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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Electric field at $r=0$

How does classical physics justify the existence of an electric field at $r=0$? Is this an edge case, an ambiguity, a "does not exist"? Is this a trivial case or indicative of an actual fault in ...
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23 views

In a system of two charges, if one charge disappears, does the force on other charge vanish instantaneouly?

It is commonly asked that if the sun dissappears, will earth shoot off in a tangent instantaneously or after some time. We know from the theory of relativity that the gravity waves travel at the speed ...
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24 views

high-energy, fast transient, EM pulse propagation in coiled-cable assemblies

During a recent trip to a compliance laboratory to perform Electrical Fast Transient (EFT, IEC 61000-4-4) testing on a product, the compliance engineer mentioned that an EFT pulse can propagate and ...
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22 views

Electrostatic concept using for dust attraction

Can I use a charged electrode to attract dust particles from any surface? If yes, then surface should be conductve or non coductive? Or any other ways to do this by electrostatic concept.
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1answer
97 views

Do Dipole Moments Obey Superposition?

Essentially, I have two surfaces which I know how to find the dipole moments for. I realize that $V_{dip}(r) = \frac{1}{4\pi \epsilon_0 r^2} \mathbf{\hat{r}} \cdot \int \mathbf{r'} ...
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225 views

Electric Potential for Concentric Spherical Shells

If you have a charged point ($q_1=+1$) inside an initially neutral spherical shell ($q_2=0$), how would you find the following: (A) Potential at the outer surface of the spherical shell? Would it be ...
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84 views

Electric Potential for concentric spheres and charged surface

A few conceptual questions about a charged sphere inside an initially neutral spherical shell and about uniform E for a charged plane. (A) How would I go about calculating potential at a certain point ...
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1answer
64 views

Can an electric field help generate a current?

What i know or am guessing:- A moving/changing magnetic field creates an electric field. So if we take a rotating magnet near a coil of copper wire, it will induce a current right. So it means an ...
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1answer
281 views

Electric field for concentric spheres

I have a couple clarifying questions: (A) in $E=kq/r^2$ for the area between a sphere inside another spherical shell, the sphere inside is considered a point charge. However, the sphere inside has a ...
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2answers
448 views

Can the electric or gravitational potential be discontinuous? Why?

I was solving the Laplace's equation for the charger thin spherical shell and noticed that the field is discontinuous at the surface (inside it is zero and outside it is proportional to $1/r^2$) but ...
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2answers
96 views

Sphere of uniform charge density with a cavity problem

Suppose we have a sphere of radius $R$ with a uniform charge density $\rho$ that has a cavity of radius $R/2$, the surface of which touches the outer surface of the sphere. The question was to ...
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68 views

Do I Understand Voltage?

Below is a formula involving voltage and potential energy. $$\Delta U = q \Delta V$$ I would like to know if I understand it: If $\Delta V$ is positive, then the charge $q$ has moved from a lower ...
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48 views

I touched a CRT television monitor and have some feelings in my hand.what is the reason? [duplicate]

It felt like some sort of vibration. Even though when I unplugged the power cable it is maintained.
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1answer
50 views

What is the “practical purpose” of Gaussian surfaces?

Without having the concept of a Gaussian surface, we know that charges induce fields in proportion to quantity. Now to take a common example, when describing flux through a (physical) surface it is ...
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2answers
86 views

Is this charge density function, from a problem in Griffiths' book, a physically valid density?

This is from the book on electrodynamics by Griffiths: A sphere of radius $R$, centered at the origin, carries charge density $$\rho(r,\theta)= k(R/r^2)(R-2r)\sin(\theta)$$ where $k$ is ...
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17 views

Electrical conductor in a non-conservative electric field

Does electrostatic shielding hold for non-conservative electric fields? I don't think so, but I cannot explain why. Please help.
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87 views

Why isn't the work minus the potential energy when bringing a charge in from infinity?

This is an example in my physics textbook, and there is just one step that I don't understand. Two point charges are located on the x-axis, $q_1 = -e$ at $x = 0$ and $q_2 = +e$ at $x=a$. Find ...
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7 views

Collection of negatively charged aerosols

Is it possible to charge aerosols suspended in air using an ion generator and collect them approx. meters away by a positive charged electrode?
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19 views

The speed of an electrical signal through different mediums [closed]

This is sort of a bio physics question and it comes in two parts. The first is: what is the speed of an electrical signal through human nervous tissue? The second part is: what is the speed of an ...
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63 views

Validity of law of charge conservation

Charging by induction and earthing gives an object a net charge but why does the law of charge conservation still hold in this case?
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28 views

Is it possible to consider loops that cut through charges when proving electric field is conservative?

My goal is to prove that the integral of E.dl along the blue curve is zero. My problem is shouldn't E field approach a discontinuity when approaching the plate? Even if we consider say a point ...
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1answer
45 views

Why in this problem I had to take the average of the electric field?

On an electrically charged soap bubble, acts an electric force outwards. We are given the total charge of the bubble, $Q$, and its radius, $R$. What is the value of the total force, acting to ...
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36 views

Can volume affect capacitance?

I know the math doesn't support it, but will a solid sphere and a thin foil, both of the same surface area, measure exactly the same capacitance? Do electrons strictly gather on the surface ...
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0answers
57 views

Gauss law for a cylinder shielded by a grounded conductor?

So I am trying to solve the following problem: My approach: Applying Gauss's law on the two regions yields the following $$\mathbf{E}=\left\{\begin{matrix} \frac{\rho _0 \rho ...
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306 views

Charge per unit length and charge per unit area

In the Halliday and Resnick book, I am asked the find the linear charge density of the inner wall of a shell. This confuses me because the inner wall of a shell is an area, not a one dimensional line. ...
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97 views

Gauss' Law and enclosed charge

In Halliday and Resnick, I am asked to find the charge on a drum (a cylinder) given the electric field very close to the drum. In the solutions manual, the author appears to enclose the drum with a ...
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1answer
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why charges reside on the surface on conductor? [duplicate]

In a hollow conductor and in a spherical shell the charges reside on its surface and there is no electric field inside it.Please tell me the reason behind it.
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296 views

Force between two charges when the dielectric constant of the material varies?

If two point charges $q_{1}$ and $q_{2}$ are seperated by a distance $l$ apart, and the space between them is filled with a variable dielectric constant. Near $q_{1}$, the dielectric constant is ...
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4answers
96 views

Where is the fallacy in this issue related to electric charge quantization? [closed]

Suppose there are two identical conducting objects; one with 5 units of positive charge and the other is uncharged. Initially these are separated and later these are brought into contact. I guess net ...
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1answer
85 views

Determining Electric Field Inside Long Cylinder (Using Gauss' Law)?

I'm working on a problem with an (infinitely) long cylinder with a charge density, and I'm trying to find the electric field. Using the charge density, I found the enclosed charge of a proportional, ...
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118 views

Force between two perpendicularly placed infinitely long wires at a distance

Well , I saw this question in my Physics Book: Diagram (MS-Paint!): The Question : AB and CD are uniform line charges of $\infty$ length having charge densities $\lambda_1$ and $\lambda_2$ and ...
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2answers
237 views

Gauss' law in differential form and electric fields

I know Gauss' divergence theorem, according to which $$\iiint_D\nabla\cdot\boldsymbol{F}\text{d}x\text{d}y\text{d}z=\iint_{\partial D}\boldsymbol{F}\cdot\boldsymbol{N}_e\text{d}\sigma$$ where $D$ is a ...
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1answer
49 views

Capacitors, Formula for Energy [closed]

I had a quick question; As you know there are three formulas for calculating the Potential Energy of a Capacitor U=Potential Energy $Q$=Charge $C$=Capacitance $V$=Voltage/Potential Difference 1) ...
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2answers
233 views

Gauss Law - Infinite line charge

I came across a sentence which made no sense to me as I was studying the electric field of an infinite line charge: The flux through the FLAT ENDS of our cylindrical Gaussian surface is zero ...
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1answer
83 views

Movement of electrons in conductors and insulators

In conductors, the electrons can easily move unlike in insulators that prevent them from moving. What properties in conductors and insulators make them act in such way? Is it related to the position ...
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2answers
223 views

Definition of a line charge with Dirac delta function [closed]

Is the following statement correct for a line charge distribution $λ(x)$? $$ρ(\mathbf r)=λ(x)δ(y)δ(z)$$ If yes - what does it say?
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81 views

Can a piece of metal have all of its conduction electrons stripped?

Can a piece of metal have all of its conduction electrons stripped? If so, has this been done and for what value?
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1answer
61 views

Computing Charge-Density from Derivative of Voltage

In the article I've referenced below, there's a step that I don't understand. For starters, the boundary condition for a sheet of charge subject to an electric field is the following: ...
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0answers
56 views

Electrostatic energy of a distribution of charges

I read, in Gettys' Physics, that, if $N$ charges moves one by one from infinity to a certain point, i.e. the first charge $q_1$ moves from infinity to the arrival point $P$ while the other charges ...
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1answer
74 views

Will Coulomb law work if both the charges are moving with same speed and same direction?

I read it on wikipidia that Coulomb law will work if both the charges are at rest relatively. Will there be an effect of magnetic field also?
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244 views

Why is the potential energy of a dipole in an electric field zero when the dipole points perpendicularly to the field?

I have read that potential energy of a dipole in an electric field is taken to be zero at 90 degree as they say that it is a reference. But there must be some reason behind it?
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1answer
130 views

Gauss law example - Electric field and dA [duplicate]

I am still very confused and lost. I still dont understand why E1 is pointing down , E3 and 2 pointing up. while dA is point the left and dA2 and dA3 are in the same direction of the E3 and E2. I ...
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1answer
35 views

Gauss law question with regard to this example

I am really confused in Gauss law. Why do E3 and E2 pointing up? and also E1 pointing down? The lecture note said infer from symmetry and you will get the following but I dont really understand. ...
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1answer
33 views

Gauss Law Question [duplicate]

Why is dA pointing up and dA2 pointing down? Electric field(E1) is pointing up so isnt it suppose to be perpendicular to the surface?
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131 views

Chapter 26 Electric Fields Physics 212

A very long sheet of charge has width $L$ and surface density $n$. The sheet lies in the $xy$ plane between $x=-\frac{L}{2}$ to $x=\frac{L}{2}$ and $y=-\infty$ to $y=\infty$. Where the radius is $r=x ...
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2answers
32 views

Finding Charge given Electric Field

This question came up in a competition, and I didn't know how to solve it. ABCD is a rectangle with width $2d$ and height $d$. At point D, there is a charge with magnitude $q_1$ At point B, there ...
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1answer
37 views

The electric field created by a uniform charge density

Given the electric field defined by: $$\vec {E(\vec r)}= x \hat {x} $$ There is no obvious contradiction with the classic electro-magnetic theory. But: $$\vec \nabla \cdot \vec E = 4 \pi \rho(\vec r) ...
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1answer
19 views

What are the potentials of a battery with respect to earth?

Assume an open-circuit voltaic cell. We know that the cell maintains a potential difference between its terminals. That is $V_+ - V_- = E$. Now, if I connect $(-)$ to earth using the earth terminal ...
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69 views

Gauss Law Question. Could anyone explain to me why does S3 is 0 in this lecture note example?

Why does S3 equal to 0 ? for E3 dot dA = 0? Could I also know why does dA1 and dA2 point up and down? while dA3 point to the right?
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2answers
393 views

Maximum limit of charging a capacitor

We say that we can charge a capacitor in proportion to the potential difference we apply across its plates and the maximum potential difference depends on the dielectric strength of the medium. Now ...