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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Why does the charge distribution on the surface of a conducting sphere remain uniform even if there is a perturbation in the inner electric field?
In a conducting sphere, the net charge is evenly distributed at the surface because of repulsion while the inner electric field remains zero as charges cancel inside. Here is an example, where the net ...
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Does the addition of a static charge or magnetic field to an antenna affect the EM waves it's supposed to receive?
I read this:
Does laser beam (EM wave) affect magnet next to it?
But I distinctly remember the use of a magnetic field to alter the polarization of light. Doc Edgerton used this technique to create a ...
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Can you use center of charge to find electric field of a not-centered point near a uniformly charged rod?
Suppose we have a uniformly-charged rod has charge density $+\lambda$, and we want to know the magnitude of the components of electric field at point $P$. The standard method of solving for the ...
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What would happen if very strong electric field is applied to the surface of conductors?
I know that if the conductor is at the negative end, it can emit electrons (field emission) when the electric field is sufficiently strong. But what if the conductor is at the positive end? Will the ...
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Trajectory of electric field lines
I came across an interesting problem of electric field which is as follows:
An electric field line from a charge $q$ is as shown. It enters a negative charge $–q$ as shown. Find the maximum height of ...
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Charge distribution in conductors
Suppose we have conducting metal cube and we give a positive charge $Q$ to it.
Now giving positive charge simply implies taking away electrons from that small region , so when we take away electrons ...
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Mathematical Ambiguity in Electric field at centre of a uniformly charged hollow hemisphere
So, there is a question in the book "Problems in General Physics" by I.E. Irodov to calculate the electric field at the centre of a hollow hemisphere.
I was able to solve this question and ...
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Electric flux through a infinite strip
We have to find flux due to a point charge at $(0,l,0)$ on an infinite strip lying in region $(0,0,0)$, $(l,0,l)$ and extending to infinity along $+x$ direction.
I am aware that a general case has ...
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Potential difference due to point charges
Now, there are many sources saying the potential difference created by a point source is given by
\begin{equation}
V=\dfrac{1}{4\pi\varepsilon_0}\dfrac{Q}{r}
\end{equation}
Which looks like it's just ...
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Are there any magnetic field while electron transfer in static electricity
I already know that the moving charge can generate magnetic field. But in this case, can magnetic field be generated.
Thank for answers
PS. This is just my curiosity.
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Provided a unit vector and Force, how can I calculate it's components? [closed]
Say I have a $F=kQ_{1}Q_{2}/r^{2}$ and a direction vector $(x, y, z).$ How can I find the component forces $F_{x}$, $F_{y}$, and $F_{z}$?
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Using symmetry in Gauss' Law
I have to find electric field at any inside point due to a uniformly charged solid sphere
I do it in following steps
$\to$ First I choose a spherical gaussian surface passing through required point ...
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Difference between grounding the inner and outer side of a thick spherical shell
I have a conducting sphere with radius $R_1$ and charge $Q_1$ inside a conducting thick spherical shell with inner radius $R_2>R_1$ and outer radius $R_3>R_2$. Both the spheres have the same ...
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Confusion in Electric flux
We define flux of an electric field $\vec{E}$ through a surface $S$ as
$$\Phi =\int_S\vec{E}.d\vec{s}$$
Now we define flux through a surface as stated above
What does it mean when we say flux coming ...
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Similarity between Potential Energy Function of Polarized Sphere and Cylinder
According to this paper,
the potential of any point on the surface at a distance '$h$' from the center of some simple conducting geometric shape is given by
For a Sphere:
$$V(x)=Mh^2\frac{xcos(\alpha)+...
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Definition Of Electric Flux
I have some confusion in definition of electric flux .
I have been told that No. of electric field lines passing through a surface area gives/represents electric flux but if suppose $n$ number of ...
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Why does the magnetic field form a full loop going from the north pole to the south pole and then back to the north pole?
My physics textbook defines the direction of the magnetic field as the direction of the force on a small north pole of a magnet. However, I am told also that if you have, say a bar magnet, that the ...
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Electric charges separation
I know that any electric charge (Millikan) is always an integer multiple $n\in \Bbb Z$ of the electron charge $e$ i.e.
$$\boxed{Q=ne} \tag 1$$
Assuming by induction or contact or by friction to ...
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Electric field outside of a conductor with charge $q$
Suppose that I have a spherical conductor (radius $R$) with a cavity at the center and a charge $q$ inside it. I know that the electric field outside of the conductor will be
$$\vec{E}=\frac{q}{4\pi\...
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A rubber ball of radius a is covered by a thin shell of metal which has negligible thickness and a charge Q Spread uniformly over it [closed]
this is a screen shot of a past paper exam, sorry that I could not get better quality.
I am struggling to answer this question (b) and (c), I believe that once I solved for (c) it should be easy to ...
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Can Gauss' Law apply to an irregular 3D region?
Let's say I have this configuration:
The figure above is a cube with a charge not in the center.
Can I calculate the flux through the surfaces using Gauss' Law, or does it only apply when the charge ...
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Charge required to lift a piece of paper
Say I rubbed a plastic ruler on my hair just enough to lift exactly one hole-punch size piece of paper, to get the paper to stick to the rod. Roughly what is the net charge on the rod, in Coulombs?
...
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Conservation or energy problem. What am I doing wrong? [closed]
For a given ion with a charge of $+1$ being accelerated by $U$ volts the distance it travels in a time $t$ is $d$ given by:
$$d = v_0 t + \frac{1}{2} a t^2$$
for $v_0=0$
$$a = 2\frac{d}{t^2}$$
and for ...
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How to find electric flux through a surface due a point charge [closed]
So, I'm trying to solve this problem for my assignment,
A point of charge, Q = 3 nC, is located at the origin of a cartesian coordinate system. What flux crosses the portion of the z=2 m plane for ...
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In the statement $\text dV = 4\pi x^2\text dx$ , how is the radius $x^2\text dx$?
I was recently studying a question based on Electrostatics. Here is the link to the question (along with the answer below). I haven't learned integration yet. But my question here is how did we get $x^...
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How much energy is stored in the field of a hydrogen atom?
How much energy is in the electric field of a single lone hydrogen atom that has no neutrons and exists at the lowest energy state possible?
Well in a universe where nothing else exists.
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Electric Potential for a Point Charge and an Infinite Conducting Plane on the Other Half-Space
In the book titled "Modern Electrodynamics" by Zangwill, on chapter 8, there is a discussion on the electric potential of a system of an infinite conducting plane and a point charge ...
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Calculating electric potential from electric field [closed]
The Electric field in a region is given as $\vec{E}=-2x\hat{i}+3y^2\hat{j}-4z^3\hat{k}$. Calculate the electric potential at point $(1,2,3)m$
Now we know that electric potential at point $A$ is ...
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If the earth is negatively charged why is lightning striking it?
So, as far as I know, the Earth is negatively charged, and there are such things as lightning strikes which travel from clouds to the Earth- that would mean the clouds in a thunderstorm are positively ...
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How does zero electric field look like?
Imagine if we have an electric dipole inside a cube (a conductor). The net electric charge inside the cube is zero. Hence, using Gauss's law, the net electric flux coming out of the cube must be zero. ...
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Why is there a loss of energy when charge is redistributed among two objects?
I am a high schooler so forgive me if I got anything wrong.
I had a question today stating that when charges are re-distributed among any two objects, there would be some loss of energy. The question ...
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Gravitationally-driven electrical potential differences in conductors
This question asks
Free electrons in a metal are attracted by gravity towards Earth. So why don't they lay down to the bottom of the conduit, like sediment at the bottom of a river?
The current ...
rob♦
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Why does the equation $\frac{1}{2}mv_i^2+K\frac{Qq}{r_i}=\frac{1}{2}mv_f^2+K\frac{Qq}{r_f}$ not apply here?
Two particles at rest with positive charges $Q_1$ and $Q_2$ respectively are separated $3cm$ apart. After some time, they become $12cm$ apart. Compute the final velocity of each particle at that point....
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Electrostatic Potential and Field for an Infinite Conducting Plane with Charges on Both Sides
Suppose that we have an infinite conducting plate that occupies the $x-z$ plane. We put 3 point charges $q_1 = Q,\quad q_2 = Q$ and $q_3=2Q$ in the points $(0,a,b),\quad (0,a,-b)$ and $(0,-a,0)$ ...
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Why does electron stop accelerating after passing anode in Cathode ray experiment?
This same question was posted on quora and what I found out there that there is some graphite coating around the anode extending to just before the florescent material. This graphite coating is ...
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What does 'per unit charge' mean?
When we say "potential is the potential energy per unit charge", what does a 'unit charge' actually mean?
In a worked example from my textbook, when they find the potential difference, they ...
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For capacitors, why does the dielectric need to be inserted at a small constant speed?
Likely a very silly question.
I am aware that there is an attractive force from a charged parallel-plate capacitor in an open circuit without battery pulling the dielectric in, and that a decrease in ...
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How to argue that the potential is the same in a conductor with zero resistance when we have electricity?
I am wondering how we can argue that the electrical potential is the same in point A and B in the figure below:
I have seen the argument that in a conductor where the charges are not moving, then the ...
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Charging a metal by extracting electrons from it? [duplicate]
Suppose we have a field emission electron gun as shown in the figure, (let's ignore the voltage of the second anode), the voltage of the first anode is to extract electrons from the cathode, there is ...
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Why is there an electrostatic field in a closed current?
There is something about the derivation of the formula for parallel resistors I can not understand($1/R_t=1/R_1+\cdots+1/R_N$).
In order to derive this formula we use that the potential is the same ...
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Electric displacement - why are field lines continuous?
I recently attempted problem 4.17 in Griffiths's "Introduction to Electrodynamics" 3rd edition in which you are asked to make a sketch of the electric displacement vector D in and around a ...
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Relating potential difference of electrostatics with circuit
Since absolute potential isn't defined for a point, we take a reference point which is $\infty$, and then define potential of a point $A$ to be the work done per unit charge to move that charge from $\...
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Can current due to potential difference of earth's crust and ionosphere charge objects?
A man fixes outside his house one evening a two metre high insulating slab carrying on its top a large aluminium sheet of area $m^2$ . Will he get an electric shock if he touches the metal sheet next ...
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Concentric conducting spheres with dielectric
In the following image, there are 2 concentric conducting spheres. Initially, both are uncharged, outer one is earthed and the space between them is filled with air. After sometime, I somehow put some ...
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Eletric field inside of a conductive charged spherical shell, which has an inner conductive sphere [closed]
Suppose a charged spherical shell, centered at the origin, with outer radius of $R_0$ and inner radius of $R_i$, and it has charge $Q$. Inside the shell, there is a conductive sphere with charge $q$ ...
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Electrostatic potential resolving singularity
I'm trying to determine the electrostatic potential caused by a specified charge density function:
$$
\rho_c(\vec{r}) =\begin{cases}
1 & \vec{r} \in V\\
0 & \text{otherwise}
\end{cases}
$$
The ...
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What exactly does the line integral of an electric field over a closed loop find?
For a conservative electric field, we can always say that $$\oint \vec E\cdot\vec {dl} = 0$$
Take this scenario for example
Here $E_1$ and $E_2$ are two different electric fields. If I find
$\oint \...
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The effect of temperature on Coulomb's law
I have read a sentence in an electrical engineering article but I couldn't understand it.
It said: on Earth Temperatures around 150 million degrees Celsius are required to overcome Coulomb's law. the ...
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Capacitor-spring analogy
Imagine the two terminal of a parallel-plate capacitor are connected to the two terminal of a battery with electric potential difference $V$. The capacitance of the capacitor is $C$, the area of each ...
user312587
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Stored energy of a capacitor
Imagine the two terminal of a parallel-plate capacitor are connected to the two terminal of a battery with electric potential difference $V$. If the capacitance of the capacitor is $C$, and the area ...
user310884