Electrostatics is concerned with the field and potential of stationary electrical charges and electric charge distributions. Problems are this type are almost exclusively concerned with mathematics of geometries using the inverse-square law.

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2answers
547 views

How does one show using QED that same/opposite electric charges repel/attract each other, respectively?

Why do same charges repel each other and opposite charges attract each other (please explain the phenomenon using real laws of nature (QED) not with the approximation model)?
0
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1answer
975 views

Potential energy of the dipole-dipole interaction for two parallel dipole moments

I am looking for an equation that gives me the potential energy of the interaction between two parallel dipoles.
0
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1answer
112 views

Electric dipole, error in calculation

Currently I am calculating the dipole moment of a metal sphere in a uniform electric field $E_0$ in z-direction. From here I know that the charge density look at page 15 is given by $ 3 \epsilon_0 ...
1
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0answers
69 views

Electric field screening for arbitrarily formed charge

if I have a not necessarily homogenous electric field of a charge distribution in an electrolyte and i want to find out what the electric field at some position in the electrolyte is. is there any ...
1
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1answer
174 views

What happens if we give a single electron charge to a hollow metal sphere?

I found this related question: What happens to 5 electrons on a sphere? But this question describes the case when there can only be 5 electrons on that sphere at all times. The answer linked to the ...
0
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2answers
78 views

potential energy of a dipole?

The very popular from of potential energy of the dipole is $-P.E$. But in the derivation of it, we have negelected the potential energy of the pair of charges constituting the dipole. will this not ...
0
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1answer
429 views

Dielectric with polar molecules

Suppose a dielectric slab contains polar molecules (which are not further polarisable). When placed in an electric field, (for simplicity, an uniform field), align themselves according to the field. ...
0
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0answers
199 views

Electric field of uniformly charged spherical cap?

I was wondering what the electric field of a uniformly charged spherical cap is? Thereby I am referring to a spherical shell that was sliced into two pieces and we are only looking at one part of it. ...
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0answers
23 views

exterior electric field on a capacitor

Has it been observed that charged high capacitance capacitors do generate a strong positive electrostatic charge on their exterior insulating surfaces? Has it been observed that charged high ...
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2answers
2k views

Electric field at the centre of a charged disc of uniform charge density

The electric field at any point at a finite distance z from the centre of a charged disc of uniform charge density along the axis of the disc is given by the equation: According to this equation, at ...
2
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1answer
358 views

Two electron beams exert different forces on each other depending on frame of reference?

I am sure there is a simple explanation for my confusion, but I am a little puzzled: We are dealing with two parallel electron cannons that each produces a straight beam of electrons. They are placed ...
1
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1answer
120 views

Dielectric modification of electrostatic equations?

I have learnt that in cases of electrostatic fields inside a dielectric of any source charge, the field is reduced by a factor of K( if K, the dielectric "constant", is taken everywhere to be same). ...
0
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1answer
173 views

Electrons drift velocity and capacitors

My friend said this to me and just want to make sure this is right " when we connect the a battery to a LED and the 2 poles are connected, electrons flow from the (-) to the (+) but with very low ...
0
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1answer
131 views

One terminal of an ideal voltage source connected to earth->Massive current will flow?

Assume we have a "somewhat" ideal voltage source like a DC power supply powered by mains. Take just one terminal and form a conductive path between it and earth ground. Assuming that no conductive ...
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1answer
1k views

How to find electric scalar potential of infinite wire with Poisson/Laplace equation?

I though it will be easier then calculating the electric field and then integrating, but I am stuck. lets say we have an infinite wire, charged $\lambda$ per unit of length and its located at the ...
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2answers
369 views

Why is electric flux defined as $\Phi = E \cdot S$?

Flux, as I understand it, is the amount of substance passing through a particular surface over some time. So, from a simple perspective, considering photons that go through some virtual surface $A$ ...
3
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0answers
170 views

How to set up Schrodinger's equation for an electron (as a charge distribution) under its own electrostatic field

After reading about the hydrogen atom and understanding how Schrodinger's equation explains most part of the atomic spectrum of an hydrogen atom, and also came to know that, it explains most of the ...
1
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1answer
74 views

How can we consider charge to be continuous? [duplicate]

In electrostatics, we usually consider charge to be continuous on any body, to calculate the electric field of the body. For eg. I had proved the Shell Theorem taking an infinitesimal charge of $dq$ ...
3
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1answer
232 views

Coulomb potential

It is known that the Coulomb potential can be obtained by Fourier transform of the propagator from E&M. Is this because one of Maxwell's equations have the form $\nabla \cdot \mathbf{E}=\rho$?
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2answers
855 views

Is Newton's universal gravitational constant the inverse of permittivity of mass in vacuum?

Is it possible to consider Newton's universal gravitational constant, $G$, as inverse of vacuum permittivity of mass? $$\epsilon_m=\frac {1}{4\pi G}$$ if so, then vacuum permeability of mass will ...
-2
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1answer
127 views

Source of potential energy in a capacitor being pulled apart

When the plate spacing is large the capacitor system is storing more energy than when it is small. If one manually changes the spacing, where does the additional energy "come from" as the plate ...
3
votes
1answer
190 views

what is the electric field intensity inside a charged metallic shell if there is a point charge inside the shell?

What I know so far: - Charges (electrons) inside a conductor will repel (Coulomb's law). - The charges will experience repulsion which results in maximum separation distances between the charges. - ...
2
votes
1answer
402 views

Question regarding Drift velocity in general?

The derivation of drift velocity in case of electrons is equivalent to the case of an charged ionic gas and therefore all the arguments also apply there. Now for an ideal "ionic" gas which interacts ...
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3answers
151 views

Clarity in Electric field Definition?

The electric field at a point is defined as q/$r^2$. How does this definition take the nature of source and test charge into consideration. If I bring any positive/negative charge around the source ...
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1answer
190 views

Battery and current confusion?

How exactly does a battery produce a current in the circuit connected across its ends? I dont want to know the chemical reactions in the battery core, but just the essence of it. I believe it doesn't ...
0
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1answer
473 views

Charging by induction (and grounding)?

The very familiar phenomenon of charging by induction includes bringing a charged object near an uncharged sphere to induce a separation of charges in it and then grounding the charge (same as the ...
2
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2answers
114 views

Why doesn't an electrometer's capacitance influence the measurement of voltage?

I've read on the subject in several books, and none of them mentioned whether we can neglect electrometer's influence on the measurement of the voltage or not. Maybe my question sounds a bit stupid, ...
3
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1answer
208 views

Method of images tutorial?

I'm having an exam in Electrodynamics soon. I think I have most of it under control, but the method of images I'm not quite sure about. There is not much in my book about, so I was thinking some of ...
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4answers
107 views

Capacitors' working in a circuit

Does charge in a capacitor containing circuit stop flowing when the potential of the capacitor becomes equal to the potential of the battery??
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2answers
110 views

In electrostatics total flux linked from the closed surface enclosing the charge is equal to $Q/\varepsilon_0$. This is according to Gauss Law

In electrostatics total flux linked from the closed surface enclosing the charge is equal to $Q/\varepsilon_0$. This is according to Gauss Law. Is this the experimental value or defined value. If ...
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1answer
114 views

Dipole moment dilemmas

Dipole moment for a couple of charges, say q and -q, separated by a distance 'd' is given by 'qd' But what is for dissimilar magnitudes,say (q and 2q) or (q and -2q)? And are dipole moment defined ...
2
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3answers
384 views

Question regarding inverse relation of resistance with area of cross section

It is said that resistance is inversely proportional to area of cross section. But greater area will have greater electric flux, and greater electric flux will have greater magnetic flux, and greater ...
2
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1answer
930 views

How are excess charges distributed over non-spherical conductors?

My textbook gives the following explanation on how excess charges are spread over conductors: The excess charge on an isolated conductor moves entirely to the conductor's surface. However, ...
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2answers
219 views

What is a good read about Manning condensation? [closed]

I was assign in a course to give half an hour talk about Manning condensation. I read Wikipedia article about it as a starter, but it's only two paragraphs long and only point to the original paper ...
2
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1answer
156 views

Mathematical problem in integral arising in electrodynamics

I want to calculate the total electrostatic energy of the Cavendish Experiment (two concentric spheres of radii $R_{1,2}$ which are connected, outer one gets charged, then removed, then after removing ...
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2answers
1k views

Electric Field Lines between two non parallel plates [closed]

A potential difference is applied between two metal plates that are not parallel. Which diagram shows the electric field between the plates? A is the answer BUT WHY explanation needed !
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2answers
167 views

How charge distribution takes place when a battery is connected to a conductor?

When one terminal of a battery say of 1.5 volt connected to a short length wire, few electrons get transferred from battery terminal to the wire raising the potential of the wire also to 1.5 volt. We ...
0
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2answers
163 views

Field lines question

A friend of mine asked me this question, that is asked in an entrance examination. It shouldn't be that difficult, but I fail to find a rigorous answer for it. The figure shows three charges, that ...
4
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3answers
1k views

Conductors connected with a wire

Let's say I have two spherical conductors with different radii and different amount of positive charge on them. The spheres are far enough from each other. I connect them with a conducting wire. I'm ...
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0answers
148 views

Deflection/diffraction of static electric field

I know the fenomenon of diffraction (one slit) in case of electromagnetic waves. http://en.wikipedia.org/wiki/Diffraction What happens if there is only a static electric field? Let' see a figure: ...
3
votes
1answer
804 views

Electric field a distance $z$ above the center of a circular loop. The Hard way [closed]

Problem 2.5: Find the electric field a distance $z$ above the center of a circular loop of radius $r$ which carries a uniform line charge $\lambda$. This problem is in refereced here (with ...
2
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1answer
100 views

Behavior of the electric field on boundary surfaces

Consider this picture. Integrating over this infinitesimal box gives the following equivalencies: $$\int_{\Delta V} d^3r~{\rm div} \vec{E}(\vec{r}) = \int_{S(\Delta V)} d\vec{f} \cdot ...
4
votes
1answer
53 views

Charge in a layered ball

A ball (radius $R$) has three layers. For $0<r<a$ it is a conductor with free charge $+Q$. For $a<r<b$ it is a linear dielectric $\epsilon$ with free charge embedded in it with density ...
3
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0answers
56 views

Modeling the formation of a stellar system and matter accretion

I am trying to figure out what do I need to know to properly simulate the creation of a solar system from a particle cloud with random distribution of hydrogen atoms. Being more of a programming ...
2
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1answer
168 views

Boundary conditions for Laplace's equation

Given a grounded conducting sphere, $V=0$ and $radius = R$, centered at the origin with a pure electric dipole (dipole moment $\vec p$) situated at the origin and pointing along the positive $z$ axis, ...
0
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1answer
143 views

How can the accurate value of electric field intensity be calculated?

When we calculate electric field intensity for a point charge at any point inside electric field the field intensity is $E = F/q$ where $F$ is the force acting on charge $q$. In this case, the charge ...
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0answers
93 views

Is Gauss' law useful to determine the electric field strength of a charge distribution? [closed]

Under what conditions is useful Gauss' law to determine the electric field strength of a charge distribution? Can someone help me with this question?
5
votes
1answer
618 views

How much negative charge do I accumulate by touching the earth?

The Earth carries a negative electric charge of roughly 500 thousand Coulombs (according to different sources I've seen). If I touch the Earth I should therefore pick up some of this electric charge ...
8
votes
2answers
326 views

Hexadecapole potential using point particles?

We can get monopole $1/r$, dipole $1/r^2$, quadrupole $1/r^3$ and octupole $1/r^4$ potential falloff by placing opposite point charges at the corners of a point, line, square and cube, respectively. ...
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0answers
463 views

How the value of permitivity of free space is determined?

when electric charges are placed on the medium then force of interaction between them decreases. We say this factor permitivity of the medium. The force of interaction between the charges is max if ...