# What is Electromagetic field: Definition and 58 Discussions

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1. ### I Macroscopic objects in free-fall

Hi, very basic question. Take an object like a rock or the Earth itself. If we consider their internal constituents, there will be electromagnetic forces acting between them (Newton's 3th law pairs). From a global perspective if the rock is free from external non-gravitational forces, then it...
2. ### Magnetic equivalent circuit for a UU-core inductor

Hello, I am trying to develop a magnetic equivalent circuit for a UU-core inductor with two parallel bus bars in the middle of the slot. I am not sure as to how to model the MMF in such problem. The logical way in my mind is to have two current sources to represent the fields of each bus bar...
3. ### I How does the electrical field become bent instead of following a straight line?

Why is electrical field bent like that rather than following a straight line across to the relevant point over there?
4. ### Engineering How to calculate the interference voltage?

Hello everyone, I have this circuit and I need to determine the interference voltage. I am not sure, where the interference voltage is applied and how to determine it. I think the interference voltage is uv nad my equivalent circuit looks like this: Am I in heading into the right direction...
5. ### I Two molecules with different polarizability in an EM field

If I have two separated and non-interacting molecules with different constants polarizabilities ##\alpha_1## and ##\alpha_2## and I send an EM field of frequency ##\omega## first on the molecule no.##1## and then on the molecule no.##2## so that the two molecules will have a dipole moment...
6. ### B Virtual photons as force carriers

(My multipart question is from a very naive perspective, so sorry if it is rife with misunderstandings. Please answer conceptually, with as few & as simple equations as possible. I think that all of the answers to these questions should be understandable to a high schooler, though maybe the...
7. ### Amplify ferrite core solenoid electromagnetic range

Hello all, I'm playing around with a PIC + LCC Tank to send - at a 5MHz frecuency - some numeric data via BPSK. The receiver is a loop antenna placed in the ground. The sender antena (L) is a ferrite core solenoid (N=10). As having a larger core, or increasing the Number of coils around the...
8. ### A Question on Skin Effect and Eddy Currents

When you try to create time varying magnetic fields in solid metals, there is severe heating due to eddy currents, when you increase the frequency, just like in NDT(non destructive testing) the magnetic field is pushed away from the core to the periphery due to eddy currents opposing the field...

11. ### An Interesting Question on Faraday's Law of Electromagnetic Induction

On examining Maxwell's third equation which is about time varying magnetic fields (Faraday's electromagnetic induction) we find that time varying magnetic fields produce loops of electric fields in space irrespective of whether a coil is present or not, if any coil is present then these loops of...
12. ### Four-momenta trend as a function of proper time

As a starting point I immediately thought about the equation: ##\frac{dp^\mu}{d\tau}=qF^{\mu\nu}v_\nu## From this I proceed component by component: ##\frac{dp^0}{d\tau}=qF^{0\nu}v_\nu=q\gamma E_yv_y## ##\frac{dp^1}{d\tau}=qF^{1\nu}v_\nu=q\gamma v_yB_z##...
13. ### Lorentz transformations for electric and magnetic fields

Good evening, I'm trying to solve this exercise that apparently seems trivial, but I wouldn't want to make mistakes, just trivial. Proceeding with the first point I wonder if my approach can be correct in describing this situation. From the assumptions, the two fields are in this...
14. ### Waveform produced by a collapsing magnetic field

A thought experiment: A electron is moving in a straight line at velocity v. It instantly stops dead. It doesn't move another femtometer. Obviously its magnetic field collapses and produces light. What is the waveform of the light produced? Is it something like this...
15. ### I Irreducible Representations of EM-Tensor Under Spatial Rotations

Can we consider the E and B fields as being irreducible representations under the rotations group SO(3) even though they are part of the same (0,2) tensor? Of course under boosts they transform into each other are not irreducible under this action. I would like to know if there is in some...

41. ### Electromagnetic Coil 2 SS Rods Converging

Howdy all, I'm looking at having two (preferably) stainless steel rods inside a plastic tube (for insulation and so they don't touch) with a push spring inside and between the two rods pushing each other away from one another, when not activated inside of an electromagnetic coil. When the coil...
42. ### Capacitor with uniform space charge between them

Homework Statement 2 large plates are separated by a distance d and a space charge of uniform charge density p is placed between them and a potential difference V is applied across the plates. Find the electric field stength at a distance x fromt the positive plate The answer is -V/d...
43. ### What composes the E Field of the Electromagnetic Wave?

What composes the E Field of the Electromagnetic Wave where "disturbances" for propagation occurs? If electromagnetic waves cause disturbances in the Electric Field… what “is” in this E Field which photons Interact with? I ask because in Vacuum, there are no electrons to excite. So what is...
44. ### A Why is the Matter wave analogous to photon and derived from it?

The electromagnetic wave derivation uses the fact that charge enclosed is zero and it goes to obey plane wave equations. Lets say we were deriving a wave equation from maxwell's equations for electron wave motion, but we assume that charge enclosed is not zero, and come up with some...
45. ### Particle in an Electromagnetic Field

Using the Lagrangian : L = ½mv^2 - qφ + qAv What is the physical intuition of Av ? I know that A is the magnetic vector potential and that v is the velocity of the charged particle. I just don't know what their dot product means physically .
46. ### The Decay Rate of a Hypothetical Antimatter Container

Hi All, First time poster here, and I've got a couple questions. Straight up, I'm writing a sci-fi story where antimatter is utilised as fuel (feel free to laugh at the cliche), and I want to portray it as realistically as possible. To that end, I've come up with a storage method and I want to...
47. ### Prove that a capacitor driven by an AC voltage radiates EM

Homework Statement When the capacitor driven by DC voltage ##V_0##,it has the electric field distribution ##f(x,y,z)## When ##V=V_0e^{iwt}##,how to show the EM travel in the space forever like the light? Homework Equations ##-{\nabla}^2E-u{\epsilon}\frac{{\partial}^2{E}}{{\partial}t^2}=0...
48. ### Different formulations of the covariant EM Lagrangian

Homework Statement I'm reading through A. Zee's "Quantum Field Theory in a nutshell" for personal learning and am a bit confused about a passage he goes through when discussing field theory for the electromagnetic field. I am well versed in non relativistic quantum mechanics but have no...
49. ### Electrodes liquid contact electromagnetic flow meter?

Hello, I'm interested in building a small non-invasive battery powered device that wraps around a pressured 1/2" pipe for measuring potable water. From https://en.wikipedia.org/wiki/Magnetic_flow_meter and watching youtube videos, it seems they all use electrodes which contact the liquid...
50. ### Why a conductive shield doesn't block the magnetic field?

Hi While studying the shielded wires, i noticed that the magnetic field of the inner conductor can penetrate the shield conductor (can be calculated in the region 3). However, the boundary condition of the magnetic field at the surface (between dielectric and perfect conductor) of a perfect...