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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35 views

Applying Biot-Savart to a circular loop along central axis

I'm trying to understand the solution to the magnetic field of a circular loop along its central axis. The solution I'm looking at is page 9 of this document: ...
3
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1answer
50 views

Would a solenoid move if a magnet went through it?

If you were to have a solenoid (0 current) floating still in space, and shot a magnet through it, would the solenoid move, or would it only create a DC current (what if it has a closed/open circuit)? ...
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17 views

Surface current density and infinite solenoid

I have an infinitely long cylinder with radius $R$ and axis lying on the $z-$axis, charged with volume density $\rho$ and surface density $\sigma$. The cylinder is spinning with angular velocity ...
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26 views

Force Between Two Solenoids

How does one calculate the magnetic force between two coaxial solenoids, placed in a way their currents are in the same sense? There is a simple way to treat both as dipoles and then calculate the ...
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0answers
42 views

How does lightning flip a car?

http://www.standard.co.uk/news/london/car-flips-into-air-after-being-struck-by-lightning-in-freak-electrical-storm-accident-10366208.html and a few others ...
3
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1answer
57 views

What force decays an oscillating charge?

Consider this scenario: We have a charge on a spring. As it oscillates, it loses energy to radiation. What force decays the oscillation? As far as I can see, the only forces in the scenario are ...
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70 views

Are non-atomic electrons scattered exactly like electrons in atoms?

Has the Compton effect ever been described in a beam of electrons in a Crookes tube or the like? All the references I found refer to electrons in atoms: In Compton's original experiment, the ...
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49 views

What is the strength of the magnetic field required to penetrate an average human body?

Introduction Suppose you are an experimental nanobot researcher trial-ling a new form of medication that involves activation and control of nanobots within the cells of the interior of the human body ...
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44 views

Magnetic field on axis of solenoid

So first I'd like to say that I have asked similar questions to this one. However, all the answers involve a level of calculus that I do not yet know. (Still on limits, going to spend the rest of ...
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2answers
53 views

Why are the formulas for magnetic or electric fluxes as such?

For electric flux, the formula is given by $$\Phi_E=EAcos\theta$$ For magnetic flux, the formula is similarly given by $$\Phi_M=BAcos\theta$$ But would it not make more sense to describe flux as the ...
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2answers
134 views

Induced EMF, additive to conductor's closed circuit?

Assume the following conductor, with current flowing, powered from a source $S$: Now, I've introduced a magnetic field($B) to the conductor covering a small area of it like so: The change in ...
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1answer
34 views

Magnetic field re-routing

Can a magnetic field be directed in a particular direction, that is re-route it, such that the magnetic field comes out in only one direction?
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4answers
59 views

Why are excess charges in a conductor at the surface?

I’ve been told that coulomb repulsion pushes excess electrons to the surface of a conductor (i.e. sphere) electrostatic equilibrium, and this symmetry causes the net electric field inside to be zero. ...
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20 views

How to describe frequency spectrum with samples?

I posted this same question in math, but nobody is answering, so I thought I'd give a try here too... To me the question is pretty straightforward, but nevertheless I have to explain its background ...
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0answers
39 views

Why do Superconductors make Magnetic Fields Bend Away

When superconductors reach their "threshold temperature" their electrical resistance turns 0. This makes the magnetic field lines not pass through the superconductor but instead bend itself around it ...
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1answer
60 views

What are the interpretations of ampere's circuital law for a single moving electron?

I understand from Ampere's circuital law that when a current passes though any open surface with a boundary (a circular boundary, for simplicity), then limit of summation of the scalar products of ...
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0answers
37 views

Gravitomagnetic railgun

Would a gravitomagnetic analogue of a railgun work as expected, in theory? Consider replacing the electric currents on each rail with mass currents. Then place a mass between the rails, moving with ...
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1answer
20 views

An electric motor that does not reverse current flow

If an electric motor did not reverse the direction of its current every half-turn, what would be observed in the armature? Would it spin from left to right clockwise, then spin back anti-clockwise ...
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1answer
45 views

is it possible to get an object to travel over 200 mph with magnets [closed]

Is it possible by magnetic forces to cause a certain material to travel at speeds over 5000 mph<>?
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75 views

Why is magnetic field perpendicular to that plane?

Magnetic field is perpendicular to the plane containing direction of flow of current in a straight wire and radius vector.What I have been told is that,to explain lorentz force magnetic field was ...
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1answer
69 views

The truest/most general Maxwell's equations in isotropic, linear, inhomogeneous media with sources

Sources use $\mu H=B$ and $\epsilon E= D$, assuming homogeneous media. Obviously if $\mu$ is space varying, $\nabla . (\mu H)$ need not be equal to $\nabla . B$ What is the most general form for ...
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20 views

Correlation of magnetic field range to induced current?

If a magnetic field($B$) is increased in range(size of coverage,or flux area is larger)at the same strength, would there be higher output of current if there is a conductor with velocity($v$) passing ...
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0answers
17 views

Poisson Spot vs. Shadows

In textbooks, whenever I read about the Poisson spot, it involves a disk, and having light waves diffract around it and interfere constructively in the center. At the same time, when I read about ...
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1answer
83 views

Can the fundamental dimension of Electric Charge be Mass only? [closed]

After solving dimensions of electrical equations, I found out that the fundamental dimension of Electric charge is mass only. This also leads to the derivation of dimensions of other Electrical units ...
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4answers
236 views

Method of calculating eddy currents of a conductor, is this correct?

I have a conductor with volume $V$, passing a magnetic field($B$) with velocity($v$): I'm trying to calculate the Eddy currents to figure out the magnitude of the drag force($F_d$) generated the ...
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0answers
31 views

Developing an analytic equation set for a complicated solenoid

So, I'm a bit stumped by this. I've been asked to develop an analytic function for the magnetic field of a complicated axisymmetric solenoid with free parameters to be determined by making a fit ...
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24 views

Electromagnetic transfer function

In a paper on the superlens, I came across the term of "transfer function". I understand that the transfer function relates the output to a given input, but I've been unable to find a formula for the ...
3
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1answer
44 views

The role of amplitude, frequency, and intensity in mechanical vs. EM waves

As far as I know (correct me if I’m wrong), for a mechanical wave (e.g. sound), the frequency determines the pitch, the amplitude determines the loudness, and the amplitude is proportional to the ...
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0answers
38 views

Physical cause of Negative Permittivity

What is the physical cause behind a material having a negative real part of its dielectric function? Given the complex permittivity, $\epsilon(\omega)=\epsilon(\omega)'+i\epsilon(\omega)''$, the Drude ...
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1answer
54 views

Why can't two charged particles know about each other's presence instantaneously?

Why can't two charged particles know about each other's presence instantaneously? Does such a state of affairs produce contradictory or counter intuitive results?
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16 views

is there any element or material that ionized when pressure is applied to it?

I want to know if there is any material, that produce free electrons and ions when it undergoes to high pressure.
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31 views

Two equal charges accelerating parallel to each other

Let's say constant acceleration for simplicity. Ignore possible logistic concerns, such as what is accelerating them or how they stay in path. Lets just assume they are in a conduit made of a solid ...
3
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1answer
70 views

Does charge bend spacetime like mass? [duplicate]

Does charge bend spacetime like mass? I'm not asking if electromagnetic forces can be described geometrically, but if EM fields could correspond to particular curvatures of spacetime, like gravity ...
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0answers
35 views

Transfer function of a space varying wave equation

$$\frac{\partial ^2 \psi}{\partial x^2}-\mu \epsilon \frac{\partial ^2 \psi}{\partial t^2}-\mu \sigma \frac{\partial \psi}{\partial t}=0$$ Is the wave electromagnetic wave equation in lossy, source ...
3
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1answer
51 views

Gradient in the Frenet-Serret coordinate

I was simply thinking that the gradient in the Frenet-Serret coordinate at a particular point is similar to the gradient in the Cartesian coordinate. I simply assumed that Frenet space is an ...
3
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2answers
121 views

How can magnetic fields have energy and yet be unable to do work with that energy? [duplicate]

Magnetic fields can't do work. However, we use the following equation to describe the energy density of a magnetic field. $u = \frac{B^2}{2\mu_0}$ The term energy density suggests that the magnetic ...
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0answers
25 views

Recommended books that describe emission and absorption of light and light/matter interactions

Hello I am a Chemical Engineer that has ventured into the field of optics and I was wondering if there is any recommended book/books to understand the maths and also some answered exercises or ...
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0answers
33 views

Magnetic field due to current carrying sheet

I have 2 infinite plates (x direction) with the width of A (y direction) and the distance between them is d (z direction). The current density is J on the first plate and -J on the second (the ...
1
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1answer
40 views

Why the whole wire moves when lorentz force acts?

We know that magnitute of lorentz force is directly proportional to the current in the current carrying wire. But since the force is acting on the charges,shouldn't they get exited or thrown out when ...
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4answers
135 views

Do moving charges produce magnetic fields?

As I understand it, a moving charge produces a magnetic field. Now it may be that I have have a misunderstanding here and if so I need to have the proper understanding of this. So if I do have a ...
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2answers
100 views

“X-rays”, “gamma rays”, “sun rays”… But electromagnetic waves are NOT rays and DO NOT consist of rays?

In a separate question I'm struggling to figure out the nature of EM waves. But it's a vast topic and I'm trying to narrow it down to small specific questions. It turns out that all electromagnetic ...
3
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4answers
104 views

How does an inductor store magnetic energy?

I am trying to figure out what the potential energy of an inductor with a current really means. In a capacitor, the energy stored works like this: if you let the plates attract each other, before ...
2
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2answers
123 views

Is the wobbly rope depiction of a radio wave inherently wrong? And how do vectors of parallel waves align with each other?

I don't have a scientific education, yet I'm scientifically curious. Among other things, I'm struggling to understand the nature of electromagnetic waves. What I have recently realized is that the ...
10
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4answers
1k views

Do electrostatic fields really obey “action at a distance”?

In an electromagnetic theory class, my professor introduced the concept of "action at a distance in physics". He said that: If two charges are at some very large distance, and if any one of the ...
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0answers
42 views

How can electric and magnetic fields have any component in the direction of propagation of electromagnetic waves?

In case of waveguides we talk about $E$ and $H$ having non zero component in the direction of propagation of wave. But the entire basis of EMW is that $E$ and $H$ are perpendicular to the direction of ...
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1answer
66 views

Is gravity weak negative electric charge? [duplicate]

This could be true since the both have infinite range and other common properties. They both have fields.
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1answer
61 views

How is light slowing down in a medium thought of in the photon picture? [duplicate]

The speed of light in any medium besides vacuum is smaller than $c$. In a classical way, I just look at that as a wave that propagates less fast, the change in EM-field is passed on slower. How should ...
0
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1answer
31 views

Is internal resistance relevant in motional EMF?

When a conductor passes a magnetic field and connected to a circuit, the induced voltage is calculated via the motional EMF($\epsilon$): $$\epsilon=-vBL$$ Is the conductor's resistance (or internal ...
2
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1answer
105 views

How can radiation be a transverse wave? Does light really resemble a rope? How can a 3D field be a medium for non-spatial 1D waves? Need mental model

I understand longitudinal waves. For example, I've got a clear mental modal of air waves: a slice of air becomes overcompressed, then the slice next to it becomes overcompressed and the first slice ...
0
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1answer
88 views

Could electromagnetic charge curve something like spacetime in analogy with general relativity? [duplicate]

Newtonian gravity and electrostatics have the same form; this analogy is extended when we look at full dynamic electromagnetism, and correspondingly "gravitomagnetism". We are quite capable of ...