Questions tagged [coulombs-law]

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

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Is there any role of permittivity of medium in finding electrostatic force between two charges in that medium in CGS system?

like from coulombs law,we know electrostatic force, $F=\frac{Qq}{4πεr^2}$ .....in SI System But in CGS this whole term $\frac{1}{4πε}$ got replaced by 1.,i just want to know like in SI, for different ...
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How to (derivate and) apply the electric field formula? [closed]

this question might be straightforward but I'm getting lost and I feel like I wouldn't be able to proceed if I don't get this clear from the get-go. I get the basic idea behind finding the electric ...
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Gauss' Law in differential form applied to charged sphere [closed]

I need to use the differential form of Gauss' Law $$\nabla · \vec E = \rho / \epsilon $$ applied to a charged sphere to obtain that the exterior field is given by $$\vec E = \frac{Q}{4 \pi \epsilon r^...
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Electric potential and force in terms of Rydberg

Given charges +Q and +q, separated a distance r[nm], find the electric potential and repulsive force. I am given a solution to a problem that is evaluated in terms of the Rydberg energy, but I don't ...
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Does charge always reside at the edge of a conductor's surface

Say I have a circular metal sheet with a charge $Q$ on it do the field lines come out from the edges alone or from across the entire sheet?
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Why do elements, as they have more protons, need a higher amount of neutrons to stabilise them? [duplicate]

I've seen the graphs of the stability line but I can't find any reason as to why this happens, I understand radiation, just not why radiation needs to occur in the first place if that makes sense.
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In Helium, why does more tightly bound mean the electrons are further apart?

In helium, the triplets ($S=1$) are lower in energy (more negative) than the singlets $S=0$. One reason given by my lecturer is that in a triplet the spins of the two electrons are the same, then by ...
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How should the singularity of the Coulomb's law be understood? [duplicate]

The electric field at the point $\vec r$ due to a point charge $q$ at the origin $$\vec E=\frac{q}{4\pi\epsilon_0}\frac{1}{r^2}\hat{r}$$ blows up at the origin. In other words, the force between two ...
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Potential at a certain point inside a non-uniform hollow conducting sphere [closed]

A thin metallic spherical shell contains a charge $Q$ over it. A point charge $+q$ is placed is placed inside the shell at point $T$ separated from the center by a distance $a$ ( $a < R$ ). Another ...
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Why isn't electromagnetism incompatible with special relativity?

The notion that newtonian gravity is incompatible with special relativity is often suggested by declaring the familiar equation $$F_g=\frac{Gm_1m_2}{|\vec{r}_1(t)-\vec{r}_2(t)|^2}$$ and stating that ...
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Which charges pushes exactly a charge inside a conductor to the surface and why does it prefer curved surface?

I know this has a lot of questions about it, however my question is different: why does a charged particle inside a conductor get pushed toward the surface? The usual explanation is that in a ...
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Applying Coulomb's law to find the field strength at a point which is not between the two charges involved [closed]

In most of the questions I encountered, I used the coulombs law only to find the force on a particle positioned between two charges. For the question below, I was not sure whether to multiply the ...
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8 votes
5 answers
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Can positrons attract electrons? [duplicate]

Now, it is established that positrons and electrons have the same mass but opposite charges. Since they have opposite charges, do they create a force of attraction and collide thus annihilating each ...
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Electric Field vs Electric Field Intensity

In my 1st year Physics college course, Electric Field at a point is defined as $\vec E = \frac {\vec F}q $. However, during high school, it was defined as An electric field is a region of space where ...
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Work done in assembling charges

We have this system here Says that the total energy required to assemble the system is 0 for q1 (kq1q2)/l for q2 And (kq1q3)/l+(kq2q3)/l for q3 Therefore the total work is But why is the work done ...
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Virtual photons

Is it true what is said about photons that carry electromagnetic force or field? are they virtual photons too? Where exist real photons? I don't understand the concept of virtual photon, in ...
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Volumetric charge density of a Gaussian surface $\rho$

If I have a long cylinder (infinite length) and has a radius R=4cm , A cross section of it has length $L=15m$ and charge $q=3\mu C$ , The cylinder is surrounded by a thin shell (Thickness$\approx0$) ...
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Quantum mechanically speaking: why is it that electrons get bound to a nucleus? ..and why doesn't the electron's wavefunction get infinitely small?

I have a pretty good intuitive understanding of quantum mechanics. But one thing that I don't really intuitively understand is why electrons end up in bound states. An electron might have some ...
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Where do the limits of integration of this electric field problem come from?

If we have a uniformly charged ring with negligible thickness, we can say that $$\text{d}E=K_e\frac{\text{d}q}{r^2}$$ Then after resolving $\text{d}E$ into its two components, we find that the ...
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2 answers
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Confusion about $x$ & $y$ components of Coulombic Force?

I am new to this website and have a question about components of Coulomb's force. I know that we can find the $x$-component and $y$-component of a coulombic force by taking $|\mathbf{F}|\cos(\theta)$ ...
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Sphere analogy of non-contact force formulas like electrostatic force should again produce infinite Force when 1 charge of 2 spheres gets closer

Everybody is giving the sphere explaination but 2 touching parts of a sphere, I mean the touching charges in the smallest parts of these spheres that has the smallest charge on it again create ...
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Why electrons in orbitals have negative energy?

The potential energy of electron is negative so; kinetic $+$ potential $= \ \ -$energy ; but the kinetic energy gets lower as an electron is farther from nucleus; needs less acceleration to orbit I ...
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1 answer
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What happens when a negative particle faces a positive one?

First let me stress the fact that this question is not a duplicate, there are many similar questions that have missed the point, in particular this Why doesn't an electron ever hit (and stick on) ...
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How does Newton's Third Law apply to non-contact forces?

I always intuitively understood how Newton's Third Law applies to simple contact forces because I could imagine how to reciprocate the force of one object on another, the recipient's molecular ...
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2 answers
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Point charges symmetrically spreading out

The Problem There are $3$ positively charged particles fixed in a frictionless horizontal plane, positioned in the vertices of a triangle. The $i$-th particle has mass $m_i$ and charge $Q_i$. When ...
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What is the net force F for this equation? [closed]

I'm new to physics and I have this equation to solve, a detailed answer would be much appreciated! Two charged particles q1= -5 μc and q2= -4 μc are 50 cm apart on the x-axis. What is the net force F (...
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How to prove Poisson's equation for gravity? [duplicate]

When deriving, by integration from the Newton's law, the gravitational acceleration field inside a sphere we get: $$\mathbf a = \frac{4}{3}\pi G \rho (\mathbf {r_c-r_p})$$ where $\mathbf {r_p}$ is a ...
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5 answers
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Why is there no electric field inside a conducting shell but a gravitational field inside a massive shell? [duplicate]

Is there a simple explanation of this observation? One could even take a liquid mass shell (like a soap bubble) to make the analogy even closer. Why is there such a difference inside the shells ...
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1 answer
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If the net electric field inside a conductor is zero, how did alpha-particles deflect in Rutherford's expeirment?

The electric field in a metal is zero in electrostatics. But in Rutherford gold foil experiment, alpha particles get deflected from the gold foil showing presence of electric field there. I discussed ...
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When solving Coulomb's Law, should the answer be always absolute or positive?

When solving Coulomb's Law, should the answer always be absolute or positive? or are there other things to consider? Like for this, Should it be: F = −3.80 ×10^11 N or F = 3.80 ×10^11 N
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Is there a particle with charge to mass ratio such that the gravitational attraction cancels electrostatic repulsion?

Consider two masses $m$ with electric charge $q$ at a distance $r$. Magnitude of Gravitational force = $\frac{Gmm}{r^2}$ Magnitude of electrostatic force = $\frac{kqq}{r^2}$ So, If the forces are ...
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4 answers
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Some books write coulomb force is medium independent and some write it is medium dependent why so?

Some authors say coulomb force is medium independent others say it is medium dependent. I know value of universal gravitational constant does not depend on medium.But value of permittivity does depend ...
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Problem with Lorrain and Corson 2nd Ed?

I have both the second editions of Lorrain and Corson's Electromagnetic Fields and Waves and Jackson's Classical Electrodynamics. I was reading Jackson's two chapters on Relativity and at one point he ...
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If protons were negative and electrons were positive, would Coulomb's Law change?

Coulomb's Law is $$F=k\frac{q_1 q_2}{r^2}$$ where $F$ is the force, $k$ is the Coulomb's universal constant, $q_1$ and $q_2$ are the charges, and $r$ is the distance between the two charges.
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Inverse square law voltage loss when input and output wires to metal sphere

A rather basic physics question. How does the circuit below behave, if the sphere is solid copper, and proportionally much larger than the input and output conductor diameters? The wires are connected ...
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2 answers
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Factor of 2 difference in force using image charges?

Consider a point charge $q$ a distance $z$ from an infinite grounded conducting surface in the $xy$-plane. Using the method of images, we know that the potential $V$ can be found in the region $z>0$...
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3 answers
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Can Lorentz force law be derived from Coulomb's law and Special Relativity? [duplicate]

If two stationary charges experience 1N of force, two moving charges should experience 1N of force as well right? (Due to the fact the the moving charges see each other as stationary.) So can we use ...
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Electric field $\propto \frac{1}{r^3}$ [closed]

If some charge is given to a solid metallic sphere, the field inside remains zero and by Gauss’s law all the charge resides on the surface. Suppose now that Coulomb’s force between two charges varies ...
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Would this theoretical battery be practical: 2 charged objects close to one another? [closed]

Consider a system which stores energy by forcing two charged objects (of the same charge) close to one another. When the energy needs to be used, a latch could open and the objects would accelerate ...
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What would happen if I had an insulated 5 cm sphere charged with 1 coulomb of positive or negative charge?

I have a ball measuring 5 cm in diameter covered with a very insulating material. What would happened if I charged the ball with 1 coulomb of net charge (positive or negative)? Would it fly and reach ...
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How can supercapacitors not implode?

How can supercapacitors store $5\,\mathrm{coloumbs}$ and not implode due to the enormous force between the plates ($10^{15}\,\mathrm{N}$ if the plates are $1\,\mathrm{cm}$ apart)?
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What happens when the plate of an electrophorus is touched more than a short duration?

In this video it is said that in an electrophorus by putting a finger on the plate, negative charge is taken off. Also, it is said that between the plate and the cake, no current flows, as on a "...
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Electrodynamics, including Lorentz force, using only Coulomb's law?

The paper Direct derivation of Lienard–Wiechert potentials, Maxwell’s equations and Lorentz force from Coulomb’s law by Hrvoje Dodig, purports to derive electrodynamics from Coulomb's law, without ...
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Is it possible to find the proportionality constant in Gauss's law for an electric field without knowing Coulomb's law?

Using the definition of electric flux, and knowing that the electric flux through a closed surface is proportional to the charge enclosed (that proportionality constant being $ \frac{1}{\epsilon_0} $)....
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Superposition principle and fixed positions charges

I am trying to understand this sentence of my course: The superposition principle implies that the net force between any two charges is independent of the presence of other charges. This is true if ...
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Understanding attractive Feynman diagram [duplicate]

I’m curious about the origins of the positive/negative charge and why there might be the two, and only the two, electric charges. I saw a great example just now which I think was referencing a Feynman ...
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1 answer
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Proof for property of proportionality used in deriving physical laws like law of gravitation and coulombs law

$$\text{F} \propto m_1m_2$$ $$\text{F} \propto \frac{1}{r^2}$$ Therefore $$\text{F} \propto \frac{m_1m_2}{r^2}$$ In physics one quantity $\text{F}$ is directly proportional to two other quantities ($...
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2 answers
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Question about resolving electrostatic force in 2 directions [duplicate]

This may be a very stupid question but in the following scenario where particle A (fixed at (0, 0)) exerts an attractive force on particle B (free to move at (4, 3)), can I resolve the force in two ...
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$1/r^2$ force and "photon decay"

Background: My question is about the interpretation of the $1/r^2$ force in terms of the fundamental processes of the underlying QFT. We know that if the photon had mass $m$, then we may have a "...
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Confusion In Derivative of Electrostatic Potential Energy Of 2 Charge System

In my textbook, the derivative shows a -ve sign in front of the integral. My confusion is why is that -ve sign there? Isn't the direction of external force and displacement the same and hence shouldn'...
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