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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Tilted metallic plate touching two capacitor plates
A parallel plate capacitor of capacitance $C$ is as shown. A thin metal plate A is placed between the plates of the given capacitor in such a way that its edges touch the two plates as shown. Find the ...
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Electric Field due to line charge
There is a particular paragraph in Electricity and Magnetism by Purcell that I'm not able to understand. It's the last para in section 1.13, pg-30 which goes like this
The field of an infinitely long ...
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What does dot product really mean?
While calculating the flux of a vector field through a region, we need to find the normal components of the vector field i.e perpendicular to the surface. Now I don't understand why we take the dot ...
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Charge distribution on two charged bodies connected by a wire
A question specifies two identical conducting spheres, both of negligible radius (I take this to mean they're to be treated as point charges), and with charges of opposite sign. They're separated by ...
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Why the any point has same magnitude of electric line of force?
The $n~$ point charges have been placed on the same straight line.
$\theta_{i}:=\text{angle between 2 line segments of point A like shown as the above diagram.}$
We want to deduce the below equation ...
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Relation between quasi-static and fully dynamic $\vec E$ and $\vec H$
Imagine an infinitely long coaxial cable with an inner wire of radius $a$ and outer radius $b$. The space in between the cable is filled with air ($\epsilon=\epsilon_0$).
Suppose the inner cable ...
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Potential Energy of a Sphere
A spherical volume of radius $a$ is filled with charge density $\rho$. What is the potential energy $U$ of this sphere (what is the work done in assembling it)?
I can't really wrap my mind around ...
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Is it possible to overload a thin conductive object with electrons?
A parallel-plate capacitor is a very simple device. To make one, you can take two metal plates, separate them with a dielectric material, and voilà! You have a capacitor.
Given a dielectric ...
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How is $\nabla\cdot \mathbf P$ sufficient to describe the volume polarization $\mathbf P$
I'm self-studying Panofsky and Philips' Classical Electricity and Magnetism. In Section 1-10, they talk about the potential due to a volume polarization $\mathbf P$ being effectively divorcing into ...
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Where should I put a fixed amount of dielectric to maximize the capacitance between two widely separated plates?
Imagine that I have a capacitor made from two parallel finite plates, separated widely enough that there is a significant fringe field. (Thus, the capacitance is not given exactly by $\epsilon_0 A/d$....
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Mathematically proving that field in a conductor is zero for equilibrium condition using Lagrange multipliers
I was reading this article here and near the half of it, the author discusses a way to prove that potential is a body is constant is the state which minimizes potential of a body. I was able to follow ...
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How is magnetic dipole "created"?
I know that the electric dipole can be created when the electron cloud is displaced realative to the nucleus. I am trying to draw parallel to this and to better understand this topic, so please help ...
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Radiations in static fields by poynting Vector
Why is the Poynting vector $\vec S=\frac{1}{\mu_0}(\vec E\times \vec B)$ not able to produce radiation when fields are static?
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Electric field computation with two point-charges and an infinite conducting sheet [closed]
Coordinates in this question are in metres:
An infinitely large conducting metal sheet is located at z=0 (covers the xy plane). Point charge of 20 μC is at (0, 0, 1) and of -10 μC is at (2, 0, 1). ...
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Why does potential of a conductor decreases if a negatively charged conductor is brought near a positively charged conductor?
Also, how should I imagine potential in my mind? How should I picture it?
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Equipotential surfaces for a knotted charge distribution
Suppose we have a compact submanifold $K$ of $\mathbb{R}^3$ with uniformly distributed charge. Neglecting multiplicative constants, the electric potential $\Phi(\vec{x}) = \int_{K} \frac{dK}{|x - k|}$...
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Work required to bring point charge towards conducting planes [closed]
Consider the following configuration: A point charge sits in the upper right $(x>0,y>0,z)$ space. The other quadrants are separated by two conducting planes in the $(x=0,y,z)$ & $(x,y=0,z)$ ...
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Why can't all plastics form electrets?
What property should a dielectric need to become an electret?
At first, I though polar dielectrics formed electrets, but non polar dielectrics like polypropylene also form electrets.
So what property ...
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How can I calculate the $D$ field when all the free charge is on a conductor embedded in a dielectric?
Let $K$ be a bounded piece of conductor, embedded in an isotropic, homogeneous, uniform dielectric of permittivity $\epsilon$.
Let $ \vec r$ be a point in the exterior of the conductor. Let $\rho_f$ ...
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Electric field inside a conductor is zero
My professor has stated that the electric field inside a conductor is 0.I understand this
However, he has also said that even if the conductor has some hole in it, the electric field inside this hole ...
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Is principle of superposition valid for extended conducting objects whose charge distribution is affected by presence of other charges nearby?
let me explain my question with an example. Say we put a charge at the centre of an metallic hollow charged sphere and measure electric field at a distance larger than the radius. It is easy to ...
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Minimizing electric potential means potential difference is zero
I had been working on a problem recently and i stumbled upon something I did not quite get. So the relevant part of the problem is like this:
Suppose we have two conducting spheres with radii a and
b ...
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How is charge confined to the region in which it is placed on a non-conductor?
"A charge placed on an insulator is confined to the region in which it was placed. An insulator has no charge carriers that are free to migrate within the boundaries of a body"
(Whelan & ...
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Linear charge density of a path on a surface
My problem is somewhat general. I do not think it has been posted before, however, I am new to Physics Stack Exchange so please, if I'm wrong, feel free to let me know.
I will give an example problem ...
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$E\times B$ drift in strongly nonuniform fields
Potential is defined as $\{\phi,\, 0,\, A,\, 0 \}$; fields are static and depend only on the axial coordinate $x$: $E_x=-\partial_x\phi$, $B_z=\partial_x A$. Charged particle moves in the $\{x,y\}$-...
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Leyden jar-How does the storing process work?
We can view the Leyden jar as a capacitor and a dielectric (glass). When the metal parts are charged thus is due to influence in the dielectric a counter electric field to be found.When we separate ...
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Doubt regarding grounding of a sphere and charge distribution [closed]
An insulated sphere with dielectric constant $K$ (where $K>1$) of radius of $R$ is having a total charge $+Q$ uniformly distributed in the volume. It is kept inside a metallic sphere of inner ...
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What are the physical principles behind human earthing? [closed]
"Earthing" is a kind of trend where people walk around barefoot claiming that they achieve a neutral charge by being in direct contact with ground with no insulator in between. What are the ...
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Relations between symmetries in sources and fields
I've edited this question way more times that I like to admit. I'll do my best
Relation between highly symetric charge distributions and $\nabla\times\mathbf{D}$:
In electrostatics, for some charge ...
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Electric field on the surface of an infinite sheet of a perfect electric conductor
let's consider ai infinite and flat sheet of charge distributed on a conductor. Well, it is known that the electric field at steady state on its surface (which is orthogonal to it) is equal to:
$\ E =...
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Potential between a metal sphere and spherical shell which are not quite concentric
I have been struggling with this problem for some time by now.
An insulated metal sphere of radius $a$ with total charge $q$ is placed inside a hollow grounded metal sphere of radius $b$. The centre ...
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Two Charges on sides of an Uncharged Metallic Cube How to Find Electric Field Inside the Metallic Cube? [closed]
The Electric Field must be zero inside the Metallic cube but as per the text book answer there is electric field at Point P which is closer to the left side of the Metallic cube. There is a ...
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Even though the field becomes infinite near the charge a gaussian surface can pass through the continuous charge distribution. How? [duplicate]
Even though the field becomes infinite near the charge a gaussian surface can pass through the continuous charge distribution and have a finite value of flux. How?
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Capacitance of spherical capacitor when inner surface of outer sphere is earthed [closed]
Let there be two concentric shells in which the outer sphere contains charge Q1 and inner sphere contains charge Q.Capacitance of spherical capacitor when the inner surface of the outer sphere is ...
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Charge density of a point charge [duplicate]
Is it right to say that the charge density of a point charge is infinity? if I were to take a uniformly charged ball with radius R and take the limit $R\to 0$, won't I get an infinite charge density ...
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Electric field due to a ring/disk at a point straight above a hypothetical point on the axis of ring/disk [closed]
Its easy to find the electric field due to a uniformly charged ring or disc at a point on the axis of ring/disc. But I cant figure out a way to find the electric field or even potential at a point at ...
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Is static electricity an "electrical discharge"?
I understand that any electrical discharge such as corona discharge is the scattering of electrical charge through a medium; most likely a gas ("discharging charges").
As the air is a gas, would it ...
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In an $RC$ Circuit, when polarity of a battery is reversed, how much energy is dissipated into heat?
https://ibb.co/tPL02dZ
In the figure, a $ 20 nF $ capacitor is connected in parallel across a $ 30 nF $ capacitor. There are $2 $ resistors of $10 Ω$ connected in series with the capacitors. A ...
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Charge inside a charged hollow conducting sphere with a hole
How are the following results theoretically explained?
As part of an electrostatics exercise we were to measure the charge on the outside and inside surfaces of a charged hollow conducting sphere ...
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A point charge near a conducting cylinder
As we could figure out the point charge induced image charge on a conducting sphere in Jackson's book. Is there any way to figure out the point charge induced image charge form on a conducting ...
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Oil droplet in Electric field [closed]
suppose a horizontal plate capacitor. They are separated by $d=0.005 \text{m}$. In a homogeneous field, the oil droplet ($m=3\cdot 10^{-15} \text{ kg}$) sits at the bottom of the lower plate. Like a ...
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A travelling field; Feynman lectures on Physics Volume 2
In Feynman's Lectures on Physics, volume 2, Chapter 18 (18-5), we look at the creation of a electromagnetic field, due to a moving infinite sheet of charge,
By looking at the Maxwell equations ...
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Condemnable limit for the electrostatic field? [closed]
When we define the electrostatic field (law's Coulomb), generated by a $Q$ charge calculated in a point $P$ of the space, we place a particle with a small positive charge $q_0$, called a test charge ...
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Discontinuities in electric fields
I'm a mathematician self-studying physics for fun and I'm trying to wrap my head around a simple concept, which is a consequence of approximations. Basically, by Coulomb's law, if I have a point ...
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Single electron in conductive cavity
It is a basic result in electrostatics that a charge $q$ in an arbitrary cavity of an ideal conductor will generate a total charge $-q$ on the surface of the cavity in such a way that the electric ...
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Reason for repulsion of like charges
Like charges repel and unlike attract. Like magnetic poles repel and unlike attract. Since electricity and magnetism are fundamentally linked , is this attraction/repulsion due to the magnetic fields ...
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Integrand discontinuity of surface integral of electric field of dielectrics
I am reading an article here on dielectrics
Equation $(4.10)$ is:
$$\Phi(\mathbf{r})=\dfrac{1}{4\pi \epsilon_0}\int_{V} \dfrac{d^3r'}{|\mathbf{r}-\mathbf{r'}|} [\rho (\mathbf{r'})\ -\nabla'.\mathbf{...
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Charges in different mediums [duplicate]
Generally we read or solve problems about charges in the same medium.
I wonder what would happen if the two charges were placed in different mediums. eg.) One is placed in vaccum and other is placed ...
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Energy Density Confusion [closed]
The energy density of an electromagnetic field with a linear dielectric is often expressed as $0.5 E \cdot D$. It is also known that energy can be found by $\int_{V} \rho V dV$. Using the latter, the ...
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Dependence of electrostatic force on the surrounding medium
Two unlike point charges held at a fixed distance from each other. The force between them is measured. Then a brass rod is placed exactly in the midpoint of the line joining the 2 charges. Will the ...