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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38 views

Basic EM: Infinite energy of magnetic field?

I thought I was done with EM, but then I encountered a strange question: A ring of test mass (m) and test charge (q) with radius R is sitting still in space filled with a uniform B-field in the ...
2
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1answer
49 views

Induced motional EMF where the wire is stationary and the field source is moving?

If a wire is moving in a magnetic field $B$, there is a Lorentz force acting on both the postive and negative charges, separating them to create an electric field, which is a great explanation to aid ...
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1answer
34 views

Alpha Particle moving through a magnetic field [closed]

How would I find the acceleration of an alpha particle moving through a magnetic field given the force of the magnetic field, the charge, the initial velocity and the strength of the magnetic field.
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0answers
44 views

How 7.0 Tesla can yield better image resolution with less teslas?

I am studying the book 7.0 Tesla MRI Brain White Matter Atlas 2nd edition by F. Calamante for 1.5, 3.0 and 7.0 Tesla images, respectively I do not understand how the image resolution can be greater ...
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0answers
19 views

Why are magnetic quantum numbers assigned like they are assigned in the paper on WS2 monolayers?

Now I'm reading the following paper: Sie, E.J., et al., 2015. Valley-Selective Optical Stark Effect in Monolayer WS2. ‎Nat. Mater., 14, 290-294 And they assigned magnetic quantum number to valence ...
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1answer
47 views

Magnetic force and torque for 2D neodymium ball simulator

I'm trying to write a simulator for neoballs. I'm doing only 2D for a start, in which each ball has a magnetic moment, m, that is in the x-y plane. The simulator will use time-step integration at 60 ...
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2answers
61 views

Will rotating magnets slow down one another when interacting?

Will rotating magnets slow down one another when interacting? Two discs are spinning. Both have separate magnets attached. Disc one has a diameter of $8~\mathrm{cm}$ and disc two has a diameter ...
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2answers
53 views

Is energy only transmitted through electromagnetic and particle radiations? [closed]

Which are the other ways of transmission if any? If energy does not require any medium for transmission(as for sunlight reaching earth, the heat too), is it transmitted in quanta in particle radiation ...
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1answer
22 views

Does the direction of magnetic field in a solenoid point from north to south anywhere? [closed]

Is there any case where the direction of magnetic field inside a solenoid points from its North Pole to its south?
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2answers
55 views

Possiblity for particle to be carried by a wave such as a photon or electromagnetic wave/waves in general for means of transportation/travel? [closed]

I am wondering whether it is possible for a photon/EM wave to carry a very small particle like an elementary particle or smaller on it like a highway carries a car traveling on the highway or an ocean ...
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0answers
64 views

What happens to a radar signal when it meets with a superconductor? [duplicate]

A radar system has a transmitter that emits radio waves called a radar signal, consisting of electromagnetic radiation. What happens when it meets with a strong superconductor, considering the fact ...
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1answer
28 views

Why can't diamagnetic and paramagnetic materials be magnetized?

Ferromagnetic materials can be made into permanent magnets. How come diamagnetic, and paramagnetic materials be made into magents? Does it have to do with the valence electrons, and how they are ...
3
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1answer
102 views

Find magnetic field of parabaloid-spiral particle path

Given the components of the particle's path (tcos(at), tsin(at), R(x^2 + y^2)), where a and R are constants, how can I find the magnetic force causing this? I would like to understand if this can be ...
10
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2answers
217 views

Charged Accelerometer in Orbit

It is well known that an accelerometer (or any other object for that matter) in a gravitational orbit will register nearly zero acceleration. According to this answer, this is because the object is, ...
4
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0answers
64 views

Landau quantization: degeneracy of first level

In some books the degeneracy of one Landau level in a two-dimensional gas of free electrons is calculated in the following way: Note: The electron spin is not considered. Number of states of a free ...
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1answer
42 views

Electromagnetic lifts, and work

Magnetic field doesnt do any work, so when an electromagnet lifts, say a car or something, where is the energy coming from?
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2answers
99 views

What is the physical meaning of Lorenz gauge condition? [closed]

What is the physical meaning of Lorenz gauge condition? And what part of the solutions we throw?
5
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1answer
142 views

A “figure-8” EM field created by a dipole antenna

This question pertains to the EM field of a Pulse W5017 dipole antenna. The data sheet of this antenna can be found here (which contains information regarding the radiation patterns). There are TWO ...
2
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1answer
71 views

Confusion regarding conductors and their behavior

Consider two thin plates and one thick plate(all conducting). A and C are the thin plates, B is the thick one. Now B is inserted between the parallel plates A and C. A is given a charge 2q and C is ...
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0answers
25 views

B field, reaction to magnetic medium

I've read 'if you put a magnetic medium into a conductor loop the B-field will change everywhere while if you put an electric charge into a dielectric sphere the dielectric sphere won't have any ...
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1answer
24 views

What would occur between the parallel plates of the capacitor?

In capacitors dielectric materials are sometimes inserted between the parallel plates. What would happen if a diamagnetic, or a paramagnetic material is inserted between the parallel plates of a ...
8
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4answers
281 views

A contradiction between Biot-Savart and Ampere-Maxwell Laws?

I came across a problem that I cannot get my head around. Consider two very small spherical metallic balls given charges +Q and -Q. Assume that they can be approximated as point charges. Now, they ...
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2answers
52 views

Does a displacement current have to be included in the Biot Savart Law?

Consider two spherical balls given charges of equal magnitude and opposite signs. Now, we connect them with a conducting straight finite wire. A current will flow in the wire till the charges on the ...
2
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0answers
77 views

Is radiation perpendicular in brehmsstrahlung?

wiki says: Bremsstrahlung is electromagnetic radiation produced by the deceleration of a charged particle when deflected by another charged particle, typically an electron by an atomic ...
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3answers
62 views

Electron deflected by moving magnet

My original question was far too long, so I am editing it down to this much smaller version: The Lorentz force for an electron traveling through a uniform magnetic field with no electric field is $F=...
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0answers
19 views

Does removing half of toroidal ferromagnetic core significantly reduce flux density in the remaining half?

Assuming a DC current in a cable has induced a magnetic field around the cable, and a ferromagnetic toroid is used to concentrate the field; if half of the toroid were cut away (so the cable is no ...
16
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4answers
2k views

To what extent can speed of light be reduced? [duplicate]

Light slows down upon entering different transparent objects, and the ratio is taken as refractive index of the object. If light can be slowed down, then is there a limit up to which it can be slowed ...
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1answer
38 views

Why can't weak core-less electromagnets be used in conjunction with strong permanent magnets to perpetually harvest energy?

Why can't weak core-less electromagnets be used in conjunction with strong permanent magnets to perpetually harvest energy? Magnets will attract ferrous materials but some materials like copper or ...
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0answers
20 views

Time derivative of total angular momentum in Dirac equation

I would like to calculate the time derivative of the total angular momentum of a Dirac particle in an electromagnetic field $(\vec A, \phi)$: $$\vec J = \vec r \times (\vec p - \frac{q}{c} \vec A) + \...
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0answers
14 views

Using a magnetometer in a sub-sea application, how to get a good magnetic bearing?

Mechanical engineer here, getting in over my head concerning magnetic sensors, electronics and the like :-) Quick situation description:For a work-application I am looking at using a MEMS based 3 ...
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2answers
63 views

Why would a moving infinite region of magnetic field exert an electric force?

I'm confused about the Lorentz force in relation to the frame of reference. There are many questions about that here, but I still don't get it. I've tried to break it down to the most basic example. ...
3
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1answer
25 views

Transmission line model proof?

Why 2 distributed lines is represented with series inductor and resistor along with parallel capacitor and resistor? What is the motivation for that? In circuit theory I Knew the assumptions to ...
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2answers
63 views

Could superconducting magnets be used to form a shield around a spacecraft?

If superconducting magnets could be used in space to form a field around a spacecraft of a similar field strength on the earth 25 to 65 microtesla's? Would the temperature in space at -246c be OK ...
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0answers
15 views

Will non-ferrous materials like Gold that have been magnetised by a slight electric current become attracted to much more powerful permanent magnets?

If a magnet interacts with Gold it will magnetise it to a very slight degree but if the gold is in turn magnetised by passing a generally weak current through it will the gold more easily attract ...
2
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1answer
21 views

Appears the world more reddish due to our vitreous body in our eyes?

Our vitreous body in our eye consist mostly of water. The refractive index of water is 1.33. If ligth is refracted the frequency stays the same but the wavelength will get shorter to equal to the ...
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1answer
70 views

Feynman path integral interpretation of the Aharonov Bohm effect [closed]

I have recently been reading about the interpretation of the Aharonov-Bohm effect via Feynman's path integral (see viXra:1403.0950). I do not know whether I am missing something, but I do not ...
3
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1answer
32 views

Why does a laserbeam bent downwards when shined through a solution of salt?

When you have a aquarium with salt on the bottom and add water to it the salt will solute in water, but most of it will initially probably stay more or less down. Now is you shine a laserbeam through ...
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0answers
41 views

How does a charged body sense the presence of another charged body? [duplicate]

If a charged body B is placed within the electric field of another charged body A,then B senses a repulsive or attractive force exerted by A. But how does this information actually transfer from A to ...
3
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1answer
43 views

Electron traveling through gravitational and magnetic field

When an electron travels through a magnetic field it experiences the Lorentz force. The force acting on the electron causes an acceleration and therefore Cyclotron radiation is emitted. After reading ...
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0answers
46 views

Can Lenz's rule really be used to determine the direction of induced current?

Faraday's Law states that the induced emf in a closed circuit is the negative of the rate of change of magnetic flux through the surface enclosed by the loop. To obtain the direction of the induced ...
4
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1answer
279 views

Why do planets not radiate EM waves in their orbits?

Despite being overall near-netural, I would expect the individual electrons and proton to radiate long EM waves as we accelerate around the Sun or rotate around our poles. Is the acceleration so small ...
4
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0answers
57 views

Why isn't cosmic microwave background radiation on Earth drowned out by thermal noise

The Penzias/Wilson experiment, which detected the CMB, doesn't sound feasible given thermal noise. When Penzias and Wilson reduced their data they found a low, steady, mysterious noise that ...
2
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0answers
86 views

Does the motion of a free electron in a plane wave electromagnetic field have analytical solutions?

Does the motion $[x(t), y(t), z(t)]$ of a free electron in plane wave electromagnetic field have analytical solution (oscillating E and B fields)? The Lorentz force is : \begin{align}m_e\begin{...
2
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2answers
40 views

How strong is Earth's magnetic field in space?

I've been searching around Google and Youtube about the strength of Earth's magnetic field. By the help of wikipedia, I have found out that it's magnitude is 25 to 65 microtesla or 0.25 to 0.65 Gauss ...
3
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0answers
65 views

Can the Hall effect drive a current?

In the Hall Effect current is passed through a wide strip of metal in a perpendicular magnetic field. Since (some of) the negative charges in the metal move but the positive ones stay put, the ...
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1answer
46 views

Good book to grasp physics [duplicate]

I'll try to be clear. I'd like to ask you if you know some books or chapters in textbooks which explaining the "meaning" of some physical phenomena or entities. I may try to be more specific using ...
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2answers
31 views

How to prevent magnetic field from generating in current carrying conductor?

Is there anyway to prevent generating magnet field or nullify it.
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0answers
47 views

Hamiltonian formulation of the semiclassical Model of electrons

I'm currently reading the book Solid State Physics by Neil W. Ashcroft and N. David Mermin. In Chapter 12 they introduce the "Semiclassical Model of Electron Dynamics". In short: After having solved ...
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0answers
35 views

Clarify example of Faraday's law

Im wondering if it is possible to induce a high voltage current (above 1k Volts), simply using a falling magnet and a copper wire - it probably is, but then what does it take to do so. I've done ...
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1answer
27 views

Can antennas work with high frequency EM waves?

Antennas usually work with FM waves, and AM waves, which mostly used in telecommunications. Information is transferred on FM, and AM waves by a transmitter transmitting information on these EM waves. ...