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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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
30 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
30 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
29 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
17 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
22 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 ...
0
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3answers
59 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 ...
0
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1answer
32 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
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3answers
216 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 ...
8
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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 ...
1
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0answers
31 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
79 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 ...
1
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2answers
22 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
37 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
votes
2answers
38 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
66 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
102 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
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5answers
90 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
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1answer
101 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
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1answer
29 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'} ...
0
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2answers
38 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
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1answer
21 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
79 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
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2answers
48 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 ...
0
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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 ...
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1answer
44 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
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0answers
80 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
35 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
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1answer
28 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
21 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
30 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
41 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
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1answer
44 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, ...
0
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0answers
65 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
21 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: ...
0
votes
1answer
46 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
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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
60 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
84 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
57 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
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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
108 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
56 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
53 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
34 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
50 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?? ...
0
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1answer
26 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
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0answers
24 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?