Electromagnetic Definition and 1000 Threads

Hi, I'm a high school science teacher. Most textbooks classify EM radiation as kinetic energy. But this doesn't seem right to me. As a photon is massless it's hard to see how it can have kinetic energy which is 1/2 mv^2. It could be said that it has energy hf and therefore mass hf/c^2. Then its...

The wavelength is inversely proportional to the foton energy. So, the limit can be stated by the mass of the full universe. But how much near that limit can the light be?

We know that Poincare matrix which is 0 Kx Ky Kz ( -Kx 0 Jz -Jy ) describes the boost and rotation is very similar to -Ky -Jz 0 Jx...

It’s commonly held that left and right photons interact with matter in exactly the same way, because electromagnetism “conserves parity”. But we know that P-symmetry, in our world, is generally broken. Even according to the Standard Model, when light propagates through some media, it interacts...

I know that light are affected by gravity since they have both momentum and energy, but what about other magnetic waves such as radio waves or x-rays or other electromagnetic waves

The antisymmetric 2-tensor ##F_{ij}## is given by ##F_{ij}\equiv \partial_{i}A_{j}-\partial_{j}A_{i}## so that ##F_{ij}={\epsilon_{ij}}^{k}B_{k}## and ##B_{i}=\frac{1}{2}{\epsilon_{i}}^{jk}F_{jk}##. I was wondering if the permutation tensor with indices upstairs is different from the...

Electricity flowing through a wire creates it's own magnetic field. So when the electricity is flowing through a wire, it's magnetic field works AGAINST the generator, slowing it down. So is there is any way to stop slowing down process without increasing amount of current ??

I am wondering if it is at all possible to create a magnetic board which is capable of repelling magnets. I am looking up magnetic levitation and would like to make a DIY version at home. Any tips/tricks to make this. Thanks in advance!

I'm trying to calculate the battery requirements for an experimental home built air compressor. I understand that electromagnetic air compressors operate using attraction and repulsion forces created by electromagnets using the basic magnetic principle that like poles of two magnets repel and...

Homework Statement There's a uniform infinite line charge with the charge density λ. A point particle with charge q moves with a velocity v parellel to infinite line. What is force exerted on point particle? What is magnetic field seen in ths moving frame(particle frame)? Homework Equations...

I know that the electromagnetic waves are alternating electric and magnetic fields. But I don't get why the fields can't stand still and alternate at the same point. Why they always move ?? I would prefer a logical and verbal answer rather than a mathematical answer. But if mathematics helps...

I was bored today so I took this diamond shaped crystal made of glas and simply put in infront of the light emitting from the sun. What I noticed was a lot of lines on the wall that were strangely colored, just like the electromagnetic spectrum. One end was blue, then progressively went to red...

Antennas work with variable current that leads to accelerations and deceleration ofor the electrons, the frequency of the photon or the electromagnetic radiation I want to generate depends on the change in kinetic energy of the electron E= hf= change of kinetic energy of the electron, according...

- What exactly is the equilibrium of the waves that is shown on graphs? My understanding is that the oscillations are in the strengths of the field, and different sides of the equilibrium represent different directions of the fields. However, I feel as though this contradicts itself in some...

Which is better and how to do it? Make a spaceship an electromganetic field and go through a sensor so at the end of the race it must pass between the sensors to win, and what sensor would you need for very close width. Saying the spaceship is 20ft wide and both sides must be between the 80ft...

I read in a book that Electromagnetic fields propagate at speed of light and carry energy and momentum. Let's take electric field for example. Electric field is none other than a force per unit coulomb.So 1.How could a force(here field) move as force has no property of moving as force causes...

What is this electromagnetic device called? I've seen a couple. There is this one: as well as one similar but you must keep the magnet in motion to generate electricity. I would like to make one of these, but I don't know the name of it which makes it hard to search for instructions and a...

I've been attempting to model a simple electromagnetic coil using HFSS, and have so far been unsuccessful. I have no problems constructing the coil; this is a simple geometry problem. I have a wire of a known geometry with insulation surrounding the wire, then a construct a helical path and then...

Hi there When a charge is accelerated it produces electromagnetic radiation. I was wondering if anyone knew the equation relating the frequency of emitted radiation to the size of the charge and the value of the acceleration. My understanding is that it relates to Maxwell's equations, but I was...

Homework Statement When there is a changing magnetic flux, emf is induced in the solenoid. The solenoid is made up of circular loops of wire. My first question is, since emd is induced in the solenoid, is there a site of higher voltage and another site of lower voltage? My second question is...

(Sorry for my poor english.) I'm just wondering why is it necessary to have oscillating EM fields for life existing on Earth. The sun has a magnetic field (I think a static one), so why it's not enough to life exists? Also, why we and other animals only see the objects if the fields are oscillating?

I'm trying to understand how we set up the lagrangian for a charged particle in an electromagnetic field. I know that the lagrangian is given by $$L = \frac{m}{2}\mathbf{\dot{r}}\cdot \mathbf{\dot{r}} -q\phi +q\mathbf{\dot{r}}\cdot \mathbf{A} $$ I can use this to derive the Lorentz force law...

Say you have a coil connected in a closed circuit. You then move a magnet inside of the coil and it remains stationary inside of the coil. Is the magnet, even though it is stationary, still inducing an emf in the coil or is it not? I'm guessing it doesn't induce an emf in the coil because...

I'm trying to show that \partial_\mu T^{\mu \nu}=0 for T^{\mu \nu}=F^{\mu \lambda}F^\nu_{\; \lambda} - \frac{1}{4} \eta^{\mu \nu} F^{\lambda \sigma}F_{\lambda \sigma}, with the help of the electromagnetic equations of motion (no currents): \partial_\mu F^{\mu \nu}=0, \partial_\mu F_{\nu...

When does the rate of change of magnetic flux in linkage with a coil rotating in a uniform magnetic field equal zero?

Homework Statement A circular disk rotates about its axis with angular velocity ##\omega##. The disk is made of metal with conductivity g, and its thickness is t. The rotating disk is placed between the pole' faces of a magnet which produces a uniform magnetic field B over a small square area...

(I'm sorry for my poor English.) I draw a sketch showing the intensity of the magnetic field at two points p1 and p2, where the distance from the source (a wire carrying a current, for example) to p2 is greater than it's for p1. Is the shape of the curve correct? Is it correct that t2-t1/c is...

Hi, I have a trivial question about electrodynamics. If you have a very long coil, a long solenoid. Keep the current constant and you will have no \vec{B} outside (magnetostatics). Let's write down the Maxwell equations: \begin{matrix} \nabla\cdot\vec{B} &= &0 \\ \nabla\times\vec{E} &=...

In the case of two protons in the nucleus. I've seen charts with that info, but I don't know how... How can I calculate that ratio? I've looked everywhere, and I can't find anything... Thanks

Guys, I have read Lenz's law and Faraday's law. My question is when the current is overall trying to keep the magnetic flux constant as that in initial time then if I permanently change the flux then why the current is not flowing through the conductor continuously to keep initial flux constant...

Trying to understand how a magnetic field induces an electric current Suppose you have a wire in the magnetic field like this: If you move the wire with a velocity of V to the left. Then the magnetic field should exert a force on the wire which ultimately on the charges in the wire. According...

Homework Statement Homework Equations I am not really good at this topic, but I think you would need both the right hand rules (one that involves finding direction of current via magnetic field as well as the one for finding magnetic force) The Attempt at a Solution So I drew out magnetic...

Greetings. I am a new member posting for the first time. I teach chemistry and I have spent considerable time attempting to get a definitive answer to this question but have found only contradicting information. My query is regarding the nature of the electric force within and between atoms and...

Homework Statement An infinitesimally small bar magnet of dipole moment ##\vec{M}## is pointing and moving with the speed v in the x direction. A small closed circular conducting loop of radius a and negligible self inductance lies in the y-z plane with its centre at x = 0, and its axis...

Homework Statement Maxwell's Lagrangian for the electromagnetic field is ##\mathcal{L}=-\frac{1}{4}F_{\mu\nu}F^{\mu\nu}## where ##F_{\mu\nu}=\partial_{\mu}A_{\nu}-\partial_{\nu}A_{\mu}## and ##A_{\mu}## is the ##4##-vector potential. Show that ##\mathcal{L}## is invariant under gauge...

Hello everybody, It is known that electric field operator is shown as \hat{E}(r,t)=-i\sum_{k,\lambda}\sqrt{\frac{\hbar\omega_k}{2\epsilon V}}\left(a(t)^\dagger_{k,\lambda} e^{-ik.r} - a(t)_{k,\lambda} e^{ik.r} \right) \hat{e}_{k,\lambda} But if I need to represent an electrostatic field in a...

(sorry for my poor english) I've read that a electromagnetic wave only exists in a particular point of space if in such a point there is a nonlinear change of the electric field in respect to time. Then I took a graph calculator and I derived Coulombs equation for the electric field. The results...

Homework Statement [/B] In a thin rectangular metallic strip a constant current I flows along the positive x-direction, as shown in the figure. The length, width and thickness of the strip are l,w and d, respectively. A uniform magnetic field B is applied on the strip along the positive...

Homework Statement I am attempting to create a generator using electromagnetic induction. I am using a push pull system to move a bar magnet through a coil to create current. But I am unsure of the dimensions to build it with and when I attempt to use the equation I get stuck. I am looking for...

Homework Statement A harmonic EM-wave is propagating in glass in the +x-direction. The refractive index of the glass ##n = 1.4##. The wave number of the wave ##k = 30 \ rad/m##. The magnetic portion of the wave is parallel to the y-axis and its amplitude ##H_0 = 0.10A/m##. At ##t=0## and ##x =...

Homework Statement Homework Equations no equations required 3. The Attempt at a Solution so here are my answers, can some please verify if these are correct. Thanks in advance :) a) i have no idea if I am labelling the poles correctly, or if the induced current is in the right direction ...

Homework Statement A uniform conducting ring of mass π kg and radius 1 m is kept on a smooth horizontal table. A uniform but time varying magnetic field ##\vec{B} = (\hat{i} + t^2\hat{j} ) T## is present in the region (where t is in sec and the positive y-axis is in vertically upward direction...

Homework Statement [/B] A 0.393 m long metal bar is pulled to the left by an applied force F. The bar rides on a parallel metal rails connected through a 42.9 ohm resistor as shown in the figure. So the apparatus makes a complete circuit. You can ignore the resistance of the bars and the rails...

Homework Statement ⃑E = Eo cos(4.0y−1.2 × 109 t) ̂ (N/C) where y is in meters and t is in seconds. The intensity of the wave is 200 mW/cm2 . (a) In what direction is the wave propagating? (b) What are the wavelength and frequency of the wave? (c) What is the peak value of the electric field...

Homework Statement Homework Equations Not really? I just used the right hand rule and Lenz's law The Attempt at a Solution By the right hand rule, outside of loop 1, the magnetic field is out of the page. However, increasing resistance means that field is weakening. We know by Lenz's law...

Here's my idea for a robotics actuator resembling a muscle. Lots of tiny electromagnets closely packed attracting each other to flex an artificial muscle. It seems like such an obvious idea, why isn't anyone using it?

Kind of a silly question here, but one that has nagged at me for some time: Does the word "light" refer to all wavelengths of the electromagnetic spectrum, or only to the visible light that we can see? Also, if light only refers to visible electromagnetic radiation, then what about ultraviolet...

Hi, light as an EM wave attributes wave-particle duality. In general, are the other bandwidths of EMW (UV & IR for example) qualifies the same duality? How? Why and why not?

Why are there no problems at the end of chapters one and two in Stratton Electromagnetic theory like there are at the end of all the other chapters??

Hi Experts, I'm doing an experiment of Electromagnetic Induction (producing current by changing magnetic field i.e. by circulating magnetic wheel of N52 Neodymium Magnets around copper coil), but what i found when the speed of wheel is HIGH, the Output Current is LOW (in range of .02...