Fields Definition and 1000 Threads

Hi I am looking around for some way to model magnetic fields through a simple core with an air gap similar to this image : I was thinking Comsol... but Comsol is so hard to figure out, their documentation is terrible... I was looking at FEMM, but its only on windows. Does anyone know how to...

Sorry, I know this has been talked about many times before but I like to put the question in a direct way so I may understand. Since there are more than 10^80 particles and radiation, how can a single point in space carry the values for all these fields at the SAME time all the time if they are...

Homework Statement Explain why the gas becomes conducting only when the electric field in the tube reaches certain value? 2) why does fields does from higher potential to lower potential? Homework Equations F=QE The Attempt at a Solution If we increase the E then the Force will also increase...

Does a static uniform E field in space appear to be a mix of E and B fields to an observer on Earth (ignoring the Earth's motion)? My GR is not so great, but would the rigorous way to calculate the new fields be to parallel transport the Maxwell 2-form ##F_{\mu\nu}## from free space, where it...

Hello Forum, A conservative vector field G(x,y,z) is one that can be expressed as the gradient of a scalar field P(x,y,z). Could a time-varying vector field like D(x,y,z,t) be a conservative vector field? If not, why not? Can it be conservative (or not) at different time instants? Thanks!

In the 1953 science fiction novel Childhood’s End by Arthur C. Clarke, characters use two crossed fields in outer space to block some of the solar radiation traveling towards earth: “Somehow, out in space, the light of the Sun had been polarized by two crossed fields so that no radiation could...

As I understand it, the need for quantum field theory (QFT) arises due to the incompatibility between special relativity (SR) and "ordinary" quantum mechanics (QM). By this, I mean that "ordinary" QM has no mechanism to handle systems of varying number of particles, however, special relativity...

Does the shape of atomic orbital changes when exposed to electric or magnetic field?

Suppose there is a solenoid near an accelerating electron. The electron must create a changing magnetic field. By Lenz's law, an emf is induced in the coil. One question is, how *fast* is the emf induced in the coil? Is the emf just there instantaneously or does it take time to formulate? And...

Hello.Looking at Jackson's ch 9 on radiation, I am trying to calculate the fields E and B from the potentials in the far field but it is very confusing. Given now the approximation for he vector potential \textbf{A}_{\omega}(x) = -ik \frac{e^{ikr}}{r} \textbf{P}_{\omega} with...

Homework Statement Two long parallel wires are a center-to-center distance of 1.10 cm apart and carry equal anti-parallel currents of 9.70 A. Find the magnitude of the magnetic field at the point P which is equidistant from the wires. (R = 10.00 cm). (See Attachment for orientation) I = 9.7 A...

Vector fields confuses me. What are the differences between (##t## could be any variable, not just time): 1. If the position vector don't have an argument, ##\mathbf{r}=x\mathbf{\hat e}_x+y\mathbf{\hat e}_y+z\mathbf{\hat e}_z=(x,y,z)## so ##\mathbf{E}(\mathbf{r},t)=E_x(\mathbf{r},t)\mathbf{\hat...

Why is it that quantum fields interact? How do they do this? Does every exitation of any field affect all other fields? I'd appreciate an explanation that uses as little math as possible, I don't have a science background.

Homework Statement Describe semiquantitatively the motion of an electron under the presence of a constant electric field in the x direction, E =E0x^ and a space varying magnetic field given by B = B0 a(x + z)x^ + B0 [1 + a(x - z)]z^ where Eo, Bo, and a are...

The Euler-Lagrange equation obtained from the action ##S=\int\ d^{4}x\ \mathcal{L}(\phi,\partial_{\mu}\phi)## is ##\frac{\partial\mathcal{L}}{\partial\phi}-\partial_{\mu}\big(\frac{\partial\mathcal{L}}{\partial(\partial_{\mu}\phi)}\big)=0##. My goal is to generalise the Euler-Lagrange equation...

Homework Statement Suppose given an electric field \vec{E} and a magnetic field \vec{B} in some inertial frame. Determine the conditions under which there exists a Lorentz transformation to another inertial frame in which \vec{E} || \vec{B} Homework Equations If we give a Lorentz boost along...

The problem Consider field ##(F, +, \cdot), \ F = \{ 0,1,2,3 \}## With the addition table: Find a multiplication table. The attempt Please read the most of my answer before writing a reply. My solution was $$ \begin{array}{|c|c|c|} \hline \cdot & 0 & 1 & 2 & 3 \\\hline 0 & 0 & 0 & 0 & 0...

Alright, I feel this may be a pretty basic question, but I have not gotten a satisfying answer yet. I'm taking Electromagnetism right now and I got to thinking: how do fields physically interact? What I mean by this is, on a subatomic level, a field can create a force on another particle or...

Homework Statement Hi, I have a question about my lab report that I am doing. The only question that I am having problems to understand is the first one, it says, "why are the equipotential lines near conductor surfaces parallel to the surface and why are they perpendicular to the insulator...

Hey guys. So, as i was going through Griffith's Electrodynamics, and i came across this problem: In the solutions: How to they actually get to that expression for V = (V(bar)+vAx(bar) )Ɣ? I understand everything after that, but this just made me very confused. How do they get this from the...

I've been trying to understand what an electromagnetic wave is, and have spent quite a while now reading around and piecing different bits of information together to try and get an answer. I haven't yet found an answer to my title question. It might just be because I have a lack of...

I've discovered a potential treasure horde tucked away in the deep dark folds of the world wide web. A 1625 page mammoth on all aspects of quantum field theory by Prof. Hagen Kleinert. There's a draft ed. for free available here -...

Homework Statement Homework Equations Biot-Savart's law and ampere's law expressing B = mu0 * I / (2 * pi * r) The Attempt at a Solution [/B] I know that for the first drawing, we have magnetic fields going into the page from both of the wires, and we have them being (infinitely) long, so...

Homework Statement Hi everybody! I'm currently training at surface integrals of vector fields, and I'd like to check if my results are correct AND if there is any shortcut possible in the method I use. I'm preparing for an exam, and I found that it takes me way too much time to solve it. I...

Maxwell's equations reveal an interdependency between electric and magnetic fields, inasmuch as a time varying magnetic field generates a rotating electric field and vice versa. Furthermore, the equations predict that even in the absence of any sources one can have self propagating electric and...

I'm reading McGreevy's lecture notes on holographic duality but I have two problems now: (See here!) 1) The author considers a matrix field theory for large N expansion. At first I thought its just a theory considered as a simple example and has nothing to do with the ## \mathcal N=4 ## SYM...

Hi. This question most probably shows my lack of understanding on the topic: why are scalar fields Lorentz invariant? Imagine a field T(x) [x is a vector; I just don't know how to write it, sorry] that tells us the temperature in each point of a room. We make a rotation in the room and now...

How is the alpha decay of a given nucleus affected by the presence of an external electromagnetic field? It's probably an easier question that I think but I've been unable to find a treatment of the tunneling of the alpha particle using WKB method in the presence of a magnetic field.

It is natural to make quantum fields out of electromagnetic wave or even the weak force. But is there experimental proof for the need to create fermion fields like separate electron fields for the electron.. quark fields for the quarks.. When de Broglie tried to propose matter wave from analogy...

Bill_K submitted a new PF Insights post Tetrad Fields and Spacetime Continue reading the Original PF Insights Post.

Why is the weak field a force of nature.. while the higgs field is not a force of nature.. what is the signature or things to look for before a field can be considered as a force of nature?

I am trying to follow Nakahara's book. From the context, it seems that the author is trying to say if moving a point along a flow always give a isometry, the corresponding vector field X is a Killing vector field. am I right? then the book gives a proof. It only considers a linear approximation...

Sharks are extremely sensitive to magnetic fields, attracted by low end frequencies and repelled or overstimulated by higher/stronger fields. I want to map the spectrum in between using and electromagnetic coil in the water with sharks. I have sharks and a boat but need help building the coil...

I am having a very difficult time picturing space-time and fields and all... Anyone here have a sort of flow chart or procedural chart that I could use to try to better wrap my head around what this place is? Sort of starting with universe and then going into spacetime and from spacetime to...

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...

Hi there! It has happened to me these days when I went to a conference that I realized maybe my PhD topic is something I would like to work in after it (IF I continue in the academic path). My current research is based on applying QFT in condensed matter physics, particularly related to the...

The field strength of gravitational, electric and magnetic fields vary as the inverse square of the distance from the source. Is this because all of the above fields are generated by fermions and they behave identically regardless of the nature of the fields ? Do the above fermions have rest...

Dummit and Foote in their book Abstract Algebra give the following definition of an algebraically closed field ... ...From the remarks following the definition it appears that the definition only applies to $$K[x]$$ ... Does it also apply to $$K[x_1, x_2], K[x_1, x_2, x_3], \ ... \ ... \ ...

Dummit and Foote in their book Abstract Algebra give the following definition of an algebraically closed field ... ... From the remarks following the definition it appears that the definition only applies to ##K[x]## ... Does it also apply to ##K[x_1, x_2], K[x_1, x_2, x_3], \ ... \ ... \ ...

Hi, I've been trying to figure several simple things about electric and magnetic fields, their relationship with current. If you could please help me understanding this, it would be really helpful. From what I've read these were presented as natural laws: 1. Changing magnetic field induces...

I was researching the relationship between magnetic dipoles and chemical bonding and I came across a very interesting paper. I'm hoping some of you can shed some light on how magnetic fields are making dissociation of a molecule possible and how to measure it...

I thought I'd post this here since it's not exactly a homework question or discussion regarding a specific operation in a field/subject. Out of the following, which fields gravitate more towards applied physics/engineering (but not necessarily such a discipline)? Or maybe if that's confusing...

Hey all, I'm having some issues with electromagnetism here. Let's say we have a particle with magnetic moment ##\vec{\mu} = \mu_0 \hat{x}## and magnetic field ##\vec{B(x)} = B_0 \frac{x}{a} \hat{x}## where ##\mu_0,B_0,a## are constants. If we assume that the magnetic field ##B_0## is far, far...

By electitc field, i do not mean the magnetic field produced by a current carrying wire, but rather between charged particles. If a compass is placed between the electric field, will the compass needle delfect or will it just continue pointing in the initial direction?

I know that magnetic fields create moving charges (an electric current) normal to the plane of the magnetic force lines. I also have heard that magnetic and electric fields create each other in a perpendicular direction to the other (badly worded). Electric currents are moving charges (usually...

<<Moderator note: Split from thread Photon the smallest particle>> @Orodruin - Let me ask a question. This is an aspect of QFT that has always puzzled me. Suppose we have an RF cavity or a laser cavity with a standing E-M wave. I understand that we can view the field in the cavity as a...

Homework Statement In the figure two large, thin metal plates are parallel and close to each other. On their inner faces, the plates have excess surface charge densities of opposite signs and magnitude 7.76 × 10-22 C/m2. What is the magnitude of the electric field at points (a) to the left of...

I've read a few other threads on the site, and many say that it's hard to get a job that has to do with Physics, at least with only an undergraduate degree. Is that true? I'd like to get onto physics because I'm curious to know more about the science, but I wouldn't like to end up working as an...

When we encounter particle-collision problems that call for invoking the conservation of four-momentum, are we tacitly assuming a field-free idealization (or at least negligible potential energy)? For example, say particles 1 and 2 collide elastically. Then the conservation of four-momentum...

I'm interested in Killing vector fields and want to ask whether anybody can name me a good textbook or online-source about them, preferably with a general treatment with local coordinates as examples and not at the center of consideration.