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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Electric Potential of a Charged Sphere
Problem Consider a sphere with radius $R$, and with a charge distribution $\rho(r)=\rho_0r$. Using Poisson's equation, calculate the electric potential inside and outside the sphere.
Solution I don't ...
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1answer
96 views
Will I recieve a shock if I charged a capacitor then i touch the 2 poles in same time?
What happens if I charged a capacitor then i touch the 2 poles in same time?
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1answer
114 views
electrostatic potential, analytic properties
An electrostatic potential associated with some delocalized charge $\int \rho(\mathbf{r}) d{\mathbf{r}}$ is given by:
$$v_H(\mathbf{r}) = \int ...
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1answer
310 views
how to calculate electric relative permittivity of fluid or medium
I am confusing in calculating permittivity of the fluid. Permittivity differs from one fluid to another.
$$\varepsilon=\varepsilon_r\varepsilon_0$$
Since it is an electrical property combined with ...
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1answer
46 views
Can we transfer the charge on a plate of a capacitor elsewhere?
I know it is hard , but can we transfer the charge on a capacitor plate elsewhere?
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111 views
Charging a metal plate
I am supposed to find a way to charge a metal plate with a defined charge ( in nanocoulomb) and it must have a + charge so basically i want to know if this way is correct and applicable, and if there ...
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0answers
73 views
What happens when I bring a sphere of positive charge near to the sphere of negative charge?
I am wondering what would be the charge density distribution when I bring a sphere of positive charge $Q$ near to the sphere of negative charge? What would be the charge distribution inside the sphere ...
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1answer
46 views
Charge of an electrolytic capacitors
I can't understand the electrolytic capacitors, when a capacitor has a capacitance of 100 microfarads, does that mean that when it is charged with 100 volts will the charge of the plate be 0.01 ...
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0answers
58 views
Is there a minimum charge for the electroscope to work? [closed]
I built an electroscope, and I noticed that some charged objects didn't have enough charge to show any interaction.
So i was wondering if there is a threshold minimum charge for the electroscope to ...
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1answer
99 views
How does one come up with the Coulomb's law?
My teacher mentioned that field line density = no. of lines / area and the total area of a sphere is $4\pi r^2$ and so an electric force is inversely proportional to $r^2$. Actually, why can the total ...
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1answer
128 views
Can high charges (like $1\times 10^{-3}$ coulomb) be acheived?
How can we charge a metal electrode with large charges ? When i saw a video about measuring a charge using a visiostat on a balloon , the charge was 0.6 nano-coulomb. Is the charge of 1 coulomb ...
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0answers
202 views
Electrostatic Dust Removal
I have been recently reading a paper on dust removal and I have a few basic questions regarding it.
First off, I am citing this paper - "Dust removal system with static electricity"
Basically, an ...
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0answers
107 views
How do I find the force on the charged sphere due to a dipole sitting inside?
I have a dipole sitting inside a charged sphere i.e. at the centre of the sphere. As far as I can see the force on the Dipole is zero because the external electric field on the dipole at $r=0$ is $0$. ...
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1answer
140 views
Potential for charge distribution, finiteness
Consider a potential for charge distribution:
$$v_H(\mathbf{r}) ~=~ \int \frac{\rho(\mathbf{r'})}{|\mathbf{r}-\mathbf{r'}|}d\mathbf{r'}$$
where $\rho(\mathbf{r'})$ is the charge density.
This ...
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1answer
204 views
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1answer
162 views
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2answers
575 views
Electric field and electric potential of a point charge in 2D and 1D
in 3D, electric field of a piont charge is inversely proportional to the square of distance while the potential is inversely proportional to distance. We can derive it from Coulomb's law.
however, I ...
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2answers
481 views
How does rubbing cause the transfer of electrons from one object to the other? [duplicate]
I have just learnt about electrostatics. Why would there be a transfer of electrons? Is it because of the difference of the materials (i.e. triboelectric series)? So in the case of two different ...
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1answer
419 views
The formula of the force exerted on an electric dipole by non-uniform electric field
When an electric dipole of moment $\mathbf{P}$ is located in a non-uniform electric field $\mathbf{E}$, there is an net force exerted on it.
However, the formula of the force in some books is read ...
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1answer
290 views
Are the Maxwell's equations enough to derive the law of Coulomb?
Are the 8 Maxwell's equations enough to derive the formula for the electromagnetic field created by a stationary point charge, which is the same as the law of Coulomb?
If I am not mistaken, due to ...
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2answers
1k views
Why is electric field zero inside a hollow metal sphere ?
The figure below shows a hollow metal sphere with a positive point charge $Q$ sitting outside it. What is the electric field at the center of sphere ? The answer is zero (look at here at the beginning ...
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0answers
44 views
outward pressure in an confined electron gas
Suppose i have some electrons stored in a empty shell container with a negative ion layer in the inner surface so the electrons keep bouncing inside without being able to leave the inner cavity.
I ...
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2answers
211 views
Find the quantity of charge - given potential function
A potential function is given by $V(r)=\frac{Ae^{-\lambda r}}{r}$ Find charge density and hence charge.
I first took the gradient of potential to get $\vec{E}(r)=\frac{Ae^{-\lambda ...
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1answer
240 views
Simple quadrupole moment
I have a very simple problem: There is a charge $-q$ at $(0, 0, d)$ and $(0, 0, -d)$ as well a charge $2q$ at $(0, 0, 0)$. I have to calculate the quadrupole moment using spherical coordinates. I use ...
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0answers
69 views
Subtle problem on capacitors [closed]
Imagine we have 2 capacitors of capacitance $C_1$ and $C_2$ respectively. One is charged with charge $Q_1$, and the other is not charged.
Now we connect them in series as shown in figure:
What is ...
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2answers
344 views
electric potential at center of uniform electric field
it is said that the electric potential at the center of uniform electric field is zero.
my question is that why is it zero?
electric potential is the work done per unit charge.
$V = W/q$
and this ...
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1answer
62 views
Computing a “best-fit” of discrete points from a multipole expansion, i.e. invert the multipole moments
Take a field $\phi(\bf{x})$ created from a charge distribution contained within a radius $R$. The multipole expansion in spherical harmonics $Y_{\ell,m}$ outside of $R$ is approximated by:
$$
...
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2answers
812 views
Why is electric field strong at sharp edges?
I learned about the coronal discharge, and the common explanation is because the electric field is strong where radius of curvature is small. But I haven't found anything yet that explains why ...
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1answer
107 views
Will the plates of a parallel plates capacitor keep its charge after being charged then seperated from the non- conductor?
If i had 3 plates 2 metals and 1 glass .I put them together to form a basic parallel plates capacitor.
After charging it and approaching it to an electroscope nothing happened that's because ...
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2answers
150 views
Effect of charges near a parallel plate capacitor
If I charged a parallel plate capacitor. And then, I insert a charged body near one of the plates.
Will there be any interactions like attraction or repulsion?
What if I disconnected the battery?
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2answers
194 views
Are electrons on a conductor, in electrostatic equilibrium, stationary?
Electrostatics basically means dealing with time independent electric fields (which was produced by stationary charges)
Now consider a neutral conductor. We know that putting a net negative charge on ...
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1answer
741 views
Potential Gradient & Electric field…
Potential gradient is the negative of the electric field. Does the negative (here) means that its direction is opposite to electric field.?
If it does mean this, How is the direction of the ...
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0answers
222 views
Capacitance of this unusual capacitor
This capacitor is composed of two half spherical shelled conductors both with radius $r$. There is a very small space between the two parts seeing to that no charge will exchange between them.
...
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1answer
164 views
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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2answers
203 views
Electrostatic notion of voltage as it applies to circuits
I have a question that's been bothering me about electric fields, voltage, and circuit analysis.
Initially, I came to understand voltage as it was taught in the context of electrostatics - through ...
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1answer
80 views
Static electric charge
When some materials are chafed one to another, they obtain opposite electric charges. Does it mean that if these materials will then be connected to the ground, the direct currents of opposite ...
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4answers
969 views
Electric potential vs potential difference
What is the difference between electric potential and potential difference? In our course book, they are given as separate topics but their definition is given the same.
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1answer
425 views
Is the electric field at the edge of a uniformly charged disk infinite?
Consider a disk with a radius $R$ (I'll use $R=1$ at various points here) that has a constant surface charge density $\sigma$. Unlike the similar problem of the field in the vicinity of a infinitely ...
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5answers
445 views
Paradox with Gauss' law when space is uniformly charged everywhere
Consider that space is uniformly charged everywhere, i.e., filled with a uniform charge distribution, $\rho$, everywhere.
By symmetry, the electric field is zero everywhere. (If I take any point in ...
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3answers
884 views
What are the applications of Gauss's law in technology? [closed]
Freshmen physics textbooks use Gauss's law plus symmetry to calculate the electric field.
I was wondering if this method of finding the electric field using a symmetry is used in real applications in ...
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1answer
78 views
The Ultimate Hand Dryer
I have come across many hand dryers that attempt to dry your hands really fast after you wash them. Here are two of them:
XLERATOR
http://www.exceldryer.com/
Dyson Airblade
...
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1answer
133 views
How will water affect the electric field?
How will 2 charged bodies act when the separation medium between them is water ?
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A crazy problem
Easy
Consider the following figure
Each red point is a particle of a known mass that carries charge Q/2 and connected to a the box by a thread of known length. This problem can be solved easily to ...
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1answer
203 views
Calculating dust attraction to a charged surface
Even though dust particles are neutral, they tend to be attracted to a charged surface. I am guessing this is due to charge induction.
Is there a way I can compute the attraction? how will it vary ...
2
votes
3answers
128 views
Where does the energy for repulsion in charges come from?
If I bring together 2 objects with the same charge, they repel. But even after the repulsion has taken place, there is no loss of charge in the objects. Where does the energy come from then?
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2answers
185 views
Shape of electric charges on sphere in equilibrium state
When electric charges of equal magnitude and sign are released on a regular sphere (and assume that they stick to the surface of the sphere, but they are free to move along its surface), what is the ...
2
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2answers
147 views
Energy in electric field
I'm having some trouble understanding a homework question and would appreciate some help.
The question is as follows:
Jenny charges a capacitor with the help of a battery. She then removes
the ...
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3answers
462 views
Field due to current in a wire
Suppose a current flows in a straight cylindrical wire so that an electric field $\textbf{E}$ is maintained in the wire.
Will there be an electric field just outside the wire..?
4
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3answers
238 views
Change in attraction of charged bodies
If I insert a piece of glass between two objects carrying different charges, would they still attract?
If they attract, does the piece of glass affect the force of attraction and is there any formula ...
2
votes
2answers
93 views
Will the positive ions in an aqueous solution be attracted to a charged body ?
If I had a negatively charged body , say an electret , and i put it in a container of NaCl solution . Will the positive ions of sodium be attracted to it ? and why? If no, why do the positive ions ...
