Em Definition and 1000 Threads

I'm unsure what I'm doing wrong here... it has to be something. So let me explain the problem: I'm supposed to rank the net magnetfic field strength for various arrangements. In all of the arrangements the magnitude of the current is the same. The distance between each of the charges is the...

http://www.surrey.ac.uk/qe/pdfs/cemi_theory_paper.pdf I approached this initially with extreme skepticism, especially since it seemed impossible considering the myriad em fields we're immersed in without any perceptible effect on our consciousness, but I ultimately walked away viewing this...

Choosing the Lorenz gauge implies that sources of the EM potentials at a given point are the charge density (for scalar potential) and current density (for vector potential) that cross a collecting sphere converging at the speed of light toward that point. It is often said that the retarded...

This paper (broken into three peaces; see attachments below) introduces a re-discussion of the Lagrange density. The tool to get this result is a new mathematical operation whose existence can be guessed from some considerations concerning the calculation of the variations along the time of the...

Hi, My question: Explain how an electromagnetic wave is produced? My Answer A charged particle produces an electric field. the electric field exerts a force charged particles. Positive charges accelerate in the direction of the field and negative charges accelerate in the direction...

just want to ask what are electromagnetic waves and how are they produced? also, do you where i can get a simple application of EM waves? just really need it... thanks!

This isn't really a brain teaser as much as a game. I have a Five Crowns deck at home. This consists of a deck of 55 cards (well, two decks of cards) with five suits. 3 is lowest and King is highest. You can't do 3-King in a straight. There are jokers, but I'm not using them --...

I have a photointerrupter sensor that is near an electric motor in a scooter and I'm tyring to tap into it. When I tapped into the sensor with a wire, the scooter stops running. Initially I thought it was my speedo circuit but then i found out that if I tap into the sensor with just a plain...

Consider the following general Hamiltonian for the electromagnetic field: H = \int dx^3 \frac{1}{2} E_i E_i + \frac{1}{4}F_{ij}F_{ij} + E_i \partial_i A_0 + \lambda E_0 where \lambda is a free parameter and E_0 is the canonical momentum associated to A_0, which defines a constraint (E_0 =...

ok i have been thinking about this problem for a lil bit now and i think i have it correct but i would just like to double check: (a) twelve equal charges, q, are situated at the corners of a regular 12-sided polygon (for instance, one on each numeral of a clock face). What is the net force...

Hello: I will try to meet the terms of the 8 guidelines. 1. The behavior of light is explained with a rank 1 field theory, the Maxwell equations. Gravity is explained with a rank 2 field theory, general relativity. The two can be combined in one Lagrange density, but they are not in...

Through what medium does EM propagate in "empty" space? Einstein stated in his Leyden address (1926, I think) that an EM ether was mandatory for the transmission of EM waves through "empty" space. He was unable to reconcile this with the dynamical gravitational ether that had to exist to make...

I have always wondered about this question. How do 2 paritcles sitting at distance x come to know about each other? I know, you can say that they feel field from each other. But again, how does this field propagate? Remember electromagnetic or gravitational fields don't travel through a medium...

Hi, does anybody who knows the applications of backward type wave tell the detail of them? thank you very much!

Alright, so Einstein came up with SR to make Maxwell's EM consistent with dynamics, correct? But SR was only for non-inertial reference frames and ignored gravity, so it was replaced with GR to make SR consistent with gravity. So why have I read (from many sources) that Einstein spent his...

Electromagnetic wave are said to travel with velocity c, in vacuum and are also said to be a transverse wave. But consider this: Let a positive charge Q be at point P of a three dimensional space. Let this charge, at time t=0, begin an uniform circular motion with angular velocity OMEGA =...

I have a problem: In EM induction, when we increase the number of turns in a coil, the induced e.m.f will increase, thus the current. Why does the current also increase? But in operating a transformer, when the voltage of the output current increases, the current decreases. How come? The...

hi guys i had a quick question about EM waves given EM traveling west, B field oscilates vertically and has f= 80,000 Hz and a rms strength of 6.75e-9 T what are the frequency and rms strength of electric field and what direction... so for direction i have it...

Hi there, This year I finished two semesters of E&M, and think I understood much of it but had something of a problem understanding something concering fields and EM waves. Something always seemed sort of odd to me when reading about retared potentials and how it takes time for the field to...

Some questions in the Theory Development forum seem to be revolving around the topic of formulating electromagnetism as a geometrical theory along the same lines as gravity in General Relativity. (I couldn't post this in that forum for some reason.) This was apparently done 50 years ago...

(Any help whatsoever is greatly appreciated) I am looking for good online sources to help me understand relativistic formula's for the equations of Maxwell, and all the stuff that follows from it (like Cherenkov radiation). I realize that's a pretty vague description, so if there is no...

I am trying to start a discussion on the Effects of EM on matter (biological, electronic and other matter). I am trying to understand the relationship between quantities Electromagnetic (EM) and effects on matter. In particular many types of EM used for medical purposes and can reach certain...

Does EM wave have to actually strike a surface to induce current or can the EM fields induce current from a distance?

hi , got 2 question about radiation: 1. Microwaves , radiowaves ,gamma rays and visible light - which one cannot detected by film? 2. Gamma rays , beta rays ,neutrons and alphas - which one has the shortest range in tissue ?( assume equal enegy) thanks

Please link me to threads that may already discuss this because i do not really know what to search for when i use the word substance. I neglect to use the word matter because matter in physics world means mass and i neglect to use the word particles because in physics world they usualy...

Suppose a 50-kW radio station emits EM waves uniformly in all directions (a) How much energy per second crosses a 1.0m^2 area 100m from the transmitting antenna? (b) What is the rms magnitude of the E field at this point, assuming the station is operating at full power? (c) What is the voltage...

hi guys, having a bit of trouble answering this physics question. Wondering if any of the experts can help me out. Can the electromagnetic radiation produced by a hot gas of hydrogen atoms be exactly of one frequency? They say also that the atoms make a transition from state n=2 to n=1 and...

hi guys, having a bit of trouble answering this physics question. Wondering if any of the experts can help me out. Can the electromagnetic radiation produced by a hot gas of hydrogen atoms be exactly of one frequency? not sure if this is true or not. They say also that the atoms make a...

Hiya, Given that the electric field vector of an EM wave is described as: E=E_0[1+\cos(\Omega t)]\cos(\omega t) How would one go about finding the energy carried by this wave? On another note, what's the actual frequency of the wave that can be used in E=hf ? Graphed in a CAS, this wave...

Can the electromagnetic radiation produced by a hot gas of hydrogen atoms be exactly of one frequency? Assume that all of the atoms undergo a transition from the state n=2 to n=1. Note that the atoms in the gas are moving.

I am doing a science fair project on refraction and I am preparing for the regionals and I found a small flaw in my report and I am wondering if any of you guys can help me out here. This is what I wrote: Why do electromagnetic waves warp when it goes through the process of refraction...

I've been studying a course in EM covering the basic E, B fields, Maxwell's laws, EM waves, Induction etc in my first year undergrad Physics course. It isn't a topic I feel particularly comfortable with and am planning on spending quite a bit of my easter holidays reviewing (or more likely...

Any ideas for an easy cheap EM propulsion device? Is a homopolar generator the same thing as a homopolar motor?

Griffith's EM third ed. pp.68 equ 2.12 ... "In the case of a point charge q at the origiin, the flux of E though a sphere of radius r is \int \vec{E} \cdot d\vec{A} = \int \frac{q}{4\pi\epsilon_{0}r^2}\hat{r} \cdot (r^2sin\theta \ d\theta \ d\phi \ \hat{r})" How the hell is dA equal to...

1. The electrostatic force between two point charges is 1.2 x 10^-2 N. If the distance between them is doubled, the charge of one of the point’s doubles and the charge of the other point triples. What will be the force between them? Kq1q2/r2 3. Two charges one charge +1.5 x 10^-2 C and the...

How come my shoes are where I left them last night before I went to bed? I didnt observe them during the night since I was asleep. Did someone else observe them? :rolleyes: How come large objects tend to keep their appearence even if no one is meassuering them. I would prefer an answer...

~5 qestions~ 1. EM wave can be reflected by metal surface only. Right? 2. SONAR can be reflected by any materials. Right? 3. Diffraction only occur when parallel wavefront(not circular wavefront) passes through the gap. Right? 4. After we use cloth to rub some substances, some are positive...

Electromagnetic waves interfere with each other. They cancel each other out. They can be complimentary or destructive, but they do interact with and change each other. If that's the case, with the plethora of electronic devices that surround us and the endless radio traffic we incessantly...

The similarities between the classical wave packet and the QM photon are striking. They both move at the group velocity. They both are subjected to an uncertainty principle. A classical wave packet is like a photon a region of concentrated energy, ... So is a photon something like the...

I just learned the scalar and vector potentials arising from the electric and magnetic fields have a physical reality in relation to quantum mechanical effects, such as the Aharonov-Bohm effect. Contrary to what I've learned from my course on electrodynamics (Griffiths) this sure must mean they...

Hi, I wonder how the electron's position energy reflects the electro magnetic wave's frequency. Daniel

Sorry if this question is basic. Can a small EM field be superimposed into a large EM field without the larger one interfering with the small one?

Can anyone provide a good reference (preferably on-line), or a decent description, of how the fundamental constants of electromagnetism are experimentally determined? I'm talking about constants like the permitivity and permeability of free space. I'm also curious how the unit of charge...

Hi, there, Could you please show me the solution to Griffiths Introduction to Electrodynamics, problem 2.26? The integral is so complicated. Thanks

In the 1969 edition of the World Book Encylopedia it shows that cosmic rays are considered part of the electromagnetic spectrum. In later editions the diagram doesn't show cosmic rays is part of the electromagnetic spectrum. In Capras famous book "The Tao of Physics, he also shows that cosmic...

I am wondering just which parts of the EM spectrum can we and can we still not lase in. For the purpose of this thread, I consider the visible pretty much covered. But what about the IR, is there any thing between 3 and 10 microns? What is lasable at longer wavelengths? Are masers...

Meaning of "Permittivity" as used in EM Hello all, I am having difficulty with the concept of permittivity as used in EM contexts. What is it a measure of? What is its physical meaning? One thing that puzzles me is the relationship between electric field and permittivity: E =...

I would like to relate EM and Gravitation by trying to use energy and Quantum theory etc. Since I know nothing of Quantum Theory, you might think me a fool. To relate them, I will state one thing: Energy has direction. Now, I have seen a(and only one) Feynman diagram, and I probably...

The Objective of this Thread is: *** To Determine whether or not any definitive experiment has been done that proves that light photons do or do not possesses EM properties. *** The Question is: Have any experiments been done under UHV conditions where a beam of light has been passed...

Interesing EM "paradox" This problem has gotten me 3 different answers from 3 different profs. 1. A moving charge produces a magnetic field, and this could be measured by a stationary observer relative to the moving charge. 2. If an observer is moving parallel to the moving charge with...