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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Explain the electric dipole moment vector

For a pure dipole situated at the origin, I don't understand why the dipole moment vector is $$ \vec{p} = p\cos \theta \hat{r} - p\sin \theta \hat{\phi} $$ Since the vector does not have any $r$ in ...
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201 views

What is the energy of interaction between two infinite charged wires?

This is related to my previous question. I assume that the two wires have the same charge density with the same sign ($\lambda_1 = \lambda_2 = \lambda$) If I want to take the same approach, the ...
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1answer
644 views

What is the energy of interaction between a point charge and an infinite cylinder?

I don't remember enough from my electromagnetism course and I can't find any simple, full example on this subject. I know, that I can consider the cylinder as a wire with the same charge density ...
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1k views

Electric Potential of a Charged Sphere

Problem Consider a sphere with radius $R$, and with a charge distribution $\rho(r)=\rho_0r$. Using Poisson's equation, calculate the electric potential inside and outside the sphere. Solution I don't ...
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1answer
402 views

Will I recieve a shock if I charged a capacitor then i touch the 2 poles in same time?

What happens if I charged a capacitor then i touch the 2 poles in same time?
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1answer
145 views

electrostatic potential, analytic properties

An electrostatic potential associated with some delocalized charge $\int \rho(\mathbf{r}) d{\mathbf{r}}$ is given by: $$v_H(\mathbf{r}) = \int ...
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1answer
899 views

Calculating the electric relative permittivity of fluid or medium?

I'm unsure of how to calculate the permittivity of a fluid. Permittivity differs from one fluid to another: $$\varepsilon=\varepsilon_r\varepsilon_0$$ Since it is an electrical property combined ...
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1answer
79 views

Can we transfer the charge on a plate of a capacitor elsewhere?

I know it is hard , but can we transfer the charge on a capacitor plate elsewhere?
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78 views

Charge of an electrolytic capacitors

I can't understand the electrolytic capacitors, when a capacitor has a capacitance of 100 microfarads, does that mean that when it is charged with 100 volts will the charge of the plate be 0.01 ...
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1answer
253 views

How does one come up with the Coulomb's law?

My teacher mentioned that field line density = no. of lines / area and the total area of a sphere is $4\pi r^2$ and so an electric force is inversely proportional to $r^2$. Actually, why can the total ...
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1answer
450 views

Can high charges (like $1\times 10^{-3}$ coulomb) be acheived?

How can we charge a metal electrode with large charges ? When i saw a video about measuring a charge using a visiostat on a balloon , the charge was 0.6 nano-coulomb. Is the charge of 1 coulomb ...
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1k views

Electrostatic Dust Removal

I have been recently reading a paper on dust removal and I have a few basic questions regarding it. First off, I am citing this paper - "Dust removal system with static electricity" Basically, an ...
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233 views

How do I find the force on the charged sphere due to a dipole sitting inside?

I have a dipole sitting inside a charged sphere i.e. at the centre of the sphere. As far as I can see the force on the Dipole is zero because the external electric field on the dipole at $r=0$ is $0$. ...
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235 views

Potential for charge distribution, finiteness

Consider a potential for charge distribution: $$v_H(\mathbf{r}) ~=~ \int \frac{\rho(\mathbf{r'})}{|\mathbf{r}-\mathbf{r'}|}d\mathbf{r'}$$ where $\rho(\mathbf{r'})$ is the charge density. This ...
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1answer
1k views

Formula for electric permittivity

What is the correct formula for electric permittivity?
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1answer
757 views

Gauss Law for Electric Fields

What is the integral form for the Gauss Law for Electric Fields? or ?
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2answers
3k views

Electric field and electric potential of a point charge in 2D and 1D

in 3D, electric field of a piont charge is inversely proportional to the square of distance while the potential is inversely proportional to distance. We can derive it from Coulomb's law. however, I ...
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2answers
6k views

How does rubbing cause the transfer of electrons from one object to the other? [duplicate]

I have just learnt about electrostatics. Why would there be a transfer of electrons? Is it because of the difference of the materials (i.e. triboelectric series)? So in the case of two different ...
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1answer
4k views

The formula of the force exerted on an electric dipole by non-uniform electric field

When an electric dipole of moment $\mathbf{P}$ is located in a non-uniform electric field $\mathbf{E}$, there is an net force exerted on it. However, the formula of the force in some books is read ...
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4answers
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Are the Maxwell's equations enough to derive the law of Coulomb?

Are the 8 Maxwell's equations enough to derive the formula for the electromagnetic field created by a stationary point charge, which is the same as the law of Coulomb? If I am not mistaken, due to ...
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3answers
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Why is electric field zero inside a hollow metal sphere ?

The figure below shows a hollow metal sphere with a positive point charge $Q$ sitting outside it. What is the electric field at the center of sphere ? The answer is zero (look at here at the beginning ...
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0answers
60 views

outward pressure in an confined electron gas

Suppose i have some electrons stored in a empty shell container with a negative ion layer in the inner surface so the electrons keep bouncing inside without being able to leave the inner cavity. I ...
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2answers
1k views

Find the quantity of charge - given potential function

A potential function is given by $V(r)=\frac{Ae^{-\lambda r}}{r}$ Find charge density and hence charge. I first took the gradient of potential to get $\vec{E}(r)=\frac{Ae^{-\lambda ...
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1answer
924 views

Simple quadrupole moment

I have a very simple problem: There is a charge $-q$ at $(0, 0, d)$ and $(0, 0, -d)$ as well a charge $2q$ at $(0, 0, 0)$. I have to calculate the quadrupole moment using spherical coordinates. I use ...
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electric potential at center of uniform electric field

it is said that the electric potential at the center of uniform electric field is zero. my question is that why is it zero? electric potential is the work done per unit charge. $V = W/q$ and this ...
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Computing a “best-fit” of discrete points from a multipole expansion, i.e. invert the multipole moments

Take a field $\phi(\bf{x})$ created from a charge distribution contained within a radius $R$. The multipole expansion in spherical harmonics $Y_{\ell,m}$ outside of $R$ is approximated by: $$ ...
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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 ...
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321 views

Will the plates of a parallel plates capacitor keep its charge after being charged then seperated from the non- conductor?

If i had 3 plates 2 metals and 1 glass .I put them together to form a basic parallel plates capacitor. After charging it and approaching it to an electroscope nothing happened that's because ...
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2answers
361 views

Effect of charges near a parallel plate capacitor

If I charge a parallel plate capacitor and I insert a charged body near one of the plates will there be any interactions like attraction or repulsion? What if I disconnect the battery?
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2answers
934 views

Are electrons on a conductor, in electrostatic equilibrium, stationary?

Electrostatics basically means dealing with time independent electric fields (which was produced by stationary charges) Now consider a neutral conductor. We know that putting a net negative charge on ...
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1answer
6k views

Direction of Potential Gradient & Electric field

Potential gradient is the negative of the electric field. Does the negative (here) means that its direction is opposite to electric field? If it does mean this, How is the direction of the potential ...
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4answers
836 views

Capacitance of two almost-touching hemispheres

This capacitor is composed of two half spherical shelled conductors both with radius $r$. There is a very small space between the two parts seeing to that no charge will exchange between them. So ...
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2answers
2k views

Why is water not used as a dielectric in the condenser?

The dielectric constant of water is very high. Then why is it not used as a dielectric in the condenser?
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3answers
605 views

Electrostatic notion of voltage as it applies to circuits

I have a question that's been bothering me about electric fields, voltage, and circuit analysis. Initially, I came to understand voltage as it was taught in the context of electrostatics - through ...
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1answer
111 views

Static electric charge

When some materials are chafed one to another, they obtain opposite electric charges. Does it mean that if these materials will then be connected to the ground, the direct currents of opposite ...
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1answer
296 views

EM force, blocking force carrier photons in a static electric field

I am doing some personal research in this specific area and wanted to ask something related to photons and EM force. are involved. Here is a thought experiment that doesn't add up to observed results, ...
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5answers
16k views

Electric potential vs potential difference

What is the difference between electric potential and potential difference? In our course book, they are given as separate topics but their definition is given the same.
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1answer
2k views

Is the electric field at the edge of a uniformly charged disk infinite?

Consider a disk with a radius $R$ (I'll use $R=1$ at various points here) that has a constant surface charge density $\sigma$. Unlike the similar problem of the field in the vicinity of a infinitely ...
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6answers
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Paradox with Gauss' law when space is uniformly charged everywhere

Consider that space is uniformly charged everywhere, i.e., filled with a uniform charge distribution, $\rho$, everywhere. By symmetry, the electric field is zero everywhere. (If I take any point in ...
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3answers
5k views

What are the applications of Gauss's law in technology? [closed]

Freshmen physics textbooks use Gauss's law plus symmetry to calculate the electric field. I was wondering if this method of finding the electric field using a symmetry is used in real applications in ...
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2answers
161 views

The Ultimate Hand Dryer

I have come across many hand dryers that attempt to dry your hands really fast after you wash them. Here are two of them: XLERATOR http://www.exceldryer.com/ Dyson Airblade ...
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1answer
632 views

How will water affect the electric field?

How will 2 charged bodies act when the separation medium between them is water ?
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158 views

A crazy problem

Easy Consider the following figure Each red point is a particle of a known mass that carries charge Q/2 and connected to a the box by a thread of known length. This problem can be solved easily to ...
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1answer
979 views

Calculating dust attraction to a charged surface

Even though dust particles are neutral, they tend to be attracted to a charged surface. I am guessing this is due to charge induction. Is there a way I can compute the attraction? how will it vary ...
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3answers
515 views

Where does the energy for repulsion in charges come from?

If I bring together 2 objects with the same charge, they repel. But even after the repulsion has taken place, there is no loss of charge in the objects. Where does the energy come from then?
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2answers
391 views

Shape of electric charges on sphere in equilibrium state

When electric charges of equal magnitude and sign are released on a regular sphere (and assume that they stick to the surface of the sphere, but they are free to move along its surface), what is the ...
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2answers
238 views

Energy in electric field

I'm having some trouble understanding a homework question and would appreciate some help. The question is as follows: Jenny charges a capacitor with the help of a battery. She then removes the ...
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3answers
903 views

Field due to current in a wire

Suppose a current flows in a straight cylindrical wire so that an electric field $\textbf{E}$ is maintained in the wire. Will there be an electric field just outside the wire..?
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3answers
567 views

Change in attraction of charged bodies

If I insert a piece of glass between two objects carrying different charges, would they still attract? If they attract, does the piece of glass affect the force of attraction and is there any formula ...
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2answers
289 views

Will the positive ions in an aqueous solution be attracted to a charged body ?

If I had a negatively charged body , say an electret , and i put it in a container of NaCl solution . Will the positive ions of sodium be attracted to it ? and why? If no, why do the positive ions ...