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.

learn more… | top users | synonyms (6)

0
votes
2answers
31 views

Is the magnetic field zero inside an ideal conductor carrying a current?

By an ideal conductor, I mean one with zero resistance. The question is not about a superconductor. As I know superconductor and conductor with zero resistance are not the same thing. The question ...
-1
votes
0answers
48 views

Can we reuse the motion of a DC motor to power an AC generator

My question is, when we make a simple DC motor, can't we connect another circuit to the rotating coil and make another circuit for an AC generator?
4
votes
4answers
4k views

Is the electric field zero inside an ideal conductor carrying a current?

By an ideal conductor, I mean one with zero resistance. Inside an ideal conductor with no current, the electric field is zero, but is the electric field still zero with the ideal conductor carrying a ...
1
vote
1answer
149 views

Nature Of Bulb Glowing In Parallel LR circuit with bulbs

In the given circuit the switch is initially closed and then opened after some considerable time.Then which bulb will stop glowing first? Which bulb will glow more brightly?Why ? .After opening ...
2
votes
2answers
34 views

What conditions are necessary for Birkeland currents to form?

If charged particles flow through non-magnetised space will they form Birkeland current? Or can such currents only form along existing magnetic field lines? Part of the reason I ask is this: http://...
3
votes
3answers
131 views

What happens to forces when a charge travels at near c?

Suppose 3 electrons are travelling at $c - 1$mm at 1 cm distance The charges are at rest relative to one another in their frame, but what happens to fundamental forces Fe and Fg? What Fe does A get ...
0
votes
1answer
119 views

How can electric field accelerate fog dissipation?

I should emphasize that I view the problem as a 'research' rather than a 'textbook' level. However, as I am almost unfamiliar with the subject it may be that the answer is elementary and well-known. ...
0
votes
0answers
16 views

Electrical field in coaxial cavity

I already asked this question at electrical engineering SE, but I got the recommendation that in the Physics SE there will be a better chance to get answers. I have a geometry as follows: This is ...
0
votes
1answer
43 views

How can we detect electric field in electromagnetic wave?

Electromagnetic wave have magnetic and electric component but what is the proof for that? How "non electrostatic" electric field can be detected around coil?
0
votes
0answers
16 views

Lightning, Electrical breakdown, and Current

Recently a discussion came up about this gif: http://i.imgur.com/r9Q8M4G.gifv This lead to a few questions about electrical breakdown of insulators. The disagreement we're having is whether or not a ...
1
vote
1answer
135 views

Is resistance proportional to resistivity: $R=\textrm{const}\cdot\rho\;?$

Suppose we have a resistor in a strange shape, filled with a medium of resistivity $\rho$, assuming only Maxwell's equations apply, is it true that resistance $R$ is proportional to $\rho$, even for ...
0
votes
1answer
24 views

Applying Ampere's Law for Two Parallel Wires

This seems a simple question but I'm not able to understand it properly. Say we have two parallel wires carrying same current I in different directions. We need to calculate the magnetic field at any ...
1
vote
0answers
26 views

Experimental tests of electric and magnetic fields in a gravity field

Has anyone experimentally verified that the measured values of the electric and magnetic fields do not change due to gravity, that there is no post-Newtonian effect on the strength of either $E$ or $B$...
13
votes
1answer
1k views

If the strong nuclear force is stronger than electrostatic repulsion, why don't nuclei collapse into a point?

Today in class we were discussing the strong nuclear force, and our teacher was explaining about how the strong nuclear force counteracts the repulsion force between protons in a nucleus. When asked ...
14
votes
2answers
854 views

Can one force the electric quadrupole moments of a neutral charge distribution to vanish using a suitable translation?

For a system of electric charges $q_i$, at positions $\mathbf{r}_i$, with a nonzero net charge $Q=\sum_i q_i$, one can define a "centre of charge" in the obvious way as $$ \mathbf{r}_c=\frac{1}{Q}\...
0
votes
1answer
101 views

Question about north and south poles of a magnet

I've always been taught: North poles attract south poles. Yesterday after studying electromagnetism, I've a question to ask. Here's a diagram: In circuits like these, this is how the north and ...
3
votes
1answer
187 views

Do primary first class constraints change the electric field in the Hamiltonian form of Maxwell's theory?

In my understanding of Dirac's theory of constrained Hamiltonians, the primary (and also the secondary) first class constraints are generators of canonical transformations that do not change the ...
0
votes
0answers
27 views

Can signal transmission from mobile phones affect battery life of other devices? [on hold]

Sometimes I hear that you shouldn't keep devices that contain certain batteries close to your mobile phone continuously since signal transmission can affect the lifetime of those batteries. Is this ...
2
votes
1answer
412 views

Right hand solenoid example

I am just studying for my physics final exam. I came across this example and am not satisfied with the answer. My answer is that Z is South and the current would flow from Y to X because of the ...
7
votes
4answers
3k views

Is there any example where electric and magnetic fields are not perpendicular?

Perpendicular electric and magnetic field creates light or other electromagnetic waves. Is it a necessary property to have a perpendicular fields? If not what would happen when the fields are not ...
1
vote
2answers
145 views

How to find the parts across which emf is induced?

Is there a general rule that will allow one to find the parts where the emf is induced? Consider for example the following two cases: Case 1: A rod is made to move normally to the magnetic field at ...
4
votes
1answer
220 views

How can Drift Velocity of an electron causes change?

Assume we have a conductor that has current flowing and its placed in a magnetic field so that it experiences the Lorentz force, and it gains Kinetic energy due to that force. Would drift velocity ...
1
vote
1answer
951 views

Forces on a wire moving in a magnetic field?

When a wire is placed inside a magnetic field and current starts to flow in that wire, that wire experiences the Lorentz force = $IL \times B$ and beings to move. Aside from induced motional - $\...
10
votes
1answer
208 views

Is the uniqueness theorem correct in superconductivity?

There is an uniqueness theorem in electromagnetism. It says that the solution of Maxwell's Equations is determined uniquely by boundary conditions. We can treat superconductivity as a completely ...
-3
votes
0answers
38 views

Compensating Parallax problem of a washing machine's drum [on hold]

We would know how it is possible inside a washing machine, when the drum is full with garments, so it is very heavy, to compensate, when the drum is rotating at high speed for the parallax of rotation,...
2
votes
1answer
149 views

What is the metric of a constant electromagnetic (pure electric or pure magnetic) field?

For example, imagine a magnetic field $B_x$ directing in $\hat{x}$ direction filling all the space. What is its associated metric field? I can construct the electromagnetic stress-energy tensor for ...
1
vote
1answer
65 views

Reflectivity and transmissivity greater than 1

In plasmonics, it is often seen that reflection coefficient and transmission coefficient are greater than 1. How is energy conservation valid in such cases?
16
votes
6answers
7k views

Is it possible to project a magnetic field at a location in space?

A magnetic field strength drops-off quickly as the distance from a magnet increases. Is there any way to use electromagnetic fields to create a magnetic field at a location. For example, if there are ...
5
votes
2answers
605 views

Does a Faraday cage block outgoing signals?

I see lots of discussions about how a Faraday cage can block EM signals, but almost no one addresses the possible difference between incoming signals versus outgoing signals. It seems to me that those ...
4
votes
3answers
85 views

Why do magnetic coils consist of many thin wires?

Magnetic coils are usually made of thin wire turned into spring shape: Magnetic field which is generated by this solenoid is proportional to the number of turns N...
16
votes
8answers
10k views

Why no longitudinal electromagnetic waves?

According to wikipedia and other sources, there are no longitudinal electromagnetic waves in free space. I'm wondering why not. Consider an oscillating charged particle as a source of EM waves. Say ...
1
vote
2answers
775 views

How does the magnetic field get induced in car's tire?

I was amazed to see how my car's tire started attracting the nuts and bolts, how in the world did it induce the magnetic field? Never heard of such phenomena!!!
-1
votes
0answers
49 views

High School Physics-Electromagnetism [on hold]

An insulated smooth square frame ABCD of side $a$ is able to rotate about one of its side taken as positive axis. The plane is initially located at x-z plane. A magnetic field present in the region ...
6
votes
4answers
9k views

Does a magnetic field arise from a moving charge or from its spin, or both?

I learned that a moving charge creates a magnetic field perpendicular to its direction of motion. I also learned that charged particles like electrons have spin and they also create a magnetic field ...
-5
votes
1answer
73 views

Why can't rotating magnets in space or zero gravity be used to create infinite energy? [on hold]

I would like to know if a system like the one below will possibly work. I understand that the laws of physics forbid the "creation" of energy but despite my efforts I haven't been able to figure out ...
0
votes
2answers
3k views

Landau Levels and Magnetic length

I am looking into Landau Levels and keep coming across a magnetic length defined as follows for a 2D system: $l_B=\sqrt{\frac{\hbar c}{e B}}$ I have seen numerous sources say this is: $l_B\approx ...
1
vote
2answers
40 views

Could a strongly enough charged black hole allow for a strongly charged particle to escape the event horizon?

If there is a strongly charged black hole, and a particle with a strong charge of the same sign goes inside of the black hole's event horizon while moving quickly, is there a reason why it would not ...
0
votes
1answer
46 views

Photons inside laser cavity

In a laser, the pumping mechanism excites an electron to a metastable state. This electron remains in the metastable state for a longer time and is de-excited to the ground state by emitting photons (...
5
votes
2answers
2k views

What role does electrical charge play in black holes?

Not having studied General Relativity, I have sometimes been puzzled by references to the behaviour for "classic" black holes — as they are popularly portrayed — as being true for black ...
6
votes
3answers
723 views

How to find the direction of an eddy current?

Suppose there is a magnetic field going from left to right. Suppose a thin sheet of metal conductor (e.g. a 1m*1m square) is dropped through the magnetic field such that the plane of the conductor is ...
1
vote
2answers
71 views

Can neutrinos interact by the EM interaction and gravity?

A definition of a lepton is: A particle that does not interact by the strong force but does by the 3 other forces.$^1$ Neutrinos are leptons, so from the above definition one would expect it to ...
1
vote
0answers
21 views

Spikes and valleys of ferrofluid

I can understand that the spikes are formed because of the elongation of the ferrofluid due to the difference in forces experienced by the two ends of the particle. But I can't understand why there is ...
1
vote
0answers
24 views

Is there theoretical description of such plasmonic nanostructure?

I'm preparing a research about plasmonic nanoparticles and I'm interested about their arrays placed above a metallic film (like on the picture). Until now i found following articles: pubs.acs.org/...
3
votes
1answer
5k views

Optical constants of noble metals: the Drude model for microwave modelling

I have a question regarding the optical constants of noble metals. According to Johnson and Christy's paper Optical Constants of Noble Metals (Phys. Rev. B 6, 4370–4379 (1972), doi:10.1103/PhysRevB.6....
0
votes
1answer
40 views

Any good electricity and magnetism books for highschool students? [duplicate]

I really want to learn about electricity and magnetism for a long time but never have gotten to it, are there are good books that are conceptual on the topic of electromagnetism? I do not know ...
0
votes
1answer
42 views

Split up electromagnet coil, put in parallel.Why doesn't anyone do that?

If the goal is to make a strong electromagnet, wouldn't it be wiser to cut the coil in different sections and then connect them to a power source in parallel? total of 2k turns: (+)--- <- 1k -----...
1
vote
1answer
31 views

Why is the electric field perpendicular to a circuit zero?

Griffith briefly addresses the uniformity of the electric field in a wire using Laplace's equation by assuming that the electric field is always parallel to the wire (i.e. $\mathbf{E}\cdot\hat{n}=0$). ...
5
votes
1answer
131 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 ...
3
votes
1answer
141 views

How force get transmitted when a magnet attracts iron?

According to particle physics , every fundamental force has its force carrier particle. Photon is a force carrier particle of electromagnetic force but how does force gets transmitted when a iron is ...
-1
votes
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 ...