Electrostatics is concerned with the electrical fields and scalar potentials of stationary electrical charges and charge distributions. Use this for questions about electromagnetic situations in which currents and magnetic fields are absent, otherwise use [tag:electromagnetism] and/or ...

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How can charge be squared?

In many Wikipedia articles I have come across it refers to a Coulomb squared. What does this mean intuitively? i.e. http://en.wikipedia.org/wiki/Farad (this was the most recent place I came across ...
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In terms of work, what happens to a negatively charged particle circling around a positively charged rod?

Picture a positively charged glass rod from its end so that if you were to draw it on paper, it would appear as a circle. Now, suppose a negatively charged particle moves in a circular arc, on the ...
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2answers
4k views

Can sugar be affected by a magnetic field?

While I was making a morning coffee at work, some sugar from the spoon started to fly away, seemingly towards some foam cups. Can this be explained by magnetism?
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48 views

Two spheres (one positive, one negative) - electric field

I posted yesterday about a problem I had and I have managed to solve one of the two I think (Here is the original post: Dielectric field in a homogenous electric field ). I didn't want to edit the ...
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13 views

When two equally opposite charges placed then which type of motion will carried out b/w them? [duplicate]

I want to know that which type of motion will carried out between two equally opposite charged particles, when they placed in front of each other.
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2answers
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Inconsistency with electrostatic energy formulas

The energy of point charge configuration can be written as: $$W = \frac{1}{2}\sum_{i=1}^{n}q_{i}V(r_{i}) \, ,$$ which can take both positive and negative values. However, when we integrate the ...
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2answers
91 views

What does “charge” actually mean? [duplicate]

I know that a charged particle is defined as a particle that experiences a force in an electric field, as explained in this post: What does a subatomic charge actually mean? However, I still don't ...
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1answer
73 views

Electric field inside coaxial cable

I have a very long coaxial cable with a cylindrical core of radius $a$ that has negative charge density $\rho = -k/r$ where $r$ is the distance from the axis of the cylinder, and an outer shell of ...
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1answer
29 views

Filling a charged capacitor with dielectric material

If there is a charged capacitor (capictance $C$) connected to a battery (of EMF $V$) and the space between the plates of the capacitor is filled with a dielectric material (dielectric constant is ...
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1answer
44 views

Time dependent electric field: Mathematical expansion for local electric field

In many articles and books I see that local electric field is expanded as $$\vec E_0(\vec r(t)) = \vec E_0(\vec R_0) − (\vec a(t) \cdot \nabla) \vec E_0(\vec R_0) \cos(\Omega t) + \ldots $$ For ...
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3answers
67 views

What is the potential difference between $a$ and $b$ in this basic circuit, when the switch is open? [closed]

My professor says the potential difference between $a$ and $b$ is the difference between the voltages on the top left capacitor and the bottom right capacitor. My friend and I however both think it's ...
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1answer
29 views

Why is the energy lost due to the internal resistance always equal to $(1/2)CV^{2}$ in a simple capacitor battery circuit? [duplicate]

Suppose we have simple circuit in which a battery of EMF $E$ is connected to a capacitor of capacitance $C$. Work done by battery $W_{b}=CV\times V$ and energy stored in capacitor ...
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1answer
44 views

Force on a charged particle due to an uncharged infinite conducting plate

How can I calculate the force on a charged particle due to an uncharged infinite conducting plate? If there is a small object with positive charge placed above a metal plate, the object induces a ...
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4answers
858 views

The maximum distance for which Coulomb's law has been verified?

We know that Coulomb's law, $F_{12} = \frac{kq_1q_2}{r^2}$, was experimentally verified for small distances by Coulomb himself at the and of the XVIII century. The question is what is the maximum ...
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2answers
35 views

When two coils carrying opposing currents are placed coaxially

The current flowing through these coils increases in this case according to the book. But it does not clearly state how. This is what it says: "When brought closer induced effects should produce ...
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2answers
106 views

Is Coulomb's law valid if the electric charge is not constant in time?

If the electric charge is constant the law of Coulomb says that: $E(r) = kQ/r^2$. The question is, if $Q = Q(t)$, can I consider that: $E(r,t) = kQ(t)/r^2$? Update: It appears that the first ...
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2answers
39 views

What does it means to say an electric charged person has a higher potential voltage compared to the door?

I'm studying electric potential energy and its defined as the energy needed to move a charge inside an electric field from a point $a$ to $b$. Then, it defines electric potential energy per charge, ...
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2answers
67 views

How electrical energy is transfered trhough a wire, and what's flow of charge?

I've read these texts about misconceptions about electricity. This is my understanding: Electrons do move, mut slowly and randomly. What happens is that, in fact, they're just 'conducting' the ...
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0answers
31 views

Does chemical formula of matter influence on how would it be charged? [closed]

Suppose we rub glass ($\mathrm{SiO_{2}}$) against paper(which is made from cellulose ($\mathrm{C_6H_{10}O{5})n}$). We receive positively charged glass and negatively charged paper. Is that because of ...
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0answers
18 views

Uncharged metal rod brought near a charged electroscope. Why does divergence of the leaves decrease?

Could someone please explain the redistribution of charges (if any) in a charged conductor that is being used to induce charge on another conductor?
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2answers
42 views

Thought experiment and faraday cage

this is my first and second questions. I'll start with my assumptions and go from there to ask my questions. Please do not hesitate to correct me if any of these assumptions are wrong. Inside of a ...
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1answer
38 views

The force applied by two charges on each other when there is another charge nearby them

QUESTION 1 Let me give two simple scene of charged particles to make you understand my question. There is a fixed positive charged particle in the center. Scenerio 1 : A fixed negative charged ...
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1answer
40 views

Does an observer measure magnetic field when moving inside a static E field?

Imagine a static electric field shaped as a sinusoid created by an array of electrodes on an infinite line. Does an observer flying parallel inside this e-field measure an h-field ?
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0answers
31 views

derivation of the electic displacement D

I've been revising Maxwell equations recently and tried to prove that the electric displacement $ \mathrm{\nabla \cdot D = 0}$ in the electrostatic approximation ($\mathrm{E = - \nabla} f$). My steps ...
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1answer
34 views

Where does the net charge on a hemisphere appear to act from?

I was wondering if, like centre of mass, there is anything called "centre of charge".
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116 views

Electric Potential, Work Done by Electric Field & External Force

I did lot of searching but couldn't find any textbook nor any webpage which could clarify my doubt. Maybe my doubt is insanely stupid and I was dumb for not realizing it at the first place. The ...
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0answers
55 views

dielectric polarization

Suppose a small solid sphere made of an isotropic dielectric is introduced in the field of some given system of remote charges. Assuming that the polarization in the dielectric does not affect the ...
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0answers
39 views

How much electric charge can a copper sphere, made of N atoms, contain?

If somebody wants to charge a cooper sphere made of N atoms, what is the maximum positive charge the sphere can reach? Same question about a negative charge. Source For example if the sphere is ...
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2answers
71 views

Simple model that explain the flow of electrons in metals

I am not quite clear about how electrons (negative electric charges in general) flow through a metal. I imagine the metal as a lattice of small positive charges $+q$ that can not move and the - and + ...
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0answers
52 views

How to estimate function from PDF and covariance? [closed]

I've added a picture of what I want to compute. In the nomenclature of the picture, I want to compute a realization of y(x) given the known distributions and constants. Let's say y(x), random ...
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2answers
58 views

Divergence-free vector field on a non-simply connected domain

We know that divergence-free vector fields are themselves curls of vector fields on simply connected domains. I want to construct a counterexample in the case the domain is not simply connected. So ...
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2answers
40 views

Why can we replace a cavity inside a sphere by a negative density?

I have a sphere with radius $R$ and inside this sphere there is a smaller sphere with radius $\frac{R}{3}$. This small cavity has its center at $\frac{R}{2}$, it doesn't matter in which direction. If ...
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1answer
32 views

Integration path with opposite direction from the unit vector

The task is to calculate the voltage between points $M$ and $N$ if the electric field vector is known to be $\vec{E}=\frac{V_0\cdot x^2}{a^3} \cdot \vec{i} + \frac{V_0 \cdot y}{a^2} \cdot \vec{j}$, ...
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2answers
75 views

Electric field and electric scalar potential of two perpendicular wires

So, I've been trying to come up with an idea that seems plausible to me for the last half week or so, but I'm stuck and I can't seem to get anywhere with this problem. The problem is as follows ...
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1answer
33 views

Two points in a charged hollow sphere with zero potential difference

Two concentric spheres (I've provided a simple sketch below) with radii $a$ and $b$ are given. The space between two spheres (colored yellow) is charged homogeneously, meaning that the charge density ...
2
votes
1answer
61 views

Is Gauss electric flux law valid in all coordinate systems?

The derivation of Gauss electric flux is as follows : $$\iint{\vec{E}}\cdot{\vec{dS}}=\iint E \, dS \cos\theta \, .$$ The projection of infinitesimal area on the surface $\vec{dS}$ on the radial ...
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2answers
158 views

Why are potential differences equal across two capacitors in parallel, but charge on each capacitor is not?

Two or more capacitors are said to be connected in parallel if each one of them is connected across the same two points. In a parallel combination of capacitors potential difference across each ...
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0answers
17 views

How to understand Steady Currents within the limits of Magnetostatics

I know that the precise mathematical statement of local charge conservation is $\nabla \cdot \vec{J}=-\frac{\partial \rho}{\partial t}$, where $\vec{J}$ is the volume current density and $\rho$ is the ...
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0answers
26 views

Electric Field from a distribution of charge

We have a thin flexible rod bearing charge $Q$ of length $L$. This is bent into a semicircle. Find an equation for the electric field in terms of $Q$, $L$, and appropriate constants at the point ...
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1answer
37 views

Image charge distribution for an infinite non conducting plane

If I have a charge +q at a distance d above an infinite non conducting plane, why should the image charge at d below the non conducting plane be +q?
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1answer
24 views

Dipole moment of a displaced charge distribution [duplicate]

This one is part b) of the problem I asked a day ago. Special thanks to MarkMitchison and sbp on the first part. I finally got it. (How can I prove that the dipole moment is zero?). Alright, back to ...
0
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0answers
52 views

Spherical Conductors in Dielectric - Potential

I have computed the electric field of the following system between the two spheres, but my calculations for the potential do not make sense. The potential should be proportional to $\frac{1}{r}$ but I ...
0
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1answer
40 views

Can the surface charge density be negative somewhere on the inner surface of a spherical conductor shell?

A positive charge $q$ is located off-centre inside a conducting spherical shell. We know that the total charge on the inner surface of the shell is $-q$. Is the surface charge density negative over ...
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2answers
41 views

Battery and charge separation

In this question : What is the difference between a battery and a charged capacitor? http://physics.stackexchange.com/q/32394 It is said that the battery does not have a charge separation on its ...
0
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1answer
23 views

Explanation to the flow of charge

I came across a really cool Cymatics video: There is one part in the video which is unclear to me. Please refer to the snapshot below taken at 05:15. I see the equipment being close to a Van de ...
2
votes
2answers
87 views

Calculating effective capacitance of a circuit [duplicate]

Please refer to the image below. The question asks: 'The effective capacitance between terminals A and B in the network shown in the adjoining figure is?' Here is my working: (C5 and C6 connected ...
0
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1answer
84 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. ...
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2answers
72 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
51 views

Potential vs Potential Difference for a line charge

How would I calculate potential for an infinite line of charge a distance 'r' away from it? What does the reference point for potential difference mean? I know delta v = Q/(2pi*epsilon0*L)*ln(r2/r1) ...
1
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2answers
60 views

Parallel Connection of Capacitor

Assume Two Capacitor filled with different dielectrics with dielectric constant $K_1$ and $K_2$ respectively in Parallel connection. Then we have same voltage $V$ on both capacitors. Therefore, ...