# Tagged Questions

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 [tag:magnetic-...

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### Formula for discontinuity of electric field across boundary

The formula for the discontinuity of the electric field across a boundary is given by$$\vec{E}_{\text{above}} - \vec{E}_{\text{below}} = \frac{\sigma}{\epsilon_0} \hat{n}.$$ In the derivation of this ...
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### Where has the energy gone when the test charge turned away?

Consider an insulated ball with some charge, $q_1$, inside it. Now we make a small area over that ball uninsulated, i.e we had cut a small portion. Now when we bring a test charge from infinity near ...
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### How do I get the angle for the $x$ and $y$ component of the electric field for four equidistant particles?

Four particles form a square of edge length $a= 5.00\ cm$ and have charges $q_1= +10\ nC$, $q_2=-20\ nC$, $q_3=20\ nC$, and $q_4=-10\ nC$. In unit vector notation, what is the net electric field the ...
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### System of point charges, work to move one of the systems point charge around

Suppose we have an electron at $\vec{x}_1=(0,a,0)$ and a proton at $\vec{x}_(a,0,0)$. Now i want to move the proton to the point $\vec{x}_3 = (0,0,0)$ and want to know how much work do i need for that....
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### System of point charges, Potential related question

Suppose we have two point charges in the Cartesian coordinate system. $q_1= e, q_2 = 2e$, where $q_1$ is positioned at $(0,0,0)$ and $q_2$ at $(a,0,0)$ for $a > 0$. Further there is a point charge ...
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### Surface bound charge in the electric displacement

In Griffiths, the electric displacement is written with just volume charge density, and that is because, he says, 'we cannot apply gauss law precisely at the surface of a dielectric, for here volume ...
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### Description of charged sphere with Heaviside function in cylindrical coordinates

I need to describe density of charge of uniformly charged sphere (radius R, total charge Q, position of centre (0,0,0)) with Dirac delta function and Heaviside step function. The hard part is to ...
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### Induced motional EMF where the wire is stationary and the field source is moving?

If a wire is moving in a magnetic field $B$, there is a Lorentz force acting on both the postive and negative charges, separating them to create an electric field, which is a great explanation to aid ...
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### Electric field inside coaxial cable

I have a very long coaxial cable with a cylindrical core of radius $a$ that has negative charge density $\rho = -k/r$ where $r$ is the distance from the axis of the cylinder, and an outer shell of ...
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### Tesla's radiant energy system [closed]

Would Tesla's radiant energy system work better on earth if there was no magnetosphere, and more radiant energy from the sun is able to reach the system? Thanks!
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### 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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### triboelectric effect at a liquid-liquid boundary?

In reading up on the triboelectric effect, most experiments deal with solid-solid interfaces. I've found some studies regarding solid-liquid boundaries, and even some engineering manuals outlining the ...
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### What's the difference between $E=\frac{F}{q}$ and $E=\frac{kQ}{r^2}$? [closed]

Can $E=\frac{kQ}{r^2}$ only be applied to situations outside of parallel plates?
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### Why don't charges build up on wires like plates of a capacitor?

Suppose you have a parallel plate capacitor and you want to charge it by using a battery. You will connect the plates with the two terminals of the battery. Now my book says that the charges will get ...
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### Electric field of a negative charge

How was it discovered that the electric field of a negative charge points towards the charge itself? Is it true? (Courtesy of wikipedia)
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### Why the direction of dipole moment is from negative charge to positive charge?

An electric dipole moment is defined as $p = q\times 2d$. How to understand it physically? Why the direction of the electric dipole moment is from negative charge to positive charge?
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### Theoretical questions regarding the electric field

I found some theoretical questions in an old test of my school, and would like some help with the ones I cant answer: It is said that the electric field is an intermediary of the electric ...
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### How to set up line integral of electric field? Confused over notation

In multivariable calculus the line integrals was parameterized and denoted: $$\int_C \mathbf{F} \bullet \, d\mathbf{r}=\int_D\mathbf{F}(\mathbf{r}(t)) \bullet \frac{d \mathbf{r}(t)}{dt} \, dt$$ ...
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### Refraction of the electric field lines, at the interface of separation between two conductive media

Suppose we have 2 media with electrical parameters ${\varepsilon _1},\,{\sigma _1}$, respectively ${\varepsilon _2},\,{\sigma _2}$, separated by the plane surface $\Sigma$; electrical charge surface ...
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### Why doped silicon does not undergo electrostatic discharge?

Doped silicon is charge neutral overall, but since the extra added carriers are only weakly bounded (~45meV) they become delocalized. Since the concentration of silicon is 5-9 orders of magnitude ...
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### Two different electrostatic charges in rotation

It's a theoretical problem. I mean I drawn a circle and I consider this circle exist. I would like to understand how works this device composed of a circle and two charges: Two charges fixed on a ...
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### Connecting spheres of different capacitance

If I connect a sphere of capacitance $C_1$ to a charged sphere of capacitance $C_2$, will the charge be distributed evenly on both spheres (is the charge density going to be equal on both spheres?). ...
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### electric field inside hollow conducting bodies

Let's say that there's a hollow conducting sphere placed in the presence of an external electric field and there's a + ve charge placed inside the sphere at a point other than the centre of the sphere,...
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### Capacitance as integral of electric field [duplicate]

My question refers to part of Ex. 1.17 in Jackson, 3rd Ed.: A volume $V$ in vacuum is bounded by a surface $S$ consisting of several separate conducting surfaces $S_i$. One conductor is held at ...
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### Meaning of boundary condition for steady current density?

Although I understand the derivation of boundary condition in case of steady electric current but I did not understand, that the electric field which is in direction of $J$ current density that is ...