Fields Definition and 1000 Threads

He didn’t have the modern equipment we have today.

Please forward to appropriate subforums as I wasn't sure where to post it.In the standard model there are the composite particles and elementary particles, for the elementary particles there is said to be an associated field and the particle is the excitation of that field. Apart from asking how...

Suppose I have a wire loop that I am moving away from a very long wire which carries a current upward and I want to find the induced current in the loop. The way I know how to approach this is with either Faraday's Law or motional EMF. My question concerns the motional EMF approach. My...

The usual presentation of classical statistical mechanics are based on the Liouville equation and phase space distribution. This, in turn, is based on the Hamiltonian mechanics of a system of point particles. Real undulatory systems, specially non-linear ones, have to be complex to study...

This week, I've been assigned a problem about a 3-sphere. I am confused how to approach this problem and any comments would be greatly appreciated. (a) - would I be correct to assume the metric G is simply the dot product of two vector fields with dx^2 dy^2 du^2 and dv^2 next to their...

Hi everyone, sorry we are talking about pulsed power accelerators again. In this context, it is about the HERMES III again. According to https://apps.dtic.mil/dtic/tr/fulltext/u2/a351472.pdf HERMES III, a 16 terawatt pulsed power accelerator at Sandia National Labs, which fired electron beams...

If I understand correctly, the concept of electric and magnetic fields originated with Faraday and was developed by reconceptualizing forces acting at-a-distance. For example, the electric field concept was developed by looking at the force on a test charge in the presence of a source charge...

I thought i understood the theorem below: i) If A is a matrix in ##M_n(k)## and the minimal polynomial of A is irreducible, then ##K = \{p(A): p (x) \in k [x]\}## is a finite field Then this example came up: The polynomial ##q(x) = x^2 + 1## is irreducible over the real numbers and the matrix...

If you take copper wire and wrap it tightly around a bolt will that alone create and hold a magnetic field? I add an image for clarification

My main issue with this question is the manipulation of the two arbitrary fields into a single one which can then be substituted into the divergence theorem and worked through to the given algebraic forms. My attempt: $$ ∇(ab) = a∇b + b∇a $$ Subsituting into the Eq. gives $$ \int dS ·...

The Lorentz transformations of electric and magnetic fields (as given, for example in Wikipedia) are $$ \begin{align*} \bar{\boldsymbol{E}}_{\parallel} & =\boldsymbol{E}_{\parallel}\\ \bar{\boldsymbol{E}}_{\perp} &...

Homework Statement:: n/a Relevant Equations:: n/a Sorry for the wonky mouse sketching. Teacher said that arrows must touch the plate at the other end. Is there actually such a thing or is this just preference? I thought convention was for arrow to be in the middle of the line.

The speed of the ends of the galaxies is higher than what it should be. Current solution: This could be explained by hypothetical "dark matter", which was not found up to now, or by a MOND theory (MOdified Newtonian Dynamics). Can this be explained instead with rotational frame-dragging...

The mathematical structure called a "field" is an algebraic structure that doesn't capture the properties of what physicists called a "field". What's the name for a mathematical structure that does represent the general concept of physicist's field? Is a mathematical version of a physicist's...

Hi! I know some theorists believe all quantum fields and gravitational field are different aspects of one universal field. What does that formally (e.g. mathematically) mean "to be different aspects of" and how can one prove, let's say, fields A and B are different aspects of C? By the way, I...

Is it possible for new forces or fields of nature to be connected to quantum foundations? For example, new forces or fields that choose the decoherent histories or branches. Or generally actualize one of the decoherence branches? Or should new forces or fields of nature be reserved for...

Ok, so I have long been fascinated with magnetic fields and their mysterious nature. I've been wondering what would happen when the magnetic field of Earth gets bent/disturbed/rippled by some extraneous force. I am aware the extent of effects that magnetic fields have on a planet is great, but I...

Can time and space be thought of fields? And if so, how can this affect spacetime? And then what would this mean for affect general relativity?

Hello. I was wondering if diamagnetic materials only repel varying electric field? By Ampere law only a variable flux can cause an electromotive force, so, and by what I understood diamagnetism is explained exclusively by Ampere law. Am I wrong?

Given a one parameter family of geodesics, the variation vector field is a Jacobi field. Mathematically this means that the field, ##J##, satisfies the differential equation ## ∇_{V}∇_{V}J =- R(V,J,)V## where ##V## is the tangent vector field and ##R## is the curvature tensor and ##∇## is the...

Hello, I am looking for a book that has sections on different areas of math. I’ve browsed through a few discrete math books but they have something similar to this but not at the level I am looking for. Essentially, I would like the book to serve as a tour if you will, so I can try and find a...

Here, the correct options are A,D. Solution: I got A as answer as ∫ B.dl=µI. But, the answer to the question says that it is a solenoid and therefore Bx=0 for point P. Here I'm a bit confused. I know this system resembles a solenoid in some ways, then By must have some finite value, but...

In Griffith's Introduction to Electrodynamics, chapter 12, he discusses how electromagnetic fields transform when we move from one inertial reference frame to another. On page 553, he claims He then considers how the electric field inside a conductor made up of two parallel rectangular plates...

Hi, I was reading about Euler-Bernoulli beam theory on Wikipedia and couldn't understand few points under the history section. Source: https://en.wikipedia.org/wiki/Euler–Bernoulli_beam_theory How were they making bridges and buildings back then if they were not 'trusting' science? Isn't...

$\dfrac{dy}{dx}=\dfrac{4y-3x}{2x-y}$ OK I assume u subst so we can separate $$\dfrac{dy}{dx}= \dfrac{y/x-3}{2-y/x} $$

I was watching this terrific lecture by David Tong and there was a section at the end from around 50:12 - 54:00 that I found particularly fascinating. I am very much a layman when it comes to these topics and my question may be silly, but what sort of ideas are there that state that all the...

Hello, I am reviewing how classical EM problems are treated when dielectric materials are involved. Maxwell's equations relate the following vector fields: ##E(r,t)##, ##B(r,t)##, ##D(r,t)##, ##H(r,t)##, ##J(r,t)## and scalar field ##\rho(r,t)##. The two constitutive equations are also needed to...

Is coherence the medium in which quantum waves propagate? Does coherence also exist in the future to flag decoherence events?

Hi, I just have a quick question about a problem involving Gauss' Theorem. Question: Vector field F = \begin{pmatrix} x^2 \\ 2y^2 \\ 3z \end{pmatrix} has net out flux of 4 \pi for a unit sphere centred at the origin (calculated in earlier part of question). If we are now given a vector...

In electromagnetic radiation, the electric field and the magnetic field mutually induce each other: but my impression is that it would be better to say that they are two aspects of the same wave, so that there is no time between them. However, an alternative would be that there would be that...

The calculations for the magnetic field produced by a uniformly rotating charged sphere can be found in basically every book on electrodynamics. I wonder what happen with the magnetic fields produced by rotating rigid solid that also present precession and nutation movements. The question comes...

Hello, If you have an appropriately oriented conductive ring in a constantly changing magnetic field, current will flow in the ring. There will also be a magnetic field associated with the current in the ring. I understand (maybe ... ) that the current is due to the electric field which is...

How can traveling wave exist on transmission line if wires are perfect conductors (how voltages can be different at different positions on one perfect conductor)? I mean electric fiels should be zero on equipotential source. I know if length is too long compared to wavelength, we get phase...

I have been at this exercise for the past two days now, and I finally decided to get some help. I am learning General Relativity using Carrolls Spacetime and Geometry on my own, so I can't really ask a tutor or something. I think I have a solution, but I am really unsure about it and I found 6...

Generally potential energies are associated with a system of two bodies. If more than two bodies are involved the total can be determined by summing the contributions pairwise. It would appear as though in any system, the potential energies are all internal to the system. However in classical...

a) 248*10^3 eV for 248kV Calculate the energy in J K=248*10^3*1.6*10^-19 =396.8*10^-19 J b) K=(1/2)mv^2 v=sqrt(2k/m) =sqrt((2*396.8*10^-19)/1.67*10^-27) =218^10^3 m/s c) r=mv/qB =1.67*10^-27*218*10^3/1.6*10^-19*1.5*10^-4 =15.17 mr=mv/qB...

Summary:: Seeding and visualization techniques Hi I am looking for resources where I can learn the following: Seeding strategies and algorithms for vector fields (texture-based, geometry, topological) Different techniques for visualizing vector fields (streamlines, glyph-based, LIC etc)

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Hi I made a simulation (comsol) of a piece of aluminum wire (r=1mm h=10mm) excited by 1A DC inside a sphere (r=10mm) of air. Here are the 3D plots: Since I ever only have 'seen' E&M fields depicted in textbooks and never in real life, I'm a bit surprised by the simulation result, I would at...

Hi, Here is a multiple choice question I am stuck with and would appreciate some guidance: The mark scheme for this paper says it is option A - 0N. I didn't get that at all. If a current carrying wire is in a magnetic field with some component perpendicular to the field then how can it be...

I know in 1939 Wigner published a theorem that all fields must be tensors from a couple of books, but can't find the proof anywhere. That obviously is an important result so does anyone know where I can find the proof? Another I haven't seen the proof of is the no interaction theorem. I wish...

Moderator's note: This thread is a spin-off of https://www.physicsforums.com/threads/what-are-the-most-important-open-questions-in-classical-physics.983671/ R. de Sangro, G. Finocchiaro, P. Patteri, M. Piccolo, G. Pizzella, "Measuring propagation speed of Coulomb fields", Eur. Phys. J. C 75...

Here are 2 questions that I have tried to answer and was hoping if these are right ways to go about it? Q1) Find the distance in meters (m) between centre of the Moon and the centre of the Earth, assuming that the Moon moves in a circular orbit with a period of 27.5 days. Take the mass of the...

The man floating inside the elevator travels through space at constant velocity, and soon reaches proximity to a planet. To an outside observer, the elevator appears to change course and accelerate towards the planet, so he reasons there is a force acting on the elevator, changing its course and...

I'm struggling to get the hang of killing vectors. I ran across a statement that said energy in special relativity with respect to a time translation Killing field ##\xi^{a}## is: $$E = -P_a\xi^{a}$$ What exactly does that mean? Can someone clarify to me?

I've attached my attempt at a solution below, I thought integrating it would be the best way to go but I'm just getting so confused and could use some help. This isn't my first attempt at a solution either I've been working on this for just under two hours now.

Hello! If I have some conductors in space, each at a certain potential (and assume everything is inside a conducting sphere, in order to have some well defined boundary conditions), we can calculate the potential everywhere (inside the sphere) by solving Laplace's equation. Hence a particle...

Summary:: I try to find the resultant force on "q". I think I have to find the value of Q, but I'm not sure. I Know F1 = k|q * 2Q| / 3² and F2 = k|q * Q| / 2² Hi, this is my first post on this forum I hope I posted in the right section. I try to find the resultant force on "q". I think I...

I need to do question 1. I understand the right hand rules but am lost on what to do here.

Hi. Since you can construct shells from a series of rings, why would there be an electric field inside a single ring but not inside a shell?