Fields Definition and 1000 Threads

The integral form of Maxwell's equation pertaining to induced electric fields is: ∮E(t0)⋅dℓ= −dΦ(t)/dt|t=t0Say for a long time, in some circular region there has been no B or E fields present. Then, there is a sudden constant increase of B field introduced in the middle. I know that information...

I am looking to find a combination of electric and magnetic fields that create something similar to the (d) crests Currently, I have the cracks flipped clockwise 90deg, so that the crests are concave up. And each crest can be defined by a parabolic function (which are uniform with each new...

Hello, I will be attending an undergraduate course called "Theoretical Physics" and I want to borrow some books from the library that cover the material of this course. I would appreciate any suggestions. The syllabus of the course is the following(I will be translating so I am sorry If...

Homework Statement What is the Net force (include direction) acting on charge Q2 due to Q1 and q? (ans: Fnet = 174N right) Homework Equations F=kQ1Q2/r2 E=F/QThe Attempt at a Solution I've figured out a) and b). It's just c) that's giving me trouble. I tried using the first equation - (9.0 x...

Hello, I am NF and just joined. I work on all kinds of diagnostic equipment and like to play with magnets and try to understand the correlation of all things charged.

In case of wire(having uniform linear charge density), without assuming the wire infinite long, why we can't take electric field perpendicular to the curved part of the cylindrical Gaussian surface?

Homework Statement The system consists of a long cylindrical anode of radius a and a coaxial cylindrical cathode with radius b (b <a). On the axis of the system has a thread with a heating current I, creates in the surrounding magnetic field. Find the smallest potential difference between the...

Hi everyone! I may have brought this up in an earlier thread, but thought I'd revisit this. I have browsed the forums for a while, and one common topic that gets brought up is about how competitive tenure-track positions are within physics (certainly within the US, and likely to be the case...

So why, in a classical sense, do we need to come up with the idea that fields carry momentum? I mean, charge 1 pushes charge 2 and charge 2 pushes back via Newtons third law. Of course, we can say that charge 1 creates a field that carrys the momentum, which then affects charge 2 etc. But...

Homework Statement Let's look at Q(a,c):Q where a is the third real root of 2 and c is a primitive cube root of unity. Then this extension is Galois and it's Galois group is isomorphic to ##D_3=S_3##. The proper subgroups of the Galois group are thus <(12)>,<(23)>,<(23)>,<(123)>. Let (12)...

Hi all, I'm about to buy the first volume of the series by Weinberg, but I'm a little worried about the edition, see I have a lot of requisites for a book before buying it. I've seen in the library the old hardcover edition and it looks fine for me: it's not written too small and the book even...

Homework Statement Through my exploration/experimentation, I came up with this little conjecture: Let ##F## be a field and ##x## some element in the field. If there exists a natural number ##m## such that ##x^m = 0##, then ##x=0##. In other words, a field contains no nontrivial nilpotent...

Homework Statement I am trying to express ##T(\phi(x1)\Phi(x2)\phi(x3)\Phi(x4)\Phi(x5)\Phi(x6))## in terms of the Feynman propagators ##G_F^{\phi}(x-y)## and ##G_F^{\Phi}(x-y)## where ##G_F^{\phi}(x-y) =\int \frac{d^{4}k}{(2\pi)^{4}}e^{ik(x-y)} \frac{ih}{-k.k - m^2 -i\epsilon} ## and...

I'm trying to understand potential energy, especially with regard to gravity. There's a double negative that's difficult to grasp: The direction of the force is negative because the vector points radially outward and the force of gravity is directed inward, and the work done to bring an object...

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...

Homework Statement A dielectric sphere with the electric and magnetic susceptibilities ε1 and µ1 is rotating with angular frequency ω in a constant electric field E~ in a medium, characterized by the parameters ε2 and µ2. The angle between the rotation axis and the direction of E~ is α. Find...

Wick's theorem allows one to write a free theory time-ordered ##n##-point correlation function as a product of free theory time-ordered ##2##-point correlation function. The procedure involves the pairwise Wick contraction of fields such that external fields are not paired up each...

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...

Consider the following time-ordered correlation function: $$\langle 0 | T \{ \phi(x_{1}) \phi(x_{2}) \phi(x) \partial^{\mu}\phi(x) \partial_{\mu}\phi(x) \phi(y) \partial^{\nu}\phi(y) \partial_{\nu}\phi(y) \} | 0 \rangle.$$ The derivatives can be taken out the correlation function to give...

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...

Homework Statement What are the electric and magnetic fields due to a charge that is moving with uniform acceleration? (Non relativistic) Homework Equations Retarded solutions for the vector and scalar potentials. The Attempt at a Solution My attempt might be an overkill because I'm using the...

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...