All Questions
70
questions
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42
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Does a charge moving in the direction of electric field produce EM wave?
I am a 12th grade student and our teacher told us that a accelerated charge particle produce EM wave .So a charge particle moving in the direction of electric field or a charge particle moving in a ...
1
vote
0
answers
38
views
Electromagnetic influences in electric field
Let us imagine a charge $q$ in space. At each point in space,there is an electric field vector associated with it. Now we start moving the charge in a direction. We know that electromagnetic ...
- 1,179
1
vote
0
answers
27
views
Creation of magnetic field from charge [duplicate]
We know that a static charge only produces an electric field and a charge in motion (be it constant velocity or accelerated) creates both magnetic and electric field. But recently I came across that &...
- 1,179
-1
votes
2
answers
99
views
Relativistic correction of Coulomb's Law
I am attempting to describe Coulomb's law but with the delay one would get because of the light speed limit. I am aware one could do that using Maxwell's equations because they are relativistic, but ...
- 1,324
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0
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66
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Can electron remain still?
Imagine we have a hollow metallic toroid, with copper wire winded around it, which carries electric current. That implies we have magnetic field inside the hollow toroid. The toroid has vacuum inside. ...
1
vote
2
answers
66
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Why magnetic and electric field static
When charge moves at a constant speed, it is said that it produces static magnetic and electric field.
Why static ? If it moves, at every points, electric field and magnetic field change as they are ...
1
vote
0
answers
84
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Why are not kinks produced for constant speed charge?
Why arent kinks produced when the charge moves at constant velocity in the same linear direction ?
I am asking this because this is the backbone of why EM wave is not created for constant velocity ...
- 525
1
vote
1
answer
112
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Why does the kink has the following vector direction?
I imagine the kink to be the following image in the EM wave.
On the image, we see the charge movement 2 times and each one is very small movement. Even though it is small, it is easy to see why each ...
- 525
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votes
2
answers
92
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Isolated Electric and Magnetic fields
From what I know, wherever there is an electric field that is propagating, there will be a magnetic field present too, because that's what an EM wave comprises of- if it is going to carry energy, we ...
- 167
1
vote
3
answers
543
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How the potential energy of the dipole is $m.\vec{B}$ when work done by any magnetic field is Zero?
We know that magnetic fields don't do any work on ANY CHARGE from the form of Lorentz force we have here. But we still have magnetic dipole getting oriented by external magnetic fields. Now, intuition ...
- 672
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votes
1
answer
92
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In a van de Graaf generator, when a spark happens, is an electromagnetic wave produced? If yes, in which direction?
In a van de Graaf generator, when a spark happens, electrons moves from one globe to the other globe.
Is an electromagnetic wave produced?
If an electromagnetic wave is produced, why is it produced?
...
1
vote
1
answer
383
views
Are electric field lines always perpendicular to a conductor's surface?
I know that in a conductor body, in an electrostatic situation (Where $\vec E=0$ in the interior), the E field must be perpendicular to the surface outside because it is solely generated by electric ...
user336281
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2
answers
42
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Is there a linear or logarhythmic relationship between scale and electromagnetic force?
Are there any instances where electromagnetic force from a point source doesn't follow the inverse square law?
- 57
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votes
1
answer
90
views
How does electric field apply force on charges?
As far as I understand magnetic field applies force on charges or charged/ magnetic materials via the electromagnetic waves(or photons) emitted by moving electrons. And electric field also uses ...
- 1
0
votes
2
answers
216
views
Electromagnetic Waves and Inertia
I have a conceptual question. Suppose we have two bodies of equal masses. One is electrically neutral and the other is electrically charged (positivley charged). Now we apply equal magnitude of force ...
- 2,517
1
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1
answer
100
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If I create a varying electric field and it will then create a varying magnetic field, so will it also create light? Will I see a light ray?
If there is an electric field which is changing in time, lets say I create one, then it should create a varying magnetic field. So that means that there is an electromagnetic field, and oscillating ...
0
votes
1
answer
49
views
Is generation of electric/ magnetic field due to motion of charge frame dependent? [duplicate]
Was introduced to electrostatics today. So I do not have much idea about it and neither I have a strong background in physics. Just a highschool student
1
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1
answer
489
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Measure Earth Magnetic Field using Hall Effect
This is about Hall Effect from this youtube video at here. The voltage across a metal will change based on the strength of the magnetic field. I am wondering whether this will be accurate in reading ...
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1
answer
85
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What implies that transverse EM fields satisfy Laplace's in TEM waves?
I am reading Pozar's Microwave engieering. When explaining the TEM waves (pag98 4th edition) he defines $\bar{e}(x, y)$ as the transverse electric field. He proves that $$\nabla_{t}^{2} \bar{e}(x, y)=...
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1
answer
52
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Does the addition of a static charge or magnetic field to an antenna affect the EM waves it's supposed to receive?
I read this:
Does laser beam (EM wave) affect magnet next to it?
But I distinctly remember the use of a magnetic field to alter the polarization of light. Doc Edgerton used this technique to create a ...
- 1,721
1
vote
1
answer
400
views
Electromagnetic field potentials
Good afternoon for everyone. I have a question in attitude towards the electromagnetic potentials. There are two terms showing two forms of Maxwells equations for electrostatic potential and vector ...
- 13
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vote
1
answer
273
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Do Electric fields really contain energy in them? [closed]
If we assume that energy was first absorbed by q1 and then released by it which then reaches q2 , the same as , electric field not being absorbable and somehow magically gives the energy to q2 and q1 ...
0
votes
1
answer
60
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Why is the magnetic field vector of light so weak compared to it’s electric field vector?
As this article describes,
https://physics.aps.org/story/v26/st13
The magnetic field vector of light is extremely weak. It seems odd to me why this has never been explained in my science curriculum, ...
- 477
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0
answers
654
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Problem-solving books on electrodynamics
What are the best books on the problem-solving of classical electrodynamics exercises?
I looking for books that help me to solve Jackson and Griffiths exercises, i.e. books on the problem-solving of ...
-1
votes
1
answer
22
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How electric charges behave in different motion conditions?
Electric charge at constant velocity produces magnetic an electric field but the particle does not radiate. But, in accelerated motion the particle radiates. But light is also a radiation and the ...
1
vote
2
answers
273
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Can you create a standing electromagnetic wave without generating an electric field?
I know it is possible to create a "standing" electromagnetic wave by generating it in a space that is limited in size relative to the wave's wavelength in some way. Is there any way of ...
2
votes
3
answers
138
views
Radiations in static fields by poynting Vector
Why is the Poynting vector $\vec S=\frac{1}{\mu_0}(\vec E\times \vec B)$ not able to produce radiation when fields are static?
- 193
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1
answer
203
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How can we use the electrostatic boundary conditions for electromagnetic waves?
The boundary conditions for an electromagnetic wave passing from one linear dielectric media to the other (both having no free charges or current) are taken as:
$$B_{\perp_1} -B_{\perp_2} =0$$
$${\...
- 2,000
-4
votes
1
answer
105
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Can I describe whole Electromagnetism only with electric field $\vec{E}$?
Is it possible to write all Maxwell's equations only in terms of $\vec{E}$ (without $\vec{B}$)? The common formulation of Electromagnetism is governed by the equations below:
The Lorentz Force: $$\vec{...
0
votes
2
answers
47
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Why is there an upper bound to the frequency at which an electronic device can be operated? [closed]
Why is there an upper bound to the frequency at which an electronic device can be operated? For example, the frequency of electricity that we receive at home is 60Hz (in the USA).
What will happen if ...
- 1,335
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1
answer
233
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Electric field evaluation in electrostatics and electrodynamics
it is known that an electrostatic field may be expressed in the following way (where r expresses the position of observation):
$E(r) = -\nabla \Phi(r)$
where $\Phi$ is the electrostatic potential. ...
- 1,319
1
vote
1
answer
79
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Point charge potential and electric field [closed]
What is the difference between the 2D and 3D electric field and the potential. Why is it that the potential increases when going from the 2D to the 3D representation but the electric field decreases? ...
- 97
7
votes
3
answers
346
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Why do clothes produce sounds after being in front of a computer for a long time?
Quite often, after sitting in front of the computer not moving a whole lot for a long time my upper body clothes (usually sweaters) make soft crackling sounds when moving or specially when taking them ...
- 171
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0
answers
341
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Electric field on the surface of dielectric sphere and outside sphere
Let a dielectric sphere of radius $r_0$ and permittivity $\epsilon_1$ is placed in medium of permittivity $\epsilon_2$. The electric field inside sphere is $\mathbf{E_1(\mathbf{r})} = E_0 \hat{z}$. ...
- 1,335
1
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0
answers
34
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creating a varying electric field across a copper strip
Hi I am trying to create a varying electric field (by position on copper strip) across a copper strip by attempting a standing wave pattern. the following is a diagram
may I have some guidance on how ...
- 111
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0
answers
230
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Retarded Coulomb's law and EM waves; Feynman texts
In this chapter, Feynman writes down the retarded Coulomb's law,
$$\begin{equation}
\label{Eq:II:21:1}
\mathbf E=\frac{q}{4\pi\epsilon_0}\biggl[
\frac{\mathbf e_{r'}}{r'^2}+\frac{r'}{c}\,\frac{d}{dt}\...
- 455
2
votes
0
answers
70
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A travelling field; Feynman lectures on Physics Volume 2
In Feynman's Lectures on Physics, volume 2, Chapter 18 (18-5), we look at the creation of a electromagnetic field, due to a moving infinite sheet of charge,
By looking at the Maxwell equations ...
- 455
1
vote
1
answer
697
views
Electric Field inside an ideal conductor
I have some doubts about the electric field inside an ideal conductor (let's call it E). Precisely, I have read two different descriptions
1) On physics books I read that the electric field inside in ...
- 1,319
0
votes
1
answer
371
views
Electric field from the intersection of two spheres with different charges
This question is repeated a lot, but I for two spheres with different charge densities, sphere one with radius a centered at the origin and charge density $\rho_1$, and sphere two with radius centered ...
- 111
1
vote
2
answers
219
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What is the relation between the frequency of the light produced and the acceleration of the charged particle
We know that accelerating charges produce EM radiation. Can we derive a relation between frequency of the light produced and the accelaration of the charge ?
0
votes
2
answers
944
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Expressing Maxwell's equations as scalar equations involving differentials in Euclidean space
I am trying to convert Maxwell's equations from the well known differential form (found on Wikipedia Maxwell's equations) into scalar equations involving partial derivatives (more than four equations)....
- 469
1
vote
2
answers
539
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inverse square law and far-field radiation
This question is related to Feynman on inverse square law of EM radiation.
It is basicly the same question except that I don't see that the question was ever answered, and I hope someone will answer ...
- 2,988
0
votes
1
answer
32
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What are the magnitude of voltage fluctuations in field surrounding the human head?
How much would the scale of the electric field caused by neuron activity in the brain vary as it radiated from the scalp? Also what would be the typical noise level over the same space attributable to ...
- 1,144
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0
answers
126
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Why is electric dipole moment represented by "p"?
I recently came across a text where the electric dipole moment was represented as "d" instead of the more commonly used "p". The reason behind using "d" here is probably that "dipole moment" begins ...
- 21
1
vote
1
answer
241
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Electric force between two parallel plates one of which got a rough surface
So if I have two parallel metal sheets separated by 0.1 meters with air as a dielectric with a breakdown strength of 3MV/m and I'm applying a voltage pulse that goes from 0 to 100kV in few ...
- 11
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votes
1
answer
50
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Simple thought experiment -> requirement for EM radiation pops out
Thought experiment (all ideal components): Two 1F capacitors wired in parallel (or ring), with open switches separating them, one cap is uncharged, and the other cap is charged with 1 Coulomb->1Volt->...
2
votes
4
answers
764
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Is the vacuum permittivity a result of defining other units first?
From Coulomb's law
$$F=\frac{1}{4\pi\epsilon_0}\frac{q_1q_2}{r^2}$$
If instead we defined the charge of a coulomb to be $\sqrt{\epsilon_0}$ times it is now, the force would be exactly the ...
- 191
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votes
1
answer
250
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Electromagnetic Wave (Without Magnetic and Electric Field)
As I know, every electromagnetic wave has magnetic and electric field component (perpendicular to the direction of wave). I have a doubt about this, as a hot iron bar also emits EM waves, and as ...
- 11
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votes
1
answer
38
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Does power dissipate on real conductor when charge move from charged object to neutral charged object?
for example we have charged sphere and we have neutral charged sphere
After we connect them with real conductor (few Ohm resistance) some charge will move from charged sphere to neutral sphere.
Will ...
2
votes
3
answers
1k
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How do near-field EM fields change to far-field EM waves at an antenna
What is the mechanism by which the near-field non-traveling electromagnetic fields in the vicinity of an antenna are changed into the far-field electromagnetic waves traveling at the speed of light? ...
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