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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Can you magnetize iron by putting it in the air cap of a two parallel plates capacitor?

Usually we magnetize iron by putting it inside a solenoid strong homogeneous field and charging/discharging the solenoid several times. I am asking if we can magnetize an iron piece by putting it ...
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Bio Savart Law and volume of sphere?

$\frac {4\pi r^3}{3} $ is the volume of a sphere and it appears in this equation. I understand the cross product is the area of a parallelogram, but am curious how this volume is involved in the ...
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Charges on conducting shell with a conducting sphere inside it

If I have a spherical capacitor which is composed of a conducting sphere surrounded by a conducting shell and the space between them is filled with a dielectric , I assumed that the charge on the ...
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The image contains the question. The image descriptions contains my DOUBT

When the charges are at the extreme positions, the velocities of both the charges will be zero. DOUBT : Can we say that the net force acting on both the charges at the extreme position is also equal ...
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Superposition principle for the electric field

I had read somewhere that superposition principle is valid for linear functions, but the electric field is not a linear function, then why is the superposition principle valid for electric field?
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What is $Q$ in the energy stored in a parallel plate capacitor?

If we have a parallel plate capacitor like the one below the energy stored in it can be give by $$ U=\frac{Q^2}{2C}$$ $\bullet$ C is the capacitance of the capacitor Now is the $Q$ the free charge on ...
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A bottle weights 4.5kg, what's its mass in TeV (Terra Electronvolts)? [closed]

I'm not entirely sure about this problem. And the second one says: An apple falls down from a height of 1 meter. What's it's kinetic energy? My thoughts: 1/2gt^2= 1 meter -> solve for t, then v=s/t ...
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How is surface charge induced on the surface of circuit wires when connected to a battery?

Understanding: I watched the newest Veritasium electricity video and he said that the electric field inside the wires of the circuit that causes the electric current to flow is created by both the ...
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A solid, insulating sphere of radius a = 4.9cn has a uniform charge density / . Find the magnitude [closed]

A solid, insulating sphere of radius a = 4.9cn has a uniform charge density on its volume of rho = 25.5 muC / (m ^ 3) . Concentric with ( this sphere is an uncharged (بالمركز conducting, hollow () ...
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Why charges does not move through the conductor here if potential at both ends of wire is same?

Two conducting solid spheres are kept apart, one with charge Q1 and radius R1 and the other with charge Q2 and radius R2. Q1=5Q2 and R1=5R2 When these spheres are connected by a conducting wire, the ...
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What is the capacitance of ferrodoxin molecule?

On Wikipedia it says that a ferrodoxin molecule is a biological capacitor which transfers electron to change the oxidation state of iron from $\text{Fe(II)}$ to $\text{Fe(III)}$. Now I simply want to ...
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The second uniqueness theorem in electrostatics

Does the second uniqueness theorem just say that if there is an electric field that satisfies Gauss's law for a surface surrounding each conductor + a surface of elnclosing all the conductor, it is ...
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Gauss' Law in differential form applied to charged sphere [closed]

I need to use the differential form of Gauss' Law $$\nabla · \vec E = \rho / \epsilon $$ applied to a charged sphere to obtain that the exterior field is given by $$\vec E = \frac{Q}{4 \pi \epsilon r^...
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Conducting shell surronded by, dielectric shell, and an outside $q$ charge

I would like some help with my solution attempt. I have a conducting shell with radius $R1$, surronded by a dielectric shell with $\varepsilon_1$ and radius $R2$, and on the outside i have a $POINT$ $...
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A proton and an electron are placed in a uniform electric field successively. Do these two particles experience the same force? [closed]

A proton is placed in a uniform electric field and then released. Then an electron is placed at this same point and released. Do these two particles experience the same force? The same acceleration? ...
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What makes silicone sticky?

I've read from 3M's Adhesion Science articles and this StackExchange question that there are three types of adhesion: chemical, physical, and electrostatic. I'm curious about what makes silicone ...
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Why were sparks created in Rutherford's alpha particle scattering experiment?

So I just read that when alpha particle hit the gold foil sparks were created. And these flashes were used to determine the angle of scattering. So were the sparks created because the alpha particles (...
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Average electrostatic field over a spherical volume due to a point charge inside

When calculating the average electrostatic field over a spherical volume due to a point charge within the volume, how do we account for the electric field arbitrarily close to the point charge? What ...
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Physics of an electrostatic water pump, is it even possible?

I have been trying to figure out how to approach this problem. Imagine a cylindrical shell made of insulating material. The top surface has a hole in its center, with a pipe extending up. The bottom ...
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Calculate the force acting on a dipole at an electric field [closed]

I have the following question: There are two electric charges at $(-a,0,0)$ and $(a,0,0)$ with the charge $Q$. A dipole with dipole moment $\vec{P}_{el}$ is placed at $(0,0,0)$ and is oriented in the ...
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Why is the electric field inside a conductor with charges laying on its surface zero? Is something wrong with my understanding of the concept?

We know that the electric field lines of a unit (point) charge is represented by drawing lines in all the directions radially outwards or inwards (depending on whether the charge is positive or ...
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Field and potential due to dipole

My TB gives the formulae for electric field and potential due to a dipole as: $$|E| = \dfrac{k p}{r^3} \sqrt{1+ 3\cos^2θ}$$ $$|V| = \dfrac{k p}{r^2} \cosθ$$ Why are these expressions are not ...
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Does charge always reside at the edge of a conductor's surface

Say I have a circular metal sheet with a charge $Q$ on it do the field lines come out from the edges alone or from across the entire sheet?
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A question regarding electric field due to finite and infinite line charges

Consider I have a finite line of charge.If I find the electric field at a point near the centre of the line charge the net field is horizontal as the vertical component get cancelled.If I find the ...
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Determining point charge [closed]

Given 3 point charges where q2 is negative and q1 and q3 are equally spaced from it. Given the charge of q2, how can one determine the amount of charge in q1 and q3.
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Would a grounded copper heat sink located near a room's ceiling be an effective way to reduce a room's temperature?

I am thinking about a cheap but effective way to reduce the temperature of my bedroom in my apartment during hot summer nights. I live in an old apartment building and the air conditioner located in ...
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Electric field lines intersection with common tangent [duplicate]

We say that electric field lines do not intersect, because that cannot be two directions of electric field. Then can electric field line intersect in the way shown below? This image shows that two ...
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1 answer
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Flux through faces of cube if charge is placed at an edge-center

The charge at edgecenter will be shared by 4 cubes so each cube will get $q/4\epsilon$ . The adjacent faces of the edge ( where the charge is located ) will have $0$ flux through them as no Electric-...
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Intuitive understanding of how area of plates influence the capacitance of capacitors connected in series

While studying electrostatics I came across "capacitors in series" topic and want to get a deeper theoretical understanding of the topic. I researched the topic in the Internet and found ...
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Will the random movement of electrons affect the electric field of a negatively-charged solid conducting metal sphere?

When discussing about a negatively-charged solid conducting metal sphere, We agree on a statement that like charges repel so that the negative charges (aka electrons) are evenly distributed on the ...
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Electric field in a center of a tiny hole cut out in a hollow sphere [closed]

Suppose we have a hollow sphere charged uniformly with a surface charge density σ. A circular hole is cut out, small compared to the radius R of the sphere. Find the electric field in the center of ...
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What would happen to charge distribution when two charged, conducting spheres are placed in contact?

I have the following thought experiment. Assume that we have two conducting spheres. Sphere A has a charge of $+ 10 \ \text{C}$ and sphere B has a charge of $+ 8 \ \text{C}$. Now assume that we place ...
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Electromagnetic Waves and Inertia

I have a conceptual question. Suppose we have two bodies of equal masses. One is electrically neutral and the other is electrically charged (positivley charged). Now we apply equal magnitude of force ...
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1 answer
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Using the sky and ground as a battery

Since there is a voltage difference between the ground and sky, shouldn't I theoretically be able to light a bulb by connecting one terminal to the ground and raising the other one to the sky (via a ...
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Relationship between volume and surface charge density in the general case

Assume we have surface $S$ enclosing a volume $V$ and assume the only charge present in this setting is located on the surface, given by a surface charge density $\sigma$. My question is about the ...
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Energy stored in capacitor over time

I know that the maximum energy that can be stored in a capacitor is: $$ U = \frac{Q^2}{2\,C}\,. $$ What I am asked is to say how much energy was stored when half of the electric charge that could be ...
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Quantization of Electric Charge and Cutting Spheres

Say you have a metallic sphere that holds a charge $Q$ uniformly. If we cut the sphere into two equal halves, each half of the sphere will hold a charge of $Q/2$. Also, electric charge is quantized. ...
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Terminology: does this situation correspond to an anisotropic but linear dielectric?

Let us assume that for a dielectric the relation $${\vec D}=\epsilon\vec E$$ holds where $\epsilon$ is independent of $\vec E$. However, let $\epsilon$ is not a scalar number but a tensor (or a $3\...
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Why do we consider external electric field in Gaussian equation of electric flux?

We know in the Gaussian equation that the net flux through a closed surface is equal to the flux of the charge inside the surface. Mathematically we see that the left hand integral consists of the ...
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Is it possible to convert static electricity into current electricity?

Generally, static electricity is created by friction between two or more different materials and it doesn't flow through a circuit. On the other hand, current electricity is the flow of electrons ...
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Potential of a Point charge in a spherical cavity

I'm solving some problems in Mathematical methods for physics. The section is about Legandre polynomials and I have problem because the problem is not mathematics. It's about electromagnetism and I ...
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What is the meaning of a conductor in equilibrium?

Electric field lines are always perpendicular to the surface of a conductor in equilibrium. what is the meaning of a conductor in equilibrium?
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Confusion about exact electrostatic potential of a pure dipole [duplicate]

I asked a version of this question before but the phrasing was unclear, so don't mind me please. Suppose you have a physical dipole with equal and opposite charges Q and -Q, with a specified dipole ...
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Will a surface perpendicular to the electric field always be equipotential

In the figure attached there are four different electric field vectors with different magnitudes, point away from A. My question is will C be an equipotential surface? i.e. will the potential ...
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Electrostatic potential due to a pure dipole

For a pure dipole, is the electrostatic potential given by the dipole term in the multipole expansion exact for all $r$ (position vector from the origin)? Or is it exact only far away from the dipole? ...
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Distribution of Charges on a Conducting Cup

A multiple-choice problem goes as follows: A small positively charged sphere is lowered by a nonconducting thread into a grounded metal cup without touching the inside surface of the cup, as shown ...
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2 votes
1 answer
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Gauss' law in the presence of surface charges [duplicate]

Assume $V$ is a volume such that $\rho=0$ in $V$ where $\rho$ is the charge density. Assume further that we have a surface charge density $\sigma$ on the surface $S$ enclosing $V$ such that the total ...
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The multipole expansion of electrostatic potential and large distances

I'm reading Griffiths electrodynamics book and I'm currently studying the multipole expansion of electrostatic potential, and I have two questions if you don't mind: Can I use the multipole expansion ...
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For the interface between two linear, isotropic, homogeneous dielectric materials with no free charge, does $E$ remain continuous?

The title basically says it all. Does the normal component of the electric field stay continuous across the interface of the two dielectrics? My intuition is that it would not stay the same as there ...
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How to find the potential difference between two charged spheres? [closed]

Here, the blue sphere (positively charged with $+Q$ charge) is at a lower potential and the pink sphere (positively charged with $+Q$ charge) is at a higher potential, even though they are equally ...
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