Fields Definition and 1000 Threads

For instance, a current through a wire makes a magnetic field around it, and the changing magnetic field creates an electrical field, which then creates a magnetic field, and so on. Are these fields pulling on the wire? If so, how exactly? Isn't every piece of the wire dx electrically neutral...

When I was taught about temperature in high school, I was told that substances that are hot have molecules that move fast, while substances that are cold have molecules that move slowly. I was also told that everything moves towards greater disorder or entropy. This is apparently because there...

So, I'm working on ODE at this point, and unfortunately I don't have the time to learn all of the Mathematica input for at least a few months. But, I was hoping someone could tell me how to graph direction fields of ODEs, either with the Mathematica input or free-form? Looking through the...

I'm so confused here. If we make the transformation of the coordinates x -> x', are we not suppose to consider the transformation of the coordinates only $$ \phi(x) \rightarrow \phi(x') $$ ? Then why are they writing $$ \phi(x) \rightarrow \phi'(x') $$ ? If $$ \phi(x) $$ is a scalar function...

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A dipole antenna will have near fields and far fields. Can both the near and far fields can be decomposed into an infinite sum of plane waves? If so, are the plane waves for far fields and near fields of different type or class? Near fields must die off at infinity but far fields do not. Thanks.

Sorry to open a new thread. There are plenty of threads on PF dealing with the issue of "wave-particle duality". Although not unanimously, many agree that the concept of "wave-particle duality" is outdated. Electrons, photons and all of the underlying entities are neither waves nor particles...

As far as I know a field is spatial&time region in which each point has a physical quantity associated with it (vector or scalar). We know from GR that in the case of the gravitational field it is due (only?) to a curvature of space. But what about the other fields? What gives the value...

When we make our lagrangian invariant by U(1) symmetry we employ the fact that nature doesn't care how I describe it, but, how come that I can associate the real physical particles with the coordinates I use to describe? Even though gauge symmetry is not a physical Symmetry,

I am not really sure which direction i am moving in with this solution

while browsing for new propulsion methods I found the following interesting: https://en.wikipedia.org/wiki/Radiation_pressure "Radiation pressure (also known as light pressure) is the mechanical pressure exerted upon any surface due to the exchange of momentum between the object and the...

Why don't interposing objects interfere with the integrity of a field's energy between the source and its absorber? For example, the Sun's gravitational field spreads uniformly through space. If there are interposing objects like Mercury or Venus between the Sun and the Earth, why don't they...

Question: Eq. 12.109: My solution: We’ll first use the configuration from figure 12.35 in the book Griffiths. Where the only difference is that v_0 is in the z-direction. The electric field in the y-direction will be the same. $$E_y = \frac{\sigma}{\epsilon _0}$$ Now we're going to derive the...

Let's say we have some observer in some curved spacetime, and we have another observer moving relative to them with some velocity ##v## that is a significant fraction of ##c##. How would coordinates in this curved spacetime change between the two reference frames? For example, imagine a...

For an upcoming presentation I am looking for a topic which covers both the field of oscillations/waves and particles in electromagnetic fields. Do you have any interesting ideas for a possible topic? Many thanks for your help in advance!

I am following along with Ballentine's (in his *Quantum Mechanics: A Modern Development*) construction/identification of symmetry generators as operators representing the standard observables (observables here being used in the sense of a physical concept which have operators representing them)...

Part a) My solution: Big R basically becomes r, and the electric and magnetic field lines are doubled because of superposition principle. Am I right?

Hi everyone. I thought I would pose the question in the title to those on Physics Forums that are currently working in physics research (either as faculty, postdoctoral fellows, or graduate students). I was thinking of setting up a poll, but the last time I had asked a similar question I...

I've been trying to pick up the fundamentals of electromagnetic theory and I reckon I'm doing alright, but I've run into a some questions about how magnetic fields behave in an anisotropic fluid medium like the ocean. There is an awful lot of conflicting information online. Ultimately, I'd like...

I had difficulty showing this no matter what I tried in (a) I am not getting it. Here for p(t) in K[[t]] : ## |p|=e^{-v(p)} ## where v(p) is the minimal index with a non-zero coiefficient. I said that p_i is a cauchy sequence so, for every epsilon>0 there exists a natural N such that for all...

Would i assume that fg = fm (force gravity holding straight wire down is equal to the magnetic force) and isolate for I? Help if you're available please!

Hey all. I started messing around with making a simulation involving charged particles moving in magnetic and electric fields and I was wondering if anyone had any good resources on the subject. I should be fine on equations, as I already have a book that should have everything I need about the...

I had 2 small magnets in my mouth for distraction while working on something else,and I had this wierd question.the two magnets were not that strong,so just a force was easy to separate them with my teeth.then they would attract to be attached to each other and then the question hit me,the 2...

Let ##L/k## be a field extension. Suppose ##F## is a finite separable extension of ##k##. Prove ##L\otimes_k F## is a semisimple algebra over ##k##.

I suppose it can shield only the external magnetic field, not the field of the magnet itself. But I am not completely sure.

hi, i have seen lagrangian density for spin 0 , spin 1/2, spin 1 , but i am not getting from where these langrangian densities comes in at a first place. kindly give me the hint. thanks

Trying to understand something fundamental about how magnetic fields are generated by moving electrons in a conductor. I have read many forums, studied Emag and am left with more questions. Looking for some practical insight not Bio-Savart derivations, etc. These still do not explain why the...

I know that I’m supposed to use proportional reasoning, but where does electric field even fit in? For whatever equation, I know I’m supposed to see how increasing the voltage by either 2 and 4 volts related to electric field. If electric field is the same as “U”, then wouldn’t it be...

Sir, heat is proportional to the vibration of atoms. If the vibration of atom is restricted to large extent due to intense gravitational field but has high quantity of total energy in the atom then does it mean it has high tempearture like the stars?

I made a tool for calculating and visualizing how the electric and magnetic fields transform under a Lorentz boost. Thought I'd share it here, in case anyone finds it interesting. https://em-transforms.vercel.app/

We define Electric Field Intensity vector at a point as the force experienced by a unit positive charge kept at a point. Is it correct to define B vector similarly that is, is B vector the magnetic force acting on an unit magnetic north pole and is it correct to call B vector Magnetic Field...

Say we have a long solenoid with a current that is fluctuating in time. Then the changing magnetic flux in the solenoid will induce an electric field around the outside of the solenoid (Faraday's Law). This induced electric field is not conservative and therefore cannot have a corresponding...

So changing magnetic fields induce electric fields (Faraday's law when the magnetic field is changed by either moving the source or by changing the current in the source that's causing the magnetic field, ie. we're not moving the conductor where an emf is induced so there's no f=qvXB). Also...

Hello : Trying to find references on drawing direction fields of higher order differential equation by hand as 1st step then by computer , do you know any reference I can read ( PDF , books ,...) , and hope it is not only some short notes Best regards HB

I asked myself why different scientists understand the same thing seemingly differently, especially the concept of a metric tensor. If we ask a topologist, a classical geometer, an algebraist, a differential geometer, and a physicist “What is a metric?” then we get five different answers. I mean...

Assume I could produce a stream of calcium ions from a 2nm diameter nanotube by pushing them through the nanotube using coulomb repulsion. Assuming these coulomb repulsed ions produce a stream of entangled ions which then create a slowly emitting quasi static electric (near) field. Even if...

IHES = Institut des Hautes Études Scientifiques (IHÉS)https://www.ihes.fr/en/ Hugo Duminil-Copin, Mathematician, Permanent professor since 2016 https://www.ihes.fr/en/professeur/hugo-duminil-copin-2/ https://www.ihes.fr/~duminil/ - personal webpagehttps://www.ihes.fr/en/scholars/professors/

Physicists say the Higgs Field is like syrup and slows particles down from the speed of light. Wouldn’t it be easier and more correct to say there are no particles, just fields, and the strength of the coupling of the electron, photon, quark etc. fields with the Higgs field determines their...

I seem to hear about huge astronomical events that generate radio waves seem to come from objects with huge magnetic fields, such as neutron stars and black holes. Does that mean magnetic fields only come from the radio end of the spectrum, and not higher frequencies, like IR, UV, X-rays, etc?

Does electron beam in empty space generate magnetic fields around them just as with current in conductor. If yes, then is it experimentally proven that two parallel electron beam would attract each other.

Hi I am new to the forum. I am a investor, athlete, and a "field physicist." I got a bachelors in physics and Hopefully soon can get a phD. I like to do basic experiments that demonstrates physics.

I wonder if the following makes sense. Suppose we want to multiply ##\int_0^\infty e^x dx\cdot\int_0^\infty e^x dx##. The partial sums of these improper integrals are ##\int_0^x e^x dx=e^x-1##. Now we multiply the germs at infinity of these partial sums: ##(e^x-1)(e^x-1)=-2 e^x+e^{2 x}+1##...

I do not understand why electric fields cannot cross. Can't you just sum the two electric fields vectors to get a net electric field?

How would you unify the two Lagrangians you see in electrodynamics? Namely the field Lagrangian: Lem = -1/4 Fμν Fμν - Aμ Jμ and the particle Lagrangian: Lp = -m/γ - q Aμ vμ The latter here gives you the Lorentz force equation. fμ = q Fμν vν It seems the terms - q Aμ vμ and - Aμ Jμ account for...

The title pretty much covers it. I'm having to calculate the field induced inside the human body by an antenna in the near field (essentially, a phone placed close to a user's head), and I'm drawing a blank on how to relate the field generated by the antenna to the field induced inside the...

Einstein famously said “{Thermodynamics} is the only physical theory of universal content, which I am convinced, that within the framework of applicability of its basic concepts will never be overthrown.” I don't think any of us want to argue with Einstein, but it's worth noting the "within the...

Hi everyone, In his book "Quantum field theory and the standard model", Schwartz derives the position-space Feynman rules starting from the Schwinger-Dyson formula (section 7.1.1). I have two questions about his derivation. 1) As a first step, he rewrites the correlation function as $$...

I was reading Diagrammatica by Veltman and he treats the photon field as a massive vector boson in which gauge invariance is disappeared and the propagator has a different expression than in massless photon. After some googling, I found that this is one way to formulate QED which has the...

Hi. A electromagnetic wave consists of an electric and a magnetic component. I believe that the electric field strength is measured in volts per meter. The magnetic field I think is measured in Tesla. Let's imagine that I measure the electic field strength of two different radio stations and...