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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Experiments or phenomenon to look/deduce for the nonexistence of monopoles?

This is a related, but opposite question to this one I have heard about a lot of things regarding elementary and GUT magnetic monopoles, as well the quasiparticle monopoles in spin ice Since there's ...
-2
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1answer
59 views

Production of electric field [closed]

How does varying magnetic field produce an electric field? Is it a natural phenomenon having no reason? i want the process/steps of producing of an electric field by a varying magnetic field.
2
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1answer
60 views

Question on boundary condition for Maxwell's Equations and Coulomb's law

When deriving Coulomb's law using the differential forms of Maxwell's equation, the boundary condition that $\phi = 0 $ at infinity is also used. From $\nabla × E = 0, E = \nabla \phi$ for some ...
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2answers
138 views

EM wave in Real life

everyone I'm new here, but not so new in physics. I have read many articles about EM wave to find what I'm searching for and nothing still. I have seen many pictures, animations and videos about EM ...
0
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1answer
25 views

Poisson equation in non-homogenous media

If the dielectric constant be different in x, y, and z directions, how the Poisson equation would change. Is it right to say: $$ \epsilon_{xx} d^2V/dx^2 + \epsilon_{yy} d^2V/dy^2 + \epsilon_{zz} ...
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1answer
24 views

The electric tension connected to an X-ray tube

The maximal frequency from an X-ray tube is 8.4 ·1018 Hz And I'm trying to figure out the tension, voltage, connected to the x-ray tube So far I have hf max = eU where e = ?? Elemtary charge of an ...
3
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0answers
73 views

Can I hide a charge behind a black hole?

Suppose that you are standing on one side of a black hole. I'm standing directly opposite you, on the other side of the BH, and I'm holding a charged particle. Is it possible for us to be positioned ...
31
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4answers
2k views

How wrong are the classical Maxwell's equations (as compared to QED)?

Now, I don't really mean to say that Maxwell's equations are wrong. I know Maxwell's equations are very accurate when it comes to predicting physical phenomena, but going through high school and now ...
2
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3answers
119 views

Is it possible to create a beam of light with frequency of 0?

Is it possible to create a beam of light with frequency of 0? So this would involve photon(s) that move forward without fluctuating with any frequency. If yes, how could this be done? Also, ...
0
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1answer
21 views

currents in an isolated metal exposed to an alternating uniform electric field

For example, let's look at a metal sphere between a capacitor's (infinite) plates. Let's run an AC current through the capacitor, resulting in an oscillating electric field. The charges will move in ...
1
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2answers
59 views

Gravity and the Speed of Light

Let's assume that I am on an airplane that is at about 4,000 altitude and now let's also assume that I am standing on one of the wings with a light torch, if I point the light torch below to the ...
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0answers
18 views

Designing a capacitor and electrical double layer capacitor

Hello! based on the image above, I am wondering if my assumptions are correct that i can make a capacitor using this design (1) and (2) are "infinitely" long layers (1) layer is made up of same ...
2
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0answers
32 views

Calculating the magnetic permeability of a known plasma

I have a plasma, of which I know the composition, temperature, exact electron/ion/particle densities. How can I then calculate a theoretical permeability of the plasma. Is this even possible? I ...
0
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2answers
87 views

Crazy? Generate unusable electricity

I know that sound crazy, but today I am wondering if there is a way to generate a current that is unusable by almost all electic/electronic devices? The idea would be to generate that current and ...
2
votes
1answer
37 views

EM wave generated with DC battery and coil?

I did below experiment and wanted to confirm the spark is in deed Electro magnetic wave. 1) Took coil of wire , wound it over a iron rod. 2) connected one end of coil to +ve terminal of battery and ...
2
votes
1answer
50 views

Why do iron filings become magnetized along their long axis instead of in a random direction?

Iron filings can be used to illustrate the direction of a magnetic field, say due to a bar magnet. This works because when exposed to a magnetic field, the filings are themselves temporarily ...
0
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1answer
47 views

Should there be a linear force acting aside from torque?

Assume to identical motors are placed vertically on-top of a table and they are not fixed able to move/fall etc...and they have gears attached to them and are attached to one another like this image: ...
0
votes
1answer
41 views

Finding the vector potential of an infinite cyclinder with uniform surface current

This is the second part of a problem in Griffith's "Introduction to Electrodynamics 4th Edition" (problem 6.16). The first part was to find the magnetic field inside a coaxial cable (2 concentric ...
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0answers
17 views

Back force after capacitor is discharged

You have a mechanical hand crank generator connected to a capacitor. You charge the capacitor by cranking it (you obviously have a back current as you crank it so it is difficult to crank). At a ...
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0answers
27 views

Electromagnetic field to shield from EMP?

Could an electromagnetic field be use to protect against an EMP? As I understand, an EMP is an Electro Magnetic Pulse, so a sufficiently powerful field should be able to deflect one, right?
3
votes
3answers
216 views

Are electrons held together by vacuum energy?

If one models the electron as a hollow spherical conductor with charge $e$ and radius $a$ then its electrostatic energy is given by: $$E_{em}=\frac{1}{2}\frac{e^2}{4\pi\epsilon_0a}$$ However if one ...
2
votes
2answers
146 views

Em induction, sliding rod with resistance?

Consider the digram below: This consists of a rod sliding with velocity $v$. I want to find the voltage developed between $A$ & $B$. To do this I drew this 'equivalence circuit': From this ...
0
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0answers
43 views

Elementary electromagnetism problem - Electric field generated by points that form an equilateral triangle

I am a newbie at physics and i just started learning electromagnetism at the university. Some help would be very welcome on the following questions (my question and/or result and/or partial work will ...
0
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1answer
86 views

Symmetry argument for a toroid?

When using Ampere's law for a toroid (in the toroid and around a circular path) please can someone explain the symmetry argument (or an alternative argument) which allows us to assume the field is ...
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0answers
20 views

Formation of Magnetic Field from Moving Charge

Is there a derivation of the magnetic field from the electric field of a charge q moving with speed v? (I know that there are some online, but my limited knowledge in multivariable calculus does not ...
0
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0answers
35 views

Charged black hole

It is known that there is solution of Einstein's equations for charged black hole. Reissner–Nordström metric in case of non-rotating charged black hole and for rotating charged black hole is a ...
0
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1answer
33 views

Energy of anihilation in the form of heat

Suppose you have a closed system. Within it is 2 protons, an anti-proton, 2 electrons, and a positron. All particles are barely above absolute zero in temperature. A proton collides with the ...
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0answers
31 views

The affect of high frequency and high voltage AC on induction

I am designing an induction system to wirelessly transfer power a short distance. I was planning on using resonant inductive coupling to increase the efficiency. The Inductance of my coil is about ...
0
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1answer
22 views

Magnetic Flux Quantization

I remember a few years back in my introductory AC/DC circuits class reading a little bit in the back of the book about magnetism. By this point, I was well aware that magnetic fields are commonly ...
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0answers
42 views

calculating magnetic field strength for a very small electromagnet

I am trying to calculate the magnetic field (in tesla/gauss) of an electromagnet that is very small and has very few windings. For example 12 windings over 0.003 meters. I know this is not going to ...
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2answers
42 views

Intuitive picture of diffraction without fictitious secondary wavelet

This question has been asked in a similar way but no satisfactory answers came up. Huygen's principle relies on the fact that if we consider an aperture, every element dS on the surface of the ...
0
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1answer
33 views

Explanation of force amplification inside a solenoid

For a system being actuated by a motor, the force can be amplified by gearing. The energy is being used for force instead of distance, so it produces more torque but moves slower. For a system being ...
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0answers
21 views

Generation of electromagnetic waves [duplicate]

I came across this while searching about generation of electromagnetic waves-Does this mean that if I vary the electric current following through a conducting wire, it will radiate electromagnetic ...
1
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1answer
58 views

Faraday's Law and Lenz's Law: Is there any theoretical explanations on why changing magnetic field induces an electric field?

This is a more specific extension to this question I came across today One certain aspect of Faraday's Law always stumped me (other than it is an experimental observation back in the 19th century) ...
0
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1answer
23 views

Does displacement current occur in an inductor?

We have learned in school that displacement current comes about due to a change in electric field flux per time in a capacitor (Ampere-Maxwell Law). Does the same displacement current come about in an ...
5
votes
1answer
156 views

Solution of the wave equation [closed]

I am dealing with the solution of the wave equation in two different cases represented in figure by Case A and Case B. The two figures were obtained by shining a slab with an incident wave coming from ...
0
votes
1answer
44 views

If a charge needs potential difference to move

Let's consider a circuit with a ideal source of emf and a resistor. Consider the segment of wire that connects emf with resistor. If we measure potential difference at any point of the wire, this will ...
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0answers
24 views

Voltage induced in coil

Okay, so I have two coils. A ring of radius $R$ is stationary at origin. A coil of $N$ turns and area $A$ carries current $I$ and is moving along the $x$ axis such that $x = x_0 + cos(\omega t)$. ...
2
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1answer
38 views

2 level atomic system interacting with Black body radiation. Relaxation time issue

I am studying the transient regime of a 2 level atomic system ($N_1,N_2$) interacting with a blackbody radiation from a source at constant temperature $T_{nr}$. The initial state of the atomic system ...
1
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1answer
38 views

Can you create a powerful magnetic field out of confined circulating electrons only?

Would it be possible, regardless of how efficient it was to do something like this, or why you would actually do it, to generate a really powerful magnetic field simply by producing a cycling electric ...
0
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2answers
62 views

Wouldn't $D = \epsilon E$ mean that a higher permittivity constant gives a higher electric flux? (And what exactly is the displacement field?)

A quote from the Wikipedia page for Permittivity: More electric flux exists in a medium with a low permittivity (per unit charge) because of polarization effects. This makes sense to me. My ...
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0answers
34 views

Does ratio of magnetic length to geometric length of a bar magnet always remain the same?

The magnetic length of a bar magnet is nearly 0.84 times that of the geometric length(Physical length), which looks quite valid. What would happen if I cut the same bar magnet along the transverse ...
0
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1answer
62 views

Pulling a bar through a magnetic field

This is a question on magnetic flux and induced voltage. I believe that this problem's answer key is incorrect, and I want to determine whether my opinion is sound. I also want to explore one ...
0
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0answers
44 views

Can a(n electro)magnetic field be amplified to overcome the residual strong force between protons-neutrons in a nucleus?

My knowledge of physics is cursory at best, I never studied it in high school but I enjoy reading about it as a layperson, especially the posts here on PSE. I don't understand any of the complex math ...
4
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2answers
334 views

Reflected and refracted light have same frequency as that of the incident light frequency. Why?

My text book says- When a monochromatic light is incident on a surface separating two media, the refracted and reflected light both have the same frequency as the incident frequency. Can anyone ...
0
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1answer
57 views

Is it possible to make an electromagnet w 2 like ends?

HELP! Is it possible to create an electromagnet with one continuous wire with 2 like poles (i.e. both ends either north or south)?. Visualising it with the right hand screw rule for current ...
0
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2answers
31 views

Is the screen in CRT connected with a positive pole?

I don't understand this passage would you clarify it? "These electrons are then freed (liberated) from the metal and are then picked up by the screen, which is connected to a positive pole called the ...
0
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0answers
31 views

Gauge invariance and non-commuting second derivatives

I'm currently doing a homework assignment in relativistic quantum mechanics, and one of the problems involves proving the gauge invariance of a particular lagrangian. The problem is really quite ...
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3answers
79 views

Where is the energy stored in an inductor?

In an inductor, Most text books say that the $(1/2)Li^2$ is stored in the magnetic field. But is there another way to explain this? In a capacitor I understand that all the energy that the battery ...
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0answers
22 views

Mie's scattering Theory Problem

Is Mie's theory which describes the scattering of EM wave off sphere , possible to extend to spheroidal ? object or arbitrary shape with finite series expression ? I tried to replace the radial ...