Electromagnetic Definition and 1000 Threads

Why do we often treat the electromagnetic radiation effects on Hamiltonian of a matter as a perturbation? In the other words, why the effects of radiation is so little that is treated as a perturbation?

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...

Does anyone know of reaction that can generate a a steady source of light? Preferably one easier to activate than burning of magnesium strips(which is too momentary anyway, I'm trying to make a chemical reaction that can eventually power a photoresistor/ light).

This isn't really a homework question, but I felt it was better suited here than in General Physics. I'm looking for more of a general explanation than anything. I was able to do my homework for this section on my own (mostly), but I feel like I still really have no idea what is actually going...

I have a couple questions pertaining to electromagnetic waves and Maxwell's equations. I will list them numerically, for clarity: 1. From the textbook, "once [wave] is created it is self-sustaining and independent of the source." Is this statement only true when it exists within a vacuum? I...

Dear all, I have encountered an issue in understanding how microphone works and I hope you guys can assist. There are two scenarios involved. In the first scenario, there is tuning fork and a microphone. The microphone contains a small disc attached to a magnet and a fixed coil. (Please...

Homework Statement when two like charged particles are traveling in space on parallel tracks, exert electric and magnetic forces on each other, then what is their speed when they continue to move in the parallel track? Homework Equations since both are lick charges there should be a...

Homework Statement Hey guys. I have an electromagnetic wave traveling in the z direction and polarized in the x direction. The frequency is 1 MHz and average power density is 1 W/m^2. An antenna in the shape of a circular wire is in the xy-plane centred at the origin. I would like to use...

Hey guys. From my textbook, I understand that linear polarization occurs when the phase between components of an electric field wave (and thereby the magnetic field wave) are zero. Elliptical polarization occurs when the magnitude of the components comprising a field wave is not equal in...

Homework Statement Use the simple model for electromagnetic showers (explained below) to show that the energy spectrum of all secondary particles contained in an electromagnetic shower falls like E^{-2} for E_0 >> E >> E_c The Attempt at a Solution An electron or a photon with energy E_0...

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...

Hello, I am having a lot of trouble in determining the difference between an electromagnetic field and electromagnetic radiation. Is an electromagnetic field caused by electromagnetic radiation within the space of which the field acts over? However if I am right a point charge that is not...

Bear with me, I am a chemist :shy: As far as I understand, every accelerating charge emits electromagnetic radiation. In mass spectroscopy charged molecules/parts of molecules move in the magnetic field which bends their trajectories using Lorentz force. That means they are accelerated...

Does the electron emit electromagnetic waves?

Would anyone have suggestions for places to investigate studies for next generation electromagnetic space drives? Life sometimes takes us far from our passions, and after being a HS genius-turned-automotive engineer-turned-IT salesman-turned-yachtracer-turned HS physics teacher, I'm trying to...

Hi Guys, I'm hoping that someone here can help me. I have an electromagnet that when pulsed creates a short across the 30v supply. If I increase the resistance in series with the electromagnet to stop the short, will this reduce the strength of the electromagnet? Is there a way to...

Hi. I am having trouble visualising radio waves. Assuming a perfect isotropic antenna (I know they don't exist) an electromagnetic is just a spherical pulse that radiates outward, this is quiet easy to visualise. However all texts refer to the magnetic and electric fields being 90 degrees...

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...

I'm trying to teach myself some basic physics, and so maybe this question is stupid! But according to the wave model, the energy in an EM wave is proportional to the energy in the E and B fields, which can assume a range of values, no? But according to the quantum model, the energy of a photon...

Hello all, I am not at all good at physics or have studied it but have been asked to build something rather peculiar. I need to have an electromagnet which will have enough strength when activated to bring a 10 kg steel weight from above it down to meet the magnet. It would be positioned...

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...

Homework Statement The permittivity of a given medium is given by the equation ε = \begin{pmatrix} ε_1 & 0 & 0\\ 0 & ε_1 & 0\\ 0 & 0 & ε_2 \end{pmatrix} A wave is traveling in the \hat{k} direction in this medium where the unit vector \hat{k} is defined as \hat{k} =...

In electromagnetic spectrum, why there is no radiation less than wavelength of Gamma rays and waves higher than the wavelength of Radio waves?

Consider the system below comprising a pair of oppositely charged parallel plates, connected by a rigid rod of length r, constrained to move in the x-direction. The forces on the plates from the Coulomb electric fields and the magnetic forces are all in the vertical direction so that they do...

What kind of force is Friction, force applied on a particle? Are these are Electromagnetic in nature?

Hello everyone, One very basic thing about this phenomenon is not very clear to me. If a conductor moves in a region of uniform magnetic field, would it have an EMF induced across it? I'm confused because as per Faraday's law, a change in flux through the conductor is necessary for EMF to be...

Can an electromagnetic wave be deflected by electric or magnetic field.

Hello everyone, My Name is Dwayne McIntosh. I am not that good at Physics or Mathematics however i do have a problem. I was brainstorming the other day and i wanted to know, what if one was to use say electromagnetic waves (may be different wavelength,frequency or Photon Energy, but with...

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...

Hi, I am having problems in constructing a stress-energy tensor representing a constant magnetic field Bz in the \hat{z} direction. The coordinate system is a cylindric {t,r,z,\varphi}. The metric signature is (+,-,-,-). I ended with the following mixed stress-energy tensor: Is this...

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...

Say I have a volume of hydrogen gas that is raised to a temperature T so that 99.9 percent of the gas is ionized. If now, with the plasma at some pressure P, the volume is compressed a small volume dV such that no energy leaves the volume I'm curious of a total accounting of where the energy PdV...

Suppose you did an experiment in the lab where you exposed Cu and Ag to electromagnetic radiation and you wanted to graphically determine whether the metals underwent the photoelectric effect. (a) Sketch the graph, on the same set of labeled axes, that you would anticipate. (b) What...

By De-Broglie,light also exibits matter property. According to him, wavelength=planck's constant/ momentum. And again momentum is the product of mass and velocity. We again know that, mass of light i.e. photon is zero. Then from De-Broglie's equation, is the wavelength of light infinity? If...

1. In an EM wave traveling west, the B field oscillates vertically and has a frequency of 88.8 kHz and an rms strength of 7.8 * 10^-9 T. Determine the frequency and rms strength of the electric field. What is its direction? The electric field of an electromagnetic wave is given by Ex=E0 cos(kz...

1. a. coil is moved up and down in the same direction of flux. b. coil is rotated around an axis that is parallel to the flux. c. coil is rotated to the direction of the flux like a dynamo. 2. Electromagnetic inductions laws. 3. I'm really having a hard time...

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...

Is there any program (preferably free) that simulates electromagnetic fields and their interactions with charged particles? I've found a couple gravity simulators, but none for EM, which isn't any fun, because I reckon it would be great to play with a realistic EM program.

I am a biochemist and so my physics knowledge is limited. But for a long time I have been wondering on how exactly the electromagnetic field associated with a single photon propagates in space. I understand (using a cartesian image of the electric and magnetic field change) the oscillating...

Well I have a question , if we would already have the device that uses electromagnetic force to propel a capsule or whatever object like a satellite into space , now unlike a rocket this device would propel the object needed to carry to space in one certain direction at a given angle , now once...

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...

It is known that a charged particle moving with some acceleration emits electromagnetic waves. For example, this may be a particle moving at a constant speed on the circle. In this case the radiation of a particle is called the braking radiation, the cyclotron radiation, or the synchrotron...

Does anyone know how the machining tolerance in the construction of an electromagnetic lens affects resolution in a scanning electron microscope?

We know that the conservation of electromagnetic energy is expressed via the continuity equation below: \large{\frac{\partial u}{\partial t}}+\vec{\nabla}\cdot\vec{S}=-\vec{J}\cdot\vec{E} with u=\frac{1}{2}(\vec{E}\cdot\vec{D}+\vec{B}\cdot\vec{H}) and \vec{S}=\vec{E}\times\vec{H} . It...

Hello everyone. I'm studying wireless communications at school, and I have a question... If frequency is the amount in time that something oscillates, in this case, electrons, wouldn't a higher hertz, mean faster data transfer? A 2.4 MHZ way is must slower than a 2.4 Ghz wave correct? So...

Homework Statement GPS determines your distance from a satellite by measuring how long it takes an electromagnetic wave to travel from the satellite to you. Imagine that a satellite is located at a distance of 127.2km and is moving away from you at a speed of 12.0km/s. a)how long will it...

Homework Statement Homework Equations The Attempt at a Solution see last attachment I am not sure if I used the right equations or not.

Hi, I would like to do more studies and research in electromagnetic spectrum. And I am interested very much in these waves and it's interaction with human or living things or matter. So please provide me with the information about what kind of courses I should take. I will complete my post...