Electromagnetic field Definition and 222 Threads

In 2-5, an analogy is given for electromagnetic field: two corks in water, and the effect of jiggling one cork on the other (probably the up and down motion). Now, that sounded more like water is a medium propagating the energy. But the electromagnetic waves require no medium for propagation...

Homework Statement A charge q is released from rest at the origin, in the presence of a uniform electric field and a uniform magnetic field \underline{E} = E_0 \hat{z} and \underline{B} = B_0 \hat{x} in frame S. In another frame S', moving with velocity along the y-axis with respect...

Hi! In some texts (Sakurai - advanced qm and others) I found this expression for the lagrangian of an em field: L=F_{\mu \nu}F_{\mu \nu} but I'm a bit confused... L must be a Lorentz invariant, so I would write instead: L=F_{\mu \nu}F^{\mu \nu} \;\; Which form is the correct one? Or...

The Dirac electron in the Higgs vacuum field v and an electromagnetic field with vector potential A_\mu is described by the following equation: i \gamma^\mu \partial_\mu \psi = g v \psi + e \gamma_\mu A^\mu \psi where g is the coupling constant to the Higgs field and e is the coupling...

Hello everyone, First to preface I am not a scientist and have the heart of one (I purchased the heart from eBay... jk). Anyway I have a lingering question regarding Europa: Ok, I get the science about the tidal forces on Europa that flexes the rocky portion of Europa heating up the...

Instead of quantizing the vector potential A^μ why we do not directly quantize the B and E fields in electrodynamics.

A classical electromagnetic field requires you to know how far away from the source of the field you are, if this requirement is carried over to QED, how is the EM field of a particle known when we only know the probability of this particle being in a certain place?

point charges in an electric field Homework Statement Problem: A +8.75 micro C point charge is glued to a frictionless table. It is tied to -6.5 micro C point charge by a 2.5 cm string (weightless and nonconducting). A uniform electric field of magnitude 1.85*10^8 N/C is directed parallel to...

I would appreciate some help regarding the movement of an electron in a plane-wave linearly polarized electromagnetic field. Its simple enough question, but I am not sure what approach to take. Let's say the electron is at rest in our frame of reference and the plane wave is continuous...

Hi all I am wondering as this diagram shows. Which way is the electromagnetic field(s) moving? http://www.biophotonicsresearchinstitute.com/Picture1.png Thanks.

I'm having hard time understanding how exactly current that passes through inductor transforms energy into magnetic field and then into voltage, with 90° phase shift. I drew schemes representing sinusoidal imput current, its magnetic field and voltage relation. Is it correct? Would...

If it can block portions of anti-matter I am assuming. Could it possibly be true, that it can deflect asteroids?

[PLAIN]http://img23.imageshack.us/img23/421/electromagneticquestion.png A positively charged particle, which charge q and mass m, reached an area with an electric field and a magnetic field. Electric field E is at y>0 and its direction is -y. Magnetic field B is at y<0 and its direction is...

What is "the" electromagnetic field? I'm not a professional scientist, just a software engineer with a fascination for how our world works. I thought I'd plug into some of the smart minds here to see if I could make some sense of some things I'm not quite understanding. I've been reading...

Bob Reference Frame: A charged particle moves through a uniform magnetic field with velocity V. No electric field is present and gravitational forces may be neglected. The charge thus experiences a force due to this magnetic field equal to F = qV x B. B is the strength of the magnetic field...

i am having some problem in unerstanding a concept explained in my book in the chapter harmonic oscillators. as an example of this, it says, is the electromagnetic field, where A (vector potential) plays the role of the co ordinate and its dot plays the role of velocity in the oscillator...

hi, just to be sure, I believe that an electron in complete vacuum, that does not interact, carries an electromagnetic field, and that this electromagnetic field is mediated by virtual photons even when there is only one electron, in vacuum, that does not interact. is that statement correct?

There is a situation, we have an electric field and a magnetic field, both are static. And we know the density of energy is u=E·D/2+B·H/2, so dU/dt=0, but Poynting vector S=ExH is not zero, which means energy is flowing. This confused me. Static field also has energy flux?

Do electric and magnetic fields occur simultaneously in the same spot anywhere around the globe? (other than during solar flares) If the field is named "electromagnetic" wouldn't that means exactly this simultaneity? Thank you.

F_{\mu\nu}=\frac{\partial A_{\nu}}{\partial x^{\mu}}-\frac{\partial A_{\mu}}{\partial x^{\nu}} F_{\mu\nu}=-F_{\nu\mu} F_{ii}\equiv 0 F_{11}=F_{22}=F_{33}=F_{44}=0 where A_{\mu}=(-\vec{A},\frac{1}{c}\varphi)(F_{\mu\nu})=\left(\begin{array}{cccc} 0& -B_z&B_y& -\frac{1}{c}E_x\\ B_z&0&-B_x&...

We have \vec{F}=\int_V\vec{f}dV=-\frac{d}{dt}\int_V(\vec{D}\times \vec{B})dV \vec{g}=\vec{D}\times \vec{B} \vec{F}=-\frac{d}{dt}\int_V\vec{g}dV \vec{F}=\frac{d\vec{p}_{mech}}{dt} \frac{d}{dt}(\vec{p}_{mech}+\int_V\vec{g}dV)=0 \vec{p}_{mech}+\int_V\vec{g}dV=\vec{const} In total field law...

hi, I have a question about the uncertainty principle. if an electron is in attractive OR repulsive electromagnetic field, is its uncertainty about its position lower than if it is a free electron? I believe particles are more random, with a higher entropy when there is less...

How to quantize electromagnetic field in media? Especially in the case where the medium is dispersive and anisotropy.

Homework Statement A thin, circular ring of inner radius a and outer radius b carries a uniform surface charge density \sigma (i) Find an expression for E at a point on an axis perpendicular to the plane of the disk, the axis passes through the centre of the disk. (ii) Keeping the surface...

As I understand it photons govern the electromagnetic field. I don't have an intuitive knowledge of what that means. Does anyone have an explanation, link or reference for an intuitive interpretation? So if I rub a latex balloon against my clothes and then put it near my arm, I'll see all...

I wonder why we always assume that electromagnetic field energy density is w = \frac{1}{2}(E^2+B^2) . In fact energy of the filed can be any function w for which there exists such vectror field \vec{S} that continuity equation is fulfilled: \vec{E} \vec{J}+\frac{\partial w}{\partial...

Homework Statement How would you find the magnetic field B inside the large field coil after you measured the induced emf on a test coil? Homework Equations i am not sure. The Attempt at a Solution i need some help in how to start this as i have 0 clue

Hey guys, help needed! Bad lecture, no idea what to do! The Q1 is: Q. 1 Three point charges are placed at the apexes of an equilateral triangle as shown in diagram. Calculate the net force on (a) the 5 μC (= 5 × 10‐6 C) charge and (b) the ‐6 μC charge. Give each answer in the form a i + b...

Hi! I'm not a physicist. Just trying to get a feeling og matter, space and time without having to do the math (How DO you understand it?!?) Still I have a question. Is the electromagnetic field of a particle quantized - except for either being there og not being there? Does - for example -...

I am looking for an electromagnetic field detector that can detect use to detect the intensity of wave on a grid and return the results to a computer. the higher the resolution the better. does anyone know where this can be purchased? how could one be designed?

Dear Friends A particle having charge q and mass m moves in a region where an electric field E = ( 0 , E_0 , 0 ) and a magnetic one B = ( 0 , 0 , B_0 ) exist. For t = 0 its position is R = ( 0 , 0 , 0 ) and its velocity is V = ( V_0 , 0 , 0 ). I have worked out the...

Homework Statement Prove \nabla \bullet E =4 \pi \rho from \partial_{\beta}F^{\alpha \beta}=4 \pi J^{\alpha} where J^{\alpha}=(\rho, J^{1}, J^{2}, J^{3}). Homework Equations We are given that F_{\alpha \beta} is 0~~~~E_x~~~E_y~~~E_z -E_x~~~0~~~~-B_z~~B_y -E_y~~B_z~~~~0~~~-B_x...

Homework Statement We are given monochromatic point source of EM radiation which power is P=100W. The task is to compute E(r) and B(r). We can assume that r is large enough to treat wave as a plane wave. Homework Equations The Attempt at a Solution First of all - what for do we...

Homework Statement Show that the rank 3 tensor S_{\alpha \beta \gamma}=F_{\alpha \beta , \gamma} + F_{\beta \gamma , \alpha} + F_{\gamma \alpha , \beta} is completely antisymmetric. I just don't feel comfortable doing this stuff at all. Each of the three terms seems like they should be...

An electromagnetic field, as a plane wave, has a known space-time dependence: E = E0cos(ωt-kx). In a transparent medium it is the same except for involving the refraction indices n. Now, let us look at the field in a moving reference frame - that with v = c/n. What solution is for the...

Hi, I am not sure whether this falls into a math category or here, I hope you can help me. I came across a problem in a book [bare with me, please] (Fundamentals of engineering electromagnetics by Cheng) and asked my electromagnetics profesor, but his response did not help me into getting to the...

I have a bit of trouble with understanding how electromagnetic fields. More specifically, how the magnetic and the electric component of the field interact. I am aware that a time-varying electric field will generate a magnetic field and vice versa. What I am having trouble understanding is how...

https://www.youtube.com/watch?v= I have a little problem with a formula, that I think it's not ok. It gives to me the result of units of electric potential (\vec A ) and velocity \vec v . The result seems to be volts per velocity, and I don't know it there exists this unit, or is a mistake...

hi i just read this article,which discussed about getting the Schroedinger's equation for a particle in a em field by transforming the psi, http://www.vttoth.com/gauge.htm .can anyone please tell me if we can get the dirac's equation for a particle in a em field by transforming the psi thanks...

Is there any deep reason for introducing the electromagnetic field tensor other than the fact that Maxwell's equations can be written in a very succinct form in terms of it? Would it be possible to write down a lagrangian involving a normal kinetic term for A^{\mu} that reproduces the physics...

Can somebody tell me how can i create a powerful electromagnetic field using magnetic wires. I don't want it to be big. The diameter of the circle should be as big as an average water bottle. It can be really thick but the height should be about 1 to 2 inches. I guess i can buy some other...

What is a field? Say, a velocity field or an electromagnetic field. How we actually define a field? I think the most precise definition is mathematical: a set of numbers associated with each point that can describe some physical properties on that point, namely, a function with respect to space...

I have some specific, related questions, for which I haven't been able to find answers: 1. At any instant in time, is the physical size or extent (e.g., length, width, diameter) of the electromagnetic field of a single photon (of a given wavelength) traveling through a vacuum determinate...

How does an EM field, with both an electric and a magnetic component, each of which "disappears" produce an apparently steady photon? A point charge has an electromagnetic field it creates...A stationary observer with respect to the charge sees and electric field; an observer in motion sees...

Four interesting questions: 1: Is there a maximum range of a given electromagnetic field? 2: Is there a maximum strength of an electromagnetic field? 3: If the maximum electric field or magnetic field different from each other? 4: Can you make an electric or magnetic field so strong...

An EM Field is described as follows : The electromagnetic field is a physical field produced by electrically charged objects. It affects the behaviour of charged objects in the vicinity of the field. The electromagnetic field extends indefinitely throughout space and describes the...

Hi all, I am designing vending machine to be used outdoors in a train station. I am a mechanical engineer and i don't know much about electromagnetic fields. The fact is based on what I have read, in train stations in which the train is working with electric power, the power lines are high...

What is the importance of dual electromagnetic field tensor? Generally this is not included in the action. What will be the advantage/disadvantage if I include terms like F_{\mu \nu}\tilde{F}^{\mu \nu}, \tilde{F}_{\mu \nu}\tilde{F}^{\mu \nu} in the action? (The tilde denotes the dual tensor.)...

[SOLVED] Geometric Algebra: Signs of electromagnetic field tensor components? Here's a question that may look like an E&M question, but is really just a geometric algebra question. In particular, I've got a sign off by 1 somewhere I think and I wonder if somebody can spot it. PF isn't...

How is the electromagnetic field different from aether? if there is an em field why is it not considered to be at absolute rest