# Tagged Questions

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

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### What does the Dirac delta function physically do while deriving Gauss Law form Coulomb's law?

While doing this derivation, the the source coordinates are mentioned as "$s$" and the coordinate of the point at which field is to be calculated is mentioned as "$r$". Kindly follow this Wikipedia ...
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### Finding Charge given Electric Field

This question came up in a competition, and I didn't know how to solve it. ABCD is a rectangle with width $2d$ and height $d$. At point D, there is a charge with magnitude $q_1$ At point B, there ...
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### Problem from Purcell and Morin's Electricity and Magnetism: Holding the charge in place

This is the problem given in Purcell and Morin's electricity and magnetism book. (Problem 3.2 If you have the book) Figure: I was able to figure out that the charges on A,B,C,D cant be held ...
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### How do non-contact forces work?

One question has been bugging me ever since I started learning physics, the textbooks successfully describe the empirical observations but haven't given any reasoning behind it. What I want to ...
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### Special relativity, electromagnetic fields, charge and Q

Is it true, were Coulomb's constant k to be several orders of magnitude smaller, that there would be no (or increasingly negligible) magnetic fields generated by moving charges? The reason being the ...
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### Photon as a mediator of electric field

How can a photon (which has momentum) from one electrically charged particle to an oppositely charged particle cause these particles to be pulled toward each other - or how can a magnetic field cause ...
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### Will Coulomb law work if both the charges are moving with same speed and same direction?

I read it on wikipidia that Coulomb law will work if both the charges are at rest relatively. Will there be an effect of magnetic field also?
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### What does multiplying of charges means?

Today I learned Coulomb's law, and I didn't get what does this multiplication $q_1 * q_2$ gives? I want to understand this visually.
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### What's the Relation between Potential of mechanics and electricity?

As we know that for a conservative force field, there is associated a Potential with the force. But we know there is a potential in electricity (That's voltage). My question is that is there any ...
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### Repulsive force between same charged plates?

I understand that the attraction force between parallel plates of capacitor is the derivative of stored energy with respect to distance of the plates. But how could we find the repulsive force between ...
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### If the field concept was invented by Faraday, then how did Newton interpret the $g$?

This is Newton's law of universal gravitation. $F=G\frac{m_1.m_2}{r^2}$ Gravitational field $g$ is derived from this formula $g=G\frac{m_1}{r^2}$ This is named gravitational "field" strength. If ...
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### How much time would it take for a positively charged particle to get to an infinite, negatively charged wall?

There is a negatively charged wall($q$), which has equal charge density. There is a positively charged particle($Q$) with a mass of $m$, the distance between them is $d$. How much time would it take ...
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### Electron Beam Welding equation

I am studying for a nuclear physics course right now and came across a question and topic that sparked my interest - Electron Beam Welding. As I understand it, the process heats up the metal by ...
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### Is many-body Hamiltonian valid in strong-correlated system

Condensed-matter textbook often states that there is a many-body Hamiltonian $$H= \sum_i \frac{ p_i^2}{2m_i} + \sum_{i>j} V_{ij} \tag{1}$$ where $V_{ij} = Z_i Z_j/r_{ij}$. This Hamiltonian ...
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### Sphere of electric charge revisited

I am thinking about a sphere of homogeneous charge distribution (see Electric field due to a solid sphere of charge, for example). Here we use a Gaussian surface (blue area) to find the electric ...
### Is my representation of $\varphi$ Work function correct?
Let's say there is a charged tube(cylinder with no top or bottom) with radius $a$, length $l$ and charge $q$ and a point which is collinear with the centre of the charged tube. Anyway, since we can ...