. thanks!
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1answer
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QED applied to two charged particles [closed]

To get the hang of how bosons actually work, could someone please provide me (the real question being, is it even possible to provide me) with a complete description of how photons are behaving and ...
2
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1answer
161 views

Why does $\frac{1}{4\pi}$ appear in many formulas? [duplicate]

Why do most of the physical equations have $\frac{1}{4\pi}$ as constants? I have seen that many equations have $\frac{1}{4\pi}$ as constants like Coulomb, pendulum problems, etc. Can anyone tell me ...
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1answer
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If force on neutral particle in electric field is zero then how come a comb can attract a neutral piece of paper?

If force on neutral particle in electric field is zero then how come a comb can attract a neutral piece of paper?
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2answers
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How is the tension of a wire an electromagnetic force?

I found that tension is an electromagnetic force. I suspect the cause is that it's due to the cohesion of elements of the wire which is due to dipolar attraction of wire which is due an electric field....
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1answer
39 views

Electric field strength of a location infinitely close to its source

The equation of the electric field strength is $$E = \frac{k Q_1}{r^2}, $$ but then wouldn't the strength of the field at a location infinitely close to the charge be infinity? If a neutral air ...
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1answer
196 views

Gauss' Law and Symmetry

While reading my lecture notes about Gauss' Law, here's what I found: Gauss' Law is obeyed by a wider range of fields, than those represented by the electrostatic field. In particular, a field that ...