Tagged Questions

Electrostatics is concerned with the field and potential of stationary electrical charges and electric charge distributions. Problems are this type are almost exclusively concerned with mathematics of geometries using the inverse-square law.

learn more… | top users | synonyms

0
votes
1answer
9 views

Charge density on a plate of a realistic capacitor

Suppose we have a realistic capacitor,connected to a constant voltage source, with plates at some distance $d$ and a varying charge density across plate due to edge effects. Is it correct to assume ...
-1
votes
1answer
19 views

Capacitance of two non parallel plates

What is the formula for capacitance of two non parallel plates at an angle with each other?If the plates were parallel then the value can be calculated as (PermittivityX area of one plate)/distance ...
-2
votes
1answer
46 views

What exactly is density in the context of field lines? [on hold]

While I was reading I encountered a statement which says [...] density of field lines passing through a circle of radius $r$ is $\pi rn/2$. But why will we divide by circumference for density? ...
0
votes
2answers
14 views

What happens to the electric charge of a rod and a cloth if the rod is rubbed with a cloth? [on hold]

We have a rod and we rub it with a cloth. Will the rod have a positive charge and the cloth have a negative charge? Will both the rod & cloth have a positive charge? Both rod & cloth have a ...
0
votes
0answers
10 views

Introducing a conductor in a capacitor [on hold]

1) A capacitor is taken and a Conductor (Not a dielectric) is inserted in between the plates (made of a different material other than the conductor) like: What will be the new capacitance, How much ...
0
votes
0answers
13 views

electrostatic charge distribution in geometrically arbitrary shape

If I have a small point charge Q suspended into the cavity of a bowl, then obviously it will induce some negative charges onto the surface of the cavity, but will the induced charge be equal to -Q in ...
0
votes
0answers
10 views

Determining range of integration for electric filed of a semi-circle contour

Suppose we have a semi-circle contour in $xy$ plane ( it is oriented so that all of it lies at $y<0$) , and an arbitrary point on $z$ axis. It has linear charge density $\alpha$ and radius $a$ The ...
0
votes
1answer
32 views

Want to know about divergence [duplicate]

Can anyone please explain how to know whether a vector field has divergence or not by seeing its diagram? I have read that a vector field must change for having divergence but why is divergence zero ...
12
votes
5answers
415 views

What keeps electrons on a negatively-charged conductor from leaving?

Imagine a negatively charged conductor in a vacuum. The excess electrons will be spread out over the surface such that the net electric field inside the conductor is zero. What keeps these extra ...
0
votes
1answer
34 views

Energy of a charge inside spherical conducting shell

A point charge $q$ is at the center of an uncharged conducting spherical shell of finite thickness, with inner and outer radii $a$ and $b$ respectively. Find the work done on the system when $q$ is ...
1
vote
1answer
29 views

Electric Potential-can anyone give the concept behind this?

Three points A, B and C lie in a uniform electric field (E) of 5 x 103 NC-1 as shown in the figure. Find the potential difference between A and C. I think there is some trick? How can the pd ...
0
votes
1answer
15 views

Electrostatic Potential-I tried many times ,but failed

A positive charge Q is placed at point O. Is the potential difference (Va-Vb) positive,negative,or zero,if Q is (i)positive,(ii)negative? Can anyone give the concept behind this?
4
votes
1answer
60 views

Is the charge distribution for an electric field unique?

If the electric field and boundary conditions are known exactly for a region of space, is it true that there exists only one charge distribution in that region of space that could have produced it? ...
0
votes
1answer
29 views

Derivation of a work done by forces on charge

Feynman claims is his lectures the following statement: Suppose we have two charges $q_1$ and $q_2$ separated by the distance $r_{12}$. There is some energy in the system, because a certain ...
0
votes
2answers
44 views

How does the force between two charges becomes zero?

In case of Coulombs law, $$ F=k\frac{q_1q_2}{d^2} $$ So, if $F=0$, then $q_1q_2$ must be 0. Is this true?
2
votes
1answer
48 views

Laplace equation vs Gauss theorem

Two concentric conducting spherical shells of radii $a_1$ and $a_2$ ($a_2>a_1$), are charged to potentials $φ_1$ and $φ_2$, respectively. Determine the electric potential and field in the ...
0
votes
0answers
9 views

Output frequency of bistable multivibrators [migrated]

I was wondering if there was a way to determine why the output frequency is half the value of the input frequency based on the schematic. I am currently learning about multivibrators in the Navy and ...
-1
votes
0answers
23 views

Electrostatic Force [closed]

Two nickel coins with identical charges are separated by 1.5 meters. If the forces exerted by the coin to one another are both 2.o Newton. What is the charge on each coin?
-2
votes
0answers
11 views

Electric field of cylindrical charge distribution-Advanced [closed]

I need to set up the integrals that describe the electric field outside a uniform, finite, cylindrical charge distribution. Distribution can be of length L and diameter R and have its longitudinal ...
0
votes
0answers
23 views

A Question about Two Electrically Charged Particles [closed]

There are two electrically charged particles $A$ and $B$ on a level frictionless surface. Particle $A$ is fixed at the origin of a rectangular coordinate system on the surface, whereas particle ...
2
votes
1answer
67 views

Usage of Poisson's equation?

I revisited electrostatics and I am now wondering what the big fuzz about Poisson's equation $$\nabla^2 \phi = -\frac{\rho}{\varepsilon_0}$$ is. Wiki says One of the cornerstones of electrostatics ...
0
votes
1answer
13 views

How does the dieletric displacement change among two dieletric materials?

Here's a question I am working on. "A sphere of linear dielectric material with permittivity $\epsilon_1$ and radius $a$ is surrounded by an infinite region of linear permittivity $\epsilon_2$. In the ...
3
votes
1answer
40 views

Flashing a fluorescent light bulb with high voltage

My son and I built a Wimshurst machine (our second try) over the last couple of weekends. It works -- not terribly well, as it only makes 2cm sparks with 20 cm disks (something like 60 kVolt when it ...
0
votes
0answers
22 views

electrostatic force vs gravitational force [duplicate]

I have question regarding the forces caused by electrostatic charges and gravity. From the explanation here in the link just by existing an object with mass distorts space-time. Will there be a ...
0
votes
0answers
14 views

How does the Triboelectric effect work? [duplicate]

The general description for the Triboelectric effect (the main cause of static electricity in everyday life) is that when two certain materials come into contact, electrons are transferred between ...
0
votes
1answer
26 views

Finding energy stored in a capacitor

i am given a voltage time graph for a capacitor circuit. How to find energy stored in that capacitor at various time instants? Can we just calculate by using $\frac{1}{2}CV^2$ We are given capacitance ...
0
votes
2answers
39 views

Relation between electric field and dipole moment

I want to show the following equality $$\int_{\left|\vec{r}\right|<R}d^3r\vec{E}\left(\vec{r}\right)=-\frac{\vec{p}}{3\epsilon_0}$$ where $\vec{p}$ is the dipole moment of a charge distribution ...
1
vote
1answer
94 views

How is the electostatic field propagated by the vacuum? How does a charge feel the presence of another charge when there is NOTHING between them?

Is the word "vacuum" equal to "nothing"? Imagine two charges of opposite sign, far from one another in vacuum, and moving with constant velocity - s.t. none radiates energy, none emits photons. At ...
0
votes
2answers
35 views

Polarization vector of dielectric electrostatics

I know two laws for Polarization vector of a dielectric material $$\vec P = N q \vec{\Delta L}$$ Where N is the number of dipoles per meter cube, $\vec{\Delta L}$ is the vector that represents the ...
1
vote
2answers
56 views

Electrostatics and two electric charges

How can two identical metallic objects have the same but opposite charges (one loses electrons and one gains electrons) when we know that metals have the ability to lose electrons only?
0
votes
0answers
27 views

Human between capacitor plates

I was wondering what would happen if we were to put a person between two ideal capacitor plates such that electric field between plates is for example $10^{10} \frac{V}{m}$ and the plates are at a ...
1
vote
1answer
81 views

Charge distribution on a doughnut shaped conductor

In a spherical solid conductor the charge is always on the outer surface.Even if the sphere has a cavity,the surface of the inner cavity can not carry a charge due to Gauss's Law. What would be the ...
0
votes
3answers
42 views

Explaining the current flow of the positive shunt clipper (diodes)

I am currently studying clippers or parallel limiters in the Navy and I was wondering if someone could clear up a few things for me. Here is a picture that fits my description: A clipper has a ...
0
votes
1answer
29 views

Tranverse electromagnetic waves

TEM waves do not exist in waveguide. Is this the correct explanation- Both curl and divergence of TEM are zero inside the waveguide and because of the boundary conditions (electric field zero at every ...
0
votes
1answer
39 views

Forces between charged particle

I am given two charged particle of same charge at distance of $r$ , they initially apply force of magnitude $F$ now infinite dielectric(of constant 4) of width $\frac{r}{2}$ is introduced between ...
0
votes
1answer
29 views

What are the consequences of connecting a non-ideal conductor to a battery in open loop?

Suppose I have a battery with $\Delta V=5[\mathrm{V}]$. Now I connect a piece of a metal wire to the "+" side of the battery only. Let's assume that the ambient air is not conductive at all: Are ...
1
vote
3answers
235 views

Why capacitance is given as constant value in Farads, and not as max charge in Coulombs?

The equation for capacitance is $Q=CV$ or $V={1\over C}Q$. I don't understand what is the physical meaning of this "$C$": Does the charge in a system changes linearly with voltage under all ...
0
votes
0answers
10 views

Magnitude of Electric field vector on the axis of a conducting half sphere

I need to calculate the electric field of a conducting half-sphere shell ( just the outer shell, it has no base ) of a radius $a$ and surface charge density $\sigma$ on the arbitrary point on axis ...
0
votes
1answer
36 views

Why does energy rise in a constant voltage capacitor after inserting a dielectric?

For example from this link: http://te.fisica.edu.uy/fuerza_en_Capacitor.pdf we can deduce, that the work the electric field inside a constant-voltage capacitor does during the insertion of a ...
1
vote
1answer
16 views

Find quantity of electricity of two circular faces

So, there are two circular conductive sheets with quantities of electricity of Q and -Q. If I know that the distance d between them is 0.002 meters and their radius is 0.1m and the voltage between ...
1
vote
2answers
46 views

Using Coulomb's law to solve for a continuous charge distribution [closed]

I have been trying to evaluate this specific integral and have been completely stuck. $$\frac{1}{4\pi \epsilon_0} \int^L_0 \frac{2\lambda z}{(x^2+z^2)^\frac{3}{2}}dx.$$ I am a freshman and have been ...
0
votes
1answer
8 views

discharging static

Quick question, if you have a buildup of static charge causing sheets of paper to stick together, can you have a grounding foil touching the paper to dissipate the charge to prevent pages from ...
1
vote
0answers
38 views

Electric field at a point [closed]

We consider a thin disk whose center is $O$ and radius is $R$, which has an electric surface charge density of $\sigma$. We want to find the expression of the electric field $\vec{E}$ at a point ...
0
votes
1answer
37 views

Electric field and potential between two charges [closed]

There are two point charges on the $x$ axis and $x'$ is a place where the potential, relative to infinity, is the biggest. Why is the electric field zero at this point?
1
vote
0answers
36 views

Electric field in a “concave” conductor

I am aware that the electrons are distributed across charged conductor surface so that the areas with smaller radius of curvature have more charge per surface area. But what happens when the ...
0
votes
0answers
35 views

Calculate electric field without using Gauss law

Given a uniformly charged sphere ( total charge $5 nC$ ) of radius $R=10 cm$, write the equation of electric field vector for any distance $r (r > R)$ from sphere center and calculate total ...
0
votes
0answers
23 views

Addition of forces in dielectric material

In this paper (page 2 of document) it is said that: Because this calculated force was comparable to the gravitational force, they assumed that the same would be true for the forces on a ...
2
votes
3answers
57 views

Calculate the flux of a point charge with Gauss's law

I know from my class that to calculate the flux of a point charge with Gauss's law, I have to make a surface that intersects with all of the flux lines resulting from the charge, and then make this ...
0
votes
1answer
21 views

Finding voltage between two points in space

If electric field vector is defines as : $\vec{E} = \frac{V_0x^2}{a^3} \vec{i_x} + \frac{V_0y}{a^2} \vec{i_y} $ where $V_0 $ and $a$ are known constants, $\vec{i_x}$ and $\vec{i_y}$ unit vectors of ...
0
votes
0answers
23 views

Electric Field Resulting from a Conductor

In preparation for an upcoming exam, I've been attempting to visualize the electric field produced by a conductor in a variety of situations. I asked myself the following question and attempted to ...