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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An experiment related to Faraday's laws

This question is out of an Indian competition. I do not know calculus yet. I have some idea about how magnetic fields and electric fields work together but i don't know how to go about thinking ...
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0answers
29 views

Electron travel speed in spinning object [closed]

My question is in the hypothetical circumstance that you could spin a disk or something close to the speed of light how would that effect the travel of electrons through the material. Picture a circle ...
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1answer
22 views

Are deflection of compass and speed of electron relative to each other?

If one holds an electron in one hand and a compass in the other hand, and the starts running at the speed of light holding those, then will there be any deflection of the compass ?
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2answers
80 views

What does the Poynting flux represent?

I know that the Poynting flux is the cross product between $\vec E$ fields and $\vec B$ fields, but I'm wondering, are the field lines of the Poynting flux considered as electromagnetic energy? Let's ...
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1answer
35 views

Gauss law and electrostatic induction. Concentric spheres

Imagine you have hollow concentric spheres A and B with radius a and b (b>a), respectively. If A is a conductor and B has a certain density charge, I´ve been taught that B will induce some net charge ...
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1answer
29 views

How does sunlight undergo interference as shown in the video?

As far as I know, for interference to happen in a double-slit experiment, the light source should be coherent and monochromatic. If that is the case then how come sunlight undergo interference and ...
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1answer
41 views

Why do electric motors stop working when physically stopped (burned up)? [closed]

I found a rock lodged between the fan and the radiator on my motorcycle. Now the fan does not work when the computer prompts it to. I tried directly attaching the 12 volt battery to it as well. No ...
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3answers
70 views

Why don't E&M fields change orientation after hitting a surface?

In essentially every derivation of the Fresnel equations, the general problem of radiation hitting a surface at a certain angle is broken into two parts (out of which we hope the solution any general ...
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0answers
40 views

Question about the fields in a solenoid

I am very familiar with using Ampere's Law to find the B field inside a solenoid ($\mu_0nI(t)$). Then I can use Faradays to find the E field inside ($\propto\dot I$). I want to get this result ...
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2answers
51 views

Is magnetic field of a uniformly moving charge constant everywhere?

As far as I understand, for the field of a uniformly moving charge, curl of $\mathbf E$ is zero everywhere. Since $\nabla \times \mathbf E = -\dfrac{\partial\mathbf B}{\partial t}$, magnetic field ...
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2answers
35 views

Find the radius of the path of an electron in a magnetic field [closed]

In a question I am asked to find the radius of the circular path that an electron follows in a magnetic field. The field strength is $B=10^{-5}T$ along the positive y axis, the velocity of the ...
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0answers
23 views

What is the effect on measured values of potential differences if we assume that potential difference of earth is +100V instead of zero? [closed]

What is the effect on measured value of potential differences of earth is +100V instead of zero?
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13 views

Easiest way to levitate a ferromagnetic material that is not a permanent magnet?

I want to levitate an iron cube that is not a polarized permanent magnet. What is the easiest way to do this?
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0answers
13 views

Can a diamagnetic levitator levitate non-permanent ferromagnetic materials?

I am building a diamagnetic levitator that will eventually levitate a small neodymium cube. However, is it also possible for an iron cube to be levitated as well? I know that diamagnetic materials ...
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1answer
30 views

Is it possible to levitate large objects through diamagnetic levitation?

I am currently building a diamagnetic levitator with a strong neodymium magnet, two slabs of bismuth (a diamagnetic material), and a small neodymium cube to levitate. However, I was wondering if it ...
2
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1answer
64 views

Why doesn't the changing field of a moving charge create EM waves? [duplicate]

EM wave phenomenon is usually described as "changing electric field creates changing magnetic field which creates a changing electric field etc." But fields of a uniformly moving (not accelerating) ...
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2answers
53 views

how do we actually count the number of magnetic field lines and what does the gap between those lines describe?

on the internet,(http://nuclearpowertraining.tpub.com/h1011v1/css/h1011v1_53.htm), there is a statment which says that 1 Wb is $1\times 10^{8}$ magnetic field lines. My question is, How do we count ...
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1answer
29 views

Wave Velocity vs. Phase Velocity

I am trying to understand the difference between 'wave velocity' and 'phase velocity'. I know that generally they are equal, but when is that not the case? I, of course, tried to google it, and ...
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0answers
31 views

Electromagnetics B and H quadratic relationship! [closed]

So the ques is $B=\dfrac{H}{3} +(H^2\mu)$ and I have to find $\mu_{r}$ when H = 120 A/m. H:Magnetic field intensity $\mu$ is magnetic permeability $\mu_{r}$: relative magnetic permeability! Now ...
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1answer
49 views

Questions about Magnetic field [duplicate]

I have two questions about Magnetic Field. Given a particle with mass m, charge q and uniform B field. B is going into the page, and particle is moving to the right Like this. The textbook says ...
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1answer
21 views

How, if at all, does the behavior of a parallel plate capacitor change in the presence of a magnetic field?

I'm an AP physics student curious about magnetism and my teacher couldn't answer this question. We already learned about velocity selectors, so I know that, when the plates of the capacitor are in the ...
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2answers
35 views

is it possible to shape electromagnetic field?

Is it possible to produce a magnetic field of specific shape? For example a magnetic field that will be confined in a cylindrical shape of specific dimensions.
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1answer
39 views

Can an electromagnetic potential be in two gauges at once?

I have a plane wave vector potential found using the free field form of Maxwell's equations and the Lorentz gauge: $\vec{A}(\vec{r},t) = \vec{A}_0 e^{i(\vec{k}\cdot\vec{r}-\omega t)}$ If I take the ...
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0answers
16 views

Load matching in a transmission line [duplicate]

Can somebody explain me easily and clearly why when you want to transform a 50 ohm load impedance through a piece of transmission line in an arbitrary one let's say Z (complex number); that is exactly ...
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1answer
91 views

High Level Understanding Q: What *is* a magnetic/electric field?

Note: I have seen this question -> (What is a magnetic field) and would still like some clarification. I have also seen https://www.youtube.com/watch?v=hFAOXdXZ5TM and ...
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0answers
41 views

How to compute the magnetic force between two electromagnets?

I wanna compute the magnetic forces between two solenoids with iron cores, is there any analytic formula for this? I guess that dipole-dipole interaction in the link ...
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1answer
53 views

Does the field of a unifirmly moving charge satisfy Maxwell's wave equation?

The so-called "electromagnetic wave equation" is so general that it should obviously hold for every point in space and for all field configurations (if there are no charges). Here it is: $$ \left(c^2 ...
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1answer
24 views

Motion of an electric charge within an electric field with two electric charges

Assume that air resistance and gravity are negligible and the only significant force acting in the scenario is the electric force. There are two electric charges, both with an equal and positive ...
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0answers
21 views

Explanation of absorption from Bloch Equation

Suppose in a magnetic resonance experiment the microwave/rf field is applied in x-direction.How to say that the component of magnetization which is out of phase with the microwave magnetic field leads ...
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0answers
39 views

Coulomb Gauge under Lorentz Boost

In the Coulomb gauge for the Maxwell potential we have $$ A^0 = 0 \\ \partial_i A^i = 0 $$ Under an infinitesimal Lorentz Transformation with parameter $\epsilon$, we have $$ A^\mu(x) \rightarrow ...
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2answers
71 views

Is the CHAMP missile capable of doing what they say it does? [closed]

CHAMP, A new counter-electronics directed energy USAF weapon was created by Boeing Phantom Works with the intention to damage and / or destroy electronic target equipment without causing structural ...
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2answers
84 views

Can we use magnetic energy to produce electricity?

Magnets attract each other with a force (magnetic force), because they possess magnetic energy. My question is, is there any way, by which we can convert that magnetic energy into electrical energy? ...
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2answers
42 views

Do Weyl fermions carry electric charge?

Do Weyl fermions carry ordinary electric charge? That is, do they interact with, for instance, electrons or photons?
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1answer
27 views

Relation between potential difference and electric field

I was reading an article about resistivity when I faced this equation: $$V_P-V_O=\int_P^O E.dr$$ The equation is in one dimension and $P$ and $O$ are points on the $x$ axis. The Electric field is ...
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1answer
20 views

Will a cone of magnetic material increase the strength of earth's magnetic field?

If it's possible to guide magnetic field lines using a shaped magnetic material(cone) and the increase in magnetic field strength is proportional to the ratio of the areas of the two ends of the ...
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1answer
18 views

In Crookes (roentgen) tube where does electrons come from?

In Crookes (roentgen) tube X-rays are generated by bombarding metal target by accelerated electrons. Where does the electron come from? Are they produced by ionization of residual air or from the ...
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0answers
12 views

How to calculate pull force of a solenoid with permanent magnet plunger (NdFeB)?

The solenoid is air core. If we use permanent magnet like NdFeB as a plunger, how to calculate the pull/push force of the solenoid with plunger?
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1answer
32 views

Newtons third law and magnetism?

If I take a really big magnet and use it to pull a large metal object then clearly there will be a force pulling this metal object toward the magnet. But is Newtons third law obeyed here? Will the ...
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0answers
20 views

Why is the direction of E field inside a Linear Dielectric same as an external field?

If an uncharged linear dielectric is exposed in a uniform external field, an e field inside is induced that points in the same direction as the External field, Why is this so? Isnt the field be ...
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0answers
7 views

Thickness uniformity comparison between a bilayer and superlattice

For a heterostructure grown using pulsed laser deposition to be used in polarized neutron reflectometry, is there any difference between a superlattice and a bilayer in terms of thickness uniformity ...
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1answer
49 views

Velocity in the Drude model

In the Drude model, we have the equation of motion for electrons in the presence of an EM wave: $$m \frac{\partial\mathbf{v}}{\partial ...
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1answer
30 views

Tensile strength of a chain of electromagnets

I was having a discussion about the tensile strengths of various materials. Could something like a chain of electromagnets be made to have a tensile strength proportional to the power applied to it? ...
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1answer
30 views

Macroscopic & Microscopic Electric Field

What are the precise mathematical definitions of the macroscopic & microscopic electric fields? For example, when I study the boundary conditions for an static electric field $\vec{E}$, the ...
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3answers
1k views

How is the curl of the electric field possible?

Taking the curl of the electric field must be possible, because Faraday's law involves it: $$\nabla \times \mathbf{E} = - \partial \mathbf{B} / \partial t$$ But I've just looked on Wikipedia, where it ...
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0answers
11 views

Why does a 2-sided propagating EM wave become 1-sided if B is made proportional to E?

If you simulate the propagation of an electromagnetic wave in 1D free space (no charges or currents) with initial conditions of $E\neq0$ and $B=0$, and you look at a movie of $E$ vs time, then after ...
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1answer
18 views

Why is second harmonic Intensity periodic in coherent length?

Solving for the intensity of second harmonic generation we get that intensity is $sinc^2(\pi/2*L/L_{coherent})$. How is calculated that the intensity is periodic in L_{coherent} (coherent length, L ...
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0answers
26 views

Problem with understanding boundary conditions in electromagnetism

In some books on electrodynamics they stress that electric current won't radiate if it is placed on a perfect electrical conductor (PEC), citing image theory: exactly opposite current will appear and ...
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0answers
19 views

Is absorption probality modulated by interferance instanteneous or retarded effect?

Let say the absorption probability at some atom 1 location is modulated by photo ionized electron wave (ionized from 1) that scatters by neighboring atom 2 and returns to the 1. (Around the absorption ...
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0answers
12 views

How much damping is there being exerted on a vertically stable magnet moving across a superconductor surface?

I'm thinking of a flat magnet with opposite poles on the wide ends, though perhaps some other arrangement is more stable. Assuming such a magnet is levitating in a completely stable state and is ...
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1answer
62 views

How to conserve momentum when numerically-integrating the path of a charged particle through a magnetic field

I have the python script attached below, which is intended to track the trajectory of a charged particle in a static, uniform magnetic field. It is very simple to calculate the instantaneous force ...