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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Potential in uniform fields

First in a book I found that the electric field strength $\mathrm{E}$ of a uniform electric field from a charged plate is equal to $\frac{q}{2\times \epsilon_0 \times S}$ where $q$ is the charge of ...
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Why am I getting that work it's always the same in both directions?

I'm studying electrostatic and I'm getting pretty frustrated because with the definition of work I'm getting that it's always positive and it doesn't make any sense. So here I have 2 positive ...
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Could you give boundary conditions to the gravitational potential given the density distribution?

We´re doing a project that's all about solving differential equations with separation of variables. We´re trying to find the gravitational potential given the density distribution (that has azimuthal ...
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Electric field inside a conductor placed in uniform electric field

When a conductor, with a cavity containing a charged species, is kept in uniform electric field, will any change to the external electric field result in a change in the internal electric field inside ...
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1answer
39 views

Why does the molar conductivity decrease with increasing charge density?

This is a question in a problem sheet I have been set. Is it do do with the following equation: $\Lambda=\Lambda_0-a\sqrt c$? Surely charge density is proportional to concentration so therefore molar ...
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37 views

Uniform Electric Field

I was going through the first chapter in Resnick Halliday related to electromagnetism and then I came across something called a uniform electric field. It was written that "If E is uniform (that is, ...
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Electrostatics and tv screens

My physics textbook states an activity- "Cut out thin strips of paper and lightly iron them. Take them near a TV screen or computer monitor. The strips get attracted to the screen and may cling to the ...
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Why does a field-effect transistor with wrap-around gate work at all?

In the recent years several publications have presented field-effect transistors (FETs) that are based on semiconductor nanowires with a gate electrode that is wrapped around the whole nanowire ...
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118 views

Electric potential energy and signs

I know that electric potential is negative near a negative charge and positive near a positive charge. But does this mean a small positive 'test' charge has a negative electric potential energy near a ...
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38 views

Electric Field At Centre Of Non Uniform Ring

In the above solved example why only the cos components have been taken for calculation of electric field at centre ? Why not the sine components ? BTW in case you say that the sine components ...
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52 views

Why can we ignore self energy?

I have been doing some practice questions in a text book [Electricity and Magnetism by Purcell and Morin]. So I know that the energy the potential energy of a system is the total work required to ...
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27 views

Does a negative and a positive charged body repel vs. attract a suspended negative charged ball with the same strength?

In this question I'm in trouble about my statement, that the measurement instrument does not influence the electron's electric field. It seems to me that only the repelling force between negatively ...
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Find out gradient of electric potential at ${\bf r}$ created by eletric dipole of moment ${\bf p}$ [closed]

Suposing an electric dipole of moment ${\bf p}$ located at the origin which creates an electric potential at ${\bf r}$ given by ...
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Workdone in an equipotential surface is zero?

An equipotential surface is one in which all the points are at the same electric potential. If a charge is to be moved between any two points (say from point A to point B) on an equipotential surface, ...
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Description of charged sphere with Heaviside function in cylindrical coordinates

I need to describe density of charge of uniformly charged sphere (radius R, total charge Q, position of centre (0,0,0)) with Dirac delta function and Heaviside step function. The hard part is to ...
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48 views

The Electric Quadrupole

I've read the following sentence: "Every electric circuit with two pairs of accessible terminals is called a quadrupole." I was wondering why does it happen that the multipole expansion gives us a ...
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51 views

Electric Dipole force exerted by a charged wire on a dipole

Why is force exerted by a charged wire on a dipole given as $F = P×(dE(r))/(dr)$ where P is the dipole moment? Please explain in simple words and avoid using too much technical derivations.I am a ...
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Does the electric force on a charged particle in a uniform electric field increase?

If I have a proton in a uniform field between two parallel oppositely charged plates and the proton accelerates, the electric force acting on it stays constant seeing it is a uniform field and as a ...
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1answer
35 views

Electric field in space created by intersection of spheres of charge

I am trying to calculate the electric field in space created by a body assembled by the intersection of 2 spheres. The upper sphere, its center is at $\frac{d}{2}\mathbf{\hat{z}}$ with radius $R$ and ...
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27 views

How can a cable pass signal

I am currently study electrostatics. And I don't get how can electrons pass signals in a cable, can somebody explain this to me specifically?(I am only twelve years old) Thank you very much!
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Galerkin-type weak formulation for electrokinetics

I am currently working on finite element simulations about electrokinetics. My solver (getdp) accepts directly galerkin-type weak formulation of equations. I am thus trying to write my equations in ...
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0answers
29 views

Neumann Green's function inside semi-infinite conductor [closed]

Consider a semi-infinite conductor with uniform conductivity $s$ occupying the space $z>0$. What is the Green's function with Dirichlet and Neumann boundary conditions inside the region $z>0$? ...
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3answers
62 views

Can we have negative Electrostatic potential

What does it mean to have a negative electric potential? not talking about potential difference or voltage.
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5answers
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How does insulating footwear prevent an electric shock?

The reason I have always heard to explain the reduction of electric shock when we wear insulating footwear goes as follows: When electricity passes from our body to the ground, an electric circuit ...
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How to determine whether a statically charged object is positively or negatively charged?

for example, I rub a ballon on carpet. What is an experiment I can do to tell which object is net positive charged and which is negative?
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What does grounding a plate mean happens to the charge?

In the context of image charges. Let say I have a very large grounded/earthed plate. If initially the total charge on the plate is 0 then we place a positive point charge, $Q$ just above its surface ...
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4answers
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Potential difference between point on surface and point on axis of uniformly charged cylinder

Question: Charge is uniformly distributed with charge density $ρ$ inside a very long cylinder of radius $R$. Find the potential difference between the surface and the axis of the cylinder. Express ...
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Laplacian of $1/r^2$ (context: electromagnetism and poisson equation)

We know that a point charge $q$ located at the origin $r=0$ produces a potential $\sim \frac{q}{r}$, and this is consistent with the fact that the Laplacian of $\frac{q}{r}$ is ...
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Why is there electric field OUTSIDE a battery?

Correct me if I'm wrong, but a battery's electric field is like an electric field of a capacitor consisting of two parallel plates. But we know that the electric field outside the two plates is zero. ...
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1answer
67 views

Closed surface intuition [closed]

In topology, closed surface is simply defined to be the surface that has no boundary as opposed to open surfaces. This is the layman's definition of closed surface. Example is notably a sphere. ...
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How to calculate the capacity of an electroscope out of the geometry and why is it independent on the pointer deflection?

How can one calculate the capacity of an elektroscope like the following from the geometry of the setup? How does this formula implies that the capacity does not (approximatly) depend on the ...
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3answers
161 views

Induced charge in a mobius strip

I know that when a positive charge is placed at the center of a circular ring, the "inside" of the ring will have a negative induced charge and the "outside" will have a positive induced charge. ...
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2answers
144 views

How does electromotive force (emf) influence electrostatic force in a circuit?

I am learning about emf and I am using university physics of Hugh D. Young which states that when the emf source is not part of a circuit the non-electrostatic force of the source moves charge form ...
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1answer
148 views

Charge distribution on a doughnut shaped conductor

In a spherical solid conductor the charge is always on the outer surface. Even if the sphere has a cavity, the surface of the inner cavity can not carry a charge due to Gauss's Law. What would be ...
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1answer
35 views

Question regarding Van De Graff generator Belt

I have made a VDG generator with a rubber band as the belt and a glass roller. It doesnt seem to work because I think the rubber band may be conductive. I was thinking of using other materials for ...
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1answer
95 views

What is the meaning of permittivity of free space?

We all know about the value of permittivity of free space but is this actually enough of for our knowledge? We should be taught that what actually does permittivity of free space means.
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Does the electric field inside a circuit cause a potential drop with distance?

We know that when the system reaches steady-state(current does not change with time),the electric filed inside the circuit is constant. In many textbooks and lectures,professors make a graph like this ...
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341 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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How to prove using symmetry that electrostatic force acting parallel to the line joining two charges?

The unit vector $\hat{r_{21}}$ shows that the force is parallel to the line joing the charges. It could be otherwise unless space itself has some built-in directional property. . . This can be ...
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2answers
99 views

Flux through plane surface in hemisphere [closed]

Suppose a charge is placed at the centre of a hemispherical surface of radius $R$ then what would be the electric flux passing through the planar surface opposite to the charge in the hemisphere? I ...
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2answers
39 views

Continuity of Potential of an electric field

Consider a point charge $q$ at $(0,0,0)$, the potential at $\bf{r}$ is given by $V(\bf{r})$ $= \frac{q}{4\pi\epsilon_0r}$. If you consider a path through $(0,0,0)$, you encounter a discontinuity in ...
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1answer
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Image charges and capacitors?

Consider these two situations: A (infinite) parallel plate capacitor in which one plate is held at a potential $V$ and the other is grounded. A point charge near an infinite plane and grounded ...
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1answer
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Explanation for electrostatic energy expression

My question is about the electrostatic energy $We$ expression for $n$ point charges. I just can't figure out where the factor "$\frac{1}{2}$" came from: $We=\frac{1}{2} \sum_{i=1}^{n} q_iV_i$
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Force between charges when there's a slab of dielectric between them [duplicate]

Consider the following arrangement - Blue and red are two opposite charges +q and -q separated by a distance R. A dielecric slab is placed between them. The thickness of the slab is t. What will ...
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2answers
181 views

Electrostatic Potential Energy Integral

I'm trying to calculate the total energy of a simple two charge system through the integral for electrostatic energy of a system given in Griffiths' book: $$U = \frac{\epsilon_0}{2}\int_V E^2 dV .$$ ...
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1answer
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Why may an air passenger experience an electric shock when he touches the door knob of the toilet of an aeroplane flying at a high altitude?

Why may an air passenger experience an electric shock when he touches the door knob of the toilet of an aeroplane flying at a high altitude?
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1answer
162 views

Gauss Law for a Modified Coulomb's Law

A problem out of a certain popular book on electricity and magnetism dealt with the resulting electrostatic theory if Coulomb's law was replaced with the following equation: $$ \mathbf{F} = ...
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1answer
56 views

Definition of charges

We say that a body is negatively charged when it has excess electrons otherwise say positively or uncharged. We also say that electrons are negatively charged. By the above statement, it has more ...
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Why are there dust particles on TV screens?

My professor gave us the following reason: The screen is positively charged. When dust particles fly near it, the positive charges in the screen induce a charge in the dust particle, pulling the ...
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Energy Loss during Sharing of Charge between two Capacitors

It is fairly easy to show that there is always a loss energy when two capacitors share their charge to attain the same common potential, but is it with the same ease that one can explain why it ...