Questions tagged [electrostatics]

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-fields]

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Why is the electric field negative?

I have a doubt in an exercice of a Thomson's apparatus deflecting an electron beam. The problem is: Electrons pass undeflected through the plates of Thomson's apparatus when the electric field is ...
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Black hole nucleus in hydrogen

The hydrogen atom gets the spectrum it has because you analyze the Schrodinger equation in spherical symmetry with the potential given by $V=-\frac{1}{4\pi\epsilon_0}\frac{e^2}{r}$. Yet the same ...
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Electric field inside a homogenous distribution for slightly different Coulomb's law

I am trying to show that the electric field inside a homogeneous distribution of superficial charge is of the order of magnitude of $\delta$, with: $$V(\textbf{r})=\int d^3\textbf{r'}\frac{\rho(\...
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37 views

Why does a water jet bend in a static electric field? [duplicate]

The phenomenon is shown for example in this video where a thin water jet is formed by letting water fall from a small hole punched under a plastic cup, and the jet is bent when a charged rod is moved ...
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Is the net force on atomic/molecular constituents of a solid body zero

So my question is this that suppose we consider a solid everyday object, say a spherical stone. Now, if I consider an atom or a molecule of the stone away from the center of the stone, then I can say ...
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3answers
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Why is there a 1/2 in the expression for electrostatic energy U?

The expression for electrostatic energy is $$U= \dfrac{1}{2} \times \int \rho\,\phi\, dV$$ where $\rho$ is the charge density and $\phi$ is the potential at that point in ($dV$) Let me explain what I ...
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1answer
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If electric field is conservative then line integral along closed path is zero, then why is potential not zero?

Here in the first image it is said $\displaystyle \int_a ^b E\cdot \mathrm dl\,$ is $0 $: Here in the second image it looks like $\displaystyle \int_a ^b E\cdot \mathrm dl\,$ is not $0$: If field ...
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1answer
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How does change in magnitude of a point charge reflect change in its electric field at a particular point in space with respect to time?

We know that electric charge of an object results in an electric field formed around it. We also know that varying the magnitude of a point charge does not instantly produce a change in the electric ...
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Electric field of a finite line uniformly charged

A charge $Q$ is uniformly distributed along the $z$ axis. Why because of the symmetry of the configuration is the electric field zero at z=0? I understand the electric field cancellation in a ...
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Finding Electric Field Outside Solid Sphere of Charge (Treated as Many Discs of Charge)

All of the methods on finding an electric field outside a solid sphere of charge use Gauss's Law. However, is it possible to derive the electric field by treating the solid sphere as combined ...
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Energy with dipole [closed]

What is the energy required to rotate an electrical dipole of $q=2e$ and $l=1.5$ nm by 50 degree when it is placed in a uniform electric field that has a magnitude of $45.2$ N/C?
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Mechanical energy conservation

Is the mechanical energy conserved when the speed is constant? What if we have a charge that entered an electric field due to an external force -which is making a dynamic equilibrium with the ...
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$E$-field of a uniform distribution of charge at 3D point [closed]

How can I find Electric field of a uniform distribution of charge at 3D point?
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Electron to electron interaction

I am interested to know if it would be possible to calculate the magnetic attraction between two electrons at zero space between their magnetic poles against electrostatic repulsion between them in ...
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Will momentum be conserved in case of electrostatic force?

If a charged particle approached another particle of same charge held by some external force, then by coulomb's law the particle will start electrostatic repulsion. Thus coming to a closest distance ...
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1answer
42 views

Work Done and Potential Energy in Electrostatics

This is a question from class 12 Physics NCERT Part 1: I am having so much trouble with this, I can't figure out where I'm going wrong. I solved part (a) here: (a) U= -27.2 eV (b) Here, the kinetic ...
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1answer
34 views

Tangential component of electrostatic field on a charged surface?

This is a question from class 12 Physics NCERT Part I: Show that the tangential component of electrostatic field is continuous from one side of a charged surface to another. [Hint: Use the fact ...
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Static Attachment [closed]

How could I get stretch wrap to stick to paper or toilet paper type material? I have a stretch wrap machine that shrink wraps large rolls of paper, and the current method of attaching the stretch wrap ...
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2answers
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Components of Electrostatic energy to components of electric field?

I'm trying to understand the relationship between electrostatic energy and the electric field so that I can compute electric field components from electrostatic energy components. Is it correct to ...
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1answer
47 views

What exactly happens when a charged conductor comes into contact with an electric insulator?

Let us say we have a negatively charged conducting sphere: If we put an insulator into contact with the sphere: Would the negative charges located in the contact region transfer from the surface of ...
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1answer
45 views

Why is the electric field of a conducting sheet of charge double the electric field of just a sheet of charge?

I was reading Feynman's Lecture on the Application of Gauss' Law and I came across this: Source This really confused me. What are the "other" charges he talks about? How does the additional field ...
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Charge distribution for three connected conductor spheres

In the auxiliary material of the physics textbook of Halliday, first chapter about electrostatics, there is an example that has the following statement and solution: basically there are three ...
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1answer
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About fixing the potential on the surface of a conductor

In Purcell's Electricity and Magnetism, p.116 section 3.3, the author spoke about Laplace's equation and said that the boundary conditions for the potential$\,\phi$ on the surface of the conductor may ...
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3answers
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Why don't capacitors hold charges on the outer walls of the plates? [on hold]

Suppose I have two metal plates in a vacuum and I give this system some electric charge,the charge would distribute itself according to Gauss law on both the inner and outer walls of both plates...but ...
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Force of attraction in capacitor [duplicate]

In a question, it was asked the force of attraction between the plates of a parallel plate capacitor. and it was solved as $$\frac{(1)(C)(V^2)}{2}=(F)(d)$$ $$F=\frac{(1)(C)(V^2)}{(2)(d)}$$ and I ...
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Understanding distances and unit vectors in this problem

A charge $-q$ is at $x = -a$ and a second charge $+q$ is at $x = a$ Between the charges, the contribution from each charge is in the negative direction. An expression for $${\overrightarrow{E}} = \...
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Significance of the negative sign in $V=-\int \vec E · \mathrm d\vec r$ [duplicate]

Why is there a negative sign in the relation $$V=-\int \vec E · \mathrm d\vec r$$ between the electric field and the electric potential? Is this because of some derivation in vector calculus because ...
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Why can't we have an $E$-field like this one inside a conductor?

From what I understand, there can be no $E$-field inside a conductor in an electrostatic situation, because had there been any field within it, the charges on the surface would start to move, thus ...
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1answer
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How does induction work when a body is charged (ie) not neutral?

I know that for a neutral body, if a point charge is placed next to it, induction works something like this: Consider a uniformly charged conducting body with charge Q on it. We place a positive ...
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2answers
57 views

Accurately calculating the work to move a charge? [on hold]

I'm applying a force $F_{me}$ to move the charge $q_2$ towards $q_1$. If they are both equal charges, I'm assuming a repulsive force $F_R$ opposing me. In order to get $q_2$ to the final position ...
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“Conductors having excess charge can attain static equilibrium”, is this an empirical law?

Is the redistribution of excess charge in a conductor onto its surface, thereby reaching static equilibrium (a steady state), only an empirical observation? Or, equivalently, is it guaranteed, i.e. ...
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1answer
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Doubt in the derivation of Gauss's law in dielectrics

so in the 2nd page,when the dielectric material is introduced the gauss's law becomes $$\oint _ { S } \vec { E } \cdot \vec { d S } = \frac { ( q - q _ { i } ) } { \epsilon _ { 0 } }$$.But my ...
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Does a uniformly moving charge induce electric quadrupole moment densities in surrounding space?

The electric field of a uniformly moving charge is cylindrically symmetric around an axis parallel to its velocity vector. It varies inversely to the square of the distance. The electric field of a ...
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2answers
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Regarding the $E$-field at the location of discrete point

Most textbooks define the $E$-field at the location of $q_{1}$$\\$ as: $$\textbf{E}=-\frac{q_{2}}{r_{21}^2}\hat{\textbf{r}}$$ which is finite. However, the field is also defined as the force per ...
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Regarding charge densities and the amount of charge located on a point for continuous charge distributions

Suppose we have a volume $V$ containing a charge distribution defined by $\rho (\textbf{x})$. The amount of charge $q~(P)$ located at an arbitrary point $P(x_{0},y_{0},z_{0})$ is : $$q(P)=\int_{x_{0}...
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1answer
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How can we find the charge distribution of $n$ external electrons on the surface of a conducting cube? [closed]

Suppose we take 'n' electrons and put them on the surface of a conducting cube. How can we calculate the charge distrubution and position of these electrons once the static situation has been arrived ...
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1answer
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Inconsistency regarding two charge elements on a uniformly charged disk

Let us say we have the following uniformly and positively charged thin disk: Suppose also that the total charge on the disk equas $Q$, with which we could define a constant charge density $\sigma$ ...
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1answer
84 views

Is there an experiment showing that the warping of space affects the shape of an electrostatic field? [duplicate]

General relativity assumes that space itself is warped by gravity, which is what gives rise to the shapes of the paths followed by objects subject to a gravitational field. If space itself truly ...
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1answer
51 views

Coulomb's law and the continuous charge model in an infinite charged plane [duplicate]

The $E$-field of an infinite plane with a uniform charge density $\sigma$ has a constant magnitude equaling $2\pi\sigma$. Now, this magnitude assumes a continuous charge model throughout the plane. ...
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1answer
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Force in an isolated capacitor when a dielectric slab is introduced [closed]

my question is about capacitance: a dielectric slab is inserted between the plates of an isolated capacitor. The force between the plates will remain unchanged. how? I mean the knowledge I had gained ...
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1answer
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Work done by charged particles [closed]

A proton is kept at rest. A positively charged particle is released from rest at a distance d in its field. Consider two experiments; one in which the charged particle is also a proton and in another, ...
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1answer
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Potential energy of electric dipole

While deriving the formula for potential energy of electric dipole I almost every time see that while the torque was demanding the dipole to rotate in one direction , we let the dipole to rotate in ...
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1answer
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Is there an easy way to tell whether this “Curlmeter” would rotate or not?

Let us say we have the following symmetrical apparatus: Four equal positive charges, all connected to a shaft that can rotate, the connecting rods are insulated, and so does the shaft. Now ...
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2answers
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Null electric field at infinity? How? [closed]

Suppose there are two charges (4uC each) fixed in the horizontal axis. One is in x=0 and the other in x=8m. I've obtained the electric field: $E=-k\cdot4\mu C \cdot [\frac{1}{x^2}+\frac{1}{(x-8m)^2}]...
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1answer
51 views

Infinite parallel plates have the same electric field between no matter the distance?

I saw this in a lecture about gausses law in application to infinite charged planes: How is it possible that the electric field above the top plane and below the bottom plane is always zero, given ...
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4answers
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Is charge point-like or a smear?

Coulomb gave the law for the force between two static charges while considering them to be points in space. But the differential form of Gauss' Law talks about charge densities, a thing possible only ...
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1answer
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confusion about the process of earthing

If the surface of the earth is negatively charged why do electrons move towards the earth when a negatively charged conductor is being discharged via earthing?
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1answer
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How to use the definition of volume current density?

The volume current density $ J$ is defined as $ \frac {dI}{da_{\perp}}$ where $dI$ is a small current segment flowing in the volume with cross section $da_{\perp}$ where $da_{\perp}$ is a small area ...
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2answers
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Confusion when applying Gauss's Law to a charged sphere

We have a charged sphere with charge Q and the charge is uniformly distributed with a charge density ρ. The sphere has a radius R. If we construct a Gaussian Surface with radius r, with r < R. If ...
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Electrostatic force and deformation

Can an electrostatic force cause plastic deformation of an object ? So if we two charged opposite sheets of paper and we hold with our hands the two plates will the electrostatic attraction cause ...