Fields Definition and 1000 Threads

Hi, I have a case of elevated AC Magnetic field in the house, strongest nearest the electric meter and along the service drop line connecting the house to the street power lines. Should that service drop line measure no current or fields when I shut off my main circuit breaker? it seems shutting...

How do you know what fields can be coupled with the gravitational field? Is there a general procedure for knowing it or we have to try out and see whether it makes sense or not?

Homework Statement Am amount of charge Q is uniformly spread over a semi-circle of radius R whose center is located a distance A from the origin. What point charge would have to be placed at the origin so that the E field at the center of the circle is 0? (The open end of the semi-circle is...

I’m looking for a device to produce electromagnetic fields and how can u control the frequency emitted looking to build or purchase looking to experiment any information either reply publicly or inbox me

Hi, I wanted to clarify a point about the magnetic fields of a solenoid and wire. Do the fields extend to infinity? In my opinion, they don't but they can assuming the current also goes to infinity. They don't extend to infinity for a limited amount of current because they need to follow a...

Particles follows accordingly the general equation: $$ m*\overrightarrow{a}=q*\overrightarrow{E}+q*\overrightarrow{v}\wedge \overrightarrow{B} $$ But in the case of two coupled coils the time varying current at primary coil (and its magnetic field variation) creates corresponding varying...

I am contemplating writing a science fiction story involving flexible barriers that can be erected in a very short time. Force fields are pervasive in science fiction, but from what little I've read, they're not very plausible. Is there a flexible material, or class of materials, that...

Hi, I'm just starting to read Wald and I find the notion of the commutator hard to grasp. Is it a computation device or does it have an intuitive geometric meaning? Can anyone give me an example of two non-commutative vector fields? Thanks!

When defining quantum fields as a sum of creation and annihilation operators for each momenta, we do it in analogy with the simple example of the harmonic oscillator in quantum mechanics. But why do we assume that the coefficients in the expansion can be interpreted in the same way as in the...

I keep seeing these pods along the sidelines of the professional soccer fields on TV (pro footbol pitches), and I'm wondering what they are for. There seem to be more of them at the ends of the field, and especially near the goals. Are they microphones? If so, what are they for? Who hears...

Hi, I am almost done with my 5 years of a bachelor of nuclear engineering, the main field I am working on is thermal-hydraulic but I am flexible with changing my whole path. for example, I am in between data science and CFD analysis. What kind of jobs do I qualify for?

Hello guys! The electric field created by a conductor at a point $M$ extremely close to it is ##\vec{E}=\vec{E_1}+\vec{E_2}## where ##\vec{E_1}## is the electric field created by such a tiny bit of the conductor that we can suppose it to be a plane, and since ##M## is extremely close to the...

What happens when magnetic field cancel. Where do they go. Do they just vanish or return to the vacuum? In a GFCI receptacle we have in most of our homes. The sense coil can output zero when there is deviation from net magnetic field between the line and neutral. This means the cancellation...

Hi! I'm doing my master thesis in AdS/CFT and I've read several times that "Fields transforms in the adjoint representation" or "Fields transforms in the fundamental representation". I've had courses in Advanced mathematics (where I studied Group theory) and QFTs, but I don't understand (or...

Hello, In the sources I have looked into (textbooks and articles on differential geometry), I have not found any abstract definition of the electromagnetic fields. It seems that at most the electric field is defined as $$\bf{E}(t,\bf{x}) = \frac{1}{4\pi \epsilon_0} \int \rho(t,\bf{x}')...

I think I have found a majot error in Neuenschwander's book on Noether's Theorem, but I'd like some confirmation from someone familiar with the book or with the Rund_Trautman identity for fields. As far as I can see the extension of the R-T identity for fields seems to be Neuenschwander's work...

In beginning to learn about Quantum Mechanics, I am getting confused by what seems like a lot of overloaded terminology. One example is with fields (and perhaps for another thread..."spaces"). I generally understand the idea of a field in the sense of temperature variations in a room or of...

Homework Statement Hello there! I have been studying path integral for fermionic fields, and I don't understand one detail. I have to proove that: \int d^4x\int d^4 y\, \overline{\eta (y)}S^+_F(x-y)(i\partial\!\!\!/-m)\Psi (x)=\int d^4x \, \overline{\eta (x)} \Psi (x) Homework Equations We...

Suppose a straight current carrying wire is immersed in a uniform electric field along its axis. For this problem, please don't worry about complete loops or return paths, just consider a segment of straight wire carrying a current. Since external electric fields don't get inside conductors due...

Hello, I am working on a science project to generate electromagnetic fields. From what I understand, the simplest way to do that is to coil copper wire around an iron core. My initial goal is to create a magnetic field with a maximum strength of 500 microtesla. Can this be accomplished if I...

Dipole problem (which is solved through mirror imaging) has been troubling me with its solution. I understand everything except how the dipole moment's coordinates came to be, since when converted into x-y axis, its doesn't make sense. (problem 4.6) The screenshot contains the solution which...

I am trying to solve problems where I calculate work do to force along paths in cylindrical and spherical coordinates. I can do almost by rote the problems in Cartesian: given a force ##\vec{F} = f(x,y,z)\hat{x} + g(x,y,z)\hat{y}+ h(x,y,z)\hat{z}## I can parametricize my some curve ##\gamma...

Are both magnetic fields emanated from an electromagnet fed with a current spike from a charge capacitor and a rotating static magnetic field from permanent magnets instances of time varying fields? The permanent magnet would be attached to perhaps some rotating disc thus passing over a target...

Homework Statement See picture Homework Equations Dont think so. The Attempt at a Solution I get D, the answer is D. I think it is D because only half a magnetic wave would appear on the inside of the wires as it is a sine wave. If you have more information on answering the question, please...

We say that vibrations of Faraday lines of force create electromagnetic waves.Now photon is the quanta of electromagnetic field.Is photon also the quanta of electromagnetic wave? How can the same photon represent both if so?

I always had a tough time understanding how QFT relates to reality. Are these quantum fields (electron field, ect) physically real? Are they things that exist in space or are they just mathematical abstractions that help use calculate things?

I read this article. Apparently tachyon fields and wormholes (classical and quantum) are unified. Is there any credibility? I know that with the known laws of physics we can’t go faster than light, and also that tachyons are hypothetical. What is the credibility and what are your opinions? How...

the question: My attempt: The partial derivatives did not match so i simply tried to find f(x,y) I got the set of equations on the right but that's about it.

Homework Statement This is the question Structure opposite comprises 5 ions each of which has lost one electron. The sides of the square formed by the 4 outer ions are of length 0.2nm Ion E is at the midpoint 1.What is the force on A due to ion A?Homework Equations I'd imagine: F= kq / r^2...

Are there any metrics that show which areas in physics have lots of funding and activity at this present moment? Of course it would vary by location as well. I'm mainly interested in Europe. I am basically trying to figure out if Quantum Information/Quantum Computing is a good field to...

Hello! I am reading about the S matrix, and I see that one of the assumption that the derivations are based on is the fact that interacting particles are free at ##t=\pm \infty## and I am not sure I understand why. One of the given examples is the ##\phi^4## theory which contains an interaction...

How is energy stored in the following fields, please give an example for each field: 1. Electric field 2. Magnetic field 3. Gravitational field

In Mathematical Methods for Physicists, 6th Edition, page 44, Example 1.8.2, the curl of the central force field is zero. 1. Why are central force fields irrotational? 2. Why are central force fields conservative? Any help is much appreciated...

The reason this is in relativity is ( please correct if wrong )that magnetic fields are effects created by static electricity through length contractions. If a line of electrons move pass a parallel line of positive charges and a charged observer is outside this it would see electrons being...

Homework Statement You observe a molecular cloud core with the following properties: T = 5K R = 1pc M = 10 M⊙ n = 102 cm^-3 B = 1µG RΩ = 200 cms^-1 A. Assuming equipartition of B fields and turbulence, what is the turbulent velocity of the cloud? Homework Equations Emag=1/6((B^2R^3)/μo)...

After reading about Jupiter's magnetic field on ScienceAlert, I remembered another article about tree bark and magnetic anomalies (links below). I also remembered an article on birds being able to see magnetic fields as well. It got me thinking of how and if life is possible on anything other...

Hi, I am trying to figure out whether there is a way to express the ratio of the critical current of a superconductor at zero and finite magnetic fields [denoted as Ic(0) and Ic(B)] as a function of the ratio of corresponding critical temperatures [denoted as Tc(0) and Tc(B)]. According to...

The 2018 Fields Medal has been awarded to: Caucher Birkar For the proof of the boundedness of Fano varieties and for contributions to the minimal model program. Alessio Figalli For contributions to the theory of optimal transport and its applications in partial differential equations...

I have a question regarding the interactions of electromagnetic fields. Say you have two superconducting electromagnets A and B. The properties of the magnets are known such that you can tell precisely how quickly it takes each one to produce it's full strength magnetic field and how long it...

In this Nima Arkani-Hamed paper on page 5 I found the sentence: These constraints are an artifact of using fields as auxiliary objects to describe the interactions of the more fundamental particles. In Schwartz's QFT book I also get away with the impression that the Poincaré irreps (i.e...

Do quantum fields move with respect to each other? If not, then what establishes the background spacetime for quantum fields? Is there a way in which to say that the particle wave in one field is stationary in another frame and the rest of the particles are moving with respect to it?

Very recently, Roger Penrose, along with Daniel An and Krzystztof Meissner, have submitted a new paper to PRL. In the new paper they present new empirical findings which support CCC. It doesn't seem to be out yet though, I can't find it anywhere, but I will place the link here when it is out...

Has anyone ever looked for reversible weight changes while materials are subjected to uniform, strong magnetic fields, such as those involved in nuclear magnetic resonance imaging (MRI) or spectroscopy? I suspect no one ever has, for lack of a reason, and any such effects would have to be...

According to an inertial observer the electric field of a charged ball sitting on the floor of an accelerating elevator is contracted more than the elevator is contracted. So the inertial observer concludes that an observer inside the elevator will measure that the Coulomb-force from the ball is...

I'm studying out of Classical Electrodynamics by Ohanian and in chapter 2 (Electrostatics) he makes the following claim while discussing the electric field: I'm a little confused by this, and I can't seem to find any sources that share this view. I'm even more confused because in the...

Hello PF, I was reading Carroll’s definition of the commutator of two vector fields in “Spacetime and Geometry”, and I’m having (I think) a simple case of notational confusion. He says for two vector fields, ##X## and ##Y##, their commutator can be defined by its action on a scalar function...

Hi everyone! Back in 2014, I had posted the following about what field(s) you would encourage someone to pursue: https://www.physicsforums.com/threads/what-field-would-you-actually-encourage-someone-to-pursue.742424/ Since the above thread is no longer open for new replies, I thought I would...

From Chapter 5.9 Weinberg's QFT Vol 1, massless fields are defined as: \psi_l(x)=(2\pi)^{-3/2}\int d^{3}p\sum_{\sigma}[k a(p,\sigma)u_l(p,\sigma)e^{ipx}+\lambda a^{c\dagger}(p,\sigma)v_l(p,\sigma)e^{-ipx}] With coefficients defined by the conditions: u_{\bar{l}}(p,\sigma) =\sqrt{|k|/p^0}...

Hey guys, Iam new to Physics Forums. Iam doing my Masters with Major in Electrical Engineering. My core is Digital Signal Processing as of now and my GPA is somewhat good for atleast entering PhD program. I do have ideas for a PhD but I do have some financial commitments. So, I postponed this...

Homework Statement An electric field is created by an uniform linear charge with a linear charge density is 40 nC/m. Find the potential difference between the two points, one of which is situated 5 cm from the line charge and the second at 10cm. Two charges, q and -3q, are situated at a...