A fundamental property of matter which causes it to experience electromagnetic forces.

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126 views

Radially symmetric charge distribution (dipole moment) [closed]

a) There's a radially symmetric charge density $\rho(r)$ centered around the origin. Determine the dipolemoment of that charge density. b) Let $\rho(r)$ be an arbitrary charge density now. Under ...
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2answers
103 views

Charges on capacitor after full charge by battery

When the charging is finished what will be the charge on an ideal parallel plate capacitor ? To be specific what are the charges on different faces of the 2 plates ? All the books say, after 100% ...
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0answers
45 views

Dipole Moment (spherical/arbitrary charge density) [duplicate]

I'm new here. I got to this website while searching for links to fill my gaps on some topics. I have found some amazing posts for many different topics. Just amazing. Anyway, I'm currently dealing ...
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0answers
59 views

Do virtual photons give particle charges?

I think the electric field is due to the exchange of virtual photons constantly emitted by the point charged particle such as an electron, does this apply to proton which is consisted of quarks? does ...
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1answer
54 views

Could someone simply explain how a railgun works?

Could someone simply explain how a railgun works? What could possibly accelerate an object that fast in such a short distance? I've heard it has to do with current between two rails, but I simply do ...
3
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1answer
116 views

How strong a magnetic field would be needed to deflect cosmic rays?

How strong a magnetic field would be needed to deflect cosmic rays? For example, lets imagine we wanted to protect the occupants of the International Space Station from cosmic rays. I assume we would ...
5
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1answer
143 views

Does a Tesla coil work in space?

If I took a Tesla coil into space, and then turned it on near, but not touching metal objects- would charge jump to the metal objects? It's my understanding I wouldn't see a flash, since the lightning ...
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1answer
49 views

Time derivative of Noether charge

I understand that the Noether charge can be written as $$ Q= \int d^3 x J^0$$ and the time derivative of the Noether charge is zero $$ \dot Q=0 $$ but how would you explicitly calculate it?
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2answers
80 views

Is antimatter attracted to matter by its opposite electric charge?

As it is said by many physicists that antimatter is just opposite of matter; it has opposite charge of matter, then is there is any possibility that antimatter is attracted to matter? For example - ...
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1answer
55 views

What is the “practical purpose” of Gaussian surfaces?

Without having the concept of a Gaussian surface, we know that charges induce fields in proportion to quantity. Now to take a common example, when describing flux through a (physical) surface it is ...
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2answers
88 views

Is this charge density function, from a problem in Griffiths' book, a physically valid density?

This is from the book on electrodynamics by Griffiths: A sphere of radius $R$, centered at the origin, carries charge density $$\rho(r,\theta)= k(R/r^2)(R-2r)\sin(\theta)$$ where $k$ is ...
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66 views

Validity of law of charge conservation

Charging by induction and earthing gives an object a net charge but why does the law of charge conservation still hold in this case?
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416 views

Derivation of capacitive reactance

Let $Q(t)$ be the charge stored in a capacitor $C$ in $t$ time for alternating current. Now, $$\displaystyle Q(t)=Q(0)+\int_{0}^{t}I(t)dt\\=Q(0)+\int_{0}^{t}I_oe^{j\omega t}dt\\=Q(0)+\frac{I_oe^{j\...
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2answers
140 views

Why is the charge of a proton positive? [duplicate]

Is there a reason that a proton has a positive charge while an electron has a negative charge? Are these just names that were given to the charges or was there a reason for making a proton have a ...
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0answers
68 views

signal from uniformly moving charge

As a charge moves, its field changes, and this change can only be propagated outward at the speed of light. Thus the field lines will be curves that keep changing apparent source point and direction. ...
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4answers
101 views

Where is the fallacy in this issue related to electric charge quantization? [closed]

Suppose there are two identical conducting objects; one with 5 units of positive charge and the other is uncharged. Initially these are separated and later these are brought into contact. I guess net ...
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2answers
250 views

Definition of a line charge with Dirac delta function [closed]

Is the following statement correct for a line charge distribution $λ(x)$? $$ρ(\mathbf r)=λ(x)δ(y)δ(z)$$ If yes - what does it say?
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326 views

Why is the potential energy of a dipole in an electric field zero when the dipole points perpendicularly to the field?

I have read that potential energy of a dipole in an electric field is taken to be zero at 90 degree as they say that it is a reference. But there must be some reason behind it?
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1answer
29 views

Electric field uniform circle $R$ direction cancel out

I am doing a physics problem involving a uniform circle with a total charge of X, and am attempting to find the electric field on a point charge on the axis of the circle a distance of Z away. I ...
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2answers
35 views

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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2answers
138 views

diffusion velocity

i understand that diffusion is the movement of particles from high concentration areas to low concentration, but what is the cause of that movement atomically. And especially in the case of charge ...
2
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2answers
415 views

Maximum limit of charging a capacitor

We say that we can charge a capacitor in proportion to the potential difference we apply across its plates and the maximum potential difference depends on the dielectric strength of the medium. Now ...
4
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1answer
96 views

Is it possible to push together two charged particles of the same charge hard enough so it becomes a black hole?

My chain of thought is the following: To push together two charges of the same sign you need to do work. The energy spent will be turned into electrostatic potential energy. Can we pump so much ...
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2answers
197 views

Why is charge constant in series connections?

Why does each capacitor in a series connection hold the same charge? I understand that voltages and capacitances across capacitor plate pairs in series vary, but why is it a necessity that charge be ...
2
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1answer
82 views

Balloon and Static Electrcity

I am learning about charge, but there is one thing I don't understand. In the above picture, I understand that the balloon sticks to the wall because of the attraction between the negative charge ...
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1answer
113 views

What does electrically charged mean?

So I was reading my physics textbook and it said that "Suppose we have two metal spheres, one highly charged and the other electrically neutral." What does it mean by highly charged? Does that mean ...
3
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1answer
207 views

Method of image charge for cylindrical conductor

I am simply puzzled that only for spherical and planar conducting surfaces the method of images is applied. Is it (really) impossible to find image charge or charge distribution which can simulate the ...
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1answer
245 views

How charges can be at rest if there is a force on it?

Electrostatics deals with forces between charges at rest. But if there is a force on a charge, how can it be at rest? My guess is that charges is being kept at rest by some unspecified forces that ...
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2answers
472 views

What is Gauss's Law in two dimensions?

I am trying to figure out how the equation for the field if a Gaussian surface was applied to a 2D plane. I did see another question already asked on the subject, but I didn't get a particular ...
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0answers
99 views

Relationship between electric field and distance

I am working on a lab report that asks a conceptual question related to one of the labs we did on electrostatic fields. For the context of my question, here is how the experiment is set up. We have ...
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1answer
68 views

Calculating the rate of electrostatic discharge via current density

After I asked this question, with the help of Floris' comment, I tried to learn more about the concept of current density and tried to calculate the current density in my scenerio which, it seems, is ...
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90 views

Derivation Electric force

I’m a physics of high school (SMAN 3 Bandar Lampung, Lampung, Indonesia 35116). I make the experimental apparatus in static electric field. Instrument arrangement in the image below: The theoretical ...
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1answer
97 views

Deriving the Lienard-Wiechert Potentials

Let $\mathbf{w}(t)$ be the trajectory of a moving charge. Let the observation event be $(\mathbf{r},t)$. The scalar potential is: $$\varphi = \frac{q}{4\pi\epsilon_0}\int \frac{\delta\left(\mathbf{r'...
5
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2answers
118 views

Is Quantum Coulomb still singular?

A single free charge (e.g. electron) $q$ fixed at the coordinate origin has the well-known Coulomb/electric potential $$\phi(\vec r) = \frac q{4\pi\epsilon_0}\frac 1r \tag{A}$$ where $r=|\vec r|$ of ...
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41 views

prototyping a cyclotron , a charging problem

I'd like to model a cyclotron but not with subatomic particles but with a small metallic ball but the problem is i need to charge the metallic ball with certain amount of charge and i must know it to ...
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1answer
287 views

Finding the electric field at a point from half of a uniformly charged rod

The image below is a rod of length that is uniformly charged to total charge at a point along the perpendicular bisector of the rod above distance . I know the formula for finding the electric ...
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0answers
57 views

Can you calculate the charge after rubbing two objects

If there are two insulators and you rub them together for a long time, is there a way to calculate how much charge should have transferred between them. I'm sure there is some relation to the ...
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1answer
92 views

Charging identical spheres using induction

Suppose I can induce a charge Q in a conducting sphere by the traditional induction method, then why is it that the charges would be equally shared if I put this sphere in contact with another ...
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4answers
248 views

Why, fundamentally, are particles charged?

This is something that has long bothered me, and I have asked a few physicists and chemists and never gotten a very satisfying answer. Why are particles charged? And I'm not asking (and this is the ...
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2answers
192 views

How to determine the angular velocity of a particle with mass $m$ and charge $q$ in a constant B field? [closed]

$\textbf{PROBLEM:}$ A particle with mass $m$ and charge $q$ moves in a constant magnetic field $B$. Show that, if the initial velocity is perpendicular to $B$, the path is circular and the angular ...
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0answers
71 views

Electric field radiation with moving charge and observation point

I've been working on Chapter 34 of the first volume of the Feynman Lectures on Physics http://www.feynmanlectures.caltech.edu/I_34.html#Ch34-S1. In Fig. 34–3 (reproduced above) Prof. Feynman shows ...
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1answer
35 views

Help with this question (Eletric Fields, Dipole) [closed]

The answer in the textbook in the solutions manual is the following: I didn't undestand the last step. He said he did a binomial expansion, I just can't figure out! Appreciate any help.
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1answer
33 views

Putting an Electron on a Conducting Sphere [closed]

What all might go on inside a conducting sphere if I (try to) dump an electron upon it?
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1answer
74 views

Is it possible for a conductor initially, not to have a charge?

Well I'm confused. The thing that was implanted to me is that when I hear about conductors, some charge is present and it can move freely. Now what I want to know is that is it possible for a ...
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2answers
526 views

Why do charged objects attract pieces of paper, but not pieces of metal?

I do not understand one concept in Physics: why charged objects (eg. a charged rod or comb) attract pieces of paper when brought close to them, but do not attract pieces of metal. I know that the ...
5
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1answer
159 views

Levitating capacitor

As the title already says, I would like to make a large capacitor levitate. Before you dismiss this question please hear me out: In essence, this is intended to be a way to avoid the constrains of a ...
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2answers
137 views

The source and sink phenomenological description of charge - how realistic is it?

I've heard over and over an electron described as a source of the electric field, but that is a misleading term. Source makes one thing of a tap, with a constant flow of something coming out of it. ...
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2answers
177 views

Why do we get electric shocks when most structures are insulators?

Suppose I was standing in the sea, and touched an electric fence; I would receive an electric shock, because both my body and the sea are conductors, and create a path for the electricity to flow. The ...
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0answers
67 views

Will charge transfer without friction

I know rubbing two objects of different materials together will result in a negative charge on whichever material has a higher electron affinity. However, I was wondering if a negatively charged ...
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1answer
64 views

Simple question regarding Gauss's electric law

I just read that electric flux=enclosed charge/permittivity. Considering the charge in an enclosed surface is always 0, what is the point in even having this equation? Or is the equation actually ...