Electrostatics is concerned with the field and potential of stationary electrical charges and electric charge distributions. Problems are this type are almost exclusively concerned with mathematics of geometries using the inverse-square law.

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Electric Field and Calculus: What is the physical significance of infinitesimal $dA$ in the equation of Gauss's Theorem?

In many equations we see infinitesimals $dA$, $dS$, $dx$ and so on. What is is the physical significance of these? Someone told me it signifies a small entity. For example,in case of $dA$ it signifies ...
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4answers
243 views

How can I calculate the force that is applied on a tube by another tube?

Let's say there is two tubes(cylinders with no tops or bottoms) with charges $q_1$ and $q_2$, radii $b_1$ and $b_2$, lengths $l_1$ and $l_2$. These tubes are located along the axis of each other's ...
3
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2answers
102 views

Finding the direction of the magnetic force acting on a conducting wire

I have a problem in finding the direction of the force when a conducting wire is placed in a magnetic field. If I use Fleming's Right Hand rule I get a circular magnetic field, so what will be ...
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1answer
50 views

How to distribute static charges evenly on a finite plate?

There are several ways to make charges on an object evenly distributed. For example, if the surface of the object is infinite or the object is a sphere. There is one more way which I am not sure if it ...
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1answer
54 views

Can someone show me how Green's function would apply for this simple case?

I'm reading up on some stuff on basic electrostatic here: http://hyperphysics.phy-astr.gsu.edu/hbase/electric/laplace.html Can someone use Green's function to show me the form of $V$? Update: I ...
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2answers
388 views

Inductor Charging and Discharging

Why does the inductor discharges in the same path ( same direction of current ) as that of its charging unlike a capacitor which discharges in the direction opposite to its charging(current direction ...
3
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1answer
115 views

Why would a rotating charged sphere not have time varying electric field?

I have seen Gauss Law being used for a uniformly charged hollow sphere rotating with $\omega$. How is that valid to use Gauss law since it is an electrostatic law and if it is valid, why do we get a ...
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1answer
90 views

Potential due to charge over infinite grounded plane conductor using the method of images

I am reading section 3.2.1 of Griffiths 3ed which explains how to calculate potential using first uniqueness theorem. Griffiths/3.2.1 Griffiths/First Uniqeness theorem (Its corollary actually) ...
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0answers
40 views

Contradictory boundary conditions in electrostatics problem?

Consider the following problem: A conducting cube of side $a$ is grounded. Inside there's a horizontal (i.e., perependicular to the $z$ axis) sheet with uniform surface charge density $\sigma$. The ...
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2answers
53 views

Why is Lightning referred to as High frequency source?

Lightning strike is categorized as DC because of its electrostatic nature. The negative flash/stroke is found to have 200KA of current with a voltage close to 300KV (cloud to ground). But why is it ...
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1answer
47 views

How to make charges of a charged conductor evenly distributed over the surface of the object?

Is there a way to make the charges of a charged conductor evenly distributed over the surface? I know the charges of a charged insulator are evenly distributed but I want to know that if there is a ...
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2answers
41 views

Do charges flow from strong insulator to weak insulator?

Do static charge in a strong insulator flow to a weaker insulator when both stay in contact with each other? For example, when an insulator weaker than air placed in a medium of air, would the static ...
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2answers
281 views

Grounded conducting sphere inside uniform electric field

The problem of a grounded conducting sphere inside a uniform $E$ field in the $z$ direction can be solved by imagining the field be produced by a pair of charges $Q$ and $-Q$ put on the $z$ axis, ...
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0answers
44 views

How to calculate electric force between two tubes?

Let's say the electric field due to a charged tube is $E$,length of the charged tube is $l$, radius is $r$ and the surface charge density is $\lambda$. I know that to calculate the electric force ...
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1answer
119 views

image method to calculate the surface charge density on a conducting plate

There is a charge q at a perpendicular distance z = d from an infinite conducting plate z=0. We use the image method and place -q on the other side of the plate and calculate the field. This field ...
2
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2answers
70 views

How much voltage should be applied to an object to create a certain amount of charge?

I am curious as to how much voltage should be applied to create a specific charge. Is there a formula to calculate it, and what are the parameters that can affect the relation between voltage and ...
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1answer
29 views

Electric Potential of Conductors

I understand that charges in a conductor reside on the surface of a conductor. So why is it that the neutral inside of a conductor and the charged surface are at the same potential?
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1answer
46 views

What is the best insulator for static charges? [closed]

I am trying to find a solid material that almost fully (since there is not a thing that can fully insulate electricity) blocks static charges from one layer to another. I know plastic is a good ...
2
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2answers
36 views

Electric Field in Conductor Zero?

My textbook claims that the electric field in a conductor is zero in a static condition, as otherwise, a current would flow. But what if I go infinitely close to a proton; there will be an electric ...
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2answers
1k views

Why is water not used as a dielectric in the condenser?

The dielectric constant of water is very high. Then why is it not used as a dielectric in the condenser?
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0answers
95 views

How to calculate the electrostatic force between two dielectric rings of charge?

Let's say there is a dielectric ring of charge with radius $a$ and charge $q_1$. I could calculate the electrostatic force applied on a point charge with charge $q_2$ and which is collinear with the ...
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1answer
88 views

Some general questions about static electricity ( ex : Combing the hair ) [closed]

We know , static electricity is built up when i comb my dry hair. what type of charge is gathered in comb & what type of charge in hair ? ( i.e. + or - charge ) why would charges would gather ...
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1answer
30 views

Can non-conductive materials can be grounded by a wire?

Suppose that I comb my hair. The plastic comb would become negatively charged and would attract small paper pieces. But if I touch the comb in bare hand and in bare foot standing on the ground, or if ...
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2answers
1k views

When can a surface charge density exist?

In my syllabus about electromagnetism, they state: "This surface charge density will not always be present, e.g. when considering two non-conducting dielectrics such surface charge density remains ...
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0answers
13 views

How to calculate the electrostatic force applied on an object that is along the axis of a charged tube's surface?

Let's say there is a charged tube(a cylinder with no top and bottom) with radius r and length l, charge q1 which also made out of insulating material. And also if there is an object with charge q2 ...
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0answers
36 views

How to calculate the electrostatic force applied on an object that is along the axis of a charged tube?

Let's say there is a charged tube(a cylinder with no top and bottom) with radius r and length l, charge q1 which also made out of insulating material. And also if there is an object with charge q2 ...
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1answer
48 views

Conducting sphere with a cavity

I have a conducting sphere which has a cavity in it. The cavity is not at the center of the sphere. If a charge $+q$ is placed inside the cavity (with the sphere remaining neutral as a whole), what ...
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2answers
138 views

What does really attracts a water stream to a charged object?

I saw this video by Varitasium and I was not 100% sure about the third phenomena, a statically charged object attracting a stream of water, especially because he explicitly mentioned that it is not ...
13
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2answers
3k views

Why two objects get charged by rubbing?

It is always told as a fact without explaining the reason. Why do two objects get charged by rubbing? Why one object get negative charge and other get positive charge?
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3answers
97 views

How does an object regains its neutrality after being charged by rubbing?

Objects (like comb) can be charged by rubbing as charged particles, particularly electrons, are transferred from one object to other. This can be seen as the object (comb) attracts small bits of ...
2
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1answer
46 views

What would happen if charged plates are placed horizontally?

My idea is placing charged conducting plates in such a way that they won't see each others' surfaces unlikely to the typical design of parallel plates. If they are placed like this, would be the force ...
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3answers
133 views

Variation - Electric pressure on a sphere?

I solved the following question(Answer is correct): Find the force with which two hemisperical parts of a uniformly charged hollow sphere repel each other?(charge density: +$\sigma$) Answer: ...
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1answer
65 views

Does charge distribute itself uniformly on a conductor?

An excerpt from a beginning E&M book [...] In other words, the surface of a conductor is an equipotential surface under static conditions. [...] Summarizing the boundary conditions at the ...
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0answers
36 views

What do we mean by electromagnetic charge? [duplicate]

What do you mean by charge? Why should a particle have a charge?
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1answer
72 views

How can I apply to the differential form of Gauss' Law? [closed]

I'm trying to learn Maxwell's equations but I got stuck. I couldn't understand the usage of the differential form of the Gauss' law. How can it be applied to questions? For example, let's say there is ...
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1answer
59 views

How to calculate the force between line of charges?

As far as I know Coulomb's law only works for point charges but what if there are not any point charges? For example, let's imagine there are three rectangles with different sizes. First one is 50 cm, ...
3
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1answer
51 views

Why is electric potential positive?

If there is a positive charge $q$ at the origin of a coordinate system, the electric potential $\phi$ at a distance $r$ from $q$ is (by definition, if we take the point of zero potential at infinity): ...
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0answers
26 views

name for 2D Electrostatics as Integrable System

I am trying to understand 2D electrostatics of $n$ point charges. Roughly, $$ H = \sum_{i=1}^N n_i \ln |z- z_i|$$ However, I keep bumping across the Gaudin model instead with this Hamiltonian $$ ...
2
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1answer
86 views

Potential energy of a dipole in a uniform electric field convention?

When finding the potential energy of a dipole in a uniform electric field, I was told by my lecturer that the convention is that the potential energy is 0 when the dipole moment and electric field ...
4
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2answers
150 views

What restores balance to a repulsive electric force on an electroscope?

I am an amateur physics enthusiast (during the day I am a police officer), and recently, I learned how to build an electroscope. I regret that I am learning how wonderful our universe is so late in my ...
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1answer
278 views

Electric field strength at the center of an equilateral triangle

Questions: Three $x$ m long rods form an equilateral triangle. Two of the rods are charged to $+q$ C and the third to $-q$ C. What is the electric field strength at the center of an equilateral ...
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0answers
112 views

Fluctuation interaction between two uncharged spheres

I'm trying to figure out quantitatively what is the force, acting between two uncharged conducting spheres and I've got stuck. It is not a kind of homework - it is just a simple act of curiosity. I'd ...
0
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3answers
4k views

Why does ebonite rod gets negatively charged when rubbed with fur [duplicate]

What I think is : The protons are present at the centre of the atom with rotating electrons around it so when it is rubbed by fur the electrons get passed from the ebonite rod to the fur leaving the ...
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1answer
184 views

How does food plastic wrap get positive and negative charges on opposite sides of the plastic?

Related: Why two objects get charged by rubbing? After reading the above question’s answer given by Luboš Motl in terms of the triboelectric effect, I believe I have a good grasp on how charge is ...
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0answers
30 views

Earthing of conductors [closed]

Can anyone please explain me the process of earthing of a spherical conductor in detail. I am aware about the basic idea of earthing but I am not able to understand and visualize it properly.
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2answers
43 views

Can I calculate the current of any setup with capacitance by the same formulae?

There are known formulae relating a capacitor's voltage and current in its classic form (battery, wires, a capacitor circuit), but what if we had a charged plate (-ve), then we put on one of its ...
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0answers
66 views

Sign error in calculating the electric field of point charge

I have to determine the electric field of a point charge, I get a true result except for a sign. Here is my passages. $$\nabla \cdot e = \frac{\rho}{\epsilon}$$ $$e = - \nabla u$$ $$\nabla^2 u = - ...
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1answer
54 views

Flaw in the radius of a spherical electron model (classical electron radius)

My textbook asks me to derive an equation for the potential energy ($U$) of sphere ($r_0$) filled with an electric charge of uniform density ($\rho$), expressed in terms of the total charge $Q$. The ...
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0answers
33 views

Why does proton and electron attract each other? [duplicate]

Not that their charges are opposite! "+" & "-" are the signs we named them. By nature Why do they attract each other? And Why do they repel each other?
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2answers
135 views

Can effect of gravity be broken (counteracted) by electric force?

Can we make a jacket using an electronic circuit that uses electric force to cancel the effect of gravity so that we get lifted in air.