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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Charges on capacitor after full charge by battery

When the charging is finished what will be the charge on an ideal parallel plate capacitor ? To be specific what are the charges on different faces of the 2 plates ? All the books say, after 100% ...
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52 views

Potential vs Potential Difference for a line charge

How would I calculate potential for an infinite line of charge a distance 'r' away from it? What does the reference point for potential difference mean? I know delta v = Q/(2pi*epsilon0*L)*ln(r2/r1) ...
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60 views

Parallel Connection of Capacitor

Assume Two Capacitor filled with different dielectrics with dielectric constant $K_1$ and $K_2$ respectively in Parallel connection. Then we have same voltage $V$ on both capacitors. Therefore, ...
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1answer
39 views

Transfer of electrons and static electricity

From what I currently understand about static electricity, electrons "jump" from one object to another, which object loses electrons depends on where it falls on the Triboelectric series. For example ...
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23 views

Physical Invariance and Method of Images

I will motivate my question, then state explicitly. If I have a system with one point charge and a grounded plane as here, then I can solve for the potential by solving a similar system with two ...
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0answers
58 views

Are the boundary conditions for a sphere in an electric field affected by its charge?

Find the potential outside a charged metal sphere (charge $Q$, radius $R$) placed in an otherwise uniform electric field $E$ I know this question can be solved by the method that so called ...
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1answer
40 views

Work done by Electric Field vs work done by outside force

I'm confused as to the signage of the equation: W=qv, W=-U, W=-qv? When is work positive? When is it negative? Why is this different for the work done by the electric field vs the work done by an ...
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1answer
35 views

Field inside an infinite uniform rectangular box, diverges?

I was solving by direct integration the problem of an infinite rectangular box, with a nonzero width, e; charged with a constant density, $\rho$, as shown in the following picture: The integrals ...
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2k views

Is it (practically) possible for a large building to be a Faraday cage?

In my sophomore year of high school, my P.E. teachers kept on complaining about how phones didn't have a network connection in our gym, regardless of model, service provider, etc. A couple of feet ...
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20 views

Electric field of a charged conductor

It’s been said that the electric field of a conductor is always perpendicular to its surface. However, I’m having difficulty understanding this. There are only a limited number of excess charges on ...
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19 views

How Maxwell's equations are derived from fundamental equations for electrostatic and magnetostatic models [duplicate]

How Maxwell's equations are derived from fundamental equations for electrostatic and magnetostatic models.
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14 views

General electrostatics in dieletric

I was told that the electrostatic potential inside a dielectric is the sum of the solution of the Poisson Equation for the boundary condition V=0 for |t-t'|->Infinity plus a solution of the Laplace ...
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0answers
187 views

Method of Images - Line Charge Above Infinite Grounded Plane [closed]

For a uniform line charge, $\lambda$ placed on an infinite straight wire at a distance $d$ above a grounded conducting plane. We let the plane run parallel to the x-axis, and directly above it ...
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1answer
62 views

How big of a capacitor would I need to release 5 amps for 0.2 seconds? [closed]

Just what the title says, 5 amps for 0.2 seconds. Please bear in mind that I have absolutely no grasp on electrical wiring, so I would appreciate simple terms. What I need to do is release a burst of ...
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1answer
85 views

Capacitors in a series circuit with dielectric

When a dielectric slab is inserted between the plates of one of the two identical capacitors in Fig. 25-23, do the following properties of that capacitor increase, decrease, or remain the same: (a) ...
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1answer
21 views

Intersection of electric field lines where the two lines have the same slope at intersection

We know that the electric field lines cannot intersect in this way: But what about this way?(where the two lines have the same slope at the point where they touch) : Could the second situation ...
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1answer
66 views

Two capacitors in parallel vs series - electric field?

If we have two parallel plate capacitors in parallel, do the electric fields between their plates have to be the same? What happens if we have a coaxial cable of length $L$, which looks like this: ...
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1answer
28 views

Work done when applying an electric field?

On these example questions from MIT in the solution to 4.1 they write the work done by applying the electric field to be: $$W=V_0 \int \vec E \cdot d \vec D$$ Where does this equation come from and ...
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1answer
58 views

What actually happens in a capacitor?

I have this doubt wandering through my mind for a long time. A capacitor, according to the definition of physics, is a charge storage device. In a simple parallel plate capacitor, when electrons ...
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1answer
24 views

Why is this the interaction energy?

Why is $\epsilon_0 \int_{\text{all space}} \vec{E_1}.\vec{E_2} dV$ the interaction energy of two charges bodies, where $\vec{E_1},\vec{E_2}$ are their electric fields at a point?
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2answers
328 views

Gauss's law… if the integral defining $\boldsymbol{E}$ diverges?

I have been told (here) that, under particular conditions, the electric field produced by a charge present in space $D$, defined by ...
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1answer
52 views

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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1answer
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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19 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
71 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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23 views

Electrostatics effect on resistance values [closed]

Consider two parallel metallic plates separated by a silicon dioxide layer of thickness tox (like a capacitor). In this case I am applying a positive voltage to the top metallic plate. Now due to ...
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1answer
139 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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57 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
52 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
109 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
376 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
59 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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67 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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1answer
47 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
44 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
76 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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0answers
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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2answers
65 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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0answers
6 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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1answer
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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1answer
47 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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1answer
26 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
39 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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0answers
35 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
41 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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0answers
211 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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1answer
70 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
254 views

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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1answer
80 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 ...