For questions that utilize the concept of electric fields (commonly denoted by the letter E), or for questions whose answers likely involve electric fields. More specific than the [tag:electricity], as questions about the phenomenon & theory of electricity do not necessarily involve the discussion ...

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Relation between potential difference and electric field

I was reading an article about resistivity when I faced this equation: $$V_P-V_O=\int_P^O E.dr$$ The equation is in one dimension and $P$ and $O$ are points on the $x$ axis. The Electric field is ...
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1answer
47 views

Surface density charge, divergence of the electric field and gauss law

It´s known that the divergence of the electric field at a certain point is given by this formula: $$\nabla \cdot E=\dfrac{\rho (r)}{\epsilon_{0}}$$ Being $\rho (r)$ the volume charge density at that ...
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3answers
1k views

How is the curl of the electric field possible?

Taking the curl of the electric field must be possible, because Faraday's law involves it: $$\nabla \times \mathbf{E} = - \partial \mathbf{B} / \partial t$$ But I've just looked on Wikipedia, where it ...
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0answers
14 views

Why does a 2-sided propagating EM wave become 1-sided if B is made proportional to E?

If you simulate the propagation of an electromagnetic wave in 1D free space (no charges or currents) with initial conditions of $E\neq0$ and $B=0$, and you look at a movie of $E$ vs time, then after ...
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2answers
56 views

Non-Zero Electric Field Inside A Conducting Shell

Statement: "The electric field is zero everywhere inside the conductor, whether the conductor is solid or hollow." Question: A coaxial cable consists of a long, straight filament surrounded by a ...
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1answer
60 views

Energy stored in electric field [duplicate]

I know that energy stored in electric field / unit volume = $\frac{1}{2} \epsilon\,E^2$. so can I say that for any configuration calculating $\int \frac{1}{2} \epsilon\, E^2 \,d^3r$ over whole space ...
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0answers
29 views

How do we calculate electric field on the axis of a disc using gauss law and the concept of solid angle?

We can easily find the electric field at the axis of the disc by considering a differential ring and then integrating it to form a disc, but I was searching for rather a bit simplified proof using ...
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3answers
76 views

What is the maximum reach distance of electric field? [duplicate]

if i charge small object by removing electrons and put that object in the middle of huge vacuum chamber (million of light years in size) does the electric field lines of that charged object still be ...
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2answers
111 views

Relation between Electric field and potential

I am unable to understand from this - sign comes. Which step I have done wrong?
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1answer
35 views

Inconsistency in solving energy in free space given electric potential

So we have the equation $$ W= \frac{1}{2} \int_{volume} \rho_v V\,dv$$ and then after applying a vector identity which is $$\nabla \cdot (V\vec{D})=V(\nabla\cdot \vec{D})+\vec{D}\cdot (\nabla ...
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0answers
25 views

Would a spinning carbon steel (high magnetic permeability) sphere become magnetized?

Would a spinning carbon steel (high magnetic permeability) sphere "falling" through Earth's magnetic field become magnetized? Would a spinning, evenly charged sphere generate a magnetic field?
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1answer
35 views

Coaxial cable with electric flux

I had a question when I solved some examples of coaxial cables. I want to find the E and D field using $\rho_s = {Q \over {2\pi r L}}$. Here is my question: Why is the inner surface of the cylinder ...
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1answer
50 views

Electric field at surface of a spherical shell

The shell theorem provides a well known result that for a spherical shell with uniformly distributed charge $Q$ and radius $R$, the electric field at a distance of $r$ from the center is: ...
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2answers
68 views

If Electric field is constant in a region, does it imply potential is also constant?

I am a bit confused about these concepts- when is electric field or electric potential constant so i would appreciate if anyone could brief me about these things as well. Here i am referring to ...
0
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1answer
42 views

Inserting dielectric slab into a capacitor

I studied that inserting the slab into a capacitor which is connected to a battery is difficult and we have to do the work, and inserting the slab into a disconnected capacitor is easy and we don't ...
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0answers
21 views

Choosing between a parallel-plate and spherical capacitor model

This problem is solved in the solutions manual by making reference to equations for the parallel-plate capacitor. I have some basic understanding of why this is the case (the local curvature is small ...
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1answer
44 views

What does minus charge mean?

According to my simple knowledge, Charges are negative but sometime I read -for example- : q = -2*10^-8. What is the rule of "minus" if the charge is already negative. The solution for calculating ...
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2answers
41 views

Spherical Conducting Shells, Potential

When we have a spherical conducting shell and charge on outer surface of the shell then the potential inside remains constant i.e, kQ/R (R=radius). But say the inner surface of the shell is charged ...
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0answers
22 views

Please Can Anyone help Me to drive the equation for Electric Field Around a test Charge Around A uniform Ring. [closed]

Please can i get a mathematical relation for electric Field around a test Charge Lying in the region of influence around a uniformly Distributed Charged Ring .
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1answer
27 views

Is it possible to express Fleming's Left Hand Rule and Right Hand Rule in terms of vectors?

I recently studied Fleming's Right Hand Rule and Fleming's Right Hand Rule for electromagnetism (For locating direction of Force, Magnetic Field and Current). Using my hands to find the direction is ...
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0answers
35 views

Electric field of a non-uniformly charged quarter circle

I was studying for my Electromagnetism test when I stumbled upon this problem and haven't been quite able to do it correctly, mostly because I can't find any symmetry for me to calculate the Electric ...
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2answers
186 views

Why is Electric field flux through a closed surface in Gauss's law not zero?

I learned that the vector flux through any closed surface is always 0. So if you have a sphere(closed surface) and you put it in an uniform electric field, then the total flux is 0. However, the ...
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1answer
12 views

grounding spherical shells

a Q1 charged spherical shell A with radius of a is inside a Q2 charged spherical shell B with radius b. now A is grounded. since no force is acting on Q1 all of them should be neutralized. and at the ...
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2answers
17 views

Electric potential energy of a charge

Potential energy is the work done by the particle against a conservative force. Isn't it? when a charge is fixed on a free space and then when we bring another charge from infinity to a distance r ...
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0answers
22 views

Electric field intensity near to a small conducting plate?

I know the electric field intensity near a infinite charged conducting plate. when the plate is very large we assume that there is a symmetry and take the electric field intensity as same as for ...
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0answers
12 views

Constant electric background field from theta-term in QCD?

The theta-term of $1+1$ dimensional QED corresponds to a constant electric background field. Does the theta-term of QCD also induce a constant electric background field, which could be measurable in ...
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1answer
30 views

Total potential energy in electric field?

if there are 2 charges generally potential energy of the system should be the sum of individual potential energy. but why the potential energy is half of the sum of every individual charge's potential ...
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0answers
37 views

Method of image charges — Why is a *grounded* plate needed?

In the classic image charge problem of a charge $q$ above an infinite grounded plane, it is well known that the field lines essentially behave as though there were a negative charge behind it, and the ...
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0answers
42 views

When deriving potential between plates of parallel plate capacitor, why isn't the charge distributed on the top *and* bottom of both plates?

Let's say we have a canonical parallel plate capacitor with area $A$ and separation $d$ where $A>> d^2$. A charge of $+Q$ is placed on the top plate and $-Q$ is placed on the bottom plate. We ...
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1answer
34 views

Does a conductor in an external electric field have a positive charge density and electric field inside?

I'm thoroughly confused by conductors. Let's say you have a round(ish), perfect conductor. Solid and uncharged. Some distance from it, we place a point charge $q$, giving rise to a field $\vec{E}$. ...
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2answers
30 views

Why a common potential is attained?

Lets say we have a 50 v conductor .Now is we touch the conductor,by another conductor , both the conductors will attains a common potential.Why is this so? How do they acquire such a common ...
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0answers
21 views

Null point (vector) between n point charges

I have derived the result for 2 positive charges, and for one positive one negative can be obtained by using the minus sign correctly. But I was unable to extend it or solve for n charges. Is my ...
0
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1answer
23 views

Can electric strength between two parallel plate be calculated by its given electric potential difference and distance?

The electric strength between two parallel plates does not depend on its separating distance, and only depend on the number of charges the two plates carried. Therefore $\epsilon$ cannot be calculated ...
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3answers
64 views

Electric Field Inside a Conductor at Different Charge Densities [closed]

We say that the magnitude of the electric field inside a conductor is zero, whether a hollow or solid. However, at certain charge densities, the magnitude of the electric field inside the conductor ...
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1answer
33 views

Thermionic emission

I have a pretty basic question regarding the beam of electrons as a result of thermionic emission. In an electron gun, the emitted electrons from the cathode become incident at a point on the other ...
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3answers
224 views

Is the electric field strength along an equipotential surface constant?

I'm trying to determine whether or not the electric field strength $|\vec{\mathcal{E}}|$ is constant everywhere on an equipotential surface. I know an equipotential surface is defined as $$ S = ...
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0answers
37 views

Do fields have to be continuous and smooth? [closed]

As far as I understand it, a field in physics is a physical quantity that has a value for each point in space and time. However, I'm not sure whether these physical fields that we commonly use (such ...
1
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1answer
58 views

Electric flux of a charged rod through a uniform disc

I have an assignment regarding electric flux. The question I was given has the following sketch: The first question was about the force on the rod from the disc at the $z$-axis. I reached the ...
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6answers
1k views

Are electric field lines always conserved?

Suppose we have a positive +q charge and a -6q charge at some separation. Then will every field line originate from the +q and end up to -6q or will there be some extra lines coming to -6q from ...
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0answers
32 views

Components of electric field deriving from potential equetion [closed]

My question is abut finding components of electric field from potential function. $V=\frac{1}{4\pi\epsilon_0}\frac{\vec{p}\cdot\vec{r}}{r^3}$ (1) I can write it as ...
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2answers
88 views

Electric field between 2 parallel plates

The question state that 2 large parallel plates are a distance $d$ apart and the field at $d/2$ is $E$ if the distance between the plates are reduced to $\frac{d}{2}$ what is the field strength ...
0
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1answer
38 views

Changes of Electric fields with motion

I have seen a website which is in Russian language and they expressed that the electric force line will bend along a axis if the charge keep moving, which will be looked like this: But could you ...
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2answers
30 views

How to find the graph of electric field when the potential is given [closed]

Suppose the electric potential due to an electric field is given as $x^2-y^2$, then what will be the graph of the electric field? My attempt: Differentiating the potential partially with $x$ ...
0
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0answers
39 views

How do pulse properties relate to the pulse's peak power?

Let's say we know the temporal shape of an optical pulse, which is $E(t) = E_0 \cdot f(t)$, where $E(t)$ is the electric field, $E_0$ its amplitude and $f(t)$ the shape function (e.g. $sech^2$, ...
3
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2answers
46 views

Electric field due to a charged irregularly shaped balloon

There is a question in my textbook that says: A rubber balloon is given a charge $Q$ distributed uniformly over its surface. Is the field inside the balloon zero everywhere if the balloon does not ...
0
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2answers
84 views

Putting a capacitor into a strong magnetic field, will this change the capacity?

I'm wondering, does a magnetic field change the number of electrons, placed and displaced on the two plates of a capacitor. To prove or disprove this, I think the capacitor could be connected to an ...
0
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3answers
126 views

Why doesnt magnetic and electric field lines collide?

Why cant they meet or cut each other. I know magnetic field lines dont intersect with magnetic field lines and electric field lines dont intersect with electric field lines but why dont these ...
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5answers
96 views

How is the electromagnetic field made?

I know that an electric field is created by a particle with a charge and that a magnetic field is created by a moving charge but how do they combine to make a electromagnetic field?
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1answer
122 views

Why do fundamental particles have charge? [duplicate]

More specifically, what is in the nature of these particles that they carry a charge, and thus repel objects of similar charge and attract those of opposite charge? Also, why would the charge of an ...
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1answer
32 views

Derivation of polarizability

I am currently reading some papers on Dirac and Weyl physics on condensed matter. Very often, the following result for the polarizability is used: $$ \Pi(q,\omega) \propto \sum_{k,s,s'} ...