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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62 views
The electrical field of a conductive sphere containing a charge - gounded vs not grounded
Let's suppose we have a sphere but unlike theoretical ones it'll has have some thickness say $\Delta r$ and inner radius $R$. What I was wondering about is how will it behave if we place some charge ...
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0answers
33 views
Is Gauss' law useful to determine the electric field strength of a charge distribution? [closed]
Under what conditions is useful Gauss' law to determine the electric field strength of a charge distribution? Can someone help me with this question?
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1answer
167 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 ...
4
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1answer
89 views
How much negative charge do I accumulate by touching the earth?
The Earth carries a negative electric charge of roughly 500 thousand Coulombs (according to different sources I've seen). If I touch the Earth I should therefore pick up some of this electric charge ...
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1answer
74 views
Electric dipole moment, which charge is the $q$ for?
Electric dipole moment says $p = qd$. Which charge does the $q$ equal to?
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3answers
106 views
continuity of the electric potential due to a surface charge
The Electric potential due to a charge distribution on a surface is :
$\Phi \left ( x \right )=\int \frac{\sigma \left ( {x^{}}' \right )dx{}'}{\left \| x-x{}' \right \|}da$ I want to show that it's ...
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0answers
39 views
How the value of permitivity of free space is determined?
when electric charges are placed on the medium then force of interaction between them decreases. We say this factor permitivity of the medium. The force of interaction between the charges is max if ...
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3answers
837 views
Charge Distribution on a Parallel Plate Capacitor
If a parallel plate capacitor is formed by placing two infinite grounded conducting sheets, one at potential $V_1$ and another at $V_2$, a distance $d$ away from each other, then the charge on either ...
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1answer
154 views
Force due to combination of free space and dielectric
I will make a generalized form of my question.
There are two point charges $q$, $x$ distance apart.
And there is a dielectric slab of thickness $t$ and of dielectric constant $K$.
Should the force ...
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1answer
197 views
Finding Electric Field outside a Charged Cylinder
I'm trying to solve a problem that involves finding the electric field due to a uniformly cylinder of radius $r$, length $L$ and total charge $Q$. Well, my thought was: if I am to use Gauss' Law, I'll ...
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0answers
21 views
Electric Field and Electric Potential [closed]
How can electric field and electric potential function for charged conducting and uniformly charged non-conducting spheres?
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1answer
52 views
Electromotive Force Definition for Induced Current
If in DC , Emf is the work done to carry a unit positive charge from -ve to +ve terminal .
What is induced EMF then , in a similar sense ? To carry a unit charge around a loop once along a fixed ...
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2answers
45 views
About the electrostatic voltage
What's the difference between electrostatic voltage and normal voltage, like the battery's voltage.
How to calculate the charge on a charged plate if we knew its electrostatic voltage?
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2answers
64 views
Kinetic energy of two charged balls at infinite distance between them
If I have two balls with masses and charges $m_1, q_1^{+}$, $m_2, q_2^{+}$, initially held at distance $d$, and then released, how can I know the kinetic energies of each of the balls at infinite ...
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1answer
68 views
What is the electric field in a parallel plate capacitor?
When we find the electric field between the plates of a parallel plate capacitor we assume that the electric field from both plates is $${\bf E}=\frac{\sigma}{2\epsilon_0}\hat{n.}$$ The factor of two ...
5
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3answers
255 views
Negative Mass and gravitation
Since Newtonian gravity is analogous to electrostatics shouldn't there be something called negative mass? Also, a moving charge generates electric field, but why doesn't a moving mass generate some ...
2
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2answers
119 views
Force Between Two Conducting Spheres
Aakash PHYSICS JEE (Main & Advanced) Study Package - 5 & 6 (Class XII)
Chapter - Electric Charges and Field
Assignment (page 12)
SECTION - A; Q.no - 1
...
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1answer
53 views
Why is the void devoid of an electric field?
For a region devoid of charge, maxwell's equation yields $\nabla \cdot \mathbf{E} = 0$ which still allows a constant field. So why is in electrostatics for the vacuum always $\mathbf{E} = 0$ assumed?
...
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1answer
213 views
Potential due to a spherical surface charge
The potential at the surface of an insulating sphere (radius R) is given by
$$V(R,\theta) = k \cos(3\theta)$$
where $k$ is a constant. Use separation of variables to find the potential inside the ...
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2answers
618 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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1answer
27 views
Speakers and Static from Hands
Why is it that when you touch the a bare male end of a speaker feed that the speaker makes hissing noises? Is it just (eddy?) currents running through you?
4
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3answers
1k views
“Find the net force the southern hemisphere of a uniformly charged sphere exerts on the northern hemisphere”
This is Griffiths, Introduction to Electrodynamics, 2.43, if you have the book.
The problem states Find the net force that the southern hemisphere of a uniformly charged sphere exerts on the ...
3
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1answer
87 views
What are the limits of applicability of Coulomb's Law?
Coulomb's law is formally parallel to Newton's Law of Universal Gravitation, which is known to give way to General Relativity for very large masses. Does Coulomb's Law have any similar limits of ...
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2answers
49 views
Do black holes have charges?
Do black holes have charges? If so, how would they be measured? Also, does electricity behave the same way? Black holes affect photons, which are carriers of EM radiation, so do black holes have any ...
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2answers
169 views
Is there a momentum for charge?
Since mass and charge behave similarly, so, just like center of mass, I define a point center of charge, that is defined by
$$\vec r_{qm} = \frac {\sum{q_i \vec r_i}} {\sum{q_i}}$$
where $\vec r_i$ ...
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3answers
151 views
Gauss' law and an external charge
Gauss' law states that the net outward normal electric flux through a closed surface is equal to $q_{total, inside}/\epsilon_0$. However, I'm a bit confused of why the presence of an external charge ...
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2answers
619 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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1answer
76 views
electrical forces of two charges repelling each other
If I place two positive charges of different magnitudes on the x-axis (one at the origin, one at the some position x), as the two charges repel each other are the forces that they impart on each other ...
5
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3answers
125 views
Horizontal $E$-field for a charged conducting disk
For part of a simulation I am writing, I need to know the electric field emitted from a charged conducting disk. If the disk was laid out in the $x$-$y$ plane, I am interested in the field in that ...
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1answer
274 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 $p'$, ...
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6answers
387 views
Electrostatic Potential Energy Derivation
How is the boxed step , physically as well as mathematically justified and correct ?
Source:Wiki http://en.wikipedia.org/wiki/Electric_potential_energy
As work done = $- \Delta U $. for Conservative ...
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3answers
220 views
What's the right way to calculate charge on a capacitor?
How much charge is on each plate of a 4.00-F capacitor
when it is connected to a 12.0-V battery?
I said 2.4 x 10^-5 C because there are two plates of a parallel plate capacitor. But the key said only ...
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1answer
55 views
What types of materials can be electrically charged by rubbing?
What types of materials can be electrically charged by rubbing? Is there a certain type of materials in which static electricity can be produced by rubbing together two different materials?
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3answers
482 views
When I connect two charged capacitors side by side, what will be the voltage across them?
Say, I have two charged capacitors, one 3mF and one 2mF. The voltage across them are 20V and 30V respectively. Now if I connect the two capacitors side by side as shown below, what will be the voltage ...
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2answers
157 views
Definition of electric charge and proper explanation
Is there a definition of electric charge and proper explanation of it?
It is said "Electric charge is the physical property of matter that causes it to experience a force when close to other ...
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2answers
84 views
The electric potential and the electric field
I'm preparing for my school exam in physics and I found that I don't understand the derivation of $E = -\nablaφ$. Here is a derivation from my book:
1) Imagine that 1 and 2 are infinitely close ...
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2answers
71 views
Why does the area of the plates affect the capacitance?
Why does the area of the plates affect the capacitance? Lets say I have a parallel plate capacitor with a charge of 10C and a potential difference of 5V. By the definition $C=Q/V$, the capacitance is ...
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4answers
114 views
Capacitance of a capacitor
Why does the capacitance of a capacitor increase if the distance between the two plates of a parallel plate capacitor is decreased? I think, with decreasing distance between the two plates, the force ...
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2answers
74 views
Confused about the electric field at the surface of a conductor
We know that the electric field at the surface of a conductor only have a normal component equal to $\rho/\varepsilon$ (finite number).
But let’s consider the point $\text{P}$ (at the surface of a ...
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0answers
23 views
Electrostats and Photoelectric effect [closed]
Here I think ,
one beam will knock out just one electron. So I am not able to even understand what the question says , please someone give a hint as to what the question asks
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1answer
43 views
Electric Field in Dieletric
I have a simple doubt. The textbook I'm working with says that if $E_0$ is the electric field in some region without diletric, then if we introduce a dieletric of constant $k$ the new field will ...
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4answers
1k 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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0answers
32 views
Energy content after moving point charge [closed]
I have the following exercise:
In point A there is a charge with $Q_1 = 3.3\times10^{-5} C$
In point B charge $Q_2 = 8.5\times10^{-6} C$
In point C charge $Q_3 = -6\times10^{-6} C$
This happens ...
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2answers
62 views
Electrostatic Potential Definition
In the book, Introduction to electrodynamics by David J. Griffiths, he introduces potential separately as a function and potential energy through that function.
How can potential be defined before ...
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1answer
39 views
Sign issue on electrostatic potential energy
I have been working on a problem about finding the electrostatic potential energy stored on a capacitor of concentric spheres with inner radius $a$ and outer radius $b$ and with charge $Q$. I've got ...
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1answer
52 views
Fundamentals of electrostatics
Suppose I have a Gold Leaf Electroscope and the leaves are observed to diverge by a certain amount. Now if I send a beam of X-rays and allow it to fall upon the electroscope for a very short period of ...
5
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4answers
221 views
Energy Gain with capacitor?
I have a question about energy gain in capacitors. Assume the following system:
As the electron gets accelerated inside the capacitor, it will have more kinetic energy coming out than going in. But ...
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0answers
59 views
Curie's principle in electromagnetic field theory
I am looking for some explanation and if possible also some references about the applications of Curie's principle in electromagnetic field Theory, precisely in the computation of magnetic (resp. ...
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1answer
66 views
Induced charge on sphere
I have a conducting sphere ($radius = a$) at potential $V_0$. It is enclosed by another thin shell ($radius = b, b > a$) which has a charge density $\sigma (\theta) = \sigma_0 \cos(\theta)$ for the ...
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4answers
333 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 ...
