The classical theory of electric and magnetic fields, both in the static and dynamic case. Also covers general questions about magnets, electric attraction/repulsion etc. Distinct from electrical-engineering.

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23 views

Electric force vs. Magnetic force

E, electric field ------------ H, magnetic field D, electric flux density --- B, magnetic flux density D=εE ------------------------ B=μH ...
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1answer
12 views

Is it possible to have both a conduction current and a displacement current at the same time?

According to Ampere's law, is it possible to have both a conduction current and a displacement current at the same time? In the classical derivation of the displacement current using a parallel plate ...
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0answers
14 views

Superposition of electromagnetic waves and energy localization

Sorry for the long question. I didn't know how to make it shorter. I'm trying to understand how energy is spatially localized in an electromagnetic wave. My premises are: Electromagnetic energy is ...
-7
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1answer
76 views

Is this even possible to understand this proof? [on hold]

Can someone explain what kind of sorcellery is this proof about Maxwell's equations: http://proofs.wiki/Maxwell%27s_equations_predict_that_the_speed_of_light_is_constant. Is this a joke?
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0answers
9 views

magnetization strength of earth's magnetic field [on hold]

what is the magnetization strength of earth's magnetic field (on the surface of earth) on different material/composite?.how it will get magnetized?if the material/composite is magnetostrictive,will ...
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1answer
17 views

magnetostrictive effect due to earth's magnetic field

is there any magnetic field sensor,which produces stress or strain as output,when that sensor is sensing earth's magnetic field on the surface of earth(0.25 gauss to 0.65 gauss)?or any ...
2
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1answer
123 views

Is it possible to “focus” a radio wave to target an area much smaller than its wavelength?

Recently I was reading about a technology that uses radio waves to stimulate neurons to fire. The radio waves have the advantage of being able to pass through the skull (hence being non-invasive) but ...
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0answers
8 views

Is it possible to generate extremely high-resolution patterns of magnetic fields? [on hold]

Recently it has been shown that people can use magnetic fields to stimulate specific neurons (by using a nanoparticle that heats up when stimulated by magnetism, and another protein that opens ion ...
2
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0answers
14 views

Relativistic Induced Magnetic Field in particle's frame

Suppose there is a constant magnetic field: $\vec{\mathbf{B}} = B \hat{z}$. A charged particle orbits that magnetic field perpendicular to the magnetic field, and induces a magnetic field in the ...
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2answers
133 views

Electric Field lines that close on themselves

What causes an electric field line to close on itself as opposed to other cases?
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1answer
20 views

What's the frequency of unmodulated electromagnetic engergy? [on hold]

Radio electromagnetic fields are said to have a frequency wave. This is due to modulating the field. What would the frequency of unmodulated electromagnetic energy be?
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0answers
23 views

Induced electric field due to a moving wire

An infinite wire carrying a constant current $I$ in the $\hat{z}$ direction is moving in the $y$ direction at a constant speed $v$. Find the electric field, in the quasistatic approximation, at the ...
12
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2answers
390 views

Why are electromagnetic waves not able to pass through a hole with a diameter smaller than the wavelength?

I am doing research on Faraday cages for school, and I want to know how it works. Faraday cages can have holes in them, and if the diameter is smaller than the wavelength of waves you want to block, ...
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1answer
54 views

Exact formula in simplest terms for Magnetic field at a point outside a solenoid [on hold]

I need the COMPLETE formula for magnetic field outside the solenoid. So the situation I am stuck in is I have to solve this question: The magnetic field at the centre of coil of $n$ turns, bent in ...
3
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5answers
210 views

How do we know that time dilation applies to objects other than light?

Here is a traditional derivation of time dilation: There's a train with a lamp in the ceiling, moving at velocity v with respect to an observer. In the frame of the observer, the path taken by the ...
2
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2answers
99 views

Why is the Luminiferous aether theory wrong? [on hold]

I saw on this page about the constant speed of light that there are two ways of interpreting this constant speed: General relativity The Luminiferous aether theory I understand why the theory of ...
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0answers
37 views

A few questions related to Magnetic fields [on hold]

Before starting the question, I would like to say that these questions might be easy to solve, the concepts required may be simple, but I did not understand how to do these questions, and so I am ...
2
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1answer
81 views

Resemblance between Coriolis force and magnetic part of Lorentz force

If we interchange velocity with charge and omega that is rotation of a system with $B$, magnetic field, we get the same thing. Is there any deeper meaning to this same mathematical form?
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1answer
73 views

Electrons and Magnetism

Electron at rest generates Electric field. Electron moving without acceleration produces electric and magnetic field. Electron moving with acceleration produces electromagnetic waves. Please explain ...
3
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1answer
82 views

“And God said…and there was light.” What does these equations mean? [duplicate]

Today while I was on the Internet I came across an interesting picture, that caught my eye. It's : I don't have to explain why this picture seems interesting to someone who knows the meaning and ...
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0answers
17 views

Landau levels. Gauge symmetry [on hold]

If we try to find wave function for different vector potential, we will get wave functions, that do not have the same probability at any point( $|\psi_{E,p_y,p_z}|^2 \neq |\psi_{E,p_x,p_z}|^2)$ For ...
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1answer
21 views

Wave guide boundary conditions

Why only the normal component of Electric field and the parallel component of Magnetic field exist at the surface of a wave guide or any conductor?
-2
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1answer
60 views

Possible dangers of power lines radiation, wi-fi and gsm technology [on hold]

I'd like to know more about the topic mentioned in the title. I have 3 questions. I'd be happy to hear your thoughts on any of those. So if high voltage power lines can cause harm to a human in some ...
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2answers
86 views

Where does the permittivity of free space constant come from

Does anyone know why the permittivity of free space is defined as: $\epsilon_0 = \frac{1}{\mu_0 c^2}$ ?
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1answer
35 views

How much does the magnetic force change in a solenoid with the distance between turns?

I was looking for answer in my physics book and in Internet but not. I guess that more distance should be an smaller magnetic field but I do not know how much.
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1answer
67 views

close or open circuit?

A electric source provides a non electrostatic influence on the charges inside the source which pushes the positive charges from the negative terminal to the positive one. Does this happen when the ...
3
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0answers
52 views

Biot-Savart for current carrying wire

A homework question has made me doubt my understanding of the application of the Biot-Savart law. Question: The magnetic field 43.0 cm away from a long, straight wire carrying current 5.00 A is ...
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3answers
45 views

Different frequencies working together

How do the different waves of EM spectrum present in the environment not interfere with each other? If they do, how does everything work properly? The radio waves of mobile phones and wi-fi work ...
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1answer
37 views

For AC current is it better to have a solid or a strandled wire?

For alternating current in wires there are two effects that make energy losses (increase effective resistance): Skin effect which comes since alternating current produces alternating magnetic field ...
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1answer
41 views

Equation of Trajectory [closed]

I was reading about Lorentz force law and motion of a charged particle under Electric field or magnetic field and I understood how they move in it. But as I was moving further I came across the ...
3
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2answers
66 views

How does the magnetic field gain energy through the induced non-conservative electric field?

This is a further question derived from this question about storing energy in an inductor. The accepted answer showed that, during the current increasing, it is the induced non-conservative electric ...
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0answers
30 views

Near Infrared for distance determination

Would near-infrared be an efficient frequency to use in determining the distance from the source of the infrared signal to an object, maybe in the range of 5 to 20 meters away? I need a formula for ...
0
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1answer
67 views

Why does the superposition principle work? [closed]

I am reading Feynman volume 2. (I was reading Griffiths at first.) I don't really understand why the superposition principle of electrical forces (or fields) works. Is there anything deeper in that? ...
8
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4answers
228 views
+100

Difference between spin and polarization of a photon

I understand how one associates the spin of a quantum particle, e.g. of a photon, with intrinsic angular momentum. And in electromagnetism I have always understood the polarization of an EM wave as ...
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1answer
34 views

In which direction due to a polarizing grid the photon's electric field is oriented?

After a photon passes the slit, is it's electric field oriented perpendicular or parallel to the slit and why this is so?
3
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1answer
55 views

What topics do I need to study electromagnetism on the quantum scale? [closed]

What topics do I need to study (in order) so that I can study electromagnetics on the quantum scale? What is the name of the discipline studying electromagnetism on the quantum scale? Do I need to ...
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1answer
70 views

How are the Lorentz force, Maxwell's third law and Faraday's law of induction clasically related?

Faraday's law of induction can be used in any situation where the magnetic flux is changing through a closed conducting loop. While giving the correct answer, it seems to me that for the following ...
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0answers
20 views

Magnetic field direction, Lorentz force direction?

I know that the direction of current flow can change the direction of Lorentz force, what about the direction of the magnetic field? Also, for induced current due to electromagnetic induction is the ...
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2answers
43 views

Is there a material that could “convert” near infrared frequency to infrared?

I have a laser with a wavelength of 650 nm (visible red light) and was wondering if there is some sort of material that could be used to absorb and disperse a different frequency of light around (900 ...
0
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1answer
46 views

How one can know the gauge field emerging from the local gauge invariance is actually the EM field? [closed]

How one can know the gauge field emerging from the local gauge invariance is actually the EM field? I understood in a simple scalar field whose Lagrangian is given by $ \mathcal{L} = ...
-2
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0answers
43 views

Discharging an electric field

Is it possible to discharge an electric field without removing the power source? I understand that electric fields have a positive charge so would it be possible to use an earthed coil to discharge ...
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0answers
22 views

Magnetic field due to wire and plane [closed]

Suppose we have a wire with some current $I$ and which at a point $o$ spreads radially in all direction along conducting plane perpendicular to wire so what will be magnetic field at above and below ...
0
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1answer
29 views

What unit of distance to use when calculating power loss?

80% of Earth's atmosphere is within 10 miles of Earth's surface. I know that power attenuates inversely as the square of the distance within the atmosphere so it occurs to me that a 50,000 watt signal ...
-1
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0answers
39 views

How to derive the light pressure from maxwell equations? [closed]

Is there any reference? Was the idea of radiation pressure known to Maxwell himself?
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0answers
43 views

Speed of a magnet

What is the speed of two magnets during the congruent moment of their attraction? Theoretically, could a large enough magnet attract a significantly smaller magnet at near the speed of light? In ...
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0answers
20 views

Mutual inductance theoretically decreasing while EMF is increasing in 2 square coil system

I have a quick question regarding electricity and magnetism. I am measuring the induced emf in a square coil of wire with an inductance of 439uH (the other coil is also 439uH and is the same shape). I ...
0
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0answers
27 views

Short Wave UV lamp [closed]

if I remember correctly, shortwave UV is very dangerous such that it can break DNA apart. Today I found this site, where parent can buy some scientific tools for their kids. Do not you think shortwave ...
1
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2answers
75 views

What does amplitude in wavelength of light physically mean?What oscilates with time in photon?

Like amplitude in wavelength of water waves signify the displacement of water particles about their mean position.
1
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1answer
106 views

Electromagnetism Boundary condition

The dielectric slab surrounded by air as shown in diagram has permittivity $\epsilon$ different from air and permeability almost same as air. Electric field everywhere within the slab is given to be ...
2
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1answer
42 views

Can asymmetrical Lorentz forces account for Relativistic affects near the speed of light?

The underlying thought here is that at low relativistic speeds all objects are subjected to emf radiation from all directions. This is basically the sum of all the radiation (light, infra-red, ...