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 ...

learn more… | top users | synonyms (1)

0
votes
1answer
39 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 ...
4
votes
3answers
271 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 = \{\...
1
vote
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
vote
1answer
62 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 ...
8
votes
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 ...
1
vote
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 $V=\frac{1}{4\pi\epsilon_0}\frac{pz}...
1
vote
2answers
102 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
votes
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 ...
1
vote
2answers
32 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 $x$ and ...
0
votes
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. $sech^2$, ...
4
votes
2answers
73 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
votes
2answers
110 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
votes
3answers
144 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 ...
0
votes
5answers
108 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?
1
vote
1answer
126 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 ...
1
vote
1answer
33 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'} \frac{f_{sk}-...
0
votes
2answers
51 views

Electric Potential of Point Charge (sign problem)

This question has been asked before, but the answers didn't clarify the problem for me, so I thought I might ask again. It's really a simple question. Let's say we're calculating the electric ...
1
vote
1answer
23 views

Net electric field of charged spherical shell and dot charge

I have positively charged hollow spherical shell at origin, with radius R. Then negatively charged dot charge at (2R, 0, 0), and I'm supposed to find electric field everywhere. What seems unclear is ...
-1
votes
1answer
81 views

Why Different charges attract while they should repel? [closed]

When I started studying magnetic fields, my teacher was always telling me that strong fields push the bodies to weaker fields, so i tried to apply the same concept to charges in the following picture: ...
0
votes
2answers
53 views

Induced charges

Consider a charge +q placed inside a cavity of conducting body. Charges will be induced as shown in the diagram below. How do we show that the electric field at a point A inside the cavity due to the ...
0
votes
2answers
22 views

Electric fields and potential

E = electric field V = electrostatic potential r = distance ' = derivative E = - (V)' therefore if E increases V decreases Also if r increases E decreases ...
1
vote
1answer
52 views

Induced EMF of this loop?

Consider a simple loop like so: And in-front of this loop are a series of wires that would cover the whole are of the loop, these wires are parallel to one another, and they have current flowing ...
1
vote
0answers
136 views

Non-parallel plate capacitor's capacitance [closed]

So far, I fully understood how to find the capacitance of a parallel plate capacitor. However, for the case of non-parallel plate one, how one could solve that kind of problem knowing that one plate ...
1
vote
1answer
43 views

$3$ dimensional representation of Electric Field lines between Two particles

I have seen in many books the $2$ dimensional representation of field lines (between two particles having equal positive charge) as- But I am trying to visualise this $3$ dimensionally as how the ...
1
vote
1answer
35 views

Simulating the Electric Field inside a Hollow Sphere of Uniform Charge

I've recently been studying Gauss's Law and have come across some results that I want to verify. For one, I am trying to verify that the electric field inside a conductor (in this case it could be ...
0
votes
1answer
25 views

Gauss Law - charges outside the gaussian surface

I have just learned Gauss Law and this question is bothering me: Suppose a cubic gaussian surface and a charge next to its right side (image below). According to Gauss Law, the electric flux over ...
0
votes
2answers
31 views

What is filtered through the linear polarization of EM light? E field, B field or both?

I know that for EM waves (i.e sunlight) for any E wave in any direction, there is B field perpendicular to it. However, when we pass that EM wave through the linear polarization filter, what actually ...
0
votes
1answer
46 views

Why can't electric field lines intersect each other? [duplicate]

I just saw this on my textbook but I didn't quiet understand the thing can someone give an easy explanation.... Thanks
0
votes
1answer
49 views

Doubt in derivation of electric field at axial snd equatorial point

Firstly, in derivation of electric field at an axial point due to a dipole we have to determine the Electric field at a point P on the axial. So there are two electric fields acting on this Point P, E(...
0
votes
0answers
80 views

Electric field at centre of two different hemispheres

I have a sphere separated into two hemispheres which are insulated from each other the bottom half is earthed and the top half has potential $V$. Radius=$a$. I am trying to find the Electric ...
0
votes
1answer
22 views

Work in electric field - formula

Suppose there's a electric field generated by a charge $Q$. If I moved a charge $q$ placed at distance $r_1$ away from $Q$ to distance $r_2$, supposedly the average force acting on $q$ will be: $F=\...
0
votes
1answer
52 views

How to determine the cylindrical gaussian surfaces position while finding the electric field?

Today I encountered a question that had the solution: electric field outside of a charged nonconductor is $$ E=\frac{\sigma}{2\epsilon_0} $$ which had the diagram below: Fig. 1 and for the ...
0
votes
0answers
17 views

Voltage drop along electron beam

A focused electron beam represents a current and unless the charges (electrons) meet no resistance to their movement there should be a voltage drop along the length of the beam. So, assuming the beam ...
0
votes
1answer
63 views

Electric field integration? [closed]

If we have a rod uniformly charged with $Q$ stretching from $-a$ to $a$ on the $x$-axis as shown in the picture And we want to calculate electric field in point $2a$ on the $x$-axis, we know that ...
1
vote
1answer
89 views

How does an Atoms electric field overcome an electrons inertia?

An electron has mass, and therefore has inertia. How does an atoms electric field perpetually overcome an electrons inertia, necessary to hold it in its shell? Does this require continual work to be ...
-1
votes
1answer
88 views

Capacitors and external electric fields

I am grading questions from the lab manual provided by the professor to review with the students. I am trying to wrap my head around one of the questions about what an external electric field would ...
0
votes
0answers
23 views

Separating Interaction of Heat from Electricity?

I have a rod where electricity of frequencies 1-360 Hz is passed through. It is affected by heat. I am evaluating the energy involved in such a process, contributed by electricity and heat. The ...
0
votes
2answers
172 views

Velocity selector and charge to mass ratio of an electron

I recently read that J.J. Thompson used a velocity selector to find the charge to mass ratio of an electron. Having learnt the principle behind the velocity selector, I see no relation between these ...
3
votes
1answer
74 views

How does parallel plate lose energy when deflecting charged particles

Say you have a parallel plate setup, each plate is charged with ±Q of charge, and is then disconnected from the power source and is insulated from the environment. There is no way the plates can be ...
2
votes
0answers
54 views

Gauss' Law and Electric Field Close to a Ball

So I've learned about Gauss' law and I have something in my head. Why does electric field that is very close to a ball is not close to infinity. Take a look at this image: As we can see, if we make ...
0
votes
0answers
35 views

Linear Charge distribution in thin (conduction) beam due to electric field

I'm trying to figure out the linear charge density in a very, very thin conductive beam of 0 net charge due to an electric field generated by a source very, very far away. Since the beam is ...
0
votes
1answer
53 views

Eddy current induce emf

Q1Suppose there is a wire having AC current so as ac current is alternating it creates back emf wether that back emf produces current ?? If yes then that current is same as eddy current or not?? ...
-1
votes
2answers
37 views

Electric fields with different frequencies, total intensity?

What happens when electric fields with different frequencies are combined? Is it possible to calculate the intensity of the total electric field? For a project, I need to simulate a brain treated ...
2
votes
0answers
25 views

Symmetry arguments and plane sheet of charge [duplicate]

The electric field due to a infinite plane sheet of charge is given by $\sigma/\epsilon_o$. Now could we have deduced by symmetry that the electric field's magnitude won't depend on distance?
1
vote
1answer
41 views

Charge outside a Sphere given charge density

If a sphere has a charge density of $\rho =\alpha r^2$, I want to calculate the Electric field outside of the sphere. Starting with Maxwell's equation $\bigtriangledown\cdot E=\frac{\rho }{\epsilon ...
0
votes
3answers
58 views

relation between amplitude and frequency of a rotating electric field [closed]

I generated a rotating electric field produced by Ex=cos(wt) Ey=cos(wt-pi/2) in x and y directions. I ran a simulation and seems only in certain amplitudes and frequencies it makes a rotating field. ...
3
votes
2answers
80 views

Some confusions regarding electrostatic shielding

A spherical conductor A contains two spherical cavities as shown. The total charge on conductor itself is zero. However, there is a point charge q1 at the centre of one cavity and q2 at the centre of ...
0
votes
0answers
23 views

strength of each dipole charge

If I have a two dimensional dipole whose line charges are located on the y axis, I know that the electric flux through a gaussian pill box containing both the charges will be zero, that is \begin{...
0
votes
1answer
75 views

A question when using $E= - \nabla V$

This problem is from Problems and Solutions on Electromagnetism. A thin but very massive disc of insulator has surface charge density $\sigma$ and radius $R$. A point charge $+Q$ is on the axis of ...
0
votes
0answers
55 views

Force Exerting on a magnetic train

A question is already asked ( How does this “simple” electric train work? ). But I've got a question about it. In order to calculate the force which is being exerted on the system including magnets ...