Electrostatics is concerned with the field and potential of stationary electrical charges and electric charge distributions. Problems are this type are almost exclusively concerned with mathematics of geometries using the inverse-square law.

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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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210 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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223 views

Effect of charges near a parallel plate capacitor

If I charged a parallel plate capacitor. And then, I insert a charged body near one of the plates. Will there be any interactions like attraction or repulsion? What if I disconnected the battery?
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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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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 ...
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534 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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1answer
573 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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370 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
100 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
193 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
6k 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
929 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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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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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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1answer
91 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
331 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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147 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
536 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
233 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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275 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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174 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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695 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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315 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
173 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 ...
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261 views

Scale invariance symmetry as a simple argument in an electrostatics problem

In the comments to this post, it was hinted that proving that the force acting on a charge at a vertical distance from a uniformly charged plane is independent of that distance can be done by ...
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2answers
891 views

How do electrons repel?

I understand the basics, protons have a positive charge, neutrons have no charge, and the electron has a negative charge. But looking at the lines of force from a proton, they flow outward and push ...
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1answer
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How is Gauss' Law (integral form) arrived at from Coulomb's Law, and how is the differential form arrived at from that?

On a similar note: when using Gauss' Law, do you even begin with Coulomb's law, or does one take it as given that flux is the surface integral of the Electric field in the direction of the normal to ...
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185 views

Task with three metal plates [closed]

There are three parallel metal plates. Two boundary plates are fixed and connected with a galvanic battery, maintained a constant potential difference $\Delta \varphi$. Middle plate was initially in ...
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1answer
337 views

Capacitance and Light Bulb And Dielectric Slab [closed]

An electric lamp having coil of negligible inductance connected in series with a capacitor and an AC source is glowing with certain brightness. How does the brightness of the lamp change on reducing ...
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Will two magnets lose magnetism if they stick to each other for infinitely long time?

Here we have two magnets and they are sticking to each other. What I've learned that could possibly explain it is one magnet holds positive charge and the other one holds negative. But when the ...
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3answers
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Why do grapes in a microwave oven produce plasma?

Some of you may know this experience (Grape + Microwave oven = Plasma video link): take a grape that you almost split in two parts, letting just a tiny piece of skin making a link between each ...
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2answers
163 views

Is it really to solve problem below by using, in the main, Gauss law?

There is an infinite cylinder surface which uniformly charged along and has a surface charge density, which can be represented as $$ \sigma = \sigma_{0}cos(\varphi ), $$ where $\varphi$ - polar angle ...
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4answers
975 views

A problem of missing energy when charging a second capacitor

A capacitor is charged. It is then connected to an identical uncharged capacitor using superconducting wires. Each capacitor has 1/2 the charge as the original, so 1/4 the energy - so we only have 1/2 ...
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1answer
229 views

difference between battery and capacitor in urdu languege [closed]

Heading List item List itementer code here Blockquote*emphasized text*
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Is there a deep reason why springs combine like capacitors?

I was solving a practice Physics GRE and there was a question about springs connected in series and parallel. I was too lazy to derive the way the spring constants add in each case. But I knew how ...
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1answer
226 views

Why do hydrogen atoms attract?

That is, why is the potential energy with the orbitals overlapping less than with the Hydrogen atoms 'independent'. Similarly, why is a noble gas configuration stabler than if an electron were to be ...
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1answer
144 views

Fields of Steady Currents Using Electrostatics

Suppose you have a uniform ring charge rotating at constant angular velocity so that you also have a uniform ring of steady current, and thus you can use the Biot-Savart Law to compute the magnetic ...
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1answer
711 views

Can two electrons never touch each other?

The Coulomb's force is given by $$ F = {k q^2 \over r^2} $$ When $ r \rightarrow 0 $, $ F \rightarrow \infty $ Does this mean two electrons never touch each other?
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1answer
260 views

What is discontinuity in Vector Fields

I am reading David J. Griffiths and have a problem understanding the concept of discontinuity for E-field. The E-field has apparently to components. (How does he decompose the vector field into the ...
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1answer
179 views

Gauss's Law in action

Need someone to tell me if I got this done correctly (a) Draw Gaussuian cylinder inside the black cylinder to find charge enclosed $Q_{en} = Q(\frac{r}{a})^2$ Apply Gauss's Law $E2\pi r \ell = ...
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1answer
94 views

What causes a spark to move along rods that are not parallel?

I took my son to a science museum where they had a gadget that many of us probably saw in movies involving a mad scientist. The gadget had two metal rods about two inches apart at the bottom. The rods ...
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323 views

Negative Mass and gravitation

Since Newtonian gravity is analogous to electrostatics shouldn't there be something called negative mass? Also, a moving charge generates electric field, but why doesn't a moving mass generate some ...
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327 views

In which cases is it better to use Gauss' law?

I could, for example calculate the electric field near a charged rod of infinite length using the classic definition of the electric field, and integrating the: $$ \overrightarrow{dE} = \frac{dq}{4 ...
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How do I integrate the Poisson equation to determine the electric potential along a particular direction (e.g., $z$)?

This question is a sequel of sorts to my earlier (resolved) question about a recent paper. In the paper, the authors performed molecular dynamics (MD) simulations of parallel-plate supercapacitors, ...
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468 views

Proof of charge existence on a grounded conductor

A question regarding the existence of charge on grounded conductors is confusing me. Could there be charge on a grounded conductor? How does this not contradict Gauss's Law? Since every conductor ...
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2answers
156 views

The appearance of volume $V$ in the Fourier series representation of a periodic cubic system

In the textbook Understanding Molecular Simulation by Frenkel and Smit (Second Edition), the authors represent a function $f(\textbf{r})$ (which depends on the coordinates of a periodic system) as a ...
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Electric potential of sphere

(a) I am a little confused about this part. The point at A to B isn't radial. The electric field is radially outward, but if I look at the integral $$\int_{a}^{b}\mathbf{E}\cdot d\mathbf{s} = ...
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1answer
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What are the units or dimensions of the Dirac delta function?

In three dimensions, the Dirac delta function $\delta^3 (\textbf{r}) = \delta(x) \delta(y) \delta(z)$ is defined by the volume integral: $$\int_{\text{all space}} \delta^3 (\textbf{r}) \, dV = ...
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985 views

When I connect two charged capacitors side by side, what will be the voltage across them?

Say, I have two charged capacitors, one 3mF and one 2mF. The voltage across them are 20V and 30V respectively. Now if I connect the two capacitors side by side as shown below, what will be the voltage ...