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 ...

learn more… | top users | synonyms

0
votes
1answer
37 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 ...
0
votes
0answers
23 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 ...
0
votes
0answers
40 views

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( ...
0
votes
3answers
97 views

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 ...
0
votes
0answers
13 views

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 ...
3
votes
0answers
93 views

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 ...
0
votes
1answer
54 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 ...
2
votes
0answers
60 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 ...
0
votes
1answer
97 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 ...
2
votes
1answer
122 views

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 ...
1
vote
0answers
36 views

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 ...
0
votes
0answers
20 views

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 ...
0
votes
1answer
50 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 ...
0
votes
3answers
75 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 ...
9
votes
2answers
176 views

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 ...
0
votes
1answer
75 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 ...
0
votes
1answer
57 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, ...
0
votes
0answers
24 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 ...
0
votes
1answer
76 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?
0
votes
0answers
32 views

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 ...
2
votes
2answers
71 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 ...
1
vote
1answer
35 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.
1
vote
1answer
49 views

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 ...
0
votes
2answers
115 views

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 ?
1
vote
0answers
40 views

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 ...
0
votes
0answers
59 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 ...
0
votes
0answers
14 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 ...
0
votes
2answers
28 views

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 ...
0
votes
1answer
64 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 ...
0
votes
1answer
33 views

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 ...
1
vote
1answer
49 views

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 ...
0
votes
1answer
41 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 ...
1
vote
2answers
496 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 ...
0
votes
1answer
76 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 ...
0
votes
0answers
36 views

In terms of work, what happens to a negatively charged particle circling around a positively charged rod?

Picture a positively charged glass rod from its end so that if you were to draw it on paper, it would appear as a circle. Now, suppose a negatively charged particle moves in a circular arc, on the ...
22
votes
2answers
4k views

Can sugar be affected by a magnetic field?

While I was making a morning coffee at work, some sugar from the spoon started to fly away, seemingly towards some foam cups. Can this be explained by magnetism?
0
votes
0answers
49 views

Two spheres (one positive, one negative) - electric field

I posted yesterday about a problem I had and I have managed to solve one of the two I think (Here is the original post: Dielectric field in a homogenous electric field ). I didn't want to edit the ...
1
vote
0answers
16 views

When two equally opposite charges placed then which type of motion will carried out b/w them? [duplicate]

I want to know that which type of motion will carried out between two equally opposite charged particles, when they placed in front of each other.
4
votes
2answers
54 views

Inconsistency with electrostatic energy formulas

The energy of point charge configuration can be written as: $$W = \frac{1}{2}\sum_{i=1}^{n}q_{i}V(r_{i}) \, ,$$ which can take both positive and negative values. However, when we integrate the ...
1
vote
2answers
123 views

What does “charge” actually mean? [duplicate]

I know that a charged particle is defined as a particle that experiences a force in an electric field, as explained in this post: What does a subatomic charge actually mean? However, I still don't ...
0
votes
1answer
170 views

Electric field inside coaxial cable

I have a very long coaxial cable with a cylindrical core of radius $a$ that has negative charge density $\rho = -k/r$ where $r$ is the distance from the axis of the cylinder, and an outer shell of ...
2
votes
2answers
51 views

Filling a charged capacitor with dielectric material

If there is a charged capacitor (capictance $C$) connected to a battery (of EMF $V$) and the space between the plates of the capacitor is filled with a dielectric material (dielectric constant is ...
2
votes
1answer
47 views

Time dependent electric field: Mathematical expansion for local electric field

In many articles and books I see that local electric field is expanded as $$\vec E_0(\vec r(t)) = \vec E_0(\vec R_0) − (\vec a(t) \cdot \nabla) \vec E_0(\vec R_0) \cos(\Omega t) + \ldots $$ For ...
1
vote
3answers
114 views

What is the potential difference between $a$ and $b$ in this basic circuit, when the switch is open? [closed]

My professor says the potential difference between $a$ and $b$ is the difference between the voltages on the top left capacitor and the bottom right capacitor. My friend and I however both think it's ...
1
vote
0answers
37 views

Why is the energy lost due to the internal resistance always equal to $(1/2)CV^{2}$ in a simple capacitor battery circuit? [duplicate]

Suppose we have simple circuit in which a battery of EMF $E$ is connected to a capacitor of capacitance $C$. Work done by battery $W_{b}=CV\times V$ and energy stored in capacitor ...
1
vote
1answer
70 views

Force on a charged particle due to an uncharged infinite conducting plate

How can I calculate the force on a charged particle due to an uncharged infinite conducting plate? If there is a small object with positive charge placed above a metal plate, the object induces a ...
13
votes
4answers
963 views

The maximum distance for which Coulomb's law has been verified?

We know that Coulomb's law, $F_{12} = \frac{kq_1q_2}{r^2}$, was experimentally verified for small distances by Coulomb himself at the and of the XVIII century. The question is what is the maximum ...
1
vote
2answers
40 views

When two coils carrying opposing currents are placed coaxially

The current flowing through these coils increases in this case according to the book. But it does not clearly state how. This is what it says: "When brought closer induced effects should produce ...
0
votes
2answers
163 views

Is Coulomb's law valid if the electric charge is not constant in time?

If the electric charge is constant the law of Coulomb says that: $E(r) = kQ/r^2$. The question is, if $Q = Q(t)$, can I consider that: $E(r,t) = kQ(t)/r^2$? Update: It appears that the first ...
1
vote
2answers
59 views

What does it means to say an electric charged person has a higher potential voltage compared to the door?

I'm studying electric potential energy and its defined as the energy needed to move a charge inside an electric field from a point $a$ to $b$. Then, it defines electric potential energy per charge, ...