# Tagged Questions

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

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### Can Maxwell's equations be derived from Coulomb's Law and Special Relativity?

As an exercise I sat down and derived the magnetic field produced by moving charges for a few contrived situations. I started out with Coulomb's Law and Special Relativity. For example, I derived the ...
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### How is Gauss' Law (integral form) arrived at from Coulomb's Law, and how is the differential form arrived at from that?

On a similar note: when using Gauss' Law, do you even begin with Coulomb's law, or does one take it as given that flux is the surface integral of the Electric field in the direction of the normal to ...
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### 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 ...
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### Does Coulomb's Law, with Gauss's Law, imply the existence of only three spatial dimensions?

Coulomb's Law states that the fall-off of the strength of the electrostatic force is inversely proportional to the distance squared of the charges. Gauss's law implies that a the total flux through a ...
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### Why are so many forces explainable using inverse squares when space is three dimensional?

It seems paradoxical that the strength of so many phenomena (Newtonian gravity, Coulomb force) are calculable by the inverse square of distance. However, since volume is determined by three ...
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### Coulomb force in SI and cgs

Coulomb force in SI is $F = \frac{Q1*Q2}{4\pi\varepsilon R^{2}}$ while in CGS $F = \frac{Q1*Q2}{R^{2}}$ why is it? I mean doesn't it any make difference in dimension? since $\varepsilon$ ...
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### Protons' repulsion within a nucleus

Do the protons inside the nucleus repel each other by the electrostatic force? If they do, why doesn't the repulsion drive the protons apart so that the nuclei get disintegrated?
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### Coulomb's Law: why is $k = \dfrac{1}{4\pi\epsilon_0}$ [duplicate]

This was supposed to be a long question but something went wrong and everything I typed was lost. Here goes. Why is $k = \dfrac{1}{4\pi\epsilon_0}$ in Coulomb's law? Is this an experimental fact? ...
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### Are the Maxwell's equations enough to derive the law of Coulomb?

Are the 8 Maxwell's equations enough to derive the formula for the electromagnetic field created by a stationary point charge, which is the same as the law of Coulomb? If I am not mistaken, due to ...
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### Similarity between the Coulomb force and Newton's gravitational force

Coulomb force and gravitational force has the same governing equation. So they should be same in nature. A moving electric charge creates magnetic field, so a moving mass should create some force ...
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### 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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### Is Newton's universal gravitational constant the inverse of permittivity of mass in vacuum?

Is it possible to consider Newton's universal gravitational constant, $G$, as inverse of vacuum permittivity of mass? $$\epsilon_m=\frac {1}{4\pi G}$$ if so, then vacuum permeability of mass will be:...
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### Why is there no permittivity-type constant for gravitation?

When I look at electric or magnetic fields, each of them has a constant that defines how a field affects or is affected by a medium. For example, electric fields in vacuum have a permittivity constant ...
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### Precision of Coulomb's law

Up to which precision has the coulomb law proven to be true? I.e. if you have two electrons in a vacuum chamber, 5 meters appart, have the third order terms been ruled out? Are there any theoretical ...
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### Coulomb's Law in the presence of a strong gravitational field

I was under the impression that the $1/r^2$ falloff of various forces were because of the way the area of a expanding sphere scales. But that strict $1/r^2$ falloff would only be globally true in a ...
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### Force when distance between charge is zero

According to coulomb law $$F = \frac{q_1q_2}{r^2}$$ I want to know what happens to force when $r=0$. If $F \to \infty$ then the charges can't be separated! But if an unlike charge of higher ...
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### Gravity force strength in 1D, 2D, 3D and higher spatial dimensions

Let's say that we want to measure the gravity force in 1D, 2D, 3D and higher spatial dimensions. Will we get the same force strength in the first 3 dimensions and then it will go up? How about if ...
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### What is the range of the validity of Coulomb's law?

What is the smallest and biggest distance in which Coulomb's law is valid? Please provide a reference to a scientific journal or book. Just saying that this law is valid from this range to that range ...
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### How does one show using QED that same/opposite electric charges repel/attract each other, respectively?

Why do same charges repel each other and opposite charges attract each other (please explain the phenomenon using real laws of nature (QED) not with the approximation model)?
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### 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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### Force inversely proportional to the squared distance

Newton's law of universal gravitation: "Newton's law of universal gravitation states that every point mass in the universe attracts every other point mass with a force that is directly proportional to ...
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### Classical vs. quantum energy of the hydrogen atom

If I have an electron and a proton and calculate the classical energy which I get by bringing the electron from infinity to the distance of a Bohr radius to the proton, I get 27.2 eV, but the electron ...
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### What are the limits of applicability of Coulomb's Law?

Coulomb's law is formally parallel to Newton's Law of Universal Gravitation, which is known to give way to General Relativity for very large masses. Does Coulomb's Law have any similar limits of ...
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### 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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### Coulomb's law with an $r^3$, not $r^2$, in the denominator [duplicate]

I am reading an older physics book that my professor gave me. It is going over Coulomb's law and Gauss' theorem. However, the book gives both equations with an $r^3$, not $r^2$, in the denominator. ...
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### Electric potential due to a point charge in Gaussian/CGS units

I learned electrostatics in SI units. In SI, the electrostatic potential due to a point charge $q$ located at $\textbf{r}$ is given by $\Phi(\textbf{r}) = \frac{q}{4 \pi \epsilon_0 |\textbf{r}|}$. ...
I could, for example calculate the electric field near a charged rod of infinite length using the classic definition of the electric field, and integrating the: $$\overrightarrow{dE} = \frac{dq}{4 \... 4answers 1k views ### The maximum distance for which Coulomb's law has been verified? We know that Coulomb's law, F_{12} = \frac{kq_1q_2}{r^2}, was experimentally verified for small distances by Coulomb himself at the and of the XVIII century. The question is what is the maximum ... 3answers 100 views ### Do we know why the field produced by charge extends to infinity? Do we have any model to show why charge field or magnetic field extends till infinity. Edit: I agree that according to coulombs law 1/r^2 cannot be 0 but do we know why this happens.I think I am ... 1answer 219 views ### Gauss's Law of Electric Field how it actually works? & How Gauss derived it? I want to know how Gauss derived his equation of Electric Field. Did he derive it from Coulomb's law? I don't think so. Please tell me some details about how this law works? inside a Gaussian ... 1answer 561 views ### How the inverse square law in electrodynamics is related to photon mass? I have read somewhere that one of the tests of the inverse square law is to assume nonzero mass for photon and then, by finding a maximum limit for it , determine a maximum possible error in \frac{1}... 3answers 152 views ### How is the conservation of momentum satisfied in long-range attraction such as electromagnetism and gravity? I'm not a physicist, but my understanding is that electromagnetism (including attraction between opposite charges) is mediated by the photon, and gravity is probably (hypothetized to be?) mediated by ... 4answers 558 views ### Attractive force between capacitor plates A textbook question requires me to calculate the force of attraction between plates of a parallel-plate capacitor. The answer provided is \frac{1}{2}QE. I am not entirely sure how they arrived at ... 1answer 1k views ### Deriving Coulomb's law from quantum electrodynamics [duplicate] Is it possible to derive the Coulomb's law using the principles of quantum electrodynamics? How? 1answer 292 views ### Why doesn't an electron's charge rip the electron apart? [duplicate] Like charges repel. What keeps an electron's charge from repelling itself? This problem would come up if an electron was divisible and its parts had fractional charge. A related question is, ... 2answers 521 views ### When studying electrodynamics do we assume Maxwell's Equations or derive them? This question is because something made me confused. I always thought that the idea behind electrodynamics was to postulate some things, like Coulomb's law in electrostatics and so on, and then ... 2answers 327 views ### Does the electric force on a charged particle in a uniform electric field increase? If I have a proton in a uniform field between two parallel oppositely charged plates and the proton accelerates, the electric force acting on it stays constant seeing it is a uniform field and as a ... 2answers 383 views ### Newton's Law of Graviation: Why G and not e.g. \dfrac{1}{4\pi G_0}? I've been wondering, in Coulomb's Law, k_e = \dfrac{1}{4\pi\epsilon_0}. Therefore, why do we use G in Newton's Law of Gravitation? What if the constant is more like Coulomb's Law, e.g. G = \dfrac{... 1answer 166 views ### Units for physical constants Someone told me that units for G and \epsilon_0 (gravitational constant and Coulomb's constant) are placed there simply to make equations work dimensionally and that there is no real physical ... 1answer 318 views ### Is there a fundamental relationship between Coulomb's law and Newton's Law of Gravitation? [duplicate] It seems like the two equations are identical indicates that there is something more going on that unites them both, maybe in a cool way or something. Why are these two laws so similar? 1answer 532 views ### Rigorous proof of Gauss' law for an arbitrary charge distribution from Coulomb's law Most of the books about electromagnetism prove Gauss' law for a point charge in vacuum:$$ \Phi = \int_{\Sigma} \mathbf{E} \centerdot d \mathbf{S} = q/\epsilon_0  and then simply state that for ...
Suppose there are two positive charges $A$ and $B$, both with equal mass $m$ and the same charge quantity $q$. The initial distance between $AB$ is $R$; and the initial velocity of $B$ relatively to \$...