Electromagnetic Definition and 1000 Threads

Just posting to ask if anyone has any tips to give for a student in a Junior level Electromagnetic fields class. We usually get about 10-20 problems/week and I manage to only get 6-7 of them done every time. Also, though I generally do well with it, I'm struggling to find the energy to read...

Hello everyone, I've been told many times that when the right frequency of electromagnetic radiation hits an electron, it is excited to another energy level. My question is this, "why do electrons get excited to higher energy levels when hit by electromagnetic radiation?" Why does the...

I can't represent me mentally what is an electromagnetic wave. I know that a mechanical wave is the propagation of a disturbance in a material medium and mentally I can see what it is. But electromagnetic ... Last year, I did electromagnetism. We studied Maxwell equations and we saw a...

hello i need some help, i know very little about EM. i would greatly appreciate any advise u can lend me. i need to make an electromagnet but i am wondering how strong air cores can be? will an air core be able to work on and off continuously for hours at a very high rate of speed, it...

This is a question about electromagnetic waves and gravitational waves. Let's say we're on the Earth and we're looking up at the sun (safely). If the sun were --for some reason-- to violently and dramatically jerk from its position, how would we first find out? Would we first *see* the...

I have to do a presentation on why cellphones are banned in hospitals, and I'm going to have to explain how electromagnetic interference from the waves a cellphone gives off can mess with medical equipment. Can someone please explain the physics behind this?

My book takes a look at the maxwell equations in free space, shows that E and B satisfies the wave equation and then guesses on a plane wave as a solution such that you get a tranverse wave with E and B perpendicular to the direction of propagation. I don't know if I am too slow in realizing...

Hi As we know, we have two kinds of Electromagnetic Boundary Conditions for interfaces in an electromagnetic problem.one is imposing the continuity of Bz and Hr and the other is applying the continuity of A(Magnetic Vector Potential) and the discontinuity of its derivative with respect to the...

Please feel free to move this to the correct forum. After doing some reading, I've found that Electromagnetic radiation travels at the speed of light in a vacuum. EMR also travels in the path of a wave. Whereas, light and/or light photons travel in the path of a straight line. Having said...

I was watching the lectures on the MIT OCW course 5.111 where it was said that electromagnetic radiations are periodic variations of the electric field. Does it mean that when we are talking about electromagnetic radiation, frequency indicates how quickly do the electric fields change(their...

Can EM radiations produce repulsive effect on on non magnetic objects? If yes how can such fields be produced?

Can someone give me a high level defintion of electromagnetic radiation with some intuition on what the wave form represents (specifically the peaks and valleys)? I am comfortable with the electric and magnetic fields. I would like an explanation similar to the my intuition on the physical...

I am trying to figure out how I would go about finding the steady-state temperature distribution in an absorbing medium using the steady-state heat conduction equation: (1) -\nabla\cdot\left(K\nabla T\right) = q_{gen} where T is the material's temperature, K is the material's thermal...

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...

I was having a discussion with my friend the other day. He had just attended a lecture about Paul traps. He told me that the Paul trap potential has a stationary point in the middle, which is a saddle point, and that the 2 pairs of opposite poles are oscillating between being positive and...

Ive asked this question so many times on various forums and i feel there is a simple answer that i just haven't heard yet. I realize that an EM wave is represented as a sine wave, but from what i understand, that's not the physical motion the fields take. Let's say we take a snapshot at the peak...

I have seen the retarded potentials and what not, but what has always bothered me is why these field solutions reflect when they meet surfaces. I have looked and looked, but there seem to be no analytical explanations for this, only empirical ones. So my gripe is, since electromagnetic waves...

Let's say I have some source that generates a spherical wave that propagates outwards at the speed of light, and I have a vehicle that is charged. The wave will accelerate my vehicle periodically and eventually bring it to great speeds. Does this work?

Ok, so here is my question. Basically I believe that frequency and amplitude have no effect on each other. But in a black body, the intensity of the radiation is directly affected by the wavelength. With the intensity being the square of the amplitude, and wavelength being the inverse of the...

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...

I was curious about electromagnetic waves and whether or not they can be canceled in the fashion I require. First I will state a few principles that I am considering in the paragraph below and the paragraph after will pose the question in full. A Wireless router produces a signal that...

Hello all, I have a question relating to charge. I understand that when a positive charge is near a negative charge it creates an attraction. This attraction is explained by the electromagnetic force and by the exchange of electrons. My question is this, how can a new particle such as a photon...

When Gamma Rays collide it is possible to form various units of matter (ie proton, electron, etc). Does anything happen when photons collide that are of other frequencies other then a ricochet? If X-Rays collide with other x-rays does anything happen? Also, if anything does happen, what would...

I mean, you can only start to see the effects of gravity when a large amount of matter is in one place. What if all the electric or magnetic fields in every single atom of that planet or star or black hole, ect... combine into one large field, big enough to create what we know as gravity?

Suppose a permanent bar-magnet is placed inside a toroid/torus and the toroid is then completed and power applied. How will the magnet move? Will it move?

I know they're represented as sine waves but what would they actually look like in space. they wouldn't actually physically go up and down and side to side like a sine wave would they? I have seen representations of sound waves, which i assume is a longitudinal wave, but not a EM wave.

Homework Statement An iron core with a solenoid coiled around it is in a circuit with a switch and a dc current supply. In front of it, there is a iron ring tied to the ceiling such that it faces the solenoid without touching the circuit. When the switch is turned on what is observed and...

All electromangtic radiation comes under one continuous spectrum. http://en.wikipedia.org/wiki/File:Electromagnetic-Spectrum.png Different wavelengths of this radiation has different properties which is very evident in real life. However the whole concept remains extremely mysterious to...

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...

in electromagnetics , considering boundary conditions of dielectric and perfect conductor , inside conductor E = 0. So, there should not be any time varying magnetic field. But in many books i have seen that inside conductor normal component of B is 0 because there is no time varying magnetic...

I'm trying to build a small electromagnet of a 5v breadboard i had set up, but I've run into some troubles. It doesn't work, and I'm trying to figure out if I just need to pump more current through it or if the core I'm using is made of the wrong materials. Does it have to be straight up iron...

I know that gamma rays are a part of the electromagnetic spectrum and that they are also a type of nuclear radiation, created upon the decaying of a large, unstable nucleus. Is there any difference between these 2 definitions of gamma radiation? Is gamma radiation only created in the way...

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...

Why does nickel reflect infrared, but gold does not? I've seen devices that shine infrared at a metal surface and measure the reflectance. They're mainly used for looking at thin film coatings. For example, you could have a metal part made of nickel, and thinly coated in gold. The gold...

1. In the theory of electromagnetism, we say light(and others with different λ) propagates through anything by the alternation of the electric and magnetic field... I am still reading things abt the theory,haven't finished yet... But some things seem not clear... It seems 'em' is saying the...

The electric field in a cubical cavity of side length L with perfectly conducting walls is E_x = E_1 cos(n_1 x \pi/L) sin(n_2 y \pi/L) sin(n_3 z \pi/L) sin(\omega t) E_y = E_2 sin(n_1 x \pi/L) cos(n_2 y \pi/L) sin(n_3 z \pi/L) sin(\omega t) E_z = E_3 sin(n_1 x \pi/L) sin(n_2 y \pi/L)...

Homework Statement http://imageshack.us/photo/my-images/194/55132039.png/ http://imageshack.us/photo/my-images/194/55132039.png/ How much curret flows trough circuit ABCD when the center of the circuit (O) is distance r from the straight wire? I think these are the relevant equations...

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?

I understand that the EM tensor is a way of expressing the electromagnetic field in a frame invariant way, but how is it derived? Please use the (-+++) convention as I mostly use that.

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...

Hi , i am a high school student ( class 10 ) and after reading about electromagnetic induction iwas thinking about what if u place a wire coil connected to a circuit in the magnetic field / near a generator ? Because electricity is turned of for a fraction of a second there will be great...

Given the above quote reference Helium within our Heliosphere, I have a grouping of questions for the electromagnetic wise. If Earth and Jupiter were both placed within a dense Helium plasma region/field of our Heliosphere at the same time; and considering He plasma's high electrical...

Electromagnetic relay(check my solution please :) ) Homework Statement The following diagram shows an electric device that uses some of the principles discussed in this lesson. Discuss the sequence of events that occur when switch 1 is closed. *The diagram is in the attachment, you don't...

If the intensity of an electromagnetic wave is 80 MW/m^2, what is the amplitude of the magnetic field of this wave? (c = 3.0 x 10^8 m/s, permeability of free space ''miu subzero''= 4π × 10^-7 T ∙ m/A, permittivity of free space ''E subzero'' = 8.85 × 10^-12 C^2/N ∙ m^2) 80MW/m^2= 80,000,000...

Every book I ever read describes a electromagnetic wave as a phenomena generated by charged particles accelerating. This will produce a change in electric field that induces a magnetic field. But, due to Maxwell equations a change in magnetic field will also produce an electric field. So, if a...

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...

Homework Statement Which of the following will produce Electromagnetic radiation? Explain Your answers. a) Alternating current in a TV transmitter b) The cord of a vacuum cleaner while it is being used c) The circuit of a battery operated CD player d) A positively charged particle...

This is just a conceptual question that I've been personally wondering about. So light has a magnetic field wave perpendicular to an electric field wave. I don't quite understand the magnetic field wave though. I thought that magnetic fields were not supposed to have a beginning or end. They...