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 [tag:magnetic-...

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2answers
51 views

Potential Energy of Point Charges in a Square [closed]

So, an AP Prep book for the Physics 2 test has the following problem: My reasoning is as follows: The total potential energy = the sum of the PE of each of the 4 charges Which will equal 4x the PE ...
0
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1answer
52 views

Surface density charge, divergence of the electric field and gauss law

It´s known that the divergence of the electric field at a certain point is given by this formula: $$\nabla \cdot E=\dfrac{\rho (r)}{\epsilon_{0}}$$ Being $\rho (r)$ the volume charge density at that ...
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1answer
54 views

Macroscopic & Microscopic Electric Field

What are the precise mathematical definitions of the macroscopic & microscopic electric fields? For example, when I study the boundary conditions for an static electric field $\vec{E}$, the ...
0
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1answer
21 views

Since a dipole has some potential energy,it should be able to do some work !? What is it?

We say a dipole has potential energy.What work can a dipole do ?.For eg : A ball on a shelf has a PE because it has the potential to fall down and do some work on the ground if shelf wasnt there.What ...
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3answers
6k views

Potential energy of a dipole in a uniform electric field convention?

When finding the potential energy of a dipole in a uniform electric field, I was told by my lecturer that the convention is that the potential energy is 0 when the dipole moment and electric field ...
3
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1answer
43 views

Gauss Law with a hollow asymmetric surface

In this video, Walter Lewin argues that no charge will appear on the inside surface of a hollow conductor in electrostatic equilibrium. He uses a Gaussian surface contained entirely within the ...
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0answers
46 views

Electrostatics - Multipole Expansion From Taylor Series?

In electrostatics you might be given a function $$v(\vec{r})$$ satisfying Laplace's equation $$\nabla^2 v = 0$$ so that, Taylor expanding around $\vec{r} = \vec{R}$, we find $$ v(\vec{r}) = v(\...
3
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4answers
550 views

Attractive force between capacitor plates

A textbook question requires me to calculate the force of attraction between plates of a parallel-plate capacitor. The answer provided is $\frac{1}{2}QE$. I am not entirely sure how they arrived at ...
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1answer
118 views

Metal Sphere in a Uniform Electric field

An uncharged metal sphere of radius $R$ is placed in a uniform electric field $\vec{E} = E_0 \, \hat{z}$. The field will push the positive charges to the "northern" surface of the sphere, and the ...
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0answers
19 views

With the help of a given charge is it possible to obtain a charge many times greater in magnitude

Consider a spherically conducting sphere. If a charge(say positive) is placed near the sphere, then it will lead to separation of charges inside the sphere.My question is, can we create charges more ...
0
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1answer
34 views

is there any way to create electric field around two similarly charged plates?

Can an electric field exist around two similarly charged plates, like if we consider to put small paper pallets around it so that it can attract paper pallets without generating repulsion ?
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1answer
19 views

How do I account for presence of a dielectric medium while calculating potential due to a point charge?

I am not sure but I believe that the potential due to a point charge will reduce if the entire setup is kept in a dielectric medium. How do I account for it in deriving the potential?
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0answers
11 views

On rubbing two bodies together, can we predict the nature of charge on each of them? [duplicate]

Is it possible to know, without actual experimentation, which of the two bodies will get positively charged or negatively charged after being rubbed against each other?
3
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3answers
955 views

Electrostatic energy integral for point charges

The electric energy stored in a system of two point charges $Q_1$ and $Q_2$ is simply $$W = \frac{1}{4\pi\epsilon_0}\frac{Q_1Q_2}{a}$$ where $a$ is the distance between them. However, the total ...
0
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1answer
63 views

Energy stored in electric field [duplicate]

I know that energy stored in electric field / unit volume = $\frac{1}{2} \epsilon\,E^2$. so can I say that for any configuration calculating $\int \frac{1}{2} \epsilon\, E^2 \,d^3r$ over whole space -...
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1answer
23 views

Electrostatics - System of parallel plates

For a system of $n$ parallel metal plates bearing charges $q_1, q_2,\dots, q_n$, why it is so that the facing surfaces of the plates bear equal and opposite charges? How do we prove that?
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0answers
31 views

How do we calculate electric field on the axis of a disc using gauss law and the concept of solid angle?

We can easily find the electric field at the axis of the disc by considering a differential ring and then integrating it to form a disc, but I was searching for rather a bit simplified proof using ...
0
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3answers
957 views

Why does holding an electrical switch in between on and off states cause sparks?

If air is a bad conductor, then why do sparks develop when an electrical switch is held in between on and off states? Why are sparks generated when cables carrying heavy electric current are brought ...
1
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3answers
83 views

What is the maximum reach distance of electric field? [duplicate]

if i charge small object by removing electrons and put that object in the middle of huge vacuum chamber (million of light years in size) does the electric field lines of that charged object still be ...
0
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1answer
48 views

What role does the center of mass play in this situation? (electric potential)

Four masses $10\ \mathrm{g}$ each are tied together by $10\ \mathrm{cm}$ strings to make a square as shown. Two of the masses carry a charge of $2\ \mathrm{\mu C}$. The string between the two charged ...
1
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2answers
182 views

Relation between Electric field and potential

I am unable to understand from this - sign comes. Which step I have done wrong?
3
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1answer
59 views

Confusion regarding gauss law

Gauss law states that flux due to net electric field on a Gaussian surface is charge enclosed/permittivity. Lets take a spherical Gaussian surface with +q charge at centre. We can simply calculate the ...
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1answer
35 views

Inconsistency in solving energy in free space given electric potential

So we have the equation $$ W= \frac{1}{2} \int_{volume} \rho_v V\,dv$$ and then after applying a vector identity which is $$\nabla \cdot (V\vec{D})=V(\nabla\cdot \vec{D})+\vec{D}\cdot (\nabla V)$$...
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2answers
22 views

Electric charge and and cylindre

An electric charge is distributed with a uniform volume density $\rho$ in a cylindre with a radius $R$ and an infinite length. Our professor said the following: By symetry the electric field is ...
0
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0answers
16 views

Find the force that tries to rip apart a conducting shell into two halves about its equator when kept in an uniform electric field of magnitude E

The conducting spherical shell will be affected by the electric field and one can expect induced charges on the two hemispheres if visualized as cut by an equatorial plane. The induced charges ...
2
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1answer
157 views

Electric field of a finite, conducting plate

Let us assume a finite, conducting plate of dimension: $10\mathrm{m} \times 10\mathrm{m} \times 1\mathrm{m}$. I want to determine the electric field at the middle of one of the plates $10\mathrm{m} \...
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1answer
38 views

Does is make sense to speak of the value of electric field at points containing continuous charge distribution?

Before getting into the question, here are some remarks: 1)Given a single point charge, the value of electric field at the position of the charge is singular/undefined, which makes sense, since a ...
14
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4answers
19k views

Why is electric field strong at sharp edges?

I learned about the coronal discharge, and the common explanation is because the electric field is strong where radius of curvature is small. But I haven't found anything yet that explains why ...
0
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3answers
3k views

Proof that the electric field is conservative

I was told a proof that the electric field was conservative (without using $\nabla$) which used a point charge and showed the following: $$w.d.=\int_c{\vec F \cdot \mathrm{d} \vec l}=\int_c{\vec F\...
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2answers
80 views

Electric Field from a Uniformly Charged Disk

As I was reading the solution of this problem the author gave the electric field in the point P as follows: $$ \vec{E} = \sigma /(2 \epsilon ) [1-x/(x^2+R^2)^{1/2}]\ \hat \imath$$ Where: $\sigma$ ...
0
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1answer
38 views

Coaxial cable with electric flux

I had a question when I solved some examples of coaxial cables. I want to find the E and D field using $\rho_s = {Q \over {2\pi r L}}$. Here is my question: Why is the inner surface of the cylinder ...
0
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0answers
14 views

Potential energy of a shell & point system

Consider the system of a point particle with charge $q$ and a spherical shell with uniform charge $Q$ and radius $R$ whose center is a distance $r > R$ away from the point particle. I'm trying to ...
3
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1answer
58 views

Electric field at surface of a spherical shell

The shell theorem provides a well known result that for a spherical shell with uniformly distributed charge $Q$ and radius $R$, the electric field at a distance of $r$ from the center is: $$\begin{...
3
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2answers
12k views

Electric field of a negative charge

How was it discovered that the electric field of a negative charge points towards the charge itself? Is it true? (Courtesy of wikipedia)
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2answers
43 views

Relationship between work and energy in an electrostatic system

I am having problems understanding the relationship between the concepts of Work and Energy in a electrostatic system. As I know, the definition of Potential Energy is the ability to do work. In a ...
0
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2answers
83 views

If Electric field is constant in a region, does it imply potential is also constant?

I am a bit confused about these concepts- when is electric field or electric potential constant so i would appreciate if anyone could brief me about these things as well. Here i am referring to ...
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1answer
55 views

Gauss's law, electrical flux density [closed]

Q. Given a 60-μC point charge located at origin, find the total electrical flux passing through the plane z = 26 cm. I can understand what the question means, but I can't do anything. Is it using ...
5
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0answers
79 views

Mutual $E$ force due to charged coaxial rings [closed]

I found the following question in a good physics book I was solving and although this is a computer problem, I wonder if it can be done without using computers. $Q.$ Find the force of attraction ...
0
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2answers
27 views

Is Emf induced in the coil when magnetic Flux passing through it is zero? If so then what is the explanation?

I thought Emf would not be induced if the coil doesn't cut the magnetic Flux . But since the graph in my paper shows Emf is induced when magnetic Flux is zero , I got confused. I thought since the ...
2
votes
7answers
1k views

Why do two ends of a long conducting wire have the same electric potential?

I am not seeing the "big picture" here. If I have two conducting spheres separated by a long conducting wire, why would the spheres share the same electric potential? I think of the spheres as point ...
0
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0answers
28 views

When is force of interaction maximum?

A certain charge Q is divided at first into 2 parts q and (Q-q). Later on the charges are placed at a certain distance. If the force of interaction between the two charges is maximum then 1)Q/q = 4/...
0
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1answer
24 views

Distribution of charge on isolated system?

An isolated solid metallic sphere is charged with +Q. What will be the distribution of their +Q charge on the sphere ? If it is conducting then the net charge resides on surface and if not the net ...
0
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0answers
19 views

What does relative permitivity of medium mean and what does it depend on?

Does relative permitivity have someting to do with the polarization of medium , like for example how in inside the capacitor magnitude of electric field would be less due to a smaller opposing field ...
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1answer
1k views
0
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2answers
56 views

Spherical Conducting Shells, Potential

When we have a spherical conducting shell and charge on outer surface of the shell then the potential inside remains constant i.e, kQ/R (R=radius). But say the inner surface of the shell is charged ...
-1
votes
1answer
60 views

Things that must be considered when mass producing a capacitor [closed]

The question is to list four things that must be considered when a capacitor is chosen for inclusion in a circuit which is to be mass produced. Are there a specific set of four things? I've come up ...
-1
votes
1answer
44 views

Coulomb's law and electric field intensity [closed]

here is question and solution I can't understand why R_x= 4a_z please explain it detail! ;-(
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0answers
22 views

Please Can Anyone help Me to drive the equation for Electric Field Around a test Charge Around A uniform Ring. [closed]

Please can i get a mathematical relation for electric Field around a test Charge Lying in the region of influence around a uniformly Distributed Charged Ring .
1
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1answer
168 views

How to calculate the electric energy caused by eletrostatic field stored in a region, given $V$? [closed]

I have problem in apply the rules to find the energy stored in free space here is the problem Find the energy stored in free space for the region $$0.002<r<0.003m,\quad 0<\phi<\frac{\...