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)

2
votes
4answers
646 views

Induced EMF of a rectangular loop should be zero?

Considering the shape of a rectangular loop in a changing magnetic field: The induced $\epsilon$ would be zero? Since a rectangular loop is a combination of wires in series to create such a shape. ...
3
votes
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 ...
-1
votes
1answer
69 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 ...
0
votes
0answers
13 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 ...
3
votes
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 ...
2
votes
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 ...
0
votes
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 ...
1
vote
1answer
131 views

Motion of Thompson's jumping ring

Thompson's jumping ring experiment is set up as follows: There is a force acting on the ring $F(x)$ where $x$ is the vertical displacement. The force is due to the $90^\circ$ out of phase flux ...
4
votes
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 ...
3
votes
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 ...
3
votes
2answers
292 views

Magnet gyroscopic force spin

I was wondering whether a magnet exerts any measurable gyroscopic effects. I understand that magnetism is caused by alignment of spins of electrons which have angular momentum. (I realise that that ...
3
votes
1answer
130 views

Simple Explanation of Kondo Effect

Does anyone have a simple explanation of the Kondo Effect? (i.e. a simple physical picture + maybe equations to think of?) My current understanding is this: If we consider an electron scattering ...
0
votes
1answer
66 views

Cavity resonator modelling and simulation of em fields inside the cavity

I want to model a cylindrical cavity resonator and study the different modes of em fields inside it using MATLAB/COMSOL. Please refer me books/articles or other resources so that I can achieve my goal....
1
vote
1answer
119 views

Force on a magnetic dipole due to a magnetic field

Imagine a solenoid which has current $i$ and is producing a magnetic field $B$ which equals $$B=\mu N i$$ Now, imagine we put a small cylindrical magnet at the end of the solenoid. Then because at ...
4
votes
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 ...
0
votes
2answers
316 views

Magnetic flux density of a solenoidal electromagnet

I am designing an electromagnet which will be used to test magnetic sensors. So I used to formula found at hyperphysics which relates the magnetic field flux density to the number of turns, the ...
3
votes
2answers
671 views

Invariance of Maxwell's Equations under inverting variables - Reference and use

Some months ago, an ArXiv paper mentioned in passing that Maxwell's Equations were invariant under reciprocating the variables, or at least this results in a dual set of Maxwell Equations. (Actually I ...
3
votes
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 ...
1
vote
2answers
141 views

Is the Biot Savart Law applicable only for continuous currents?

There is a widely known formula for the magnetic field due to a moving charged particle. $$\frac{\mu_0}{4\pi} q \frac{\vec{v}\times\vec{r}}{r^3} $$ The usual derivation is as follows. $$ dB = \frac{...
2
votes
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 ...
0
votes
1answer
117 views

Relationship Between Conductivity and Lossiness of a material

I read that a material is loss-less if the conductivity is zero. I have always learned that conductivity is a measure of how easily the material can conduct a current. Does this then mean that the ...
1
vote
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 ...
0
votes
1answer
480 views

How to calculate flux density in a toroidal CT that has an electrical line pass through the center?

I have seen the Biot–Savart equation, but I don't know how to apply it. Does the conductor length need to be considered finite and equal to the core length, or will the calculation be for a conductor ...
1
vote
1answer
174 views

Find magnetic field in a solenoid for different regions?

A steady current I flows along an infinitely long hollow cylindrical conductor of radius R. This cylinder is placed coaxially inside an infinite solenoid of radius 2R. The solenoid has n turns per ...
0
votes
1answer
13 views

How would I construct an EMI shield for low frequency EMI?

By low frequency, I mean 30-100 Hz. Would a Faraday cage or something like it be feasible? I am trying to shield two separate locations on a high voltage cable.
2
votes
1answer
238 views

How do you derive Fleming's left hand rule?

How do you derive Fleming's left hand rule? What is the theoretical explanation for the directions of the magnetic field, current and the force on the current for being oriented in that way relative ...
1
vote
1answer
110 views

why the electromagnetic wave transmits momentum in the direction of the movement?

Ordinarily a transverse wave does not transmit momentum, as it is the case of the well-known sea wave phenomenon. But the electromagnetic radiation has both fields transversal to the movement of the ...
1
vote
1answer
286 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 ...
0
votes
1answer
107 views

EMF Induced in a solenoid

When is the emf induced in a solenoid higher,when making or breaking the circuit? Isn't it the same magnitude since change in flux is same in both rhe cases?
1
vote
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 ...
0
votes
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. ...
3
votes
1answer
193 views

Hearing background noise from earphone while there isn't any connection

Once my friend told me that he was listening some background noise while his earphones were not plugged in any device. I didn't believe him but 10 minutes ago I experimented the same. I can certainly ...
1
vote
2answers
735 views

Repelling a weak permanent magnet with an electromagnet

I have a question about magnetic repulsion. Suppose I have a permanent magnet (axially magnetized) placed on top of the iron core of an electromagnet. I want to switch on the elctromagnet to repel the ...
1
vote
1answer
52 views

Could a man float in a large enough magnetic field to simulate zero gravity?

I know the magnetic field would need to be very large, but if an organisation like NASA with huge funding and resources could build a large enough device, could a man float in that magnetic field to ...
5
votes
1answer
22 views

Reason for poor signal strength of cellular phones inside a steel frame building

I could not clearly interpret the answer of the following question. So, hereby I wish someone could just make it easy to understand. And my question is: What makes the poor signal strength of cellular ...
1
vote
1answer
488 views

The image current due to moving charges and a current carrying thin wire

Suppose we have a plane conductor and positive charged particles of mass m are moving parallel to the plane conductor at a distance d. The trajectory can be assumed to be straight. An image current ...
0
votes
0answers
24 views

superposition of two magnets

If I have two magnetic particles at x and y axis with strengths* $\mu_{x}$ and $\mu_{y}$; and another magnetic particle in x-y plane with strength $\mu=\vec{\mu}_{x} + \vec{\mu}_{y}$,then will the ...
0
votes
1answer
397 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 ...
0
votes
2answers
59 views

What does an oscillating magnetic field produce? [closed]

An alternating current produces a magnetic field. A oscillating charge produces light, which is an oscillating electric, and magnetic field mutually perpendicular to each other, and their motion is ...
16
votes
9answers
15k views
0
votes
1answer
87 views

Is the electric force a vector or a vector field?

The electric force (Coulomb's law) on a point charge $Q_2$ due to $Q_2$: \begin{gather*} \mathbf{F}_{12}=\frac{Q_1Q_2}{4\pi\epsilon_0}\frac{\mathbf{r}_2-\mathbf{r}_1}{|\mathbf{r}_2-\mathbf{r}_1|^3} \...
1
vote
1answer
36 views

Photon as a gauge boson for static fields

Excuse me if my question is naive, but I have never taken a proper QFT. I used to think of a photon as a quantum of EM field, quantum of light. But form QFT and particle physics prospective, photon ...
1
vote
3answers
42 views

Is the South Pole of an electromagnet always at the end where current is drawn into it?

I'm trying to determine in which direction a magnetic field will be produced in regards to the direction of current in an electromagnet. Will the end of the electromagnet from which current is drawn ...
1
vote
1answer
240 views

Why is an electric and magnetic field present in all universe? [closed]

Planet Earth has its fields due to the motion of molten metals in the core but how does this whole universe has its fields without any discontinuity? And, can we say for sure that fields are present ...
-2
votes
1answer
28 views

Why does the magnetic field of the induced current oppose the change in the external magnetic field? [closed]

Why does the magnetic field of the induced current oppose the change in the external magnetic field? please help me to solve this Link:http://d2vlcm61l7u1fs.cloudfront.net/media%2F4dc%2F4dc03c3b-...
5
votes
0answers
57 views

Validity of gauge fixing in classical electrodynamics [duplicate]

I am working through Griffith, and was confused by some of the restrictions he imposed on the potentials in introducing the Coulomb and Lorenz gauge. It is easy to see that adding some arbitrary ...
6
votes
1answer
356 views

Could the Faraday's rotating wire experiment be explained without using Lorentz force?

I read Faraday's rotating wire experiment which resulted in the invention of the homopolar motor. He was clever enough to think it that way and make the wire rotate around one of the poles of the ...
7
votes
4answers
302 views

How do electromagnetic waves carry energy?

Its said that electromagnetic waves carry energy. Is this because these waves are made up of electric and magnetic fields which can cause changes to the stuff that falls with in their range? Is that ...
9
votes
1answer
156 views

Optical chirality and its possible hierarchy of generalizations

Optical chirality refers to a constant of motion of the electromagnetic field, which measures in some sense how chiral a light field is. Specifically, the pseudoscalar quantity $$ C=\frac{\...