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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 [tag:electromagnetism] and/or [tag:magnetic-fields]

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Electric field of two equal charges of the same sign

Two equal positive charges are at distance d, -d from the origin on the y axis. What is the distance on the x axis beyond which a small perturbation in y will move a particle away from the x axis? ...
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Charge concept before discovery of electron [migrated]

How the concept of positive and negative chrge originate before discovery of electron.my question is about.
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1answer
45 views

Vector addition of electric fields [on hold]

I have calculated the electric fields of three points in a right triangle, the fields being $E_1 = 2.7\times10^4 ~\mathrm{N}\cdot\mathrm{C}^{-1}$, $E_2 = -9\times10^3 ~\mathrm{N}\cdot\mathrm{C}^{-1}$, ...
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1answer
40 views

Electrostatic potential of a point charge

From Wikipedia The electrostatic potential energy, UE, of one point charge q at position r in the presence of an electric field E is defined as the negative of the work W done by the electrostatic ...
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2answers
45 views

Charge Distribution on a perfectly conducting hollow shell

As shown in the figure I have a hollow shell which contains a charge at its centre and another charge is placed outside the shell (some distance apart). I know that the situation this figure depicts ...
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1answer
48 views

From where to start such a question? [duplicate]

13 equal charges, q , are placed at the corners of a 13 sided regular polygon. What is the force on a test charge Q at the centre? I couldn't figure out from where to start solving it. It would be ...
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2answers
122 views

Am I positively charged or negatively charged?

We often hear that the human body has a weak electrical charge. Is it a positive charge or negative charge? Or maybe different parts of me have different electrical charges? Or maybe there's a ...
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1answer
37 views

Electric field at center of a uniformly charged hemispherical shell [on hold]

My attempt : I divided the shell into charged rings by whom I know the electric field at the center by the following relation : $\hskip2in$ Integrating the electric fields by all the rings I get ...
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2answers
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Anomalous value of electric field due to a uniformly charged disc at a point on its central axis

Upon trying to find the electric field using integration (as done below) we get the following result : According to me there are two problems with this result : This function is not of odd parity. ...
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2answers
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Is the zero distance limit of Coulomb's law something to worry about?

Coulomb's law fails when the distance $r$ between to point charges vanishes. As $r\to 0$, the electric field between two point changes increases without limit. I should be bothered about the limit $r\...
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1answer
28 views

Is there anything special about ebonite and fur?

I'm from Czech Republic, born 1980. From elementary school, we all remember this mantra: When ebonite rod is rubbed with fox fur, electrostatic charge is created. Electrostatic charge is created ...
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Rotated dielectric slab in a parallel plate capacitor

Between two infinite plates charged with a surface density of $\pm \sigma$ there is a dielectric slab (dielectric constant $\epsilon_r$, the dielectric is linear, homogeneous and isotropic) of ...
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4answers
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Electric Field Inside matter

The dimensions of an atom are of the order of an Angstrom. Thus there must be large electric fields between the protons and electrons. Why, then is the electrostatic field inside a conductor/matter ...
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2answers
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How would a moving charged particle react within a parallel arrangement and conical arrangement of magnetic fields?

I am very interested in finding out how a moving charged particle would react if it were to enter into an area with parallel magnetic fields and also if it were to enter into an area with conical ...
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1answer
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Dielectric polarization - should not the dimensions of the polarised dielectric increase in the direction of the field?

In the classical model for polarization, if a dielectric is placed in a an electrical field (assumed to be static for the sake of simplicity), the trajectory of the electrons inside the atoms of the ...
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2answers
31 views

Fumdamentals of electric circuit

I was studying the chapter electric current and came up with a doubt in my mind . Basically when we pass electric field through a conductor then as the dielectric strength of a conductor is very high ...
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1answer
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Electric Field & Polarization

Does everytime the electric-field $E$ & the electric displacement vector $D$ are parallel for every material?
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1answer
42 views

Is there any way to determine how long a wire is?

This is for transmission lines applications. Are there any way to know how long the wire like by getting the resistance of the wire(but how). Or is it possiblee to charge the wire until it produces ...
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1answer
32 views

can generation of pressure create light?

If pressure is applied on a body , can mechanical stress produce light? , as electrons are produced in piezoelectricty. if yes , please answer or recommend any book/website/paper. Thank you
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1answer
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Will it be complicated to use Gauss's Law in this problem? [closed]

The electric field strength depends only on the $x$ and $y$ coordinates according to the law $\vec{E}=a(x\hat{i}+y\hat{j})/(x^2+y^2)$ where $a$ is a constant. Find the flux of the vector$\vec{E}$ ...
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1answer
58 views

Starting from Gauss's law, prove that the Electrostatic potential satisfies Poisson's equation [closed]

If we start from differential form of Gauss Law and take out divergence of E , I am getting it to be zero. How's is it possible? So how do I proceed further in order to prove that Electrostatic ...
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2answers
48 views

Inconsistency in the definition of electrostatic work

Sorry if there this is a duplicate but I can't find anything that deals with this. I have a point charge $q$ sitting at the origin. It takes no work for me to put it there. Then, I bring $-q$ out ...
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1answer
51 views

How a spark is produced?

When we are closed to some metal sometimes spark is created. Is this because when we come close to a metal our charged fingers charge by induction the metal ? Then a voltage between our finger and ...
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0answers
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Induction between two spheres

If there are two spheres with the same charge with the radius of one being larger than the other then the induction effect on the larger sphere is more visible than that on the smaller sphere. But if ...
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1answer
47 views

Gauss theorem and inverse square law [duplicate]

I know that the gauss law states that the Flux of the electric field through a closed surface is Q/ε , but does the gauss theorem works also for non inverse square law Fields?
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0answers
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Debye screening in $\mathbb{R^d}$

Consider the Poisson-Boltzmann equation $$ \nabla^2 V(r) = -\frac{1}{\epsilon_0}en\left(1 - e^{e V(r)/k_BT}\right) $$ which models the electrostatic potential in a spherically symmetric ideal gas of ...
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3answers
279 views

Superposition Principle for Electric Fields

If there is a collection of charges $q_1,q_2,q_3....q_n$, and we want to calculate the total Electric Field due to all these charges at a point $P$ ,then the we sum them all up by the principle of ...
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1answer
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How calculate work from an electric field on a $+q$ particle without the curve? [closed]

Well,i've a workout for home,and it is asking me to calculate the work from the electric field with equation: $\hat E=6xy \hat x+(3x^2-y^2)\hat y$ I tried to solve the line integral but it doesn't ...
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0answers
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Paradox in conservation of energy

Let us assume there is a constant electric field in an interested region (finite volume)and a non-conducting object is thrown into it with speed $v$ and now take the second scenario with the same ...
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1answer
29 views

How to compute the self-capacitance of a conductive shape?

(Depending on the answers given, this question might be better suited for Math.SE, but I don't think so.) I recently learnt about the notion of self-capacitance of a conductive shape, which now seems ...
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1answer
33 views

Why did we take gradient outside the integral sign in Scalar potential derivation?

I tried to understand the reasoning given in it but I couldn't understand it. It says that "as the gradient operation involves x and not the integration variable x', it can be taken outside the ...
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3answers
67 views

How to find electric field at a point on an arbitrary surface charge $(\sigma)$ due to it?

Electric field at any point due to any volume charge $(\rho)$ Electric field at a point outside a volume charge is given by Coulomb's law: $$\vec{E}=k \iiint_V \dfrac{\rho}{r^2} (\hat{r})dV \tag1$$ ...
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2answers
48 views

Question on capacitance

I am recently trying to learn electrics on my own but am a bit confused with regard to capacitance. By Gauss law, I understand that the electric field from a single parallel plate results in: $$ E = \...
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1answer
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Coulomb's Law modified in general relativity?

It seems difficult to track down a clear explanation of this statement: So although the Coulomb law was discovered in a supporting frame, general relativity tells us that the field of such a charge ...
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Capacitance of spherical capacitor when inner sphere is earthed

Consider the following derivation: (Source: http://www.ncert.nic.in/html/learning_basket/electricity/electricity/electrostatics/inner_sphere.htm) If a charge of $+Q$ coulombs is given to the outer ...
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1answer
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Electric field at a point infinitely close to an arbitrary surface charge [closed]

My question is of two parts: (i) I know electric field due to an infinite plane sheet of charge at a point (finite distance $d$ away) is $2 \pi\ k\ \sigma$. From this, by reducing the linear ...
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1answer
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Partially Filled Capacitors

I know that, for partially filled capacitors, one treats the space between the capacitor plates as two or more capacitors either in series or parallel. However, I don't fully understand why the ...
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0answers
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rotating capacitor question

Imagine a simple setup. I have a copper disc and another copper element held close to the disc at one of it's sides, this element is stationary but the disc is rotating, the part between the disc and ...
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2answers
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Metal rod in an electric field

A metallic rod is placed in a uniform electric field. Why is an electric field induced in the opposite direction?
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1answer
42 views

On the electric field created by a conductor

The electric field created by a conductor at a point $M$ extremely close to it is $\vec{E}=\vec{E_1}+\vec{E_2}$ where $\vec{E_1}$ is the electric field created by such a tiny bit of the conductor that ...
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0answers
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Textbooks that can help me understand the basics of electrostatics and its mathematics [duplicate]

I am currently reviewing electrostatics in classical electrodynamics. I get to know the different mathematics behind each concept. Now, for mastery, I am looking for books that has detailed ...
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1answer
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What is azimuthal symmetry? [duplicate]

What is azimuthal symmetry? When to use azimuthal symmetry and and how to know whether the problem has azimuthal symmetry or not?
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1answer
50 views

How does friction facilitate charge redistribution?

We know that when Amber is rubbed with wool, the surfaces that are in contact, taken together, have the charges redistributed in accordance with the Law of Conservation of Charge. How does friction ...
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1answer
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Why do straws get attracted to charged amber when they are not charged themselves?

Amber on rubbing with wool attracts pieces of straw. But, as I understand, the straws are thenselves uncharged, let alone oppositely charged. So how is it possible?
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1answer
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Is potential instantaneous, unlike fields which take time to alter depending on their mediators?

If there's a Charge distribution 4 Light-years away, static, we have a distinct value of Electric Field and Electric Potential where I'm measuring it through some wack-a-doodle apparatus at my home on ...
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2answers
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Van de graaff generator, Leyden jars and capacitance

How will the capacitance of a typical desktop van de graaff generator be affected when connected in series to a group of some 5-10 Leyden jars? I know that the capacitance is decreased in series ...
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1answer
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Interaction between molecules

Does the interaction with enviroment change the geometry of a molecule ? for example in H2O the angle betwen H-O-H is 104.5 degrees. Does this angle change for example if the molecule of water is near ...
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0answers
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Doubt in insulators

I have studied that there are no free electrons inside an insulator so they are unable to conduct electricity , but what if i inject externally more electrons inside it . Are those external electrons ...
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2answers
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Proof for $W_{\text{total}}$

Looking upon a certain solution of a problem in Griffiths regarding the work done in arranging two concentric spheres with inner shell having charge $q$ and outer shell with charge $-q$ and I found a ...
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1answer
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Electrostatics question inquiry [closed]

The answer is C given that the left ball is positively charged. But since the sphere is heavily positively charged, shouldn’t the sphere repel the left positively charged ball rather than the left ...