Questions tagged [charge]

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

342 questions with no upvoted or accepted answers
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6
votes
2answers
616 views

The behavior of an ionized gas in an electric field

Say, I have a gas and then I ionize it (provide enough energy for the electrons to escape the nucleus' potential).And there exists, a SLIGHTLY positively charged surface beside the gas. Now, will the ...
6
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1answer
570 views

Charge over 2 layer dielectric, image method

If I have a charge $Q$ located over a 2 layer dielectric as represented: According to the image method : the charge $Q'1$ will be located at a distance $h_1$ under the first interface and the $Q'2$ ...
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0answers
93 views

How could particles with electric charge be massless before the electroweak symmetry breaking?

How could particles with electric charge be massless before the electroweak symmetry breaking? Wouldn't the energy stored in the electric field contribute to the mass of the particle?
4
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0answers
123 views

Is there a theorem about “Electromagnetic Miracles”?

I listened to a lecture several years ago in which the speaker claimed that there is a theorem that shows that violation of charge conservation under classical electrodynamics is impossible in the ...
3
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0answers
72 views

Conserved charges without conserved currents?

I recently read (Section 9.3 of J.Kaplan AdS/CFT notes) that we can have QFT's s.t. we have conserved charges but NO associated conserved currents. How is this related to the gauging of global ...
3
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1answer
50 views

Doubt related to the use of Gaussian Surfaces

My textbook says we need to take care not to let the Gaussian Surface pass through any discrete charge. However, the Gaussian Surface can pass through a continuous charge distribution. Why so?
3
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0answers
93 views

Can the melting temperature of metals be altered by modifying the local electric charge?

I'm researching a project in which metal needs to be melted. It would be very helpful to be able to reduce the melting temperature to improve the feasibility of the project. I've been looking into ...
3
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0answers
222 views

Why doesn't a charge in gravitational field radiate (or free fall)?

I have read these questions: Why do accelerating electrons emit radiation? Why does an accelerated charged particle emit electromagnetic waves? How and why do accelerating charges radiate ...
3
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0answers
123 views

Divergence theorem non continuously differentiable

In class we calculated the electric field in- and outside a charge distribution: $$ \rho(r)= \begin{cases} \cos(r)+\frac{1}{r}\sin(r) &\text{if }r\leq R \\ 0 &\text{if }r>R \end{cases} $$ ...
3
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3answers
1k views

Method of image charges for a point charge and a non-grounded conducting plane

I know how to solve Laplace's equation for a point charge in front of a grounded conducting infinite plane. But I want to know what happens (both physics and math) when the infinite conducting plane ...
3
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0answers
274 views

Question on the Derivation of Lorentz Invariance of Electric Charge

On Zwiebach's "A First Course in String Theory" textbook, there is a problem 8.2 that derives the invariance of electric charge given a few assumptions: 1. Conservation of Maxwell 4-current $j = (c\...
3
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1answer
88 views

Does charge injection from electrodes increases the total charge in a (semi)conductive channel?

When a (semi)conductor is connected to a voltage bias, a charge is injected by the electrodes. When steady state is reached (constant current flow), does the total charge of the (semi)conductor differ ...
3
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1answer
379 views

Opacity/transparency of conductive meshes to charged particles (electrons/ions)

When using a conductive (metal) mesh, effectively a metallic woven fabric, in vacuum applications as a "grid" for charged particle optics, how does one calculate (or at least estimate) the opacity or ...
3
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0answers
247 views

Free charge movement in an electric field - including bremsstrahlung

Let us imagine a free, negatively charged object that is in rest and placed in an elecric field of a point positive charge. The positive charge has a huge mass and cannot move, so we consider only the ...
2
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1answer
60 views

Why is the $W$ boson (and none other elementary boson) the only with EM charge?

I have read this question: Working out the charge of a W Boson The role of W bosons in the weak nuclear force and beta decay The W, Z, together with the photon comprise the four gauge bosons of ...
2
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0answers
38 views

Conserved charges generate transformations

Focussing on classical mechanics of a point particle, WLOG since it captures the relevant information for field theory and generalises to the quantum case, how do we show -- in general -- that ...
2
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2answers
178 views

Common potential in Capacitors

If two isolated charged capacitors (of different capacitance) are connected in parallel to each other they acquire a common potential. But suppose if i connect positive plate of one capacitor to ...
2
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0answers
78 views

BRST Charge in QED

The pure gauge QED Lagrangian density, including the ghost fields, is \begin{align*} \mathcal{L}=-\frac{1}{4}F^{\mu\nu}F_{\mu\nu}-\frac{1}{2\xi}(\partial^\mu A_\mu)^2+\partial^\mu\overline{c}\...
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0answers
93 views

Reason for repulsion of like charges

Like charges repel and unlike attract. Like magnetic poles repel and unlike attract. Since electricity and magnetism are fundamentally linked , is this attraction/repulsion due to the magnetic fields ...
2
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0answers
38 views

Integrand discontinuity of surface integral of electric field of dielectrics

I am reading an article here on dielectrics Equation $(4.10)$ is: $$\Phi(\mathbf{r})=\dfrac{1}{4\pi \epsilon_0}\int_{V} \dfrac{d^3r'}{|\mathbf{r}-\mathbf{r'}|} [\rho (\mathbf{r'})\ -\nabla'.\mathbf{...
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0answers
17 views

Dependence of electrostatic force on the surrounding medium

Two unlike point charges held at a fixed distance from each other. The force between them is measured. Then a brass rod is placed exactly in the midpoint of the line joining the 2 charges. Will the ...
2
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3answers
139 views

Basic question about electric shock

When we are negatively charged, and we touch a doorknob for example, why does the shock happen (i.e. the flow of charge)? I understand that the electrons want to flow to positive charges, and I know ...
2
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2answers
183 views

Could there be elementary particles with electric charge $> 2e$?

There are many quantum field theories, which extend the Standard Model and have new particles. For example, X boson of Georgi-Glashow model has charge $4e/3$ and some Higgs models involve a Higgs ...
2
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1answer
110 views

Light reflection from a charged surface

Will we see differences (in intensity or spectrum) of visible light reflection from surface of positively versus negatively charged metal plate (or any non-conducting materials)? Are there data about ...
2
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0answers
138 views

Proof that true passive linear memristors don't exist

This is a sequel to the following (now irrelevent) question: My attempt to implement linear memristor Assume the "conceptual symmetry" of the fundamental passive circuit elements holds: Then let's ...
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0answers
121 views

Does Noether's theorem show that electric charge (and other charges) are not fundamental? (LAYMEN)

Just to clarify, I am just a laymen so go easy on me. I was looking into where electric charge comes from, and apparently it comes from U(1) symmetry. But what does that mean? Does it mean that ...
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0answers
68 views

Does the gravitational Doppler effect affect charge?

I know that the charge of objects large enough to have distinct gravity is for the most part irrelevant, but large bodies do have (at a given instant) a fixed charge, which, granted, might be hard to ...
2
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0answers
45 views

What is the optimum altitude for tapping atmospheric charge?

The atmosphere appears to have a large potential difference (voltage) in relation to ground. The obvious example is the thunder where this voltage becomes large enough to break the insulator - air. Of ...
2
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1answer
121 views

Spherical capacitors and their discharge rates?

Imagine that you have 2 small metal spheres (about 2 cm diameter), which are set x mm's apart from each other, with only air in between. You start to charge the spheres, one positively and one ...
2
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0answers
143 views

For a charged black hole, does the charge appear to lie on the event horizon?

In considering a charged (Reissner–Nordström) black hole, I was trying to figure out if the charge acts as though it is at the singularity or rather behaves as though it is a surface charge density on ...
2
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1answer
71 views

what is difference between region around a charge and region out of it?

Basically I want to know what makes a region around a charge particle so affective that another charge will have energy when brought in this region or it will experience a force when enters into this ...
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0answers
31 views

What happens to the air inside a dry leyden jar?

Or between two similarly charged plates? If I negatively charge two plates and push them against each other until I can feel the repulsion (I don't actually have the workbench to do this) do the air ...
2
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1answer
84 views

Do 2 conductors (1 grounded via resistor) reach equipotential, before surplus electrons drain to earth?

Case I: a negative conductor makes contact with a neutral conductor. Negative donates some electrons to neutral, until there is 0 potential difference. Then they both are slightly negative. This ...
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0answers
140 views

Will it be easier to separate a low or high density plasma into negative electrons and positive ions

I know separating plasmas into positive ions and negative particles requires energy. Now, I was wondering whether it would be easy to separate a low or high density plasma. The first thing I thought ...
2
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0answers
279 views

On two contradictory statements about the bare electron charge from two different books

Page 83 of Bruce Schumm’s book Deep Down Things: The Breathtaking Beauty of Particle Physics says that the bare charge $ e_{0} $ of an electron is infinite. However, Page 348 of Robert Klauber’s book ...
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0answers
73 views

does an accelerated charge would be slower relative to an neutral particle due to radiating and lose energy ? both in free fall

this part from this article https://en.wikipedia.org/wiki/Paradox_of_a_charge_in_a_gravitational_field "Putting together these two basic facts of general relativity and electrodynamics, we seem to ...
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2answers
110 views

Two balls are attached with a very long and thin conducting wire to two conducting plates. How does the capacitor react in this situation?

The question is as follows (taken from a previous exam): Two balls (conductors w/ Radius $R_1$ for left ball ball, $R_2$ for right) are attached with a very long and thin conducting wire to two ...
2
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2answers
352 views

Different charges of plates of parallel plate capacitor

Suppose the plates of a parallel plate capacitor have charges +2Q and -Q initially. Then if they are connected with a battery of emf V what will be the charge distribution on the plates of capacitor? ...
2
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3answers
492 views

Capacitor and Pith Ball experiment

Suppose I first charge a capacitor so that one plate is positively charged and another negatively. Now I remove the charging source and ground only one of the terminals say negative terminal, will ...
2
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0answers
285 views

Weizsäcker–Williams approximation

I'm having some trouble understanding the Weizsäcker-Williams approximation What I think it is is the following: I have a charged particle at high speed, close to the speed of light, at this speed ...
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0answers
239 views

Is the elementary charge really a constant of nature? - Accuracy of QED

There are a couple of natural constants; examples are Planck's constant or the Speed of light in vacuum. The elementary Charge is the coupling factor to all Kind of electromagnetic interactions; this ...
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0answers
161 views

Why does electrolysis require a base electrolyte instead of an acid electrolyte?

I am in the process of using electrolysis to remove rust from some old tools. This is the process where you submerge the rusted item in a bath along with a sacrificial piece of metal. You connect a ...
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0answers
306 views

Simplify QCD Lagrangian

How we can derive the electric charge of the field theory for each field? For example lets say that we have the u-quarks (3-colors) and electron that we know that has charge -e) free Lagrangian $$\...
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0answers
308 views

Electric field in a “concave” conductor

I am aware that the electrons are distributed across charged conductor surface so that the areas with smaller radius of curvature have more charge per surface area. But what happens when the ...
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0answers
490 views

Physical Consequence of Global Charge Conservation versus Local Charge Conservation?

Gauge invariance of the electromagnetic field implies local charge conservation. If the gauge is no longer invariant, then the electromagnetic field must no longer conserve charge locally. Is it ...
2
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1answer
211 views

Lorentz force in superposition of two magnetic fields

When an electron with charge $q$ travels with velocity $v$ perpendicular to a magnetic field generated between two permanent magnets with field strength $B$ and no electric field, it experiences a ...
2
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1answer
71 views

If strings of matter are of the same substance how can matter carry differing charges?

Considering that a string is a loop of energy composed of the same underlying material how is it possible for it to be either positively or negatively charged? For that matter, how is it possible for ...
2
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2answers
2k views

Charge flow between a sphere (inside) a spherical shell irrespective of the charge of the shell

A small sphere of radius $r_1$ and charge $q_1$ is enclosed by a spherical shell of radius $r_2$ and charge $q_2$. If $q_1$ is non-zero and the two spheres are connected by a wire, then, charges will ...
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0answers
51 views

System of $N$ conductors: Coeficients of Potential derivation

First of all, I have read this question and didn't found an answer. I think the notation I will use (the one my professor used) is the same used in the Reitz/Milford. Unfortunately, my Reitz version ...
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0answers
46 views
+50

Komar Charge Derivation from Killing Current

We can define a divergence-less current from any Killing vector field $\xi^a$ by $$ J^a[\xi] = \xi_b R^{a b}$$ I would like to show that \begin{equation}\star J = \mathrm{d}\star\mathrm{d} \xi.\...

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