Questions tagged [coulombs-law]
A fundamental and empirical law quantifying the electrostatic force between two charges.
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Newton's third law and Coulomb's law
Coulomb's law states that if we have two charges $q_{1}$ and $q_{2}$, then $q_{1}$ will act on $q_{2}$ with a force $$ \textbf{f}_{12}=\frac{q_{1}q_{2}}{r_{12}^2} { \hat {\textbf {r}}_{12}},$$
and $...
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Why are there 6 interactions with 4 positive charges?
From a homework assignment, there are 4 spheres spaced 1cm apart. Each of the spheres are charged to +10nC and weigh 1 gram. The question wants us to find the final speed of the charges once they've ...
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What is the function $q$ in the definition of charge density?
Supposed we define $\lambda = \frac{dq}{dl}$. If I think of this intuitively, this makes sense; the linear charge density at a point is tiny amount of charge at that point divided by the tiny length ...
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How to calculate this electric field? [closed]
I can't solve this question. Please help.
Q: Solve using Multiple integrals (Gauss is not allowed). A hemisphere of radius $R$ has a uniform distributed surface charge density $ρ_s$.
Calculate ...
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1answer
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What is the effect of charge of Sun induced on the Earth as compared to gravity?
As we know gravity is a less attractive force than the for of electric and magnetic fields. My question is where does the effect of magnetic field go while gravity has pull on earth.
At this point ...
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What would be tension developed in a conducting ring of radius $R$ which has been given a charge $Q $, uniformly in the ring? [closed]
As the question says , i thought about using coulumbs law , but for any small dq charge , all other part will be attracting it , so.how to get the total tension force ( difficulty is in as distance ...
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Is this calculator for the electric field inside of a square correct?
I made a desmos tool calculating the components of the electric field [u,v], at a point (a,b) inside of a square of continuously and uniformly distributed charge with linear charge density $c$.
https:...
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Do electrons in the same orbital but different spin feel each other's Coulomb repulsion?
Or is it irrelevant, as orbitals are QM while Coulomb interactions are classical physics?
What I think I understood of orbitals is that particles with the same quantum numbers cannot occupy the same ...
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Electric field inside of a thin square of charge centered around an axis and extruded infinitely along that axis
Consider a thin square of charge centered around an axis and extruded infinitely along that axis in both directions. Is the electric field at any point inside of this shape zero, as it is for a ...
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How to find the electrostatic potential of a hydrogen-like charge density?
I've been trying to find the scalar potential that would correspond to the charge density of a ground state hydrogen atom. The result is known, and the inverse of my problem can be found e.g. in ...
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If Coulomb's were to depend on $\frac{1}{r^n}$ instead of $\frac{1}{r^2}$ where $n\neq 2$,would Gauss's law still be the same?
What I think is that Gauss's law is an independent law of nature which shouldn't change on modifying Coulomb's law.Am I correct?
Well the relation between Gauss's law and Coulomb's law is very strong ...
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Is the electrostatic equilibrium that conductors reach a consequence of Coulomb's law?
We know that if charges were to be placed within a conductor, they would start to rearrange themselves until they reach an electrostatic equilibrium where all charges are 'still' and no $E$-field is ...
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How are inverse square laws verified? [closed]
I'm curious about how equations like $F_{g}=G\frac{m_{1}m_{2}}{r^{2}}$ and $F_{e}=k\frac{q_{1}q_{2}}{r^{2}}$ were derived. Turns out that they're actually inverse square laws. But it's still unclear ...
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Electric field of a finite line uniformly charged
A charge $Q$ is uniformly distributed along the $z$ axis.
Why because of the symmetry of the configuration is the electric field zero at z=0?
I understand the electric field cancellation in a ...
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1answer
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Understanding distances and unit vectors in this problem
A charge $-q$ is at $x = -a$ and a second charge $+q$ is at $x = a$
Between the charges, the contribution from each charge is in the negative direction.
An expression for $${\overrightarrow{E}} = \...
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2answers
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Accurately calculating the work to move a charge? [closed]
I'm applying a force $F_{me}$ to move the charge $q_2$ towards $q_1$.
If they are both equal charges, I'm assuming a repulsive force $F_R$ opposing me.
In order to get $q_2$ to the final position ...
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1answer
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Coulomb's law and the continuous charge model in an infinite charged plane [duplicate]
The $E$-field of an infinite plane with a uniform charge density $\sigma$ has a constant magnitude equaling $2\pi\sigma$.
Now, this magnitude assumes a continuous charge model throughout the plane.
...
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Work done by charged particles [closed]
A proton is kept at rest. A positively charged particle is released from rest at a distance d in its field. Consider two experiments; one in which the charged particle is also a proton and in another, ...
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Why did the experimenter touch the circular plate in this demonstration?
In this introductory physics experiment demonstration, the experimenter went through the following procedure:
First, he charged the rectangular plate by rubbing it with fur.
Next, he laid a ...
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1answer
37 views
Why is the force due to a charged loop on a charge on its axis only in the axial direction?
This may be more of a mathematics question, but I am going through the open course for physics II, from Yale, and am learning about Coulomb's Law. One of the first examples the professor gives is ...
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Electrostatic force between 2 charges when the medium's dielectric constant is continuously changing
This question just came to my mind. I don't know if it's valid or not. I'm just curious.
Question: Charge q1 and charge q2 is in a medium and it's dielectric constant changes proportional to the ...
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Electrostatic force between charges placed in 2 different mediums [duplicate]
Here is the problem.
Question: What is the force between the 2 charges?
So, If I convert medium 1 into medium 2 keeping the force constant then, (considering an imaginary charge q where the 2 ...
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1answer
43 views
Modifying the Hamiltonian when there is a presence of the Coulomb interaction
Referring to the Hamiltonian of a system of free electrons,
$$
H_0= \sum_{\sigma} \int d^3rd^3r' \psi_{\sigma}^{\dagger}(\mathbf{r})\left(- \frac{\hbar^2}{2m}\nabla^2\right)\delta(\mathbf{r}-\mathbf{...
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Discontinuities in electric fields
I'm a mathematician self-studying physics for fun and I'm trying to wrap my head around a simple concept, which is a consequence of approximations. Basically, by Coulomb's law, if I have a point ...
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How can electric field be defined as force per charge, if the charge makes its own, singular electric field?
The electric field $\bf{E}$ represents how much force would act on a particle at a certain position per unit charge.
However, if we actually place a particle in that position, the electric field will ...
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1answer
171 views
Difference between Coulomb law and QED
According to Coulomb law, the electromagnetic force between point charges separated at zero distance is infinite. Does QED explains the same result, or there is any difference?
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1answer
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Is Coulomb's law correct? [duplicate]
Why don't electrons and protons collide?
Hydrogen atoms are often ionized. After ionization, it is divided into electrons and protons, which can merge into hydrogen atoms at any time.
Why don't ...
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3answers
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Electric field generated by a small object
I've just begun to study electrostatics and I've read the coulomb law, it describes the electric field generated by a point charge as characterized by a spherical shape. I think it is due to the fact ...
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3answers
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Force between 2 plates of a capacitors , which approach is correct? [closed]
If I have a parallel plate capacitor with charge $Q$, to calculate the force on first plate we say the electric field of $\frac{Q}{2\epsilon_0 A}$ is created by the second plate and since the charge ...
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4answers
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How is linear momentum conserved in circular motion?
Consider a system of two charged particles ($+\text{ve}$ and $-\text{ve}$). Let's assume that the negatively charged particle revolves around the positively charged particle due to the force of ...
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Problem in understanding superposition principle in electrostatics
When I have a single charge, it produces a electric field and a test charge will experience a force. Now when I have two(identical,same sign) charges, they produce electric fields and when the test ...
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Relativistic Particle Motion and Numerical Methods
I want to be able to show the relativistic motion of a particle in a static electric field produced by a proton at the origin: $$ \vec{E} = \frac{1}{4\pi\epsilon_0} \frac{q}{r^2}\hat{r} $$
The ...
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1answer
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How can system of charges be static?
I am a beginner in electrostatics.
I don't understand the below:
When we have a set of charges, those charges exert a force on the test charge but what I don't understand is how are these set of ...
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For which energetic reasons are ions blocked by cell membranes?
The permeability of cell membranes is given by the following diagram from the book "Biochemistry":
The reason that ions get blocked can be explained chemically: The ions favor interactions with the ...
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How to write the Rutherford differential cross section in terms of the momentum transfer?
The Rutherford differential cross section is:
$$\frac{d\sigma}{d\Omega} = \frac{Z^2 \alpha^2}{4E^2 \sin^4 (\theta/2)}.$$
I need to write this in terms of the momentum transfer $\frac{d\sigma}{d(Q^...
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Why is it that forces like gravity and electricity (approximately) basically act between pairs of bodies only?
In classical mechanics, with the limit of little movement (so no relativity, waves, and/or "magnetic" effects), we can see that gravitation and electricity can both be described as "two-body" forces, ...
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Electric Potential: Building system of point charges
How can we prove that the amount of work we have to do to build a system of point charges is same , whether we place the point charges one by one or all at once
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Electric force between two hemispheres of different radii? [closed]
Two hemispherical thin shells made of insulating materials are concentrically
arranged in a free space as shown. The radii of the smaller and larger
hemispheres are ‘R’ and ‘2R’ and they carry ...
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1answer
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Is the direction of the Coulomb force at short distances indeterministic?
Suppose we have two electrons that apply a Coulomb force on each other. At large distances, we can consider the two electrons as point charges and the direction of the Coulomb force would be on the ...
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2answers
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Electrostatic values where there are some charge
I've started asking myself:
What is the value of the electric field at the surface of a shell with uniform distribution? In particular, is it infinite, as this point is over an (infinitesimal) ...
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When was Coulomb's constant made/established?
Charles-Augustin de Coulomb lived from 14 June 1736 – 23 August 1806. Coulomb's constant is
$$k_{\text e}=\alpha\frac{\hbar c}{e^2},$$
a form of Planck's constant is included, but Max Planck lived ...
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Is this a valid explanation for why charges in a conductor move to the outer surface?
This is a drawing of a spherical conductor with a hollow center. The black dots represent +ive charges, and the arrows represent their electric fields. I am assuming the black dots start on the inner ...
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3answers
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Can the electrostatic force be infinite in magnitude? [closed]
The magnitude of the electrostatic force between two charges $Q$ and $q$ separated by a distance $r$ is given by $$F=\frac{kqQ}{r^2}$$ but the minimum value of $r$ must be $10^{-15}\ \rm m$. Therefore,...
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How did Coulomb measure charges?
I was studying some Electrodynamics when suddenly this question popped into my mind :
The whole of Electrodynamics is based on the Coulomb's Law. There is no derivation of this law because it is an ...
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1answer
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Quantifying potential energy
As per the definition of potential energy we kept a fixed charge, and in the presence of an electric field of the fixed charge, we release another charge of the same sign moving towards the fixed ...
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Doubts in understanding some concepts of potential energy
Let us consider a system of charges in space. The potential energy of the system of charges is determined by the amount of work done by the external force to assimilate the charges in that manner. But ...
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1answer
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Why isn't electric potential infinite?
In my textbook, I've read that electric potential is the work performed to carry one unit of positive charge to electric field from infinite distance.
We know that, W = Fs
So here the distance is ...
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1answer
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Integrating Laplace's equation over a sphere
The Wikipedia page on Laplace's equation states that
if the Laplacian of $u$ is integrated over any volume that encloses the source point,
$$\iiint_V \nabla \cdot \nabla u \, d^3V =-1.$$
I can'...
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1answer
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How do we know how much charge is in an object?
It's a little science history question but I really wonder how did peoples measured the amount of charge in an ball or something or like in coulombs case how did he measured the electrical force ...
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Coulomb's Law Question
The presentation of Coulomb's Law in various books occasionally has a note that the test charge, q2, must be small enough that it doesn"t alter the field of the first charge, q1. The same limitation ...
