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 the [electromagnetism] and/or [magnetic-fields] tags.

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Macroscopic field is space-time average of the microscopic fields?

Panofsky and Phillips' Classical Electricity and Magnetism. Chapter 2, Section 3. The authors show, assuming the microscopic field $\mathbf{\mathcal E}$ and the microscopic charge density $\rho_a$ are ...
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3answers
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Is it OK to Think of Electric Charge as Mass?

Since both are physical properties, is it ok to think of them as if they are the same thing, just in different contexts? Mass affects how much an object experiences gravity in a gravitational field, ...
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Proving that the potential is continuous across a dielectric interface

Panofsky and Phillips' Classical Electricity and Magnetism. Chapter 2, section 2. It is proven for an interface between two dielectrics 1 and 2, with $\mathbf n$ being the normal vector from 1 to 2, ...
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Calculating induced charge because of qudropole field

In the given problem we have a grounded conducting disk and a qudropole field is applied which produce potential $V_{ext} = T_{0} (x^2 +y^2)$ , we are requied to prove that induced charge on the disk ...
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Gravitational field in a hollow sphere in the presence of another mass nearby non zero. Why is that so?

I have learned that charges inside a conductor align themselves in an external field such that the net electric field inside them is always zero. My teacher taught me that most concepts of gravitation ...
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Given an arbitrary electric field inside volume find generating charge distribution on the surface

This is somehow the inverse of the Poisson problem, which i could reformulate as follows: Given a volume in the empty space, bounded by a bidimensional surface, and an arbitrary electric field inside ...
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1answer
44 views

Curl of an electric field

Which of these may be representing electrostatic field lines? Why is option 2 incorrect? is it because the curl of an electric field should be zero and the figure violates the fact? Or is there some ...
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What is electric flux and how does it apply to Gauss's Law?

I have been reading different websites and watching videos but I just can't seem to grasp the concept of electric flux and thereby understand Gauss's law. Can someone provide an intuitive explanation?
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1answer
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Determining charge magnitude through comparison with force of tension

Three charges of mass $m$ and charge $q$ are tied to massless ropes of length $l_!$, and hung from a single, fixed point. At equilibrium, the charges form an equilateral triangle in a horizontal plane ...
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Electric field and potential of a given cylindrical configuration

I've been asked to find the electric field and potential of the following cylindrical configuration of length $L$, being $\rho(r) = \frac{k}{r}$ the charge distribution and the dielectric having a ...
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1answer
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Which is the difference between electrostatic potential energy and electrostatic potential stored energy?

here it's written that: The electrostatic potential energy, $U_E$, of one point charge $q$ at position $r$ in the presence of a point charge $Q$, taking an infinite separation between the charges as ...
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Possible to use alcali solution to discharge static electricity?

My question may contain wrong assumptions: I believe static electricity present in a workshop because of friction may be caused by electrons or negative ions I believe that it is somehow possible to ...
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Why can I not use the Dirac delta function in the classical potential expansion?

I would like to verify my understanding on why it is that we can represent a charge density $\rho(\mathbf{r})$ as delta functions. If we start from $$ \nabla^2V=-4\pi\rho(\mathbf{r})\tag{1} $$ then we ...
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1answer
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Electric field inside a cavity (Faraday Cage)

David J. Griffiths in his "Introduction to Electrodynamics" (chapter2), says that the Electric field inside a cavity (in a conductor) which contains a point charge is nonzero. this is ...
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2answers
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Can Gauss law can be used at this situation?

We define the following dielectric and the plate. The dielectric of the permeability $\epsilon$ exists. The plate which has the infinite length and the plate was made of the dielectric. It has been ...
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Possibility of Nonzero or All Azimuthal $E$ Field Component of a Line Charge enclosed by a Gaussian Cylinder

Source: https://openstax.org/books/university-physics-volume-2/pages/6-3-applying-gausss-law For a line charge on an axis, why is all of the E field only pointed in the $\hat{s}$ direction? How do we ...
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What is the exit velocity of a charged mass travelling parallel to field lines in an electric field (between two plates)?

I did some pretty basic calculations and I got the exit velocity as $sqrt(2qUm)/m$ where $q$ is the charge, $U$ is the voltage across the plates, and $m$ is the mass. The reason I'm sceptical is ...
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Are electrostatic field density and magnetostatic field density analogous to each other?

do electrostatic field density and magnetostatic field density have the same formula but with analogous symbols like μ for magnetic and ε for electric
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2answers
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Static electricity: High voltage but low energy

I watched a video of a serie called "The mechanical universe" recorded at California institute of technology in which was said that "A Van der Graaff generator with a voltage of near ...
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Electric potential with Galvanic cells vs electric potential with point/test charges?

For a positive source charge and positive test charge, the electric force will move the test charge from an area of high potential to an area of low potential. Therefore, if a negative electric ...
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1answer
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What trigger a capacitor to discharge when I connect a wire externally if $E$ is 0 outside?

I know that there is a $Vab$ between the plates but I know also that the charges attract each other in the inside side of plates. So, the questions are: what happens when I just connect a wire on both ...
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1answer
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Can I make device which receives all Sun ligth and changes it in electricity? [closed]

Is possible to make a device which recives all surround emg radiation in the same time? I'm not thinking about a radio. Rather something very silmilar but able recive all emg radiation in same time.
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Electric field lines outside two objects

Are A and B conductors instead of insulating bodies? What is the charge of A? Is the charge of A negative on the left and positive on the right? With only this picture, how do I know what the net ...
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What is the polarization of a EM wave emitted by a sphere charged with an alternating voltage?

Suppose you have a conducting sphere connected to a generator by an electric wire, the other wire of the generator being connected to ground. First, the generator brings the sphere to a constant ...
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Capacitance of plate or Rectangular prism

I am trying to calculate the capacitance of a rectangular prism. This would be the self capacitance with reference to infinity. If that is a tough Job, I could settle for approximating the capacitance ...
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1answer
37 views

Divergent electric potential

Consider the electric potential at the rim of a uniformly charged ring/circle of radius $a$ (not a 2D disk) with linear charge density $\lambda$. Take the origin as the centre of a the ring. $$dV=\...
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Proof that force on conductor is equal to minus the derivative of the energy

In many electromagnetism textbooks, we have the following problem: Given a collection of conductors $C_1,...,C_n$ in vacuum, each with charge $q_1,...,q_n$ and located at positions $\vec{r}_1,...,\vec{...
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2answers
56 views

What does “relative to infinity” mean?

I am currently doing this problem and although I got the answer right, I do not completely understand how the concept works. In this case, what does "relative to infinity" mean? I have a ...
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2answers
105 views

Evaluating volume integral for electric potential in an infinite cylinder with uniform charge density

Suppose I have an infinitely long cylinder of radius $a$, and uniform volume charge density $\rho$. I want to brute force my way through a calculation of the potential on the interior of the cylinder ...
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2answers
35 views

Capacitor, charges, resistance and much more

I am not able to understand if charges are circulated to charge the capacitor even if the circuit is open, then if we connect a bulb in between the capacitor and cell then that charge charging the ...
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1answer
46 views

I'm having some difficulties solving this problem about capacitor [closed]

Consider a capacitor consisting of two parallel square plates of area $A$ with a short separation $d$ ($<<A1/2$) between them. Add opposite charges $Q$ to the plates (that is, charge the ...
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How to find covariant components of an electric field? [closed]

How to solve question 4a.I have found out h1 and h2 but and the derivatives of u1 and u2.I don't know how to find the covariant components and the contra variant basis vectors.
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What is inside of a conductor?

There are many answers regarding why is the electric field inside a conductor zero. But my question is, how do you define inside? Often times, my book uses 'inside' for the entirety of the volume, and ...
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Gauss Law for infinite objects - Components

For an infinite rod, the formula would be $E=2k\lambda/R$ using a cylinder. If we have a point in space and wanted to only calculate the $z$-component, I assume we would do $E_z=\cos\theta$. How ...
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1answer
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Experiment 3: Capacitors in series and parallel circuits

Can someone please explain me the theory that explain that the total capacitance in a parallel circuit is the total of the individual capacitance of each capacitor added together.
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2answers
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Electric Field at center of hollow sphere split into two hemispheres

I have a hollow sphere which I will assume is conducting. From my understanding of Electromagnetism the Electric field at the center of the hollow sphere would be zero. If I were to separate the ...
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Capacitor creates uniform electric field and the electric potential decrease. By solving capacitor equation for electric potential conversations

Capacitor creates uniform electric field and as the charges move, electric potential decreases. State some assumptions which are taken into consideration while solving Capacitor equation for electric ...
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Find the electric potential inside a spherical shell using Legendre polynomials [closed]

I am trying to prove the following problem from Jackson’s Classical Electrodynamics: A spherical surface of radius $R$ has charge uniformly distributed over its surface with density $Q/4\pi R^{\,2}$, ...
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Total electric field or just external field in linear dielectric equation

In the equation $\overrightarrow{P}=\epsilon_0\chi_e\overrightarrow{E}$, is $\overrightarrow{E}$ the external electric field or the total electric field: external field + field due to polarization? ...
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1answer
51 views

Can electric (and magnetic) field lines be used as a curvilinear coordinate system?

Can electric field lines be used as a curvilinear coordinate system? I think they can, since they never cross, although they are likely to form only one set of the coordinate curves (alternatively one ...
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5answers
136 views

WHY is there a negative sign in the formula of potential gradient?

Before you tell me there are a bunch of other similar questions asked as well, hear me out ;( I'm really confused when it comes to work being done. When you're considering a charge moving from a one ...
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1answer
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Help with the derivation of a variant of Coulomb's Law

My E&M textbook says the following: The electric field at position $r= (x,y,z)$ generated by a point charge $q$ at the origin is given by $$\vec{E}(r) =\frac{q}{4π\epsilon_0r^2}\hat r=\frac{q}{4π\...
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1answer
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Landau's derivation of polarization

In "Electrodynamics of Continuous Media" Landau writes the following: The total charge in the volume of the dielectric is zero; even if it is placed in an electric field we have $\int\bar{\...
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Computing electric field of an arbitrary point in 3D [closed]

How do I find the electric field of an arbitrary point $K$ which is between $2$ circular planes separated horizontally by a distance $h$. The upper plane has a radius of $d$ and the one below it has a ...
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Is it possible to overload a thin conductive object with electrons?

A parallel-plate capacitor is a very simple device. To make one, you can take two metal plates, separate them with a dielectric material, and voilà! You have a capacitor. Given a dielectric ...
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Work done moving a negative charge vertically

This is the explanation according to the book: There will be work done in moving the negative charge from its initial position to y = 0. However, in moving the negative charge from y = 0 to the final ...
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What do we mean by this the charge on a body is denoted by $q$?

I am sorry if this is a silly question, we know that electric charge is a characteristic property of a subatomic particle. And, a body is electrically charged by the transfer of electrons. Then, what ...
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1answer
31 views

Two positive charges $q$ and $3q$ and are a length 10 cm apart [closed]

(a) Where could a third charge be placed so as to experience no net force? The solution is as follows $$ K_e \frac{q_1q_3}{x^2}=K_e\frac{3q_1q_3}{(x-a)^2}$$ I understand you can cancel out the charges ...
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1answer
31 views

Underdetermined system of equations for infinite parallel plates?

I am trying to mimic the separation of variable method to finding the electrostatic potential. For instance section 2.9 in Jackson 2nd edition. Consider two infinite plates of potential $\pm V$ ...
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1answer
21 views

Derivation of Coulomb's Law in Higher Dimensions

How could one go about deriving coulomb's law for an $n$-dimensional space. For example, a 9D space (I would like to know how for these higher dimensions)? I know in 3D space the volume and radius ...

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