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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Electric field of two non conducting spherical conductors [on hold]

The force between two point charges +Q and -Q placed r distance apart is f1 and the force between two spherical conductors, each of radius R with charge +Q and -Q is f2. IF THE SEPARATION " r " IS NOT ...
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1answer
29 views

Gauss's Law for slabs [on hold]

When you have a slab with thickness $t$ and infinite in other two directions , why $E \cdot A$ (flux) is zero in z direction ( shown in figure ) Problem 57 in the picture
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4answers
52 views

Why, when and where is Gauss's law applicable?

Why is it said that Gauss's Law is mainly applicable for symmetric surfaces/bodies? Why not for asymmetric surfaces? I want a logical explanation! BTW my teacher said that Gauss's law is ...
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0answers
33 views

Why charge density is higher in the sharp edges of conductor? [duplicate]

If we have a conductor which is in electrostatic equilibrium, then the charge distribution over this surface $\sigma$ is greatest at the sharp edges of that surface. Why is this the case? It is ...
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1answer
43 views

Electric field of a plate with homogenous charge density

As an example for Gauß Law's application, one can find the calculation of an electric field of a plate with homogenous charge density in nearly every textbook: $$E = \frac{\sigma}{2\epsilon_0}$$ I do ...
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4answers
941 views

Do electrostatic fields really obey “action at a distance”?

In an electromagnetic theory class, my professor introduced the concept of "action at a distance in physics". He said that: If two charges are at some very large distance, and if any one of the ...
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2answers
33 views

Charge enclosed by a Gaussian surface inside an uniformly charged thin sphere [duplicate]

Why is the electric field due to a charge enclosed by a Gaussian surface inside an uniformly charged thin spherical shell, zero?
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0answers
11 views

Dependence of dipole moment on charge of dipole [on hold]

What is the change in the dipole momemt of dipole on reducing its charge by half.Is there any change or not because from expression it becomes half but from understanding on reducing the charges the ...
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1answer
27 views

How are charges formed in clouds during lightning?

How are charges formed in clouds that are responsible for lightning?
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2answers
29 views

electric field inside hollow conducting bodies

Let's say that there's a hollow conducting sphere placed in the presence of an external electric field and there's a + ve charge placed inside the sphere at a point other than the centre of the ...
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1answer
25 views

Force acting on a dipole placed in a non-uniform electric field

Why does the net force acts in the direction of increasing electric field when an electric dipole is placed in a non-uniform electric field?
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1answer
28 views

Electric field due to an electric dipole at a point on the equatorial line

According to [tamilnadu][1] textbook Electric field due to an electric dipole at a point on the equatorial line is given as The direction of E is along ...
1
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1answer
47 views

question about Gauss law

If I have an infinite plate with the surface charge of sigma. I know that my electric field is constant $2\pi\sigma$ (using Gauss's law). If I build the Gaussian surface above the plate the charge ...
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3answers
38 views

Electric field scalar quantiy or vector quantity

I cross referenced some website yahoo answers, wikipedia & some other websites. They were providing different answers. I know that electric field intensity is a vector quantity. But what abt ...
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0answers
24 views

Electric potential of a uniform rod at coordinate beginning [closed]

I was doing a problem in electrostatics and stumbled on an interesting potential question. The problem is stated as: Suppose there is a thin metal rod of length $2a$ placed in the origin as shown ...
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3answers
88 views

Can two charges with same sign atrract?

Can two charges with same sign (++/--) separated by some finite distance attract each other ?
2
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1answer
123 views

How do you know when you need to use distributions to represent charge densities? [closed]

I tried to solve a problem using Gauss' law in the following way. Let's assume we have a spherical shell of radius $R$ with a charge $Q$ being homogenously distributed on its surface. I am trying to ...
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2answers
69 views

Confusion in understanding the proof of Uniqueness Theorem

I am having problems in comprehending the proof of contradiction used by Purcell in his book; ...We can now assert that $W^1$ must be zero at all points in space. For if it is not, it must have a ...
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1answer
49 views

Doesn't Laplace's equation describe the local property of space?

$$\nabla^2 \phi = 0$$ is Laplace's equation used "wherever $\rho = 0$, that is in all parts of space where there is no electric charge.". However,how can Laplace's equation be used outside a conductor ...
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0answers
17 views

Conductor in electrostatic equilibrium

Consider the following capacitor: The upper conductor is charged by $Q$. There's a conductor on the middle with thickness $e$. The lower conductor is connected to the ground. All of them have area ...
0
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0answers
21 views

Variations in electric field of a light speed charged particle

From the question " Is there a travelling speed of for electric field? If yes, what is it?" I get to know electric field propagates at speed of light. What if a charged particle which creates this ...
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0answers
13 views

Giant dipole resonance

Could anyone explain in simple words what exactly is meant by GDR? What does giant imply? I have read about collective excitations and am also familiar with the multipolar form of the charge ...
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2answers
65 views

Charge between parallel plates given voltage

When you connect a parallel-plates capacitor to a voltage source, why is it assumed that the plates will have equal but opposite charge? According to the formula, the voltage only fixes the charge ...
0
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2answers
48 views

Electric potential between two infinite plates

Below is a solved exercise from Griffiths' Electrodynamics. I don't understand why it's directly assumed that the configuration is independent of $z$. Shouldn't there be a contribution from it since ...
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1answer
46 views

Why is the y-component of electric field of a uniformly-charged disk near its center the same as that of infinite sheet of charge?

This is an excerpt from Edward M. Purcell's Electricity & Magnetism: As $y$ approaches zero from the positive side, $E_y$ approaches $\dfrac{\sigma}{2\epsilon_0}$. On in the negative side of ...
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2answers
87 views

Why is energy associated with the electric field given as $U = \dfrac{\epsilon_0}{2} \int E^2 dv$?

This is an excerpt from Edward M. Purcell's Electricity & magnetism: Suppose a spherical shell of charge is compressed slightly, from an initial radius of $r_0$ to a smaller radius. This ...
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3answers
62 views

Why doesn't $\vec{E} =\dfrac{1}{4\pi\epsilon_0} \int\dfrac{\rho \hat{r}dxdydz}{r^2}$ blow up at $r=0$, when $\rho$ is finite?

Electric field at $(x,y,z)$ produced by a continuous distribution of charges is given by:$$\vec{E}(x,y,z) =\dfrac{1}{4\pi\epsilon_0} \int\dfrac{\rho(x',y',z') \hat{r} dx'dy'dz'}{r^2}$$. Now, as Edward ...
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How would a closed conductor with only 1 layer of (atoms/molecules) behave if a charge is placed inside it?

I have quite a few questions actually related to this . Is it possible to have such a situation practically? If theoretically possible, how would the system behave?
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1answer
33 views

Proving assumptions used in 'method of image charges'

While studying the method of images for an infinite grounded plate, I came upon two assumption I can't seem to find the logic for: The test charge doesn't induce a charge density on the plate which ...
0
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1answer
48 views

What does multiplying of charges means?

Today I learned Coulomb's law, and I didn't get what does this multiplication $q_1 * q_2$ gives? I want to understand this visually.
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2answers
50 views

Force on a layer of charge: How can electric field impart force on the charges which created the field?

This is an excerpt from Berkeley Physics: Electricity & Magnetism by Edward M. Purcell: The Force on layer of charge: The sphere has charge distributed over its surface with uniform ...
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0answers
13 views

Distribution of fragments in fission reactions

What decides the mass and charge distribution of fission fragments? are these factors decided at or before the saddle point? and how? Why does the valley in the distribution function become shallow on ...
1
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1answer
66 views

Can lightning actually weld fillings in your teeth?

So, I remember sometime in my childhood, someone was teaching me about lightning safety, and they explained that it was important to crouch low but keep as little contact with the ground as possible, ...
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2answers
56 views

“Rotating any system of charges causes a corresponding rotation of the electric field.”- What is the proof?

While I was reading 'symmetry' from wikipedia, then I came to this statement: ...For example, an electric field due to a wire is said to exhibit cylindrical symmetry, because the electric field ...
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2answers
211 views

What is meant by “unique direction” in most of the arguments in application of Gauss' Law?

This term is really bothering me a lot. While explaining the radial direction of electric field of a uniformly charged sphere, my book writes: Notice the use of argument of symmetry. There is no ...
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1answer
29 views

Gauss' law and external electric flux through a cube: net flux is not zero while the interior charge is 0. What have I done wrong?

Consider a cube with side length $L$ and with its sides parallel to the basis vectors $\vec{i}$, $\vec{j}$ and $\vec{k}$. The $X$ axis goes right through the center of two of its faces. The closest ...
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1answer
23 views

Capacitance of three plates

I'm sorry if this has been asked before, but here it goes. Consider three parallel plane conducting plates (they can be infinite) and suppose the middle plate has some thickness $\delta$ and the other ...
1
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1answer
58 views

Why can't charge be in a stable equilibrium in electrostatic field?

I am reading Feynman's Lectures volume_II where he discussed the impossibility of the presence of stable equilibrium in an electrostatic field. There are no points of stable equilibrium in any ...
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0answers
12 views

Validity of Poisson Boltzmann in a thin channel between charged plates

I'm trying to find the pressure between two charged infinite plates either side of a solution of ions but I'm having a little trouble justifying the use of the Poisson Boltzmann equation which is used ...
1
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1answer
32 views

What is meant by 'a perfect dipole'?

Question What is meant by a perfect (electric) dipole? Additional information I came across the term in this question Force from point charge on perfect dipole and also in a textbook (which does ...
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0answers
9 views

Corona discharge v pressure in air

Does anyone have any information on how a corona discharge between two electrodes changes as pressure is reduced from atmospheric to below 1mB? I am assuming current limited. Also, what I am looking ...
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votes
1answer
30 views

Is capacitor plate length assumed to be finite? [duplicate]

infinte length plate won't have any zero potential point (not even at infinty ) and hence we can never find out absolute potential. When we say that potential on the plate to be $V$, we can think that ...
0
votes
1answer
39 views

Why is this electric field due to one plate of a capacitor $\sigma / 2 \epsilon_0$ when the capacitor plates are finite?

We know that electric field due to an INFINTE large sheet is constant and at INFINTY the electric field is not zero. But say if I take a finite sheet of length l and width w. Then the electric field ...
0
votes
2answers
99 views

Two different electrostatic charges in rotation

It's a theoretical problem. I mean I drawn a circle and I consider this circle exist. I would like to understand how works this device composed of a circle and two charges: Two charges fixed on a ...
0
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0answers
17 views

How does one start drawing electric fields? [duplicate]

How does one start drawing electric fields.you are given two charge.now there are infinite electric field lines so how do you show greater electric field by drawing denser lines.After all there can be ...
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votes
2answers
45 views

Please give your valuable opinion in this capacitor problem! [closed]

The plates of a parallel capacitor are given charges +4Q and -2QThe capacitor is then connected across an uncharged capacitor of same capacitance C. What is the final potential difference between ...
0
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1answer
27 views

Potential at the surface of a conducting sphere near a dipole

An ideal conducting solid sphere of radius $R$ and center $O$ is brought near a dipole with a dipole moment of magnitude $p$. Let the center of the dipole be called point $C$, and let the tangent from ...
1
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1answer
90 views

Method of image charges [closed]

In an attempt to understand the Method of image charges, I'll try to calculate the total charge on grounded conducting plane - with electric dipole & point charge. Given: Point charge $Q$, ...
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0answers
33 views

Multipole expansion of Woods-Saxon potential?

When can a distribution be expanded in multipoles? What is the basic requirement? Can it be done for a potential like the Woods-Saxon form?
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1answer
52 views

Capacitance of spherical capacitor when earthed

The capacitance of a spherical capacitor is given by $$C=\frac{4\pi \varepsilon_{0}}{\left ( \frac{1}{a}-\frac{1}{b} \right )}$$ How can I find out the capacitance of the capacitor when The ...