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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Electrostatics Basic Question

Why ,if we increase the charge on a conductor its potential also increases? That is, Q directly proportional to V. Why ,if an insulated conductor is given some charge it acquires a certain ...
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When to use method of images in Electrostatics?

I am a bit confused about when to use the method of images in E&M? For example, in Griffith's Electrodynamics Example 3.2, the problem reads: A point charge $q$ is situated a distance $a$ from ...
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97 views

Potential at infinity due to a point positive charge

I know it is quite basic for this site, but I am confused...is it just a convention to take it as zero, or there is some logic? I really dont think that V = kq/r r->infinity, v -> 0 is right, because ...
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102 views

Current flow through car struck by lightning

It is safe to sit under a car rather than to stand under a tree during lightning. The electric field inside the car is zero when the lightning falls on it so, after falling on car, where do the ...
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Is there a limitation on Gauss' law? [duplicate]

Recently I had a question to find the electric field at a distance $R$ from the origin, where the space is filled with charge of density $\rho$. I did this by assuming a Gaussian surface of radius ...
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684 views

Two spherical cavities hollowed out from the interior of a conducting sphere. At the center of each cavity a point charge is placed

From Griffiths: Two spherical cavities, of radii a and b, are hollowed out from the interior of a (neutral) conducting sphere of radius R. At the center of each cavity a point charge is placed – ...
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51 views

Why defects reduce electric field?

I am running a simulation with drift-diffusion equation, Poisson equation and Fourier heat equation with a metal/insulator/metal structure. In my simulation, initially electric field is at the top of ...
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1answer
157 views

Why does a conductor shield its inside from its outside, but not vice versa?

A point charge outside a hollow conducting sphere will produce no field in the hollow interior: the metal shields the interior. But a point charge inside the hollow interior will produce a field ...
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186 views

Fluctuation interaction between two uncharged spheres

TL;DR: The problem is to determine force, acting between two uncharged conducting spheres, induced by correlated fluctuations of charge densities in these spheres. I've got stucked along the way and ...
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1answer
74 views

Calculating electrostatic potential [closed]

A continuous charge distribution is spherically symmetric and has a volume charge density $$\rho(r) = \rho_oe^{−\alpha r}$$ I need to find the potential as a function of '$r$' i.e. $V(r)$. It seems ...
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124 views

Why does $E = 0$ inside conducting sphere? [duplicate]

Given this picture, I've understood that giver r>R, E = q/(4πεR^2) but I just can't get why inside the sphere, E equals 0? And the notes don't explain something. I've tried to look it up on the web ...
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Why is the electric field inside a conductor zero in equilibrium?

My textbook says the field inside a conductor must be zero in order for the system to be equilibrium and therefore there must be no excess charge inside. Their proof: 1) Place a gaussian surface ...
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1answer
42 views

What does “touching” mean in the context of charge by conduction in electrostatics?

So in our physics class today, we had a demonstration involving a charged rod and a neutral ball attached to a string (a physical pendulum). At first, when the rod was placed near the ball, the ball ...
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1answer
119 views

Where did earth's electric charge come from?

I get between .7 and 1.3 volts out of a 20 foot tree depending on the weather. I understand this is "telluric" electricity with pretty low amperage. Where is this charge coming from? The sun, right? ...
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289 views

Continuity of electric field

I was solving a problem in which i came across a radially symmetric discontinuous electric field, which puzzled me for a moment but then I figured that there must be surface charge density at the ...
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193 views

Question on conduction

I already know that a charged polyethylene plastic (done by rubbing it with paper) can be used to attract a cardboard. Now, can I 'charge' the cardboard by touching it with the plastic? Supposedly, ...
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Vector question, differentials, Electromagnetism

I was reading this demonstration of electric potential in my book: Let $q$ be a point charge at point $P$ The Electric field created at point $M$ by $q$ is : $$\vec{E}(M) = ...
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Why is Xenon favored as the propellant in electric thrusters?

Most of the articles I've read on electric thrusters mention that Xenon is generally, with some exceptions, used as the propellant (or would it be termed reaction mass?). They never mention why ...
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1answer
173 views

How is the electric potential of a localized charge distribution scaled when scaling the geometry of the problem?

I am trying to find the potential at a point on the surface of a charged polygon (rectangular). I have find a solution to the problem, but it relies on the following statement: If the potential at ...
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1answer
139 views

Gauss's law not making sense

If we have a point charge and outside of it we have a non-conducting Gaussian sphere, then Gauss's law says that the net flux should be zero. I agree that the total field lines coming in are equal to ...
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2answers
229 views

Poisson equation in 2D and 3D: geometrical reason for the difference

The Poisson equation in 3D shows a fundamental solution in 3D which decays with $\sim 1/r$, whilst in 2D it shows a much different decay $\sim -\ln r$. While in 3D not only the solution, but also its ...
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1answer
103 views

Repulsive force between same charged plates?

I understand that the attraction force between parallel plates of capacitor is the derivative of stored energy with respect to distance of the plates. But how could we find the repulsive force between ...
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2answers
70 views

Potentials with no sources

I have been reading Electrostatics from Panofsky's book. One of the exercises in his first chapter is Functions of the type $\phi = x$, or indeed $\phi = x^2 + 2 y^2 - 3z^2$ , satisfy Laplace's ...
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Electrostatics - Inserting a brass plate between two charges

The question is: if I were to insert a brass plate between two charges, what will happen to the force between the charges? Would it increase, decrease or stay the same? Does the brass plate increase ...
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4k views

Derivation of Electric Force between Parallel Plates

So the electric field between two parallel plates is given by $E = V/d.$ How do you derive this?
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35 views

Laplace equation between circles [closed]

I need to solve the simple Laplace equation $$\nabla^2f(r,\theta)=0$$ with boundary conditions: $$f(a,0)=g(\theta)$$ $$\lim_{A\rightarrow\infty}f(A,\theta)=1$$ what would be a straightforward way to ...
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530 views

What exactly is electric dipole moment & how it works?? and Why Electric Dipole Moment vector's direction is from negative charge to positive charge?

What exactly is electric dipole moment & how it works/used? (don't go into deep mathematical calculations) Please answer the question about the direction with good details. Don't just say that ...
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1answer
28 views

Potential of 2 parallel plates

How can I write down a potential of 2 parallel plates (area $A$) with charge $+Q$, $-Q$ such that V(inf)=0 and V(in) is what I would expect, $Ed = Qd/A\epsilon_0$. Do I have to write a discontinuous ...
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1answer
164 views

Does wearing jewelry increase chance of static electricity

I am the only one in my office repeatedly subject to static stock. Does wearing silver jewelry increase my chance of getting a shock?
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141 views

How to get the electric field strength of a plate as approximation of a sphere

Suppose you know that the electric field in distance $r > R$ from the center of a charged sphere with charge $Q$ and radius $R$ is given by: $$ E = \frac{1}{4\pi\epsilon_0} \frac{Q}{r^2} $$ ...
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1answer
54 views

2D room with electron-point-charges (stability)

Is there a fast way to find out stable #"point charges" & constellation for this kind of Simulation. The 2D repeating itselve in each direction till infinity, so i've a kind of symetrie here. ...
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4answers
3k views

Is an electron/proton gun possible?

In the 1944 SF story “Off the Beam” by George O. Smith, an electron gun is constructed along the length of a spaceship. In order to avoid being constrained by a net charge imbalance, it is built to ...
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3answers
684 views

How much energy is needed to create an electron?

I know how to calculate the electrostatic energy of a sphere (it has a well defined radius). But how can I calculate the electrostatic energy of an electron as it is a point particle? By electrostatic ...
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29 views

Interaction between charged particles through static electric fields [duplicate]

I generally find it pretty primitive to accept that static charges communicate with the help of static electric fields without any exchange going on between them such as electromagnetic waves. I ...
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1answer
259 views

Can an electric field align water molecules?

Water is a polar molecule, which means it has an uneven charge distribution. How much of an electric field strength would it take to align all, or most, of the molecules at room temperature?
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330 views

Need of small charge in definition of electric field?

Why do we need infinitesimally small charge in definition of electric field? Since the test charge cannot exert force on itself, F on test charge will not change whatever the value of test charge q ...
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1answer
435 views

Where can I find a database for dielectric constants in the visible range?

I am looking for a database of dielectric constants in the visible range and I could not find them by Googling, so I was wondering whether anybody here knows where I can find those parameters for some ...
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3answers
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Determine Charge With Electroscope?

You have three separate glass rods, and you know one is positive, one is negative and one is neutral. You also have an electroscope that is positively charged. How can you determine which rod is ...
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403 views

Do glass beads show any piezoelectric property?

Do glass beads show any piezoelectric property? Since glass beads is mostly made out of SiO2 which is piezoelectric, will it show any piezoelectric property. Thanks. If anything wrong with my ...
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2answers
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Electric potential inside shell

Suppose we have a hollow neutral shell and $q$ charge at $r$ from its center now we take a point a someplace other than center then will electric potential change? I don't think because electric ...
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3answers
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How can I theoretically describe the potential between two capacitors in series?

Suppose to have two capacitors in series: The voltage in the middle point will be: $$ V_X = V_1 \frac{C_1}{C_1+C_2} $$ How can this be explained? It's been asked in electronics, and explained in ...
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when we rub objects together, what determines which material will pick up electrons?

For example We know glass when rubbed by silk will become positively charged while the silk will be charged negative. What exactly makes glass appropriate for losing electrons in that experiment? (
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How can we assume that we're in electrostatics if we are talking about current?

In the textbook I am currently reading it states that to even out the flow of current throughout a circuit, the force required is of the form $f=f_s+E$ where $f_s$ is from the battery or other energy ...
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5answers
346 views

Physical interpretation of the statement $\oint E\cdot dl=0$

Can anyone provide me with a physical interpretation of $\oint E\cdot d\ell=0$ in electrostatics?
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2answers
142 views

Does zero change in magnetic flux always imply zero emf induced?

If you have a uniform B field, with a finite piece of wire inside it. Assuming the B field spans all space and the wire cannot leave the field. Are you able to create an emf by moving the wire ? I ...
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1answer
59 views

Question regarding 2 conducting spheres connected by a long fine line (electric potentional)

I'm having a bit of trouble understanding a pretty simple issue. Assuming I have 2 conducting spheres uniformly charged connected by a long fine line (as shows in the added photo) and im being asked ...
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123 views

How to prove that the electric field strength in the interlayer is radial?

This is a structure modified from a typical metal spherical capacitor: half of the interlayer is now filled with one kind of uniform, isotropic, and linear dielectric medium whose dielectric constant ...
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1answer
216 views

Charge inside a shell

There's a positive charge Q inside a neutral conducting shell. An external field is applied. I learned that there can be no effect in cavity due to external things (electrostatic shielding), so ...
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Is there such thing as an evenly-charged sphere?

Let's begin with a very typical model seen in almost every electromagnetics textbook: a solid, evenly-charged sphere. First it cannot be a conducting sphere because charge will automatically ...
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Circuit breaker Trips during thunderstorm

The circuit breaker at the electrical mains trips at home when there is a thunderstorm outside. Why does this occur?