# What is Charged: Definition and 1000 Discussions

In physics, a charged particle is a particle with an electric charge. It may be an ion, such as a molecule or atom with a surplus or deficit of electrons relative to protons. It can also be an electron or a proton, or another elementary particle, which are all believed to have the same charge (except antimatter). Another charged particle may be an atomic nucleus devoid of electrons, such as an alpha particle.
A plasma is a collection of charged particles, atomic nuclei and separated electrons, but can also be a gas containing a significant proportion of charged particles.

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1. ### I Charged box mass-energy

A charged, metallic box has an energy content higher than an uncharged box, due to the energy stored in the electric field (which is equal to the work that has to be done to bring the charges from "infinity" to the surface of the box). So, due to the mass-energy equivalence, a charge box has a...
2. ### Electron motion on axis of a charged ring

Showing the motion is simple harmonic seems routine. The 5th equation on p. 674 gives ##E=frac{1}{4\pi\epsilon_0}frac{qx}{(a^2)+(x^2)}^frac{3}{2}##, but matching expressions for ##\omega=k/m## yields only ##x=frac{ea^2}{2}##. Something in the model is escaping me. Thanks for any help offered!
3. ### I Oscillating charged particles and E.M waves

If I were to tie a friend of mine adjacent to the oscillating charge and make him oscillate in parallel to my oscillating charged particle such that to him the oscillating particle is at rest, would he observe the generation of electromagnetic waves.
4. ### C/C++ Perform RK4 between 2 Clusters in Magnetic Field

I have a simulated data of charged particles in a magnetic field. I have selected clusters, each cluster contains a set of points(x,z) and I want to perform RK4 between the first and second clusters and fill the positions in a histogram. I have selected the clusters with the initial...
5. ### Direction of movement and sign of the charged particle

From the picture, the particle experiences upwards force. But how to determine the direction of motion? I think there are two possibilities: if the particle is positive, it moves from Q to P and if it is negative it moves from P to Q. Thanks
6. ### I Kerr & Nordström Black Hole Evaporation: Q&A

When a Kerr black hole evaporates, what will the Kerr parameter do? Stay constant at initial value? Approach zero? Approach unity? Approach a target value somewhere between zero and unity? Also, Nordström black holes in practice (with matter around) would have a strong tendency to attract...
7. ### Electric Flux through a semi-spherical bowl from a charged particle

I believe this does has a couple of Calculus aspects to it but I don't really know how I'd find the surface area of inside the bowl. The answer sheet says the answer is 252 with a margin of error of +/- 1
8. ### Balance of forces for two charged spheres hanging from the ceiling

I think if we don't consider electron's/proton's mass then we can say that the amount of charge doesn't need to be equal according to Newton's 3rd Law. I mean having q on one ball and 2q on another ball , still makes the angles having the same size. Is it true ? What if we consider proton's...
9. ### Why is electric field at the center of a charged disk not zero?

The electric field strength at the center of a uniformly charged disk should be zero according to symmetry of concentric rings about the center, where each ring is contributing to the electric field at the center of the disk. For a thin ring of uniform charge distribution the formula is ##E =...
10. ### MIT OCW, 8.02, Electromagnetism: Charged Cylindrical Shell

Here is figure 2.16.6 Here is the picture I drew to set up the problem My first question is if the reasoning and integrals are correct. I used Maple to compute the three integrals. The first two result in 0, which makes sense by symmetry. Maple can't seem to solve the last integral.
11. ### Proving SHM for charged spring mass system in electric field

For part (f) Solution is I don't understand why the bit highlighted in yellow is true. Would anybody be kind enough to help.
12. ### Symmetry behind charged spring-mass system in Electric field

For this problem, If we assume that x = 0 is where the spring connects to the wall, then the rest position of the mass-spring-electric field position is x = EQ/k and the max position is x = 2EQ/k. Is there a reason for the symmetry between the rest position and max position? (The symmetry...
13. ### B Can we say that a charged balloon has a center of charge?

Doing so, we can consider the balloon to be a point charge (approximately). Can we do it in this case, when there are only electrons on its surface? Or is it stupid and we can't do it under any circumstances?
14. ### Two charged spheres hitting each other

Since the forces involved (gravity and electric force) are conservative we can use conservation of energy. The initial energy is ##E_i= k\frac{q_1q_2}{r_0}-G\frac{m^2}{r_0} ## and the final ##E_f=mv^2+k\frac{q_1q_2}{2r}-G\frac{m^2}{2r} ## so from ##E_i=E_f ## we get...
15. ### A Exploring the Electric Field of a Moving Charged Spherical Shell

The electric field inside a charged spherical shell moving inertially is, per Gauss's law, zero. If the spherical shell is accelerated, the field inside is not zero anymore, but it gains a non-null component along the direction of the acceleration, as mentioned, for example, in this paper. The...
16. ### Why Does the Electric Field Component Ex Require a Negative Sign?

hello i would like to understand to something. here is the drew now for my question: i was able to find Ey and here is my correct answer: when i try to find Ex i didnt understand something, i found the correct answer but i need to put minus before and i want to know why? here is my solution...
17. ### I Brownian motion of charged particles?

If we have charged particles having Brownian motion, would this motion be associated with (or produce) heat or electricity? Would it produce electromagnetic radiation (and if it would produce it, what type of radiation in the electromagnetic spectrum)? Could there be Brownian motion of charged...
18. ### I Question about the motion of a charged particle

Hi, I have a question about the motion of a charged particle in crossed E and B fields. if B was pointing in the Z direction and E in the y direction then the component of the motion in the Z plane = 0. The only reason for this to happen is that the electric force due to the E field depends on...
19. ### Chapter 2 Griffiths EM Problem: E-Field from a charged ring

Hi. I have solved the problem below as shown in the attached image. However I'm at a loss to figure out where I am making a mistake, and I know it is indeed a big goof up. Requesting guidance over identification and rectification of this big goof up. (Edit- I can solve this problem in the...
20. ### A radially pulsating charged sphere creates which of these effects?

I know that (a) is right, and (b) is wrong. The problem is with (c)... It seems correct to me! I can't see how this is not true. The electric charge o the sphere by itself will create an electric field, which will move the particle.
21. ### Kinetic Energy of a Charged Particle near a Charged Ring

A point charge of value q=8uC is released from rest at a point 1.5m away from the center of the axis of a ring with uniform charge density 3uC/m. The ring has a radius of 10 cm. What is the kinetic energy of this charge when it is 4.5 cm from the center of the charge ring, considering that it is...
22. ### I Radiate Single Charged Particle: Free Fall in Black Hole?

Does a single charged particle in free fall into a black hole radiate?
23. ### B Energy Conservation w/ Charged Battery Time Travel

Hi! I want to start with saying that I'm not an expert on these type of problems, but I will be gratefull for some calarifications. I've heard that there's nothing in psysics that says that time travel is impossible. I want to make a case with the time traveling battery. Could be any mass with...
24. ### Lagrangian with a charged, massive vector boson coupled to electromagnetism

I need to use hermiticity and electromagnetic gauge invariance to determine the constraints on the constants. Through hermiticity, i found that the coefficients need to be real. However, I am not sure how gauge invariance would come into the picture to give further contraints. I think the...
25. ### A A question about charged particle in a magnetic field

Suppose a molecule from our surrounding air (at ambient temperature) is being selected and is ionized. By some mechanical means, some velocity (say 100 m/s) is added to it and it has been put into a magnetic field perpendicular to its direction of motion. We all know how the molecule will behave...
26. ### Potential on the axis of a uniformly charged ring

We know that $$V_Z=\int_{\textrm{ring}} E\cdot dl$$ We therefore consider ##E=\dfrac{\lambda}{2\pi \varepsilon_0}\cdot \dfrac1r##. Then, $$V_Z=\int_{\textrm{ring}} \dfrac{\lambda}{2\pi \varepsilon_0}\cdot \dfrac1r\, dl = \dfrac{\lambda}{2\pi \varepsilon_0}\dfrac1r \int_{\textrm{ring}}dl=$$...
27. ### Gauss' Law applied to this Charged Spherical Shell with a small hole

First draw a gaussian shape outside of the sphere (a larger sphere) with radius R. The total charge from the (inner) sphere will be: $$Q = \sigma A$$ $$A = 4\pi r^2$$ $$Q = \sigma 4\pi r^2$$ Use Gauss's Law to derive electric field magnitude $$\oint_{}^{} E \cdot dA = \frac{q_e}{\epsilon_o}$$...
28. ### Find the electric field of a charged arc a distance R away

define charge at an infinitesimal length of arc $$dQ = \lambda R d \theta$$We only care about the x component of the electric field because the y components cancel due to symmetry $$dE_x = \frac{k_e dQ}{R^2} cos \theta$$ Integrate to add up the infinitesimal parts. A quarter circle means 90...
29. ### Find net velocity of charged particle in electric field (symbols only)

We know the net force on the charged particle in the uniform electric field pointing up is mg - qE. To get acceleration, divide the net force by mass to get g - qE/m Plug into kinematic equation and get velocity by itself and substitute$$\sqrt{h(2g - \frac{q \sigma}{\epsilon_o m})}$$
30. ### Experiment with an Electroscope, a Charged Rod and my hand

I know that if we bring a positively charged rod closer to the electroscope, charges of electroscope are separated and the leaves of the electroscope get away from each other. but what happens if we touch the positively charged rod with our hands and then move the hand and rod away?
31. ### Find the electric field at a point away from two charged rods

λ1 = 3 microC/m λ2= -4 microC/m __________ . __________ l----L1---l-a1-l-a2-l-----L2---l (Not to scale) L1 = length of rod 1 (1m) a1 = length of end of rod 1 to point (0.7m) L2 = length of rod 2 (1m) a2 = length of end of rod 2 to point (0.3m) k = e field constant...
32. ### A What is the charge range for two N vacancies in a defect crystal?

Hi, all I am studying the defect formation energy calculations for defect crystal. One vacancy have different charged state, for example one N vacancy range [0,+3], what the charge range for two N vacancies? From chemistry, two N vacancies should be have max charge: +6. However, most...
33. ### Magnetic field's effect on a charged particle's motion

I actually have no idea how to begin. Thanks for help 😊
34. ### Calculating Energy From Charged Particles: 0.5869 J

Generally, energy is ##U=9\times 10^{9} \times \frac{5\times 10^{-6}30\times 10^{-6}}{2+(10+20)\times 10^{-2}}=0.5869 J## <br/> After touching, they have charges ##q_1 and q_2 = 35\mu C-q_1## ##\frac{q_1}{10}=\frac{35\mu C-q_1}{20}## I was wondering where 1/10 and 1/20 coefficients come...
35. ### I Seeking the Equation of Motion for a charged mass attached to a spring

I'm surprised that this question only occurred to me recently. If a have an electrically charged mass attached to a spring and set it oscillating, the resulting production of electromagnetic waves must cause a kind of "friction", a force resisting the motion of the charged mass, so that its...
36. ### A uniformly charged rotating sphere does not radiate, why not?

The problem says I have a spherically symmetric spinning constant charge distribution of charge Q and angular momentum w; I saw two possible explanations but none of them has made me realize why it is zero, one mentions thata constant w somehow implies a constant E which would mean there is no B...
37. ### The polarization charge density ##\rho##p in a charged dialectric

Hi, I have a dialectric cube and inside the center of the cube I have a part where we have Introduced evenly electrons. I have to find the polarization charge density in the 3 regions. I know outside the cube is the vacuum, thus ##\vec{P} = 0## and inside the dialectric (non charged part)...
38. ### Potential due to a finite charged wire

Considering a reference frame with ##x=0## at the leftmost point I have for the leftmost piece of wire: ##\int_{x=0}^{x=2R}\frac{\lambda dx}{4\pi\varepsilon_0 (3R-x)}=\frac{\lambda ln(3)}{4\pi\varepsilon_0}##. The potential at O due to the semicircular piece of wire at the center is...
39. ### Self Study - Foundations of Electromagnetic Theory Problem 2-1 (two charged particles hanging on strings)

I'd like someone to check that this solution is right, and if not, give me the point of failure and not the answer. Thanks!
40. ### Potential of a charged ring in terms of Legendre polynomials

hi guys I am trying to calculate the the potential at any point P due to a charged ring with a radius = a, but my answer didn't match the one on the textbook, I tried by using $$V = \int\frac{\lambda ad\phi}{|\vec{r}-\vec{r'}|}$$ by evaluating the integral and expanding denominator in terms of...
41. ### Electric field due to a charged infinite conducting plate

As shown in figure below, the electric field E will be normal to the cylinder's cross sectional A even for distant points since the charge is distributed evenly all over the charged surface and also the surface is very large resulting in a symmetry. So the derived formula should also apply to...
42. ### A Is the Universe neutrally charged?

Are there exactly as many negative charges as positive, in the universe? If so, how can we be sure, and if not then what is the difference and why? If there is an assumption of charge neutrality at time zero, then why? Is there a rationale behind that or just an unsupported supposition?

44. ### Force between charged Ring and Rod, disproved Newtons 3rd law?

This is the initial setup of the problem: The electric field due to the ring is: $$E = \int\frac{k(dq)}{(\sqrt{R^2 + x^2})^2}\frac{x}{\sqrt{R^2 + x^2}} = \frac{kqx}{(R^2 + x^2)^{3/2}}$$ the force on the rod due to this Electric field produced by the ring is: Consider a differential element...
45. ### Engineering Calculating the flux through a certain radius (concentric charged spheres)

Question My attempt for the 1st part, when r = 1.5 m Could someone confirm my answer?
46. ### Find the maximum KE of a charged Disc

To find the initial potential energy of the system we can assume the disc to be placed inside a hollow sphere of the same radius and ##\sigma##, the potential energy inside a charged hollow shell is: $$V = \frac{\sigma(4\pi R^2)}{4\pi \epsilon_0 R} = \frac{\sigma R}{\epsilon_0}$$ the potential...
47. ### Electric field is constant around charged infinite plane. Why?

Using Gauss's Law By using a symmetry argument, we expect the magnitude of the electric field to be constant on planes parallel to the non-conducting plane. We need to choose a Gaussian surface. A straightforward one is a cylinder, ie a "Gaussian pillbox". The charge enclosed is...
48. ### B Do charged particles always have spin?

(Apologies for a basic question) Do charged particles always have spin ? Maybe a better question is, are charge and spin always associated ?
49. ### Why can a capacitor be charged by a battery (DC)?

Hello there, I'm perplexed as to why the capacitor is DC-blocking, but the battery (DC) may charge the capacitor. I'd never considered it until I recently read it in a book. I honestly have no idea what's going on. If anyone has any idea why this happens, please let me know. I've read some...
50. ### Calculate the electric field due to a charged disk (how to do the integration?)

I am interested in particular in the second integral, in the ##\hat{r}## direction. Here is my depiction of the problem: As far as I can tell, due to the symmetry of the problem, this integral should be zero. $$\int_0^R \frac{r^2}{(x^2+r^2)^{3/2}}dr\hat{r}$$ I don't believe I need to...