Electromagnetic field Definition and 235 Threads

Radio or any other wave in electromagnetic spectrum? Sound perhaps? And at what frequency(ies)

I'm learning time-dependent Maxwell's Equations and having difficulty understanding the following derivative: Given f(\textbf{r}, \textbf{r}', t) = \frac{[\rho(\textbf{r}, t)]}{|\textbf{r} - \textbf{r}'|} where \textbf{r} = x \cdot \textbf{i} + y \cdot \textbf{j} + z \cdot \textbf{k}, in...

I am confused about the coupling of the Dirac equation to electromagnetism. The 4-current that is the source for Maxwell's equation that arises from the Lagrangian \begin{equation} \mathcal{L}=i\overline{\psi}\gamma^\mu(\partial_\mu+ieA_\mu)\psi-m\overline{\psi}\psi \end{equation} is...

hello engineers, i have a question . what effect would a recovery station that is power at 20 KV and 50 hz from the local power line would have on the immediate area around it? i mean i know it will produce some electromagnetic field around it, and that is not that good for the rezidents living...

Is there a way to determine the profile of the field around a charged closed loop - particularly on the direction normal to the plane of the loop, both front and back? For generic values of V, I, B, H, etc., and any dimensions of the loop, any particular formulae possible to obtain? Thank you...

I have read this wikipedia article, but I still don't understand: http://en.wikipedia.org/wiki/Near_and_far_field Why can EM radiation only be transverse waves? Why can't it travel as a longitudinal wave? If I have two charges in a vacuum, with the straight line between them called 'x...

Suppose that we have the four-vector potential of the electromagnetic field, [texA^i[/tex] The wave equation is given by $$(\frac {1}{c^2} \frac {\partial^2}{\partial t^2}-\nabla^2) A^i=0$$ Now the solution, for a purely spatial potential vector, is given by $$\mathbf{A}(t...

Maxwell's equations solutions in vacuum - is a free electromagnetics waves. Such solutions can be obtained even without knowing anything about the charges and currents. Does this mean that such waves is the essence , not related charges, e.g. free electromagnetic waves? Moreover, the Maxwell's...

Hey guys, I'm trying to understand the properties of normal modes of the electromagnetic field inside an arbitrary cavity, but I'm having some trouble. By definition, for a normal mode we have \mathbf{E}(\mathbf{x},t) = \mathbf{E}_0 (\mathbf{x}) e^{i \omega_1 t} and \mathbf{B}(\mathbf{x},t) =...

hi to everyone L=T-V as you know it is the lagrangian equation the effective Lagrangian of the electromagnetic field is given by following relation in gaussian units. L=(1/8pi) (E^2-B^2) how is must calculate this relation? (the energy density of electromagnetic fields is given by u=(1/8pi)...

I stumbled on it while searching for electrodynamics textbooks for undergrads but this seems more advanced than Griffiths. Has anyone else used this book by Marcus Zahn? Is it a worthwhile read for an electrical engineer about to start sophomore year?

Can light travels without electromagnetic field ? Thanks

We have recently begun learning about quantization of the electromagnetic field and I would to understand more. It is tempting to want to connect the number states of a definite momentum and polarization to the concept of a classical plane wave. However it seems less straightforward than I might...

Homework Statement Consider a spherical dielectric shell so that ε = ε_0ε_r for a < r < b and ε = ε_0 for 0 < r < a. If a charge Q is placed at the center of the shell, find a) P for a < r < b b) ρ_pv for a < r b c) ρ_ps at r = a and r = b Homework Equations ρ_pv = -div(P) ρ_ps = P...

In classical physics, charged particles induce electric field ##\vec{E}_c## around them. How do we interpret this classical electric field ##\vec{E}## in quantum mechanics. Is this just the vacuum expectation value ##\vec{E}_c=<0|\vec{E}|0>##? if so, it means ##<A>\neq 0##. This would lead to...

First of all, I'm not sure if this thread belongs here or at the "Special & General Relativity" sub-forum, if I posted at the wrong place please move it. Homework Statement I encountered this problem working in my master's degree. I need to find the stress-energy tensor of the following...

Hello there! This is my first post here, hopefully I am not posting in the wrong place. Also, I am an engineer and have not used this stuff for years, so please be patient with me, I am pretty sure that my question is stupid :-) I would like to develop a simulation code for charged particles...

does anybody know where i could find a universal or nearly universal electromagnetic field equation by universal i mean instead of calculating for a solenoid or a loop of wire just calculating for a wire weather curved or not which is in the presence of another magnetic field of a predefined...

I've noticed that electromagnetic field lines are very similar to stereographic projection of 3D sphere on 2D surface. Pictures below. In such comparison, electric field represents longitude and magnetic field represents latitude. For more visualization see...

Homework Statement How much work does the electric field do in moving a proton from a point with a potential of +260 V to a point where it is -48.0 V? Express your answer in electron volts.Homework Equations V = p(A) - p(B) The Attempt at a Solution V= 260 [v] - (-48.0[V]) = 3.08×102 [V]...

1. I'm not quite sure how the laplacian acts on this integral 2. \frac{\delta S}{\delta A_{\mu}}=\int\frac{\delta}{\delta A_{\mu}}(\frac{1}{4}F_{\rho\sigma}\frac{\triangle}{M^{2}}F^{\rho\sigma}) 3. I know I have to split the integral into three integrals for x y and z, but I'm not sure if a) I...

Can anyone help me with Ex 4.1 in MTW? What is a 'generic' field? My expectation is that it would comprise an Electric Field, with arbitrary direction, a Magnetic Field, also with arbitrary direction, and a radiation field (E and B of equal magnitude) , radiating in an arbitrary direction...

1. Hey, So I have to show this proof: \int d^{4}x(-\frac{1}{4}F_{\mu\nu}F^{\mu\nu})=\frac{1}{2}\int d^{4}xA^{\mu}(\square n_{\mu\nu}-\partial_{\mu}\partial_{\nu})A^{\nu} 2. Where F_{\mu\nu}=\partial_{\mu}A_{\nu}-\partial_{\nu}A_{\mu} 3. ok, so I spent forever trying to type...

In Landau Volume 2 (page 71) an expression for determining the entire electromagnetic Lagrangian is given. What would be an explicit numerical examples of working this idea out along the lines Landau threads, or a good reference for finding these? I can't find anything despite looking in several...

I was working on an exercise in Ohanian's book. [Appendix A3, page 484, Exercise 5] I guess he means charge conservation, but wrote ##j^\nu = 0##. The Lagrangian was given by ##\mathcal{L}_{em} = -\frac{1}{16\pi} \left( A_{\mu ,\nu} - A_{\nu ,\mu} \right) \left( A^{\mu ,\nu} - A^{\nu...

I'm trying to program an application to simulate various readings of electromagnetic fields from any type of appliance or energy source. This part of physics was always my weakest. I don't remember any equations to use to get this data. The only thing I can remember is that it is related to the...

Hello, I am trying to prove that the momentum of an electromagnetic field is E \times B by considering the conserved quantity due to the spatial translation of the Lagrangian.  L = - \frac{1}{4}\int {{F^{\mu v}}{F_{\mu v}}} {d^3}x So far, I have calculated the canonical momentum...

I have been having trouble with a bunch of examples to do with the Rund Trauman Identity. I have the identity in this form/notation: \frac {\partial L}{\partial q^ \mu}\zeta ^\mu+p_\mu \dot \zeta^\mu+\frac{\partial L}{\partial t}\tau-H \dot \tau=\frac{dF}{dt} Now for the...

Hello! In an electro-magnetic context, the power that an electric source of field delivers to the field itself may be written as p_S = - \mathbf{E} \cdot \mathbf{J} where \mathbf{E} is the electric field produced by the source and \mathbf{J} is the corrent flowing on the source, forced by...

Homework Statement Derive the continuity equation for a charged particle in an electromagnetic field Homework Equations The time-dependent Schrodinger equation and its complex conjugate are i\hbar\frac{\partial \psi}{\partial t}=\frac{1}{2m}(-i\hbar \vec{\nabla} - \frac{e}{c}...

Dear ForumersI am having a bit problem understanding the phase relation between current source and the generated eletromagnetic field components. Assume a very small current element( a very small current running in direction x)(essentially an electric dipole) in a non-homogenous loss periodic...

Author: Bo Thide Title: Electromagnetic Field Theory Download Link: http://www.plasma.uu.se/CED/Book/ Prerequisities: Contents:

If we have a static electric charge, it generates an electric field. If that static electric charge is accelerating, it generates an electromagnetic field. What about if the electric charge is moving with uniform velocity? Is the field thus generated an electic field or an electromagnetic...

This thread is to move this discussion away from another thread in order to talk about it in more detail, so here is a brief recapitulation of how that went to make an opening for the discussion... A photon is quanta of electromagnetic radiation, and despite the name, despite there are, I...

Imagine a stationary charge q located on the positive y-axis at a distance r from a stationary observer at the origin. Let us assume that the distance r is large enough such that the electrostatic field due to the charge is negligible at the origin. Now let us assume that the charge q is given...

Hello, I know the electromagnetic field propagates in a 3D space so if I am horizontally aligned with the field I will receive its variation but what if I'm vertically aligned ? thanks

Is Magnetic field conservative or non-conservative in nature, I have searched online regarding this, it seems to be a divided house, MIT professor Walter Lewin demonstrated that it is non-conservative using an experiment, but still many arent convinced with the way experiment was conducted...

Homework Statement Show that the force on a moving charged particle F = qv × B from a magnetic field pointing perpendicular to the velocity produces a centripetal force and that this is equivalent to the equation pc = ABρ, where B is the magnetic field strength (in Tesla) and ρ is the radius of...

This isn't actually coursework, I'm doing some studying on my own. These are my very preliminary attempts to wrangle with tensor notation, so please be patient with me. I'm trying to get the components of the electromagnetic field tensor from \partial^{\mu}A^{\nu}-\partial^{\nu}A^{\mu} But...

Hello, I have to give a presentation on an application of electromagnetic field theory of my choosing, and I was wondering if anyone had any suggestions that might be more interesting than the ones that have been suggested. It's for a 2nd year university level physics (E&M) course, so the...

Hi! I'm currently reading 'An Introduction to the Philosophy of Physics, Marc Lange' where he is arguing about the reality of the electromagnetic field etc. While reading I caught myself in not having the concept of what that makes something real in place. How would one define something as a...

I know we can contain the energy/plasma from a fussion reaction with an electromagnetic field, but would an EMF protect from gamma rays? Would it be possible to deflect a nuclear blast with a powerful enough EMF?

According to relativity, time rate differs in regions with different gravitational potentials, i.e. the closer we are to the source of gravitation the slower time passes. Does anyone know what happens to time in electromagnetic fields?

How to express electromagnetic field tensor in curvilinear coordinates, that is given a curvilinear coordinates (t,\alpha,\beta,\gamma) with metric tensor as follows: n_{\mu \nu }= \left[ \begin{array}{cccc}h_0^2& 0 & 0 & 0 \\ 0 & -h_1^2 & 0 & 0 \\ 0 & 0 & -h_2^2 & 0 \\ 0 & 0 & 0 & -h_3^2...

Quite a vague question here, and I'm not entirely sure I'll be able to get a satisfying answer out of this one, but here goes. Fields such as the electric or magnetic field are introduced as vector fields that allow you to calculate a force at a certain point in space. In this interpretation...

we know light bends and loses energy when it travels in gravity..what abt influence on light when it travels in EM field..similarly can anyone trace out what happens in weak and strong force fields as welll.I guess its complex..

Hi everybody! Please explain to me how can we consider static electromagnetic field in point of view of Quantum Field Theory.Because varying electromagnetic field can quantize to photons,so we can consider varying electromagnetic field like a ''set'' of photons. Thanks very much in advance.

Electromagnetic fields mostly have a stress-energy tensor in which the trace is zero. Is traceless stress energy tensor always implies Ricci scalar is zero? If yes how to prove that?

Hi, I'm trying to work through something and it should be quite simple but somehow I've gotten a bit confused. I've worked through the Euler Lagrange equations for the lagrangian: \begin{align*} \mathcal{L}_{0} &= -\frac{1}{4}(\partial_{\mu}A_{\nu})(\partial^{\mu}A^{\nu}) \\ &=...

Hi, I'm wondering if there has been any actual experiments done to measure the speed at which magnetic fields propagate?