# Tagged Questions

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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### Series expansion of potential due to a dipole displaced from the origin

I learn that we can expand the electric potential in an infinite series of $\rho$ and $\cos(n \phi)$ when solving the Laplace equation in polar coordinates. The problem I want to consider is the ...
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### Where to place a charge to establish net force of 0? [closed]

A charge, Q2 = -15.00x10^-6 C, is 10.00 cm to the right of charge Q1 = 18.00x10^-6 C. Where can a third charge be placed, along the line connecting Q1 and Q2, such that it experiences no net force (...
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### How do two metal balls of radius $r$ kept at a large distance form a capacitor? [closed]

So this is something really new to me. I have learnt of plate capacitors, cylindrical capacitors, single spherical capacitors, etc. but that to, of finite distance between them. Also please explain if ...
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### distribution of electric charges

In electricity courses, in the lesson on static fields, at some point all teachers say "let's consider a large rectangular metal plate where the density of charges is uniform", and then they proceed ...
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### metal die charged, where do the charges go?

I'm puzzled by this question: I have a metal die (a regular cube, completely filled with homogeneous iron for instance); I charge it with some µCoulombs. Where do the charges go? Can the faces of the ...
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### Atoms, Gravity and Electrostatic Charge [closed]

How close do 2 atoms of any type the have can be together before gravity with an electrostatic charge that repulses?
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### Electric Field at a point some distance above a uniformly charged cylinder

In this problem I am trying to solve, I am trying to find the electric field at a point directly above a uniformly charged cylinder. The cylinder is oriented so that the two round face are parallel ...
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### Why is the susceptibility $\chi(t)$ real?

So my question is quite simple I suppose, and perhaps trivial. It is known that the frequency domain susceptbility $\chi(\omega)$ is complex, and that the two parts can be related with the Kramers-...
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### Relation between dipole moment and polarisaton

In the Landau's book "Electrodynamics of Continuous Media" he derives the relation between the polarisation $\vec P$ and the dipole moment $\vec p$. Starting with the definition of the dipole moment: ...
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### How and why do electric fields occur when we put a voltage difference between two point?

When we put a voltage differences between two points on a certain sample, I would like to know how and why the electric field occurs. In addition, I would like to know in what shape does the electric ...
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### Understanding of dipole moment and its vector property

I have a trouble understanding the electric dipole moment. The electric dipole moment formula is $${\bf p}= \int {\bf r}' \rho({\bf r}')d\tau '$$ I'm interested in the coordinate, the origin of which ...
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### Earnshaw's Theorem and Plum Pudding

I'm trying to understand what Thompson's motivation for his Plum-pudding model was. He chose the nucleus to be a sphere of uniform charge because it was mathematically nice, and chose the charge to be ...
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### Charging by induction

When we charge an conductor by induction and grounding, we first bring a negative charge to the conductor. As a result the mobile electrons of the conductor get repelled and stay far from the negative ...
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### electric field inside a conducting body [closed]

From Gauss' Law, we know that the electric field inside a solid conducting sphere varies linearly with the distance from the centre. But we also know that electric field inside a conductor is zero. ...
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### What does the tangent line to a general curved electric field line denote?

Just want to see the tangent line which indicates the line of electric force. What is tangent line?
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### Question about using Gauss' Law with a surface at infinity

While doing homework, I came across a situation where I tried to make this argument: For a finite distribution of charges, I know that the electric field drops off to zero at infinity. So therefore, ...
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### Electrostatics problems

In image method we use image charge to calculate field and potential at any point and we replace induced charge by image charge.But why dont we directly calculate field and potential for induced ...
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### Electric field's area [closed]

How much area an electric field surrounds? since we're just able to draw the electric lines of force we sometimes think that the field is though 3d but surrounds a finite area. But is it measurable or ...
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### Does Gauss's law not hold when there are charges outside of the Gaussian surface?

For example, if I have a gaussian surface and a negative charge somewhere outside that gaussian surface, there's going to be a non-zero electric flux. However, According to gauss's law, electric ...
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### Electric flux density between the 2 plates of a capacitor

I am reading a solved exercise about a parallel plate capacitor in which states that the electric flux density between the 2 plates is: $$D=p_{s}$$ where $p_{s}$ is the surface current density of ...
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### Can polarization occur if both charges are neutral?

If I keep neutral conductive pieces of some metal close to a neutral conductive sheet, what will happen? Will any of them get polarized or nothing will happen. My guess is nothing will happen as for ...
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### What does the density of points (tail point of the vectors) represent in the geometrical representation of a vector field? [closed]

While trying to understand the divergence of a vector through the geometrical representation of the vector field, I found that pictures can be misleading. Even a vectors field which looks to be ...
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### Poisson's equation inside a sphere with linear charge distribution

Consider the Poisson equation \begin{equation*} \nabla^2\Phi = -4\pi \rho \end{equation*} inside a sphere of radius $b$. The charge density $\rho(x)$ corresponds to an evenly distributed charge $Q$ ...
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### Charge on Earth [closed]

We know that the Earth is neutral. But what will happen if the Earth becomes negatively charged or positively charged somehow?
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### Physics Static Electricity [duplicate]

If a person has plastic soles, and are playing on Artificial grass and then the person touches metal goal post, the person will get a static shock.. Why?
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### Electric field on the surface of conductor? [duplicate]

I know that field inside the conductor is zero but what about the field on the surface of conductor? And is the surface of conductor equipotential?And please explain why?
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### What will be the effect on coulomb force if any conductor is placed between the electric charges?

I know that if any insulator or dielectric is placed between the electric charges then coulomb force decreases by factor known as dielectric constant.So, what will the effect when any conductor is ...
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### What does the Dirac delta function physically do while deriving Gauss Law form Coulomb's law?

While doing this derivation, the the source coordinates are mentioned as "$s$" and the coordinate of the point at which field is to be calculated is mentioned as "$r$". Kindly follow this Wikipedia ...
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### Why aren't +/- test leads connected to battery terminals attracted to each other?

Similar to static electricity, why wouldn't the negative charges accumulate on the wire connected to the negative terminal of a battery be attracted to the positive wire (lead) when their ends are ...
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### Electric Field “at” the surface of a conductor

It has been pointed out to me that the Electric field exactly on the surface of the conductor is conventionally taken to be $E=\frac{\sigma}{2\epsilon_0}$; does this come from taking the midpoint of ...
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### Capacitance of two non parallel plates with two dielectric materials

There is one answered question about the two non parallel plate capacitance here. However, it only has one dielectric material. I am looking for a formulae of the same configuration, but with 2 ...
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### Will charges attract or repel?

If the universe consist of only two particles namely electron and proton, and if they are separated away by huge distance, they will still attract each other. Can we prove it without using Coulomb's ...
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### Force from a large conducting plate [closed]

How can I find the distance to a test-charge, hoovering below a conducting plate? Newtons laws applies.  According to this information, I conclude that the force is equal zero. It is not moving....
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### Gauss Law Not Working Inside Cavity

When I apply gauss law inside a cavity within uniformly charged solid sphere then I get that $$\oint E.dA =Q _{enclosed}/{\epsilon_{0}}$$ Which should imply that $E=0$ since enclosed charge is 0. ...
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### Static electricity: Why did this happen?

The other day I experienced a discharge of static electricity. It was unusually strong, so strong that it almost hurt. I would like to hear your answers to how such a strong static charge could have ...
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### Solved Gauss' Law for $\vec{E}$ without boundary conditions?

Why can I solve for the electric field of a point charge Q at the origin without boundary conditions? $\nabla\cdot\vec{E}=\rho/\varepsilon_0 = \delta(\vec{r})/\varepsilon_0$ is a 1st order ...