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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103 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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43 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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63 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
49 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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42 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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317 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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46 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
137 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 ...
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2answers
77 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
30 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
49 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 ...
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2answers
38 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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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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113 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
101 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
33 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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15 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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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
61 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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163 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 ...
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4k 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
112 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 ...
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1answer
48 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
139 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
70 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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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
66 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, ...
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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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27 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 $$ ...
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1answer
101 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 ...
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2answers
159 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
324 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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129 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 ...
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3answers
5k 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
215 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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45 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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69 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
140 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.
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2answers
139 views

Charging a Capacitor?

How is the charge +q given to the one plate to the capacitor with the help of a battery, does the battery remove electrons from the plate and +ve charge gets accumulated on one plate?Does it? And one ...
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5answers
6k views

How can I prevent my son building up static on his trampoline?

Whenever my three year old son plays on his trampoline, it doesn't take very long for him to start building up a significant amount of static electricity. His hair stands on end (which is quite ...
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2answers
148 views

Why does charge distribute evenly between two halves of a conducting sphere?

Always while studying I was told that if two identical spheres, one charged and the other uncharged, are brought together the charge in each one of them is halved. However, why does it happen? Is it ...
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3answers
289 views

Charge On parallel plate capacitor?

Suppose if we supply two plates of parallel plate capacitor with charges $Q_1$ and $Q_2$.What would be the charge of the capacitor? As the field inside plate should be zero and hence using gauss law I ...
2
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1answer
70 views

Why do we consider the electric field of an infinite plane? [closed]

I never understood why one would calculate the electric field surrounding an infinite plane, if such thing does not exist. Is there physical motivation for using this model? Are the results applicable ...
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3answers
559 views

When to use method of images in Electrostatics?

I am a bit confused about when to use the method of images in E&M? For example, in Griffith's Electrodynamics Example 3.2, the problem reads: A point charge $q$ is situated a distance $a$ from ...
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1answer
66 views

From where does the sound come from when two charged objects meet in real life?

I am sure all of us have played with rubbing things and producing static electricity and when I was charging my comb by rubbing it on my hair and watching it attracting a small piece of paper, I heard ...