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.
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195 views
Why can we use Gauss' law to compute electric field?
For simplicity I'm considering only the sphere case.
In the Gauss' Law formulation we have some field E introduced by charges $Q$ inside some sphere, then we compute flux and integrate, and we get ...
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2answers
193 views
Ionized Depletion Region, Why aren't those charged being excited?
Ok so I understand the PN junction, and how when 2 Semiconductor materials are placed together the Electrons will jump into the Holes near the junction creating a Negatively Ionized Atoms on the ...
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1answer
123 views
Finding the electric field on a point (x,y,z) using Coulomb's Law
Using Gauss' Law, the answer is $$\frac{Q}{4 \pi \epsilon R^2}.$$
However if I were to do the integration using Coulomb's Law, I get
$$ \int_0^{2\pi} \int_{0}^{\pi}\int_r^a \frac{\rho \sin\theta dR ...
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1answer
35 views
Permanently charging a sphere by induction using a high voltage
I want to charge a sphere using a van de graff generator , it would sound easy , but using a 1 MV or a 900 KV is really hard, it is enough to break like 1 meter of air so whenever i try to ground the ...
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0answers
65 views
Electric field singularity
What's a general proof for the log-singularity of electric field near the edge of a uniformly charged surface?
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2answers
138 views
Electric field lines
If electric field lines cannot terminate in empty space, in the simple example of two equal charges what happens to the line starting from one of the charges toward the other in the middle?
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0answers
45 views
numerical investigation of stability [closed]
I am trying to find the required specifications of an paul RF trap, in which a proton can be confined.(trap dimensions,voltage frequency and amplitude used, etc). I have to solve the equations of ...
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1answer
44 views
Grounding insulative material
When grounded, can an insulative material keep its charge for any measurable length of time? Or, I suppose, if it was a perfect insulator, would it discharge at all?
An example might be a charged ...
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1answer
144 views
Finding the electric field
The charge per unit length on a long, straight filament is -91.9 µC/m.
(a) Find the electric field 10.0 cm from the filament, where distances are measured perpendicular to the length of the ...
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2answers
2k views
Dirichlet and Neumann Boundary condition: physical example
Can anybody tell me some practical/physical example where we use Dirichlet and Neumann Boundary condition. Is it possible to use both conditions together at the same region?
If we have a cylindrical ...
2
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1answer
68 views
Electrostatic charge leakage
What are the ways electrostatic charged objects leak charge in humid conditions?
Can airborne particles pick up charge by contact, then be repelled hence removing charge? If so would it be a ...
2
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1answer
151 views
Minimizing potential energy of a dipole in an electric field
My test paper asked me which way a dipole should be orientated in an electric field to minimize its potential energy. My answer was that the dipole should lie parallel to the electric field with the ...
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2answers
118 views
Calculate force of electric charges “suspended” by strings
In a question:
Two small plastic balls hang from threads of negligible mass. Each
ball has a mass of 0.110g and a charge of magnitude q. The balls are
attracted to each other, and the ...
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0answers
102 views
Metal sphere and charged ring
I think this is an interesting question, to which I don't really know the answer to. (Also, not a homework question.)
Say you have an uncharged metal sphere constrained to move in the z-axis. There ...
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3answers
323 views
Where's the energy in a boosted capacitor?
Suppose I look at a parallel plate capacitor in its rest frame and calculate the electrostatic energy, $E$.
Next, I look at the same capacitor in a primed frame boosted in the direction perpendicular ...
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1answer
192 views
Electric Fields
The problem I am working on is, "In the figure below, determine the point (other than infinity) at which the electric field is zero. (Let $q_1 = -2.45\ \mu C$ and $q_2 = 6.5\ \mu C$)
Here is a little ...
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1answer
369 views
Electric Field due to a charged sphere
Suppose we have a spherical surface with a surface charge density varying as $cos(\theta)$. Apparently one can find the electric field both outside and inside such a spherical surface by superposing ...
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1answer
154 views
Electric field of a flat metal plate and a point particle
I'm currently studying electric potential, and I'm having trouble with one of the problems on my homework:
A) A point particle with charge $+q$ is on the x-axis at a distance $d$ from the origin, ...
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2answers
97 views
How can you calculate (or convert) the Wh of a capacitor whose energy is given in Farads
When trying to compare the energy in a battery to the energy in a capacitor, the units don't match up. How can one compare a battery whose Ah are 10 and Voltage is 3 (for a total of 30 Wh) to a ...
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1answer
165 views
Revealing Electric field lines through Grass seeds in mineral oil
In one of Walter Lewin's famous lectures, he takes a small container almost completely filled with mineral oil and grass seeds (I'll keep looking for the video to link to it). He connects two ...
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1answer
151 views
Electrostatic adhesion instead of glue. Is it possible?
I am thinking about the way to attach the printed photographs to the wall but not using the frame.
And the most interesting idea for me is the use of electrostatics.
In addition I have found the ...
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1answer
37 views
Effect of electric field of plasma sheaths
How will an electric fields affect the formation of plasma sheaths?
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1answer
277 views
Electric field and insulator or dielectric
I have a uniform electric field $E$ projected from left to right and I placed an insulator or dielectric right in the middle of it. To the left of the insulator, the $E$ is the original $E$. Inside ...
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2answers
105 views
Is there a limit to the charge of a body?
Can a body be limitlessly charged? Suppose a sphere of radius $R$. Can it be charged limitlessly?
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1answer
89 views
Is it possible to charge a capacitor to any potential? Does it depend on the dielectric placed between them?
Is it possible to charge a capacitor to any potential? Does it depend on the dielectric placed between them? Or, are there other factors affecting it?
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1answer
32 views
Are the ions in a fluorescent lamps concentrated near the electrodes?
Are the ions in a fluorescent lamps concentrated near the electrodes , and just the electrons move to the other electrode or the positive mercury ions move too?
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1answer
133 views
What happens to 5 electrons on a sphere?
Let's suppose we put 5 electrons on a perfectly conducting (no resistance at all) sphere.
There's no equilibrium configuration with 5 (though there is with 2, 3, 4 or 6). So will they keep moving on ...
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4answers
311 views
No magnetic field from a static charge - Is there a simple physical argument to show why?
For a charge moving in an electric field $\vec E$, its equation of motion is given by the electric part of the Lorentz force $$\frac d {dt}\gamma m \vec v = e\vec E$$This comes from the conservation ...
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1answer
547 views
What defines the maximum charge a capacitor can store?
The formula for a capacitor discharging is $Q=Q_0e^{-\frac{t}{RC}}$
Where $Q_0$ is the maximum charge. But what property defines the maximum charge a capacitor can store?
If it depends on ...
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1answer
455 views
What is the role of battery across a Parallel plate capacitor having equal charge?
Each plate of a parallel plate capacitor has a charge $q$ on it. The capacitor is now connected to a battery. Now, which of the following options are correct?
a) The facing surfaces of the ...
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1answer
68 views
Question regarding the direction of electric field
Suppose that there are negative charges (e.g. electrons) only. There are more negative charges on left than on right. How would electric field be constructed? (So, What would be the direction?) And ...
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1answer
266 views
( Legendre Generating Function) Off axis Electric Potential from an insulated disk
An insulated disk, uniform surface charge density $\sigma$, of radius $R$ is laid on the $x,y$ plane. Deduce the electric potential $V(z)$ along the z-axis. Next consider an off axis point $p'$, ...
7
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1answer
351 views
Resistance between two points in an infinite metal sphere/cube
Let's imagine that we have a tridimensional metal object of infinite size, and decide to calculate the resistance between two arbitrary points. How would we go about doing this?
I have thought of two ...
2
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2answers
97 views
Determination of auxiliary scale in dimensional regularization
My questions are in italics. In the article [1] a dimensional regularization is presented on an electrostatic example of an infinite wire with constant linear charge density $\lambda$. It is shown ...
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2answers
209 views
Change in intensity of electric field with constant velocity
Consider a +Q charged particle is travelling towards another test charge +Q. Now what would be the difference in electric field experienced by the test charge(avoid the gradual decrease in distance ...
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3answers
265 views
Is there is any difference between Electric Flux ($\Psi$) and Total number of Electric Field lines ($E\times$Area)?
Is there is any difference between Electric Flux ($\Psi$) and Total number of Electric Field lines ($E\times$Area)?
$\psi = \Sigma Q$, and $\phi$ = Electric field intensity $\times$ Area
where Area ...
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2answers
134 views
How does an electrical field really work?
A little bit of background information: I'm planning to write a little booklet or web page about CPU/computer architecture, basically for my own education, because we didn't cover it in depth in ...
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1answer
49 views
Charging using a CRT TV set
I was doing an experiment with my CRT TV where I put aluminum foil on the screen wire it to a can and open the TV and a ring between 2 can will swing if I ground the other can. ...
2
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1answer
128 views
Do plastic shoes electrically insulate people from the ground?
I've read on the Internet that wearing plastic shoes doesn't allow electric charges we collect from our environment (PC, TV, appliances) to be earthed.
Is this reasoning correct?
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2answers
494 views
If we charge a capacitor can we discharge it into a battery?
I have read that we can charge a capacitor using a battery, but can the vice versa happen? My project needs to show a battery being charged through a fully charged capacitor.
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0answers
34 views
Working out the electron mobility from the transfer rate (1/s)
I have an electric field value for a uniform structure through which an electron travels. Given that I've calculated a transfer rate (frequency) for the electron when it goes from one molecule to the ...
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1answer
418 views
Electric field inside and outside a metallic hollow sphere
1) It is known that inside a metallic hollow sphere it will not experience outside electric field because of the charge separation of electrons and holes at the surface of sphere and creating an equal ...
2
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1answer
90 views
Working out the electric field from applied energy
I have created a simulation of one electron bouncing through a 3D mesh of molecules. The electron hopping is determined by a calculation of electron transfer rate using the Marcus equation (a result ...
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1answer
157 views
Charge on capacitor plates in series combination?
Suppose 2 capacitors are connected in series, the plates connected to the battery terminals receive charges $+q$ and $-q$, and the isolated plates in the combination receive equal and opposite charges ...
3
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0answers
121 views
Electron hopping among molecules - Marcus equation
I'm running out of professors to talk to, and I need to clarify a couple of things for the sake of making a realistic model of electron travel through a mesh.
This is about calculations of electron ...
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1answer
291 views
Finding the electric field for a shell of charge
Suppose we have charge density defined
$$
\rho(x,y,z) =
\begin{cases}
0 & 0 \leq r < a \\
K & a \leq r\leq b\\
0 & b< r
\end{cases}
$$
For some constants $K,a,b$
How would ...
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2answers
155 views
Highest man-made voltage
What was the highest voltage achieved and was it produced by electrostatic means or just some transformers and multipliers?
What are the limitations when it comes to producing voltage using ...
0
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1answer
119 views
About voltage and charge of van de graff generator
I have read that in case of Van de graff generator $V=kQ/r$ where $r$ is radius of the sphere.
If that's the case, does the same voltage results in bigger charges in bigger radii?
3
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2answers
269 views
Conservation of Charge and Method of Images
Consider the typical problem, "You have a conducting sphere of charge $Q$ and a point charge q a certain distance away, what is the force on the point charge?". The solution is a simple application of ...
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3answers
281 views
Delta Dirac Charge Density question
I have to write an expression for the charge density $\rho(\vec{r})$ of a point charge $q$ at $\vec{r}^{\prime}$, ensuring that the volume integral equals $q$.
The only place any charge exists is at ...
