# What is Charged sphere: Definition and 122 Discussions

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1. ### 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.
2. ### Electrostatic potential energy of a non-uniformly charged sphere

Hi, I'm new here, so I don't know how to write mathematical equations, and I may not be fully aware of the rules here, so I'm sorry if I made a mistake. I know how to calculate the electrostatic potential energy of a countable number of charged particles, but I don't know how to calculate the...
3. F

### Kinetic and potential energy of a particle attracted by charged sphere

Hello, I have a particle at point A with charge ##q_A##, and an unmovable sphere of radius ##R_B## at point B with a volumic charge density ##\rho##. The distance from particle A to the centre of the sphere in B is ##r##. Both objects have opposed charges, so, the particle in A, initially at...
4. ### Why is the pressure on a charged sphere only exerted on the contact area?

The force per unit area (Pressure) on a part of the sphere is given by F = (E outside + E inside)/2 * Q = 0.5 (kQ/R^2) * (Q/ 4piR^2) = (Q^2/ 32pi^2 e0 R^4). I understand the above line. The solution then says this pressure is exerted on the contact area between the 2 spheres, as given by...
5. ### Point charges placed inside a charged sphere

I traced a spherical X-ray Gaussian (green) where the negative charges were diametrically opposite. My question is this: I can transform the entire charge of the Gaussian sphere into a point charge placed in the center. So, can I analyze only the electrical forces of the two negative charges...
6. ### How to create a uniformly charged sphere?

Can we create at least any one of the following in laboratory? How? 1. A uniformly charged spherical shell of finite thickness 2. A uniformly charged sphere 3. A radially symmetrically charged spherical shell of finite thickness 4. A radially symmetrically charged sphere
7. ### Understanding the Electric Field of a Charged Sphere

This page claims that "[t]he electric field outside the sphere is given by: ##{E} = {{kQ} \over {r^2}}##, just like a point charge". I would like to know the reason we should treat the sphere as a point charge, even if the charges are uniformly distributed throughout the surface of the...
8. ### Finding the energy of a charged sphere

In class we were taught that for spherical bodies we may use the formula below where the integral is done over the volume of the body. However, if we assume that the potential in infinity is 0, the potential inside the sphere is constant and equals KQ/R, where Q is the total charge of the...
9. ### Quadrupole term for uniformly charged sphere (where did I go wrong?)

So I got an assignment returned to me with fewer marks than I had expected. One part in particular is confusing to me. The professor is only available on Monday for a tutorial, but I'd like to see what is wrong before then. Can anyone spot why this is incorrect?
10. ### Why a charged sphere whose radius oscillates in and out won't radiate?

In chapter 10 (Radiation; just after example 2 from 'Radiation from an arbitrary source') of Introduction to Electrodynamics by G. Griffiths he asserts that a charged sphere with oscillating radius doesn't radiate because, by Gauss law, ##E## stays the same no matter where the charges are...
11. ### Energy stored in a charged sphere

Hi. When I am asked to figure out the Energy stored in a charged sphere and I use this equation: ## U = \frac {1}{2} \cdot \int \phi (r) \cdot \rho(r) dV ## what is the potential ## \phi ( r) ## stands for? I tried to use the potential inside the sphere, because out side of the sphere ## \rho...
12. ### Finding the energy density outside of an isolated charged sphere

Homework Statement A charged isolated metal sphere of diameter d has a potential V relative to V = 0 at infinity. Calculate the energy density in the electric field near the surface of the sphere. State your answer in terms of the given variables, using ε0 if necessary.Homework Equations Since...
13. ### Electric field inside/outside (uniformly charged sphere)

A sphere of radius a carries a total charge q which is uniformly distributed over the volume of the sphere. I'm trying to find the electric field distribution both inside and outside the sphere using Gauss Law. We know that on the closed gaussian surface with spherically symmetric charge...
14. ### Finite element solving of Laplace's equation doesn't converge

Homework Statement I'm trying to solve Laplace's equation numerically in 3d for a charged sphere in a big box. I'm using Comsol, which solves using the finite elements method. I used neumann BC on the surface of the sphere, and flux=0 BC on the box in which I have the sphere. The result does...
15. ### Spin of a charged sphere in a non-uniform magnetic field

Homework Statement Consider a solid spinning sphere of negative charge in a non-uniform magnetic field: http://d2vlcm61l7u1fs.cloudfront.net/media%2F2f8%2F2f840122-3d7f-4af3-98a7-efa9b2e7d26a%2FphpBOhfaK.png (the rotation illustrated at the top is supposed to be counter-clockwise). What...
16. ### Why a pulsating charged sphere does not emit radiation?

Hi All, Consider an elastic sphere which is homogeneously charged and suferring an harmonic inflation and deflation. Is it correct to explain the theoretical result that it does not emmit radiation, even though all of its charge elements are accelerating, as a systematic effect of destructive...
17. ### Simple Electric field question -- Charged sphere

Homework Statement A sphere with a charge of -3.5 x 10^-9 C and a radius of 1.0x10^-2 m is located at the origin of a coordinate system. What is the electric field 1.75 x 10^-2 m away from the center of the sphere along the positive y axis? Homework Equations e = kQ/r^2 The Attempt at a...
18. P

### Charged sphere and charged conducting shell

Homework Statement A + q = 5 pC charge is uniformly distributed on a non-conducting sphere of radius a= 5 cm , which is placed in the center of a spherical conducting shell of inner radius b = 10 cm and outer radius c = 12 cm. The outer conducting shell is charged with a -q charge. Determine...
19. R

### Electric Field of a Charged Sphere?

Homework Statement A sphere of radius R has total charge Q. The volume charge density (C/m^3) within the sphere is ρ = ρ_0 (1 - r/R). This charge density decreases linearly from ρ_0 at the center to zero at the edge of sphere. a. Show that ρ_0 = 3Q/πR^3. b. Show that the electric field inside...
20. ### A neutral conducting sphere and an insulating sphere....

Homework Statement Homework Equations None The Attempt at a Solution My thinking was that the positively charged sphere would repel the electrons to the far side of the neutral sphere, creating a repulsive force between the two spheres until they touch and the charge is shared. Since the...
21. ### Proton trajectory grazing a charged sphere

Homework Statement Homework Equations potential energy = -kQq/r potenial = kQ/rThe Attempt at a Solution i am not quite sure how does l play a part in this experiment since it is far away l is insignificant and the only initial energy is kinetic energy and final is kinetic and electric...
22. ### What is the Electric Field inside this charged sphere?

Homework Statement Let me just put this here: http://i.imgur.com/dgcWAC3.png . Homework Equations E_flux=EA=(q_encl)/(permittivity) Area=4pir^2 The Attempt at a Solution Whenever I manipulate the above equations, I get a term of the form R/r, which implies, R being 5 cm, and r being the...
23. ### Calculating Total Charge on Non-Uniformly Charged Sphere

Homework Statement A sphere of radius ##a## is non-uniformly charged on its surface with a charge whose surface density is ##ρ_s(φ)=ρ_{so}(cosφ)^2## where ##φ## is the angle measures from the z axis, (0≤φ≤π) and ##ρ_{s0}## is a constant. Determine the expression for the total charge distributed...
24. ### Electric Field in a cavity of a charged sphere

NOTE: Other threads suggest solving it with Gauss' Law. I'd like to see an approach through direct integration, no full followthrough necessary.. 1. Homework Statement Consider a sphere with a uniform distribution of charge ρ (ro). Inside the sphere is a cavity (spherical). Calculate the...
25. ### Mass of charged sphere suspended between charged plates

Homework Statement A small sphere with charge 2.4 micro coulombs is suspended from a thread between 2 charged plates. The plates have a voltage of 62 and the distance between the plates is 3.1 cm. The sphere hangs at 18 degrees to the vertical. Homework Equations E = V/r FE = Eq Fnetx = FE -...
26. ### Charged sphere and neutral rod

I'm totally confused what the question is asking. I do not know how to start... please help A charged sphere with 1×108 units of negative charge is brought near a neutral metal rod. The half of the rod closer to the sphere has a surplus charge of 2×10^4 units. What is the magnitude of the...
27. ### Why V=max inside a charged sphere?

Inside a charged sphere, the electric field strength is zero because there are electrostatic forces from all directions. I can't understand why electric potential inside the charged sphere is maximum ?
28. ### Field inside a charged sphere

What is the direction of field inside a charged non-conducting sphere? Using gauss law, I can find the magnitude of electric field inside the shell by assuming a spherical Gaussian surface. But how can I find its direction? Also, if electric field exists inside a charged sphere, wouldn't the...
29. ### Potential due to a uniformly charged sphere

http://www.phys.uri.edu/gerhard/PHY204/tsl93.pdf To find electrical potential at r<R I want to know why should we subtract ##V##=-##\int_∞^R\frac{kQ}{r^2}\,dr##-##\int_R^r(0)\,dr##=##\frac{kQ}{R}## I don't know why are we subtracting these two?
30. ### Electric field due to a charged sphere

Another problem that yet I haven't managed to solve, finding the electric field due to a charged sphere of radius R using integration Homework Equations Continuous charged distribution $$|\vec E| = \frac{1}{4\pi\epsilon_0}\displaystyle \int\frac{\rho (r') dV}{r'^2}$$ The Attempt at a Solution...
31. ### + charged sphere and - charged sphere touch and separate

Homework Statement A small metal sphere X is charged by losing 500 electrons. An identical metal sphere Y is charged by gaining 1000 electrons. The two spheres are first put in contact with each other and then separated. If -e is the charge on an electron, what is the charge on each sphere...
32. ### Electric Potential Energy Inside a Charged Sphere

Homework Statement A point charge q<0 lies just outside a uniformly and positively (non-conducting) charged ball. Assume the charge can pass through the ball freely. Describe the motion of the charge. Homework Equations Coulomb's force law, energy equation. The Attempt at a Solution Obviously...
33. ### Potential of a Charged Spherical Shell

Homework Statement A hollow spherical conductor, carrying a net charge +Q = 47 pC, has inner radius r1 = 5.9 cm and outer radius r2 = 11.9 cm. At the center of the sphere is a point charge +Q/2. a. Find the potential at r = 18.0 cm. b. Find the potential at r = 10.0 cm. c. Find the potential...
34. ### Potential of a Charged Conducting Sphere

Homework Statement A conducting sphere with radius R is charged to voltage V0 (relative to a point an infinite distance from the sphere where the potential is zero). What is the surface charge density σ? Express your answer in terms of the given quantities and ϵ0. Homework Equations Electric...
35. ### Point Charge and Charged Sphere

Homework Statement A point charge q1 = -6.1 μC is located at the center of a thick conducting shell of inner radius a = 2.8 cm and outer radius b = 4.8 cm, The conducting shell has a net charge of q2 = 2.6 μC. Homework Equations E = (kQ)/r2 F = (kq1q2)/r2 The Attempt at a Solution I honestly...
36. ### Evaluating an integral for an expanding, charged sphere

Homework Statement An expanding sphere, radius ##R(t) = vt## (##t>0##, constant ##v##) carries a charge ##Q##, uniformly distributed over its volume. Evaluate the integral Q_{eff} = \int \rho(\vec{r},t_r) d\tau with respect to the center. (##t_r## is the retarded time and ##d\tau## is an...
37. ### Ansoft Maxwell guidelines -- Simulate E(r) for charged sphere

Hello, I have to compare the real solution of the electric field radiated by a sphere, having 10 cm radius, charged with 1e-012 C (perfect conductor), something like E=f(x) where x is distance from the sphere, from 0m (surface of the sphere) to 1m, with numerical solution. I tried Ansoft...
38. ### Electrostatic Self-Energy of a uniform charged sphere

Homework Statement Hello, I have to calculate the self-energy of an uniform charged electron with radius R. The distributed charge is e. Homework Equations The SE is given as: E=\frac{1}{2}\int dV \int dV' \frac {\rho(\vec r)\rho(\vec r')}{ |\vec r - \vec r'|} according to the problem sheet...
39. ### Electric field outside of charged sphere

Case 1. You have a sphere with Radius R and middle point X with the charge Q. The charge is equally distributed over the sphere. for E(X,r) = 0 for r_1 < R, E inside the sphere is 0. If r_2 > R then E ≠ 0 ; but let's say E(X,r_2) := w If you put all the charge of the sphere into X then...
40. ### Measuring polarization of a neutral object near a charged sphere

Hello, I am trying to design an experiment where I can calculate the distance at which polarization will not have a measurable effect on a neutral object, from a sphere charged by a Van Der Graaf generator. I am measuring the weight change caused by the polarization of the neutral object with...
41. ### Tightening the charged sphere

Homework Statement A metal sphere, of radius R and cut in two along a plane whose minimum distance from sphere's centre is h, is uniformly charged by a total electric charge Q. What force is necessary to hold the two parts of the sphere together? Homework Equations Elestrostatic equations...
42. ### Electric Field of a charged sphere with cylindrical gaussian surface

So the problem statement is: A conducting solid sphere (R = 0.167 m, q = 6.63·10–6 C) is shown in the figure. Using Gauss’s Law and two different Gaussian surfaces, determine the electric field (magnitude and direction) at point A, which is 0.00000100 m outside the conducting sphere. (Hint: One...
43. ### Repulsive force by itself on a charged sphere

I was wondering how could I hold a lot of charge inside, for example, a ball. I thought by wrapping it in an isolant and using a hole with a semiconductor to charge it without letting anything out. But them it also could blow apart by the repulsive force of itself. Therefore, I got curious of...
44. ### Electric Field due to Charged Sphere

Homework Statement Refer to the attached photo for the problem statement. Homework Equations Electric Field Strength = 1/(4*pi*EpsilonNaught)*q/r^2 The Attempt at a Solution So, I need to find the charge magnitude of q. Because the electric field strength is given at a point...
45. ### Voltage on a electrostatic charged sphere

I understand that voltage depends on how far the electrons are, so for a sphere it would be q*k / r. But what if a sphere with 100kv , then we put with contact to it a metal box , becoming on body, will the volt remain 100kv
46. ### Charged sphere hanging from a string-Find the charge?

Charged sphere hanging from a string--Find the charge? A small, plastic sphere of mass m = 126 g is attached to a string as shown in the figure. There is an electric field of 151 N/C directed along the + x axis. If the string makes an angle 30 degrees with the y-axis when the sphere is in...
47. ### Electric field inside a charged sphere

If we have a uniformly charged spherical shell, supposing that the shell is non-conducting, could we have any electric field inside the sphere? Why?
48. ### Electrostatics - hollow charged sphere

So we have a cross sectoin of a sphere that is charged with Q (refer to attachment). electrostatics say the electric field within a charged conductor is 0, and the electric field is perpendicular to the surface. But for a hollow charged sphere (like in the attachment), does the hollow area...
49. ### Eletric potential inside charged sphere with hole inside

Homework Statement Consider a charge density of ρ=k/r , k>0 , located between a sphere surface of r=a and another sphere surface of r=b, b>a. I'm supposed to find the electric field on all space, which I did. Now I have to find the electric potential in all space, which I also did for r>b...
50. ### Electrodynamics Potential from charged sphere. I am lost :/

~Electrodynamics~ Potential from charged sphere. I am lost :/ Homework Statement A sphere of radius R, centered at the origin, carries a charge density ρ(r,θ)=κ/r^2(R-2r)sin^2(θ). κ is constant. Find exact potential. Homework Equations 1/4∏ε∫ρ∂t/r The Attempt at a Solution Question and...