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Questions tagged [coulombs-law]

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

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Is my vector notation in electrostatics correct? [closed]

Let’s say we are expressing Coulomb’s law in Cartesian coordinates (not radial). Let the two charges of equal magnitude (and opposite sign) lie on x-axis. The equation for calculating the force acting ...
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Electric field experienced by a charge

We have two charges, say $Q_1$ and $Q_2$. The magnitude of the electric field $E$ experienced by charge $Q_2$ is: $$E = \frac{k Q_1}{r^2}$$ where $k$ is Coulomb's constant and $r$ is the distance ...
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Lagrange Multiplier as chemical potential in Lagrangian Density

Within Matsubara formalism, we often add one chemical potential term to our Lagrangian density: $\mu\phi^\dagger\phi$, claiming that the chemical potential $\mu$ is one Lagrange multiplier. But at ...
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What will happen if we keep bringing two protons closer and closer to each other, starting from a large distance?

I am asking this question for theoretical understanding of the topic: What will happen if we keep bringing two protons closer and closer to each other, starting from a large distance? I understand ...
Devansh Mittal's user avatar
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Why did we choose Coulomb's constant $k$ as $9\cdot10^9 \rm Nm^2/C^2$ while define unit of charge instead of any other number?

I understand that while defining charge, Coulomb had to choose any arbitrary value of $k$ to describe unit of charge. But, why did we chose $9\cdot10^9 \rm Nm^2/C^2$ as the value of $k$, but not any ...
Singer Asvj's user avatar
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EM 4-potential vs gravity 4-potential?

In classical field theory, the electrostatic and gravitational fields have very similar differential forms: $$\vec \nabla\cdot \vec{E}=\frac{\rho}{\varepsilon_0}$$ $$\vec \nabla\cdot \vec{g}=-4\pi G\...
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Is Coulomb's law wrong?

Recently I was reading about Coulomb's law which states that: "Magnitude of the electrostatic force F between two point charges $q_1$ and $q_2$ is directly proportional to the product of the ...
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Looking for a reference in quantum mechanics treating Coulomb potential as Inverse of coordinate operator

Most textbooks in quantum mechanics handle the Coulomb problem by solving the Schrödinger equation directly in the coordinate representation. Is there any book or reference that adopts a more formal ...
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Derivation of the Coulomb Collision Operator for Plasmas

I am attempting to learn about Coulomb collisions in the kinetic theory of plasmas. In doing so, I have come up with an "intuitive" derivation of a Coulomb collision operator. However, the ...
MeowBlingBling's user avatar
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Applicability of the $\frac{1}{4\pi}$ pre-factor for Coulomb Attraction in Nanocrystals

I am currently working on a thesis and stumbled upon a seemingly formal issue which I was not able to resolve myself. In short The classical coulomb energy between two charges (let's say, electrons ...
Alex Schmitz's user avatar
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How do two things attracted to each other move in mechanics?

Okay very simply: If you have two objects in 1D and they're both attracted to each other by some force (say there's a spring pulling them both towards each other, or Coulomb's Law or something)... How ...
Shelby Longbottom's user avatar
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Rutherford scattering closest approach distance

Consider a particle 1 moving towards a particle 2 at rest. In class, my teacher said that in order to derive the minimum approach distance when the impact parameter ( b ) is 0, we had to use ...
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Convert Coulomb's law in CGS units to SI units

I recently translated the appendix to an electromagnetics text from 1945 into English. Now the client is asking me to update the formulas (I studied electrical engineering). The formulas use CGS units ...
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Electrons repel each other forever - why? [closed]

I.e. charge is conserved. How? Why? Background I am coming here with only my intuition, and a desire to learn. My intuition "feels" that if an electron keeps on repelling other electrons, ...
Rabbi Kaii's user avatar
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Interpreting a field strength vs distance graph

The graph above is taken from my IB physics curriculum and is showing the electrical field strength vs distance for a negative charge. I am wondering whether this is showing that the field strength is ...
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Where does $4\pi$ come from in electromagnetism?

We know that in Coulomb's law, the constant $k_e$ is $\frac{1}{4\pi \epsilon_0}$. Where does $4\pi$ come from? Why is it related to the force between two charges?
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Electric Field of a Linear Electric Quadrupole Along x Axis [closed]

A charge $+q$ is at $x=-d$. Another $+q$ is at $x=+d$ and $-2q$ is at the origin. a) Derive expressions for the electric field along the x-axis as a function of x. b) show that $E∝\frac{1}{r^4}$ for $...
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Ion-Ion Scale Capacitance

Ions have three dimensions in solution and can be estimated as spheres. If ions have dimensions they can experience some degree of capacitance, e.g. an electrostatic potential which increases linearly ...
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If the value of Coulombs Constant is high, What can we conclude about the Electric force?

I wondered about that question and regardless of the obvious answer (If $k$ increases, the Electrostatic force increases), What can we conclude from $||\vec{F}_e||$?
Mavlock's user avatar
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1 answer
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Why do we use the Pythogorean theorem for the net Force in this problem rather than just summing the $x$ and $y$ components of $F$? [duplicate]

My solution was that I would need to sum the $x$ and $y$ components for the net force. However, the solution manual say that the net force should be calculated by using the Pythogorean theorem. I ...
Mary Sargsyan's user avatar
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The path-independence of work done by an electrostatic field

We know that work done by conservative forces is path-independent and so is work done by electrostatic force but how can we prove it using Coulomb's law? I know such a question has already been asked ...
Ayesha J.'s user avatar
6 votes
6 answers
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Derivation of Coulomb's law from Maxwell's equations

I'm trying to find sufficient additional conditions to derive Coulomb equation for the electric field generated by a steady point charge in free space from Maxwell equations in said conditions. I know ...
Lorenzo Vanni's user avatar
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Is there a point where the electric field strength is zero for two point charges of opposite signs put together?

I searched online that there is no 'neutral point' in the electric field of two charges of opposite signs, unlike the electric field of two positive charges. However my question is when you put 2 ...
gatiskandis's user avatar
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1 answer
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Relation between Coulomb's law and Fine-structure constant

There should be some relationship between them due to the nature of FSC, but I could not find anything about it.
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Can the Coulomb potential as the vacuum energy shift in QED also be calculated with a field quantized in the Coulomb gauge?

This answer explains how the Coulomb-potential can be calculated as the energy shift of the (photon) ground state for 2 charges fixed in place. This calculation has been done for a covariant "...
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How to distinguish Coulomb and radiative parts of the electromagnetic field?

In classical electromagnetism, the EM field can be described by a 4-potential $A^\mu$. This potential describes two different phenomena. Static fields: A static charge $q$ at fixed position $r_0$ ...
P. C. Spaniel's user avatar
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Can the electric potential of any body be calculated using the same formula?

when doing problems i have seen that only $V=kq/r$ has been used. while for electric fields many other different formulas have been used. Does potential not matter with shape of body, if yes then why ...
Siam 's user avatar
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2 answers
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What is the mechanism by which objects feel the electrostatic force?

This is more of a conceptual question than a mathematical one, but you may answer however you wish. Suppose we imagine a universe with a single proton in it, then magically create an electron one ...
ING's user avatar
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Field of an Uniformly Charged Infinite Plane Sheet

Let's consider two cases: Let's say that we have two positive point charges. If we get those charges together very very very close to each other, the repulsive force goes to infinity between those ...
Emzar Chichoevi's user avatar
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Extension of a pattern from electrostatics into more than 3 dimensions [duplicate]

I am taking an introductory physics course, and the chapter we are on is about electrostatics. One section of our textbook has talked about the electric field generated by a charged object that is ...
ACertainArchangel's user avatar
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1 answer
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Why is Coulombs formula different in the solution? [closed]

I've been trying to solve this but I'm stuck. I thought the formula for Coulomb's law was $$F = (k* q1*q1)/r^2.$$ In the solution, first the charge is divided by the distance and then the whole thing ...
EzThebez's user avatar
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Is the electric force quantum?

I'm asking if the electric force is quantum, and I'm not referring to photons, which I understand is quantized. Unless of course, the answer is that the electric force is only felt upon absorption of ...
HardlyCurious's user avatar
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1 answer
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Why is the charge of an electron defined as a percentage of itself? [closed]

An electron is usually defined to have a charge of 1.602 × 10-19 coulombs. But a Coulomb is the amount of electrons accumulated in 1 second = 6.24 x 10^18 charge carriers. An electron charge is ...
Yogi Bear's user avatar
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1 answer
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Solutions for an electron near a 1D Coulomb

I am only a amateur solving the time-independent Schrödinger equation, and I only know how to solve the 1D box. When I went to search up more realistic examples, i.e. the Coulomb well, no one seemed ...
Lolulolul Coder's user avatar
3 votes
1 answer
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If field strength (magnitude) is: $E=kq/r^2 $, what happens at $r=0$?

The formula for the Electric field strength (magnitude) is: $$E=kq/r^2$$ where $k$ is a constant, $r$ is the distance from a point charge, and $q$ is the magnitude of the point charge. Given this ...
user45664's user avatar
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Electrical Force on 2 Line Charges [closed]

Two line segments of length L are located in the x-y plane. One is on the x-axis between -L/2 and L/2. The second is parallel to the x-axis at y=L and again is between -L/2 and L/2. Each carries a ...
Charlie's user avatar
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1 answer
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Why electric potential can be evaluated by conservative electric field?

The definition of electric field is following: The electric field is defined at each point in space as the force per unit charge that would be experienced by a vanishingly small positive test charge ...
KHJ's user avatar
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1 answer
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Attractive or repulsive force between two statically charges plates [duplicate]

So I'm trying to calculate some mechanics for an electrostatic attraction/repulsion system and I want to make sure that I'm using the correct numbers. I did a bunch of research on my own and I think I ...
ADesilets's user avatar
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0 answers
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Calculating electric field produced by spherical shell [closed]

I'm having trouble solving this problem. Find the electric field a distance $z$ from the center of a spherical surface of radius $R$ that carries a uniform charge density $\sigma$. In here, $R>z$. ...
KHJ's user avatar
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2 votes
1 answer
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Potentials of two near conductors

When two conductors (let's say spherical) of charges $q_1$ and $q_2$ and radii $r_1,r_2$ respectively are brought and connected by a metal rod,we know that flow of charge occurs unless potentials are ...
madness's user avatar
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A question about Coulomb's law for one moving and one stationary charge

let one charge is moving and another charge is stationary (compulsory). Then the electric force between them can be calculated by coulomb's law?
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Definition of Coulomb's law

In the article about Coulomb's law There is following sentence: Coulomb's law is an experimental law of physics that calculates the amount of force between two electrically charged particles at rest. ...
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2 answers
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Limitation of Coulomb's law

The Coulomb's law is an expertimental law which calcuates the electrostatic force between distinct two electrically charged point particles (point charge) at rest. And Point particle doesn't take up ...
KHJ's user avatar
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3 answers
310 views

Why do gravity and electricity sometimes obey inverse square laws over the same distance scale?

Is this a chance mathematical coincidence or is there a good physical explanation for it?
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1 answer
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Validity of coulombs law for a charge in motion [duplicate]

If there is a charge $Q$ kept firmly at rest and another charge $q$ is brought in the vicinity of $q$,it's obvious that $q$ will accelerate towards $Q$. Now,when we say that coulombs law is not ...
a_i_r's user avatar
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0 answers
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Electromagnetic influences in electric field

Let us imagine a charge $q$ in space. At each point in space,there is an electric field vector associated with it. Now we start moving the charge in a direction. We know that electromagnetic ...
madness's user avatar
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2 votes
1 answer
40 views

Dipole formation in electrostatic induction

Let's bring a positively charged rod near a conductor. Now since some electrons in outer shells are not strongly bound to atoms,they will get to the side near the rod. But why does it mean that dipole ...
a_i_r's user avatar
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0 answers
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Charge distribution on an infinitesimally thin, elliptical conducting thread

Assume an elliptical conducting thread, which is positively charged. Although the thread is considered to be very thin, its stiffness is great enough in order not to allow the Coulomb's forces between ...
Mohammad Javanshiry's user avatar
1 vote
2 answers
37 views

Static condition of surface charges

We know that when charge is supplied to a conductor,they rearrange themselves on the surface thus making a static equilibrium condition. Let's suppose we have $+2e$ charge on a plane sheet conductor. ...
a_i_r's user avatar
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1 vote
2 answers
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Definition of proportionality constant in Coulomb's law

My textbook, which was written before 2019, says: $k$ [Coulomb's constant] is defined in terms of $c$ to be precisely $k=(10^{-7}\ {\rm N\cdot s^2/C^2)}c^2$ $\implies\displaystyle\frac{1}{4\pi\...
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