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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Electric Flux through an infinite sheet

This Question pertains to Gauss' Law In finding Flux through a sheet of width a which is infinitely long, kept so that a charge ($+Q$) is kept at $\frac{\sqrt{3}a}{2}$ length away from the plane of ...
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Change in potential energy due to change in position of point charge [closed]

A point charge of $+10\mu C$ is placed at a distance of $20$ cm from another identical point charge of $+10 \mu C$. A point charge of $-2 \mu C$ is moved from point $a$ to $b$ as shown in the figure. ...
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2answers
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If all the multipole expansions apart from the monopole is zero, then is the charge density spherically symmetric?

Say I have a charge density $\rho(\vec{x})$ in some finite volume $V$, such that all of the multipole expansions apart from the monopole moment (meaning dipole, quadrupole and so forth) are zero. Does ...
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4answers
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If some external charge is introduced outside gaussian surface how can i calculate new electric field on the surface

If some external charge is introduced the electric field on surface will change but the charge inside gaussian surface remains same .if i apply gauss i get the same electric field .what am i doing ...
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Question based on conductors [closed]

A conducting sphere of radius R is cut into two equal halves which are held pressed together by a stiff spring inside the sphere. Find the change in tension in the spring corresponding to the maximum ...
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1answer
30 views

Electric Potential of a sphere concentric to a spherical shell [closed]

The sphere with radius a, is concentric to the spherical shell with inner radius b and outer radius c. The charges are distributed uniformly in volume. b) Find the electric potential in region outside ...
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A question about gauss's law [closed]

Please explain how this question related to Gauss' law is to be answered.
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2answers
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About gauss's law [closed]

Gauss's law states that the net flux of an electric field through a closed surface is proportional to the enclosed electric charge. ... The electric flux is defined as the electric field passing ...
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1answer
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Understanding the different types of electric potential energy

I have a paper on electric potential energy, it should be noted that the topic was not in anyway explained back when we were on campus so whatever little understanding i have of the topic right now is ...
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1answer
28 views

What would happen if a body possessing a charge $(-1) \text { e}$ is brought into contact with an electrically neutral object?

Let's say that a body $A$ possesses a charge of $-1 \text{ e}$ (electron) and another body $B$ is electrically neutral (has a charge of $0 \text{ e}$). Now, if we bring any two objects in contact, ...
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Separating a charged capacitor plates connected to a battery [closed]

I have to find work done by external agent against electric force in separating parallel capacitor plates when attached with battery (assuming they have charge Q, distance d¹, and area A kept in ...
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6answers
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How is it physically possible that the electric field of some charge distributions does not attenuate with the distance?

Let's consider for instance an infinite plane sheet of charge: you know that its E-field is vertical and its Absolute value is $\sigma / 2 \epsilon _0$, which is not dependent on the observer position....
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A spherical cavity of radius R is made in a conducting sphere of radius 2R. A charge Q is kept at the center of cavity. Find electric field [closed]

I have not been able to comprehend the question as the charge is kept at the center of cavity which is outside of the main surface. So how will electric field will be felt?
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b) Explain why there is no point between 2 unlike charges where you can find zero electric field [closed]

Explain why there is no point between 2 unlike charges where you can find zero electric field.
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0answers
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Gauss Law conceptual problem [closed]

I am not able to create symmetry in this.
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2answers
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Solving 1d poisson equation with point source and periodic boundary condition

How can I solve poisson equation with two point charge sources in periodic 1D domain analytically. $$\dfrac{d^2\phi}{dx^2}=-\dfrac{q}{\epsilon_0}\left(\delta(x-x')-\delta(x+x')\right)\,,$$ where $...
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Wiley Encyclopedia of Electrical and Electronics Engineering [closed]

I was wondering if someone had an ebook version of this encyclopedia by Webster Actually this collection is very expansive (around 14k$ for the complete set) and not very easy to get in libraries I ...
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How do you find the potential difference between the surface and the centre of a uniformly charged sphere? [duplicate]

I encountered a question asking about what should the minimum kinetic energy of an atom (massless, point charge) be in order for it to pass through another atom (sphere, uniformly charged). By ...
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A problem on electrostatics [closed]

How do you find the potential difference between the surface and the centre of a uniformly charged sphere?
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0answers
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Electric field by polarized objects

If I have for example a cylinder with a polarization $\vec{P}=\frac{P_0}{r} \hat{r}$. Can I generally say $P = \rho d$ where d is a small separation of the dipoles inside and $\rho$ the volume charge ...
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0answers
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How this problem can.be solved [closed]

Pls help me with this question ....i am not able to find any figure related to this question...pls explain your annswer through a figure Ques- Suppose the surface charge density over a sphere of ...
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0answers
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Electric field on $(0,0)$ with 4 charges, understanding vector and modulus notations [closed]

I am doing a really simple problem of calculating the electric field on $(0,0)$, where there are 4 different charges. As I understand it, they should nullify each other if I were to calculate the ...
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0answers
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Doubt concerning force on a charged ball

There is a problem I am trying to solve where I am facing certain doubts. Here is the question: A metal ball of radius 5 cm is given a charge of 100 esu. Find the force acting on it per unit area. ...
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Can this problem be solved directly? [closed]

I tried to solve this question from Griffiths : Find the potential outside a charged metal sphere (charge $Q$, radius $R$) placed in an otherwise uniform electric field $E_0$. Explain clearly ...
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2answers
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Dielectric in Capacitors [closed]

There was a question given by our physics teacher in which a dielectric was present between two plates of a capacitor (not touching the plates) and we were required to find the effective capacitance ...
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2answers
72 views

Heat dissipated on switching the wire?

$C$ and $C_0$ are the capacitance of the capacitors. The wire marked with an arrowhead is to be switched from point 1 to 2. Resistance of wires is very very less (~0). Leaking of charge does not occur....
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How did J.J. Thompson decide that the electron was negative charge? [duplicate]

I read Ben Franklin had it wrong by stating "current is the flow of positive charge". Right from the start Ben Franklin could have easily decided to say that current is the flow of negative charge. ...
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2answers
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What does $\epsilon_r$ represents in Coulomb's Law?

Coulomb's Law is represented as $F = \frac{1}{4\pi\epsilon_{0}}\frac{q_1 q_2}{r^2}$ (in vacuum) In any other medium , $F = \frac{1}{4\pi\epsilon_{0}\epsilon_r}\frac{q_1 q_2}{r^2}$ My doubt is that ,...
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1answer
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Electric field intensity inside mixed dielectric capacitor

I have a capacitor with stacked dielectrics where $d_1 =10^{-3} \ m$ , $\varepsilon_{1} = 7$ and $d_2 =0.5 \cdot 10^{-3} \ m$ , $\varepsilon_{2} = 2$ and $V = 500V$. How would I go about calculating ...
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2answers
32 views

Field inside cavity of charged conductor

Can we use gauss law to prove that field in a cavity of charged conductor of any shape is zero?? If so how as the shape may lack symmetry? If not how can we prove the field to be zero? I know that the ...
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5answers
106 views

Why is $\oint_S \mathbf{E}\text d\mathbf{s}=q_{in}/\epsilon_0$ valid when finding electric field inside charged sphere(charges are inside sphere)? [duplicate]

Let $r < R$, where $r$ is the distance to a point from the center of the sphere where we want to find electric field and $R$ is the radius of the sphere. Why can we use $\oint_S \mathbf{E}\cdot\...
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1answer
25 views

Deflection of particle when moving out of Uniform Electric Field [closed]

A particle of mass m and charge -q enters a region between 2 charged plates initially moving along the x-axis with speed $v_x$ .The length of the plate is L and uniform electric field is maintained ...
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0answers
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System of $N$ conductors: Coeficients of Potential derivation

First of all, I have read this question and didn't found an answer. I think the notation I will use (the one my professor used) is the same used in the Reitz/Milford. Unfortunately, my Reitz version ...
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3answers
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Why $\vec{E} = \frac{\sigma}{2 {\epsilon}}$ does not has a variable for distance?

Upon solving a question where I had to find the Electric Field $\vec{E}$ due to an infinitely large uniformly charged sheet of charge density ${\sigma}$ , I found that the Electric Field at a point ...
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2answers
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Why are there electric field lines outside the conductor but not inside?

The Electric field at point P (for an electric slab) is given by $E_P=\frac{\sigma}{\epsilon_0}$, however, since $E$ inside the metallic slab is zero, the electric field at point P is contributed by ...
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2answers
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How do I electrostatically charge a plate?

Let's say I have two iron plates (P1 and P2). I want one side of each plate to have an opposite charge. The surface of P1 should be charged with a positive charge and that of P2 with a negative charge ...
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0answers
29 views

Electric displacement field [closed]

Why, if you suppose $\vec{\nabla} \times \vec{D} = 0$ you get that $\vec{D} = \varepsilon_0 \vec{E_f}$ where $\vec{E_f}$ is the electric field exerted solely by free charges?
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1answer
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Gauss law and curl

I have seen that Gauss law works mainly because $\vec{\nabla} \times \vec{E}=0$, and that we are implicitly using this when finding the charge enclosed using Gauss law. Why is that? I have seen the ...
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2answers
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Determining electric flux and electric lines [closed]

Suppose,I have a q charge and a spherical gaussian surface with radius R.If the radius becomes 2R,will the number of electric field lines be changed compared to previous one? My book says it will be ...
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0answers
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Electric Dipoles [closed]

Electric Dipole of moment $\vec{p} = p\hat{i}$ is kept at $(x,y)$ in an electric field $\vec{E} = 4xy^2\hat{i} + 4x^2y\hat{j}$. Find the force on dipole.
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1answer
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Net Force on an charged conductor in an uniform field

Lets calculate the net force acting on a arbitrary shaped conductor charged with a charge $Q$ on an uniform electric field $\mathbf{E}_0$. $$ \mathbf{F}_{Net} = \int_{S} \sigma\,\mathbf{E}\, dS $$ ...
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0answers
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Electric force due to a solid hemisphere a distance away from its centre [closed]

I have been trying to solve this problem for ages, but cannot come up with a way to do it. Would somebody be able to help me?
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1answer
23 views

Electric density on the edge of a hollow spherical conductor [closed]

Suppose I have a sphere with radius $R$ and charge $Q$ and another hollow sphere with inner radius $2R$ and outer radius $3R$ with charge $2Q$, both of them are conductive. I want to calculate the ...
5
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4answers
412 views

Maxwell equations in absence of magnetic field

I always thought that a change in electric field induces a magnetic field and vice-versa. Moreover, I imagined that any current distribution will give rise to a magnetic field. But then I wrote this ...
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1answer
69 views

Force on dielectric slab

My Doubt is regarding the procedure of calculating force on dielectric while it is being inserted between the capacitor plates (with or without battery). This is the theory behind it. Consider a ...
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2answers
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Capacitor between two equipotential surfaces [closed]

Is a capacitor possible between two equipotential surfaces? I asked my teacher and the explanation given was: There is an electric field between the two equipotential surfaces, thus energy is stored ...
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1answer
34 views

Can Gauss Law for any arbitary closed surface be derived from Coulomb's Law? [duplicate]

As far as I know, Gauss' Law is useful for calculating the electric field where Coulomb's Law doesn't work. For example, it is used for calculating the field produced by a thin sheet of charge and ...
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1answer
85 views

Electric dipole field and spherical harmonics

The field of the electric dipole is $\displaystyle\vec{E}=\frac{3(\vec{p}\cdot\hat{r})\hat{r}-\vec{p}}{4\pi\epsilon_{0}r^3}$, show that it can be written as linear combination of $\displaystyle\frac{...
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0answers
16 views

Finding total energy of stationary electric dipole [closed]

A stationary electric dipole p = p(z cap) is situated at the origin. A positive point charge q (mass m) executes circular motion (radius s) at constant speed in the field of the dipole. Characterize ...
5
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1answer
67 views

Diffusion of Ink in Water

I am investigating the diffusion of ink in water. A drop of blue ink is dropped to the center of a round plate of radius $R$. Say the drop of ink has an initial radius of $r=r_0$ (the very edge of the ...

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