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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Explanation on Electrostatics

If we rub a plastic scale repeatedly with our dry hair,then the hair stand up and separate from each other. Why does this happen?
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Ionization of human molecules

Can the molecules human body be positively charged and can the body process the electrons through exercise if retained and not discharged? Example asked by commentator: When you rub your feet on ...
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31 views

Screening of electrostatic potential at the interface between two dielectrics

The motivation of my question: Calculating the dispersion relation of plasmons in a graphene layer embedded between two dielectrics with different dielectric constants. Addressing my question: I ...
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Regarding the proof of Gauss's law

I know that this question has already been asked multiple times but I´m still not getting on the mathematical details behind the answers... So I hope that this question doesn´t get closed. First I ...
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Spherical charge distribution [closed]

I have a pretty simple exercise but i can't get it right using both integration and divergence of potential. I first did the field inside the sphere: $$\vec{E} = ...
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1answer
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Description of transparency of a Faraday cage to different frequencies?

A Faraday cage within a static electric field leaves an internal electric field equal to $\vec{0}$ (as long as there are enough mobile electrons in the conductor to counteract the external $\vec{E}$). ...
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Why is the force on the charge at the tip of a cone infinite?

Imagine a charge $q$ that is located at the top of a hollow cone with a surface charge density $\sigma.$ The slant height is $L$ and the charge $q$ sits at the vertex of angle $2\theta$. We are ...
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48 views

Laplace equation in parabolic coordinates [closed]

I'm stuck on a seemingly simple 2D electrostatics problem which doesn't allow for straightforward solution by separation of variables: A parabolic interface, with its axis parallel to the $x$ axis, ...
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1answer
58 views

Calculating the amount of work done to assemble a net charge on a sphere

I've been reviewing electrostatics using an old exam and I stumbled upon this question: Calculate the amount of work required to assemble a net charge of $+Q$ on a spherical conductor of radius ...
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58 views

Number of electric field lines and intensity of electric field

I´m currently studying electrostatics and I´m having a hard time understanding why do the number of electric field lines is proportional to the intensity of electric field? I just don´t see it. Can ...
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Why is there an electric field in a wire even though it is a conductor?

If you take a perfect conductor, there cannot be a field across it since if there were, the particles would arrange themselves in a way to cancel out the field right? Yet, why does the same not hold ...
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Question about Cavendish experiment

I got a question. In Cavendish experiment was used lead in both of spheres. Can we repeat that experiment with balls made from stone or anything else. Because lead could be a byproduct of radioactive ...
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2answers
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Physical meaning of electric dipole moment [closed]

I am reading about the electric dipole moment. What I can't understand, and seems that no one cares to explain, is what is the physical meaning of it. To my understanding everytime that dipoles are ...
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31 views

Rearrangement of oil due to high voltage electric field

I've been working on a problem for some time now and I can't figure out why exactly this happens, and I've been looking for some insight. The phenomenon can be seen in this video. We can see that the ...
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determining electrostatic field using only symmetries

As an exercise, I'm trying to (rigorously) determine as much as possible about the electrostatic field due to a infinite line of charge (along the z-axis) without using Maxwell's equations or any of ...
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22 views

Electrostatic Shielding

suppose there is a solid conducting body with arbitrarily shaped cavity inside. Now a charge is placed inside the cavity.Now the entire setup is placed in an uniform electric field. Will the ...
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20 views

Can we lock electric charges in dielectric cells?

Suppose next. We using Wimshurst machine and gathering charges in dielectric cells such as mica .Before discharge we put whole machine in vacuum chamber.Question is next. Can we storage those charges ...
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The Equi-Potential Lines of Two Like Charges

Motivation Consider two Like charges $+q$ and $+q$ located on the $x$-axis with $x=-1$ and $x=+1$. Now, the potential inside the $xy$ plane will be $$V(x,y)=kq \left( ...
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3answers
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What would be the capacitance of an unequal charged capacitor?

I searched for this question but I cannot get satisfactory answer. Say if we have a parallel plate or cylindrical capacitor and if I supply unequal charge to it how could I find its Capacitance. We ...
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Electric field in a sphere embedded in a medium

Consider a system where a sphere of conductivity $\sigma_i$ is embedded in a large medium of conductivity $\sigma_e$. An electric field $E_0$ is applied and the question is, what is the electric field ...
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Electric field due to charged disc, on the plane of the disc [closed]

A standard problem in finding the field is that of a uniformly charged disc, on its axis, but for this problem I'm supposed to find the potential and the field on the edge of the disc, i.e. in the ...
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1answer
37 views

How does electric potential relate to charge density in a wire?

Lets say we are talking about a wire with resistance connected to a battery. How is the charge density, taking into account bound and free charges, at two points connected to the electric potential ...
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56 views

What are the reasons for accepting Coulomb's law? [duplicate]

I read the Coulomb's first memoir on Electricity and Magnetism (Louis L. Bucciarelli english translated version), and found it to contain only three trials (as complained by many) to reach the ...
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1answer
45 views

Why is electric flux zero if my point charge is outside of a sphere? [duplicate]

I am currently studying Gauss Law and Electric flux , during one of my exercises they ask me to find the electric flux of a sphere with radius 5 cm and my point charge is 10 cm to the left of the ...
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Electric field of a Uniformly charged sphere with a cavity [closed]

I have the following question: Consider a sphere of radius $R$, uniformly charged with a volume density $\rho$. The sphere has a spherical hole of radius $R/4$ at a distance $R/2$ from the ...
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Induced charges, electric potential

Consider a solid spherical conductor with charge Q on it, a charge q is placed at a distance r from the centre of sphere. Find the electric potential at the centre of sphere due to induced charges on ...
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Angular current in torus

I'm trying to find the magnetic field due to a torus anywhere in space. I'm approximating it as a circular current loop. What I'm having a hard time with is the current in the theta direction, that ...
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1answer
22 views

Electrostatic induction, induced charges

Is it true that If a conducting object is not grounded, the nearby charge will induce equal and opposite charges in the conducting object? It is mentioned in Wikipedia(electrostatic induction) but it ...
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43 views

How much energy does an electron have when it is situated right next to a negative point charge?

The formula for potential energy regarding point charges is $E=kQq/r$. If $r=0$, then will the energy be approaching infinity? But what about an electron in a parallel-plates situation where it is ...
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What are the advantages of multipole expansion of potentials?

When I see the equations of multipolar expansions they "look" to me harder than the original expressions. For example: Multipole expansion - spherical form, in Wikipedia I bet that this is not ...
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1answer
28 views

How to find the polarization of a dielectric sphere with charged shell surrounding it?

A shell with negligible thickness has a given charge density as a function of theta, and is filled with a dielectric material with a given electric susceptibility. Using lovely legendre polynomials ...
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Am I too young? [closed]

I am only 14 years old but I dream of being a physicist what we learn in school seems very simple for me I am a freshmen and I learn Igsce syllabus and I don't seem to find it hard at all , but i am ...
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1answer
37 views

Why does grounding yourself prevent feeling a static shock?

Sometimes I get static electric shocks when I touch certain metallic objects. However, I seem to be able to prevent this by grounding myself by first touching that object with a small piece of metal, ...
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19 views

Analogy of Faraday Cage?

Can we think that an ideal conductor is a friction less space for electrons since under influence of electric field they create an exactly opposing field and produce shielding effect ?If so then how ...
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59 views

Laser-induced electrical discharge

Attracting lightning with an ion beam has been done in a lab but how strong of a laser is needed to reach the clouds to redirect the lightning bolt?
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Extreme charge density in thin capacitor plates

Suppose we made a 1 square meter parallel plate capacitor from two sheets of graphene separated by a very strong dielectric of arbitrary thickness. Then we charge the capacitor just short of the ...
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2answers
53 views

Are charges always uniformly distributed on conductors?

As the title says. For example, if I take a fat metal wire with non-negligible thickness, and then wind it into a spiral, but such that none of the parts touch one another (there are no topological ...
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1answer
31 views

Uniformly charged disk

A uniformly charged disk is an isolant or a conductor? Or could it be both of them? I only know its radius and its surface charge density, which is uniform throughout the disk.
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1answer
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Earth as a conductor

In a lightning rod or other safety devices, charge is directed towards the earth. How the surface of the earth can be used as a conducting path despite being composed of material that is not a good ...
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2answers
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Why Electrostatic field has a continuous curve?

An electrostatic field line is a continuous curve. That is, a field line cannot have sudden breaks. Why not ?
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Azimuthally Symmetric Potential for a Spherical Conductor

I am trying to solve problem 2-13 from my textbook "Principles of Electrodynamics" (see image below). I believe that I should be solving the potential as $ \varphi(r,\theta) = \sum_{n=0}^\infty ...
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38 views

Potential of ring of charge and a conducting sphere

My goal is to find an expression for the expression of the force on a conducting sphere due to a circular ring of total charge $Q.$ The sphere has radius $a,$ and it is placed along the axis of the ...
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9 views

Calculating pressure on a dielectric kept inside a capacitor

Firstly, the pressure is because of the opposing forces acting on both sides of the dielectric slab. On the left side of slab, the field due to the left plate is $\frac{\sigma}{2\epsilon_0}$ and ...
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2answers
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smallest possible length of copper wire, where I can measure capacitance via multimeter [closed]

I am a new highschool physics instructor and I want to show to my students the basic concept inside the capacitors. i plan on showing them via simple 2 copper wires side by side each other, supplied ...
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36 views

Will a permanent dipole placed in a uniform external electric field exhibit periodic motion if it is displaced from equilibrium position?

Because at equilibrium position, the dipole is aligned along the direction of electric field and since it is a uniform electric field ,there will be no force on the dipole but it can still experience ...
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1answer
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I have a doubt in finding workdone by a negative charge in moving it in presence of positive charge

Let say I have a positive charge at the origin. Now imagine I get a negative charge from $X=10~\text{cm}$ to $X=2~\text{cm}.$ By common sense we can say that the work done by us will be negative as ...
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Auxiliary magnetic field identically zero?

Consider a 3D space that's filled up completely with a material of fixed magnetization $\mathbf{M}$ (i.e. everywhere in space the magnetization points in the same direction and has the same ...
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1answer
34 views

Is electric potential a field?

I'm just learning about electric potential in my second-semester physics class. My textbook is emphasizing the fact that electric potential is a property of the source charges and that I'll soon learn ...
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2answers
117 views

Principle behind electrostatic shielding?

If we have a solid conducting sphere with charges around it, then the electric field inside the sphere is zero, otherwise the electrons of the sphere would not be in equilibrium as there would be a ...
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75 views

How can charge be squared?

In many Wikipedia articles I have come across it refers to a Coulomb squared. What does this mean intuitively? i.e. http://en.wikipedia.org/wiki/Farad (this was the most recent place I came across ...