# 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 ...

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### How would a closed conductor with only 1 layer of (atoms/molecules) behave if a charge is placed inside it?

I have quite a few questions actually related to this . Is it possible to have such a situation practically? If theoretically possible, how would the system behave?
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### Proving assumptions used in 'method of image charges'

While studying the method of images for an infinite grounded plate, I came upon two assumption I can't seem to find the logic for: The test charge doesn't induce a charge density on the plate which ...
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### What does multiplying of charges means?

Today I learned Coulomb's law, and I didn't get what does this multiplication $q_1 * q_2$ gives? I want to understand this visually.
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### Force on a layer of charge: How can electric field impart force on the charges which created the field?

This is an excerpt from Berkeley Physics: Electricity & Magnetism by Edward M. Purcell: The Force on layer of charge: The sphere has charge distributed over its surface with uniform ...
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### Distribution of fragments in fission reactions

What decides the mass and charge distribution of fission fragments? are these factors decided at or before the saddle point? and how? Why does the valley in the distribution function become shallow on ...
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### Can lightning actually weld fillings in your teeth?

So, I remember sometime in my childhood, someone was teaching me about lightning safety, and they explained that it was important to crouch low but keep as little contact with the ground as possible, ...
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### “Rotating any system of charges causes a corresponding rotation of the electric field.”- What is the proof?

While I was reading 'symmetry' from wikipedia, then I came to this statement: ...For example, an electric field due to a wire is said to exhibit cylindrical symmetry, because the electric field ...
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### What is meant by “unique direction” in most of the arguments in application of Gauss' Law?

This term is really bothering me a lot. While explaining the radial direction of electric field of a uniformly charged sphere, my book writes: Notice the use of argument of symmetry. There is no ...
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### Gauss' law and external electric flux through a cube: net flux is not zero while the interior charge is 0. What have I done wrong?

Consider a cube with side length $L$ and with its sides parallel to the basis vectors $\vec{i}$, $\vec{j}$ and $\vec{k}$. The $X$ axis goes right through the center of two of its faces. The closest ...
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### Capacitance of three plates

I'm sorry if this has been asked before, but here it goes. Consider three parallel plane conducting plates (they can be infinite) and suppose the middle plate has some thickness $\delta$ and the other ...
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### Why can't charge be in a stable equilibrium in electrostatic field?

I am reading Feynman's Lectures volume_II where he discussed the impossibility of the presence of stable equilibrium in an electrostatic field. There are no points of stable equilibrium in any ...
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### Validity of Poisson Boltzmann in a thin channel between charged plates

I'm trying to find the pressure between two charged infinite plates either side of a solution of ions but I'm having a little trouble justifying the use of the Poisson Boltzmann equation which is used ...
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### What is meant by 'a perfect dipole'?

Question What is meant by a perfect (electric) dipole? Additional information I came across the term in this question Force from point charge on perfect dipole and also in a textbook (which does ...
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### Corona discharge versus ambient air pressure

How does a corona discharge between two electrodes change as pressure is reduced from atmospheric to below 1mB? I am assuming a current limited source. Also, what I am looking for is a smooth ...
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### Why is this electric field due to one plate of a capacitor $\sigma / 2 \epsilon_0$ when the capacitor plates are finite?

We know that electric field due to an INFINTE large sheet is constant and at INFINTY the electric field is not zero. But say if I take a finite sheet of length l and width w. Then the electric field ...
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### 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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### How does one start drawing electric fields? [duplicate]

How does one start drawing electric fields.you are given two charge.now there are infinite electric field lines so how do you show greater electric field by drawing denser lines.After all there can be ...
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The plates of a parallel capacitor are given charges +4Q and -2QThe capacitor is then connected across an uncharged capacitor of same capacitance C. What is the final potential difference between ...
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### Potential at the surface of a conducting sphere near a dipole

An ideal conducting solid sphere of radius $R$ and center $O$ is brought near a dipole with a dipole moment of magnitude $p$. Let the center of the dipole be called point $C$, and let the tangent from ...
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### Method of image charges [closed]

In an attempt to understand the Method of image charges, I'll try to calculate the total charge on grounded conducting plane - with electric dipole & point charge. Given: Point charge $Q$, ...
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### Multipole expansion of Woods-Saxon potential?

When can a distribution be expanded in multipoles? What is the basic requirement? Can it be done for a potential like the Woods-Saxon form?
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### Capacitance of spherical capacitor when earthed

The capacitance of a spherical capacitor is given by $$C=\frac{4\pi \varepsilon_{0}}{\left ( \frac{1}{a}-\frac{1}{b} \right )}$$ How can I find out the capacitance of the capacitor when The ...
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### Analytical Calculations For a Stable Electret in Motion in Interplanetary Space. Determining the magnetic field

We know that a charging capacitor has, associated with the increasing E-field, a magnetic field. Now please consider the case of a very strong dipole or E field produced in an electret. Let us say ...
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### Gauss' Law and area vector

Recently I've been doing some physics exercises on electric and magnetic fields and read up somewhere that the vector area of a closed surface is equal to zero. That made me wonder why, when using ...
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### Electrostatic potential due to two charge system

When we calculate electric potential energy of a two particle system, say first I bring $+q_1$ and then I bring $+q_2$ against $q_1$'s electric field. Say I get that $q_2$ charge to a point $r$ ...
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### Why is the Electric Field Zero at this point?

In a Phet Lab simulation, which is all I have at the moment to do my learning on electric field forces, the point represented as colored on the diagram below is shown to have an electric field ...
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### How can a point hold mass or charge where it doesn't tell anything except position? [duplicate]

In geometry point is a dimension less quantity as it doesn't have length, breath or height. But when we define columbs law in electrostatics, we define points holding charges or Newton's law of ...
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### Why charge distribution is greatest at pointy edges of a surface? [duplicate]

If we have a conductor which is in electrostatic equilibrium, then the charge distribution over this surface $\sigma$ is greatest at the sharp edges of that surface. Why is this the case? I want ...
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### Non-parallel-plate Capacitor

Imagine you start with a parallel plate capacitor with square plates of side $s$ and gap $p$. Turning one of the plates slightly results in a small increase and decrease in gap separation $d$ at the ...
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### can a power supply with high voltage value and some current be split into multiple small voltages of same current?

For example: if I have a source that can give an output of 10,000 Volts with some unknown current value, now, can i make that 10,000 Volts to 50 (need not be 50 exactly but maybe more than 30) of 200 ...
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### How can I have a voltage in hall effect with zero magnetic field?

How can we obtain a voltage with no magnetic field is applied to the semiconductor? They told me that if the points where I measure the potential difference are not at the same level I would obtain a ...
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### Charge Distribution Across A System Of Metallic Parallel Plates

While calculating the charge distribution across a system of metallic plates, (taught as a prequel to the parallel plate capacitor), we say that the electric field inside each plate must be zero. We ...
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### Sphere of electric charge revisited

I am thinking about a sphere of homogeneous charge distribution (see Electric field due to a solid sphere of charge, for example). Here we use a Gaussian surface (blue area) to find the electric ...
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### What is the cause of the time-varying electric and magnetic near-fields around a wire with a 60Hz AC current?

I know that it's the accelerating electrons in an AC current that are the cause of far field effects. But, what about the reactive near field close to a wire that has a 60Hz AC current? What is the ...
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### 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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### Calculating rise in water surface due to a charged capacitor

﻿Two metal plates separated by a distance d & initially charged with charge +Q & -Q are kept so that it just touches the surface of a very large water tank as shown in figure a. Thus water ...
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### What does a hexadecapole look like

Two dipoles can form a quadrupole, two quadropoles an octopole. The textbook by Griffith then says ' and so on'. So how would a hexadecapole really look like? My impression was that the construction ...
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### Origin of internuclear forces

I just recently read about the existence of internuclear forces as the reason for the nucleus to remain 'stable' as in it doesn't separate out into protons and neutrons even though there is electronic ...
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### Application of Coulomb's Law

I've just finished reading a section in a book on Coulomb's Law. I'm trying to practice the math a bit and came up with the following: Suppose you have two charges, -5uC ($q_1$) and 7nC ($q_2$). ...
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### Why does the Electric Field of a dipole have no $x$ component?

According to the solution $2E\sin(\theta) = E_{net}$. I understand how the dipole works but I don't understand why the x component would be 0?
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### Can I get help with measuring particle charge using oscilloscope?

How can one measure particle charge using oscilloscope and op amp integrator circuit along with a capacitor and faraday cup. I am unable to figure out how to approach. I have the circuit ready but ...
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### Infinite, straight, current-carrying wire uniformly charged to a negative electrostatic potential

I am working on a problem that states the following: Imagine an infinite straight wire carrying a current $I$ and uniformly charged to a negative electrostatic potential $\phi$ I know here ...
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### Capacitance of a single charged plate?

Lets say we have a single plate that has a charge of +Q on it. A plate with charge -Q is infinite distance away. Will the plate with +Q have a capacitance associated with it? Why or why not? I was ...
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### Does the potential of two spheres become equal when we connect them?

I was reading a chapter on capacitors where it was asked whether given two spheres, each carrying a charge $q$ and of radius $r$ and $2r$, will charge flow between them? I assume the answer should ...
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### Five charges on a pentagon [closed]

If we keep five identical point charges at the five corners of a regular pentagon. What will be the electric field at the centre. I think it would be zero due to symmetry.. Please correct me if I'm ...
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### How to approximate trajectories and movement of two oppositely charged particles?

Imagine a single, stationary charged atomic ion, say a Lithium anion or cation (Li+ or Li-). Now imagine another a single free, oppositely charged particle--perhaps an electron or Hydrogen ion ...
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### The image current due to moving charges and a current carrying thin wire

Suppose we have a plane conductor and positive charged particles of mass m are moving parallel to the plane conductor at a distance d. The trajectory can be assumed to be straight. An image current ...
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### Would a non-conducting body ever acquire a uniform static charge throughout it's volume?

I'm studying electromagnetism and optics in first year and solving a lot of problems involving conveniently symmetrical conducting and non-conducting bodies having various uniformly distributed ...