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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Nonlocal dielectric function - what does it mean?

I'm reading this* article and in the second sentence of introduction I encountered a term I haven't heard of before. Namely: nonlocal dielectric function. What does this nonlocality mean? And how does ...
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2answers
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An IE IRODOV Electrodynamics problem

A ring (radius R) is given a negative charge -q and at the centre a positive charge +q is kept. We have to calculate the electric field on the axis of the ring at a distance X from the centre. Take ...
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520 views

Confused medical student needs explanation of the electrocardiogram

From what I understand, as the heart depolarizes it turns into a lot of electric dipoles , the resultant of which can (somehow) be measured in the extremities. But how does this actually happen? How ...
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4answers
66 views

How to calculate the work of the electrostatic forces in a parallel-plate capacitor?

The expression of the energy stored in a parallel-plate capacitor is: $$U = \frac{e_0\cdot A \cdot V^2}{2d}$$ with $e_0$ the vacuum permittivity, $A$ the surface of the capacitor, $V$ the applied ...
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2answers
202 views

Will the electrostatic force between two charges change if we place a metal plate between them?

If a thin metal plate is placed between two charges $+q$ and $+q$, will this cause a change in the electrostatic force acting on one charge due to another? What is the concept behind this? What will ...
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1answer
24 views

a point charge is kept at the centre of a metallic inducted spherical shell.then why the net induced charge on the sphere is zero?

Why the net induced charge is 0 in a inducted spherical shell when a point charge is kept in the centre of that sphere?
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2answers
60 views

Magnitude of a dipole moment [closed]

I am now learning Electromagnetism, and I am doing the practice question. However I am stuck in the following question. A uniform electric field has a dipole placed in it. If you rotate the dipole ...
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2answers
110 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 ...
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2answers
48 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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2answers
441 views

How can one explain the Kelvin Water drop experiment without assuming the container to already possess a positive charge?

Kelvin Water Dropper experiment refers to the electrostatic generator invented by Lord Kelvin, which uses falling water to generate a voltage by electrostatic induction occurring between ...
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1answer
115 views

Principle of superposition and QED

For finding a net force on a charge when it is in influence of many charges we simply do vectorical addition of all individual interaction of that charge with others. That's what is principle of ...
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1answer
47 views

Simple question regarding Gauss's electric law

I just read that electric flux=enclosed charge/permittivity. Considering the charge in an enclosed surface is always 0, what is the point in even having this equation? Or is the equation actually ...
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2answers
257 views

Numerically solving 2D poisson equation by FFT, proper units

The 2D Poisson equation is: (1)$$\frac{d^2\varphi(x,y)}{dx^2}+\frac{d^2\varphi(x,y)}{dy^2}=-\frac{\varrho(x,y)}{\epsilon_0\epsilon}$$ And in $k$-space it is in form of: (2)$$(k_x^2+k_y^2) ...
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1answer
106 views

How can electric field representation be obtained from Enge representation using Maxwell's equations?

Suppose we have a long electric capacitor. Let $L$ be its length ($z$ coordinate), $W$ its width ($y$ coordinate), and $D$ its full height (full aperture; $x$ coordinate). Let $L\gg W\gg D$. The ...
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1answer
45 views

In the case of two equally charged particles, is the electric field between them incompressible?

When approach two electrons (or two protons or ...), the electric fields do not merge and stay isolated from each other. Which I borrowed from here. Is it right to conclude that in the case of ...
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1answer
35 views

Magnetic field inside parallel plate capacitor

Inside a parallel plate capacitor, we know that the electric field due to the static charge $E= \frac{\epsilon_0 A}{d} $ Now if we want to find the magnetic field inside the parallel plate capacitor, ...
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3answers
36 views

Flux through closed surface

My class teacher says charge kept outside a closed surface will not hold any flux because number of field lines entering are same as number of field lines exiting. But when I imagine sufficiently big ...
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1answer
34 views

Electric potential of a sphere at a point on its surface

I'm struggling to figure out how to determine the infinitesimal area of the sphere given in the question. More specifically, in part (b) of the question. For part (a) it's the volume so $$V = ...
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5answers
44 views

Flux of $E$ through the shaded side

A charge $q$ sits at the back corner of a cube, as shown in Figure. What is the flux of $E$ through the shaded side? One of the solution stated that. Looking at the figure, we notice two ...
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0answers
20 views

Charging by induction and capacitors

Consider a material having high dielectric constant say A which is in the shape of a plate.Now place two metallic plates on opposite sides which do not cover the whole surface of the dielectric say ...
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1answer
16 views

dipole-dipole interaction

U= -p(vector of one dipole)*electrict field due to the second dipole does this equation give the energy of one dipole due to the electric field due to the second one, if so is the total ...
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1answer
26 views

Electrostatics - wire electric field symmetry

I was just wondering about the final part to do with the symmetry of the wire. In what circumstances would the wire not emit a field that's uniform? Would the wire have to be thick in some parts and ...
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0answers
14 views

Calculating the rate of electrostatic charge loss

Let's say we have a hollow cylinder with no top and bottom and with a charge $q$, radius $r$ and height $h$ that is made out of hard rubber whose electrical resistivity is $10^{13} \Omega /m$ at room ...
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1answer
33 views

Electric field a distance z above the midpoint of a straight line segment

In Griffiths there's an example to evaluate the Electric field a distance z above the midpoint of a straight line segment of length 2L. Which carries a uniform charge $\lambda$. In that calculation, ...
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1answer
15 views

Classic Electrostatics Image Problem Surface Charge

In the classic image problem of Electrostatics (an infinite conducting planar sheet and a point charge above the sheet), one calculates the potential and hence field in the region above the conducting ...
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1answer
96 views

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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0answers
11 views

Voltage developed along the length ofan accelerating conductor?

Does a conductor become polarized when accelerated? Starting with a conductor that is neutral and polarized. Electrons are evenly distributed within the volume and do not feel any net electric field ...
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1answer
53 views

Why do charges move at the rim of the “charged-disk” conductor in response of the field created by themselves?

Okay, one statement from Purcell's book goes like: [...]Thus, we find the potential at $P_2$: $$\phi = \frac{1}{4\pi\epsilon_0} \int_{-\pi/2}^{\pi/2} 2\sigma\cos\theta d\theta = \frac{\sigma ...
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2answers
161 views

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
117 views

Earnshaw Theorem for ionic solids

Is a single molecule of sodium chloride (say) or a cluster of molecules of NaCl unstable, although macroscopically NaCl is in fact, stable? How can I reason this based on Earnshaw's theorem?
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2answers
142 views

Does a point charge exert force on itself?

Can a point charge feel the force of its own electric field? In various texts it is always mentioned about the force on a point charge in an external electric field. I think the particle does feel ...
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1answer
108 views

Does charge of a metal charged by induction determine by which ends of the metal is grounded to?

Does charge of a metal charged by induction determine by which part of the metal is ground to? I draw a diagram to make it simple to understand: Right diagram: When ground is touched with the ...
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3answers
268 views

Electric force between charges in two different media

As far as I know, Coulomb's law of electrostatic force is applicable on two different charges situated in same medium. But if two individual charges are in different media (say one charge on a iron ...
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1answer
17 views

In magnetostatics, is there any relation between flux and current?

I have noted while trying to find analogy between electrostatics and magnetostatics, for the equation, flux = charge/epsilon, is there any corresponding equation in magnetostatics, relating magnetic ...
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4answers
95 views

Can the potential difference produced in Van De Graff generator used to generate electric current?

If this machine can build up high voltages of order of millions of volts, can we use this volt the generate current of electrons? The building up of potential difference can result in electric field. ...
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0answers
11 views

In electrostatics, what is the actual relation between flux density and flux

I know, in magnetostatics, unit of flux in webers. And unit of flux density B is webs per metre square. its clear. Now in electrostatics, unit of flux is volts metre. And unit of flux density D is ...
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0answers
15 views

Can a flowing gas create a static charge?

On the Static Electricity page of Wikipedia the claim is made that "The flowing movement of gases in pipes alone creates little, if any, static electricity" with a cited reference [ref 19] being made ...
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1answer
34 views

Breakdown field in a capacitor

Let us say that air breaks down at a field strength of $E_b$. For a capacitor to arc, does there need to be a path between the two conductors such that for every point on that path the electric field ...
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1answer
39 views

Electric field at location of a charge due to the charge itself?

Suppose a charge $Q$ is put in the space at point $(x',y',z')$. What is the electric field value at point $(x',y',z')$?
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1answer
17 views

Surface bound charge in the electric displacement

In Griffiths, the electric displacement is written with just volume charge density, and that is because, he says, 'we cannot apply gauss law precisely at the surface of a dielectric, for here volume ...
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0answers
33 views

Boundary conditions for laplace's equation rectangular conductor

Find the potential inside a rectangular conductor that is subject to the boundary conditions $$ (i)\ \phi (x = a,y,z) = \cos(\beta y)\cos(\gamma z) \\ (ii)\ \phi (x, y = b,z) = V_0\ (constant)\\ ...
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1answer
426 views

Finding Green function using eigenfunction expansion method

Given the Dirichlet boundary condition, I am to show that the functions that satisfy $$(\nabla ^2 + k_{lmn}^2) \psi_{lmn} (x,y,z) = 0$$ are given by $$\psi_{lmn} = (\frac{\pi}{2x})^{1/2} ...
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1answer
21 views

Capacitor and Pith Ball experiment

Suppose I first charge a capacitor so that one plate is positively charged and another negatively. Now I remove the charging source and ground only one of the terminals say negative terminal, will ...
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1answer
25 views

Can we charge any two bodies (insulators) by rubbing?

I am not talking about the usual glass rubbed with silk rather any two insulators found in nature. If we rub them, will they get charged? Like cotton and plastic etc.
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2answers
1k views

Meaning of boundary condition for steady current density?

Although I understand the derivation of boundary condition in case of steady electric current but I did not understand, that the electric field which is in direction of $J$ current density that is ...
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2answers
38 views

Do anodes emit virtual photons representing their positive electrostatic potential?

I understand the electrons in circuit travel down the path of least resistance, however are electrons attracted by the emission of virtual photons emitted by a source with relatively low electron ...
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1answer
33 views

Will two touching, neutral conductors in an electric field separate?

If you put two square, neutral conductors in the middle of a uniform electric field such that they are touching, will they separate? I thought yes. When they are touching, as shown in the picture, ...
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3answers
62 views

What happens to half of the energy in a circuit with a capacitor?

For a simple circuit with a battery supplying a voltage V to a capacitor, let us assume that the charge on the capacitor is Q. Now, the work done by the battery or the energy supplied is given by the ...
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1answer
26 views

Why does flux in closed surface remain constant if exterior charge is altered?

Q. Charges $q_1$ and $q_2$ lie inside and outside respectively of a closed surface $S$. Let $E$ be the field at any point on $S$ and $\Phi$ be the flux of $E$ over $S$. One of the answer is: if $q_2$ ...
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2answers
133 views

How to find the distribution of charge on two spheres connected by a conducting wire?

A solid metal sphere of radius $R$ has charge $+2Q$. A hollow spherical shell of radius $3R$, concentric with the first sphere, has net charge $-Q$. What would be the final distribution of the charge ...