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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1answer
20 views

Understanding zero field inside a conductor?

Imagine a neutral conductor of any shape, the charges are randomly distribuited among the object. No way we can say the electric field inside is zero. If I'm wrong, then what can we say about the ...
0
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0answers
14 views

Which way does the force due to current point

The current is towards the right. The particle with charge $-q$ is going with velocity towards the right. How does one find the force due to the current on $-q$? (The RHR doesn't do anything here). ...
0
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1answer
55 views

Motion of an electron in a magnetic and electric field [on hold]

I have this problem where i should find the direction and magnitude of the electric and the magnetic force on the electron. E = 1000 N/C B = 2,5 T v = 500 m/s ...
0
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3answers
35 views

Understanding Capacitors [duplicate]

I cannot understand how capacitors work. Electric field is supposedly uniform between the parallel plates of a capacitor. But how? Since $E=\frac{kq}{d^2}$, shouldn't the electric field approach ...
-4
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1answer
45 views

Why is it possible to produce electromagnetic waves using a charge and electric or magnetic field? [on hold]

Why electromagnetic waves can be produced by the motion of charge in electric or magnetic field? Explain.
-3
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0answers
38 views

Electric potential inside a solid sphere [on hold]

We have charged solid sphere and have to find electric potential inside it. I tried it by two methods, By integrating $\int \vec{E}\cdot\text{d}\vec{r}$ for both outside and inside the sphere ( ...
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5answers
335 views
+200

Can you deduce absolute motion through magnetism?

Trying to understand magnetism I stumble into this example: Suppose there are two electrons travelling side by side in deep space (say, between Mars and Jupiter) at 1 cm distance at .99 c. In this ...
-1
votes
0answers
34 views

Self enery of a sphere [closed]

If we have a sphere of radius 2R in which there is a cavity of radius R with concentric centre . Now we have to find self energy. I searched and got 3 methods : 1) U'' + U' + U* = U In this we ...
0
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1answer
38 views

electron in magnetic and electric field

I have this problem where i should find the direction and magnitude of the electric and the magnetic force on the electron. And then I'm supposed to find the direction and magnitude of the ...
-3
votes
0answers
34 views

What does a particle's path look like in a region with both magnetic and electric fields that are perpendicular? [closed]

Given a uniform electrical field E and a uniform magnetic field B that is perpendicular to it, and a charged particle q that is moving in that field, how does the particle's path look like? How do I ...
3
votes
1answer
35 views

What happens to the electric field at the boundary of a dielectric?

The question in the title is a broader one, but for now, I want to confine myself to the following problem. I have the task to find the potential difference between points A and B shown in the ...
3
votes
2answers
48 views

Electric field inside a material

I was thinking about the polarisation, and how the electric field behaves inside the material of permittivity greater than one. I think to have understood what happens to D and P, but is not clear ...
0
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2answers
66 views

Whats the meaning of this equation relating electric field and potential energy?

My electrodynamics teacher was explaining that it is required to apply some energy (or do some work) on charges in order to arrange them in space. When he stated an example about energy in a capacitor ...
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0answers
28 views

Electric potential inside a conductor inside another conductor [closed]

Suppose there is a neutral hollow conductor body $B_2$ and there is another hollow conductor $B_1$ inside $B_2$ . Let there be a charge $q$ on $B_1$ . Let the potential inside $B_2$ but outside $B_1$ ...
0
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0answers
25 views

Macroscopic electric field

How does the integral over potentials due to dipoles equal the macroscopic field as given in Griffiths page 174. Does that mean macroscopic electric field is numerically equal to the potential?
2
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0answers
23 views

Polarisation inside a sphere

Why is the electric field inside a uniformly polarised sphere not zero? I am confused because charge enclosed is zero and by Gauss' law electric field has to be zero.
1
vote
1answer
69 views

Electric Flux is zero

When is the Electric Flux zero through a closed surface? I know that if number of field lines entering is equal to leaving then it is true. Which I think is always true for a closed surface. So can ...
3
votes
1answer
91 views

High Level Understanding Q: What *is* a magnetic/electric field?

Note: I have seen this question -> (What is a magnetic field) and would still like some clarification. I have also seen https://www.youtube.com/watch?v=hFAOXdXZ5TM and ...
2
votes
1answer
32 views

What is maximum energy we can extract from electric field?

I was reading Does Electric field has mass Energy; it gives energy density k stored around an electric charge as $ k = \dfrac{q^2}{r^4}$ in skeleton form without any constants. So, a definite amount ...
0
votes
0answers
33 views

electrostatic shielding in paradox

We have electric field in side a sphere with formula E=q×r\4π€R^2 But according to electrostatic shielding electric field inside a conductor is zero. How to solve the paradox. In the above equation r ...
0
votes
1answer
27 views

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 ...
0
votes
1answer
35 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 ...
5
votes
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 ...
0
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0answers
11 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 ...
0
votes
2answers
36 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 ...
-1
votes
0answers
28 views

What is the electric field in medium 2 if the medium 1 contains an electron?

I have got this strange yet trivial problem. Say, there's an electron inside medium 1. Outside the medium, lets say we have medium 2. What is the electric field at any point in medium 2 due to the ...
0
votes
1answer
56 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 ...
0
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0answers
26 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 ...
1
vote
3answers
67 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 ...
1
vote
2answers
84 views

Relation between Electric field and potential

I am unable to understand from this - sign comes. Which step I have done wrong?
0
votes
1answer
31 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 ...
0
votes
0answers
24 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?
0
votes
1answer
31 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 ...
3
votes
2answers
40 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: ...
0
votes
2answers
52 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
votes
1answer
27 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 ...
0
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0answers
20 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 ...
0
votes
1answer
38 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 ...
0
votes
2answers
26 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 ...
1
vote
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 .
0
votes
1answer
24 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 ...
0
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0answers
29 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 ...
-1
votes
2answers
112 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 ...
0
votes
1answer
11 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 ...
0
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2answers
14 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 ...
0
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0answers
18 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 ...
0
votes
0answers
10 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 ...
0
votes
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 ...
1
vote
0answers
32 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 ...
0
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0answers
28 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 ...