Fields Definition and 1000 Threads

hello, In electromagnetism from the Lagrangian formulation, one can defines a canonical momentum and applying Euler's equation to that momentum gives the lorentz law. To get the Lorentz law, one uses a vector identity, only available because it is said the speed V does not 'feel' the...

Hello! Talking about propagation of an electro-magnetic field in a non-isotropic medium, I've got some troubles with the expression in object, used to show the Faraday rotation of the polarization of a field. Homework Statement An electro-magnetic field enters a particular medium...

I am hoping for a name change soon, but I am considering the career implications for changing my name. The name I am planning on doesn't match my race, but California (where I live) is a melting pot and there are white Lopez and Martinez and Asian Masons. People will know that I changed my name...

In the case of swarms of particles, the stress energy tensor can be derived by considering the flow of energy and momentum "carried" by the particles along their worldlines. Is there a way to interpret the field definition of the stress energy tensor from Wald, p455 E.1.26 T_{ab} \propto...

Greetings, PF forum members! I have had a sudden interest in Active Radiation Shielding (ARS), and as such, an increased interest in magnetics. I have had trouble locating any information regarding the possibility/impossibility of altering magnetic fields in such a way that changes the field's...

Hey guys, I was hoping to pick the brains of some of you more experienced students and professionals. I have roughly 2 and 1/2 years left before I receive my B.S. in physics and the farther along I get in my studies the more I realize that there is a lot that I still don't know, go figure. For...

Hello, I'm stuck on this question, and it's really annoying me. I scanned the page so it has a bit more context. It's question 3.7: "A long wire carrying a steady current is placed in a uniform magnetic field parallel to it's own length. What is the shape of the magnetic field lines...

I'm reading a book that deals with Gauss's law for electric fields in its differential form. I'm stuck now on a page that discusses taking deriviatives of the equation for a vector field: → A I'm familiar with the rules for deriviatives of products and quotients but unfortunately I cannot...

Hi all, can the angular frequency of a electric waves be used to determine the wavelength using the following; ω=2πf rearranging for the frequency, and using the following; E=hf=(hc/λ) or can this formula no be used as it is dealing with photons?

An Electric field has the following form in free space; E=Re{Eo exp[j(ωt-κy)\hat{i} I am confused as to why a unit i vector is in the expression for an electric field oscillating in the Y direction? and also what does the Re mean ? i was reading somewhere about it being to do with...

Hello, This thread is about the two books by Naber: https://www.amazon.com/dp/1461426820/?tag=pfamazon01-20 https://www.amazon.com/dp/0387989471/?tag=pfamazon01-20 The topics in this book seem excellent. They are standard mathematical topics such as homotopy, homology, bundles...

I think everyone has heard about equipotential lines and equipotential surfaces; such as lines of force too. My question is: exist surface of force too? If yes, what is it?

Hi, I know this question may seem a little trivial, but is there any real difference between \left (\partial_{\mu} \phi \right)^{\dagger} and \partial_{\mu} \phi^{\dagger} and if so, could someone provide an explanation? Many thanks. (Sorry if this isn't quite in the right...

How do you determine the direction of fields at the location o the source. if given that the charge is negative, the electrostatic force is away from the source . Do you reason that since the test charge is positive and the charge is negative, it will go towards the center?

I have a question pertaining to mathematically possible E fields. I've always known the curl of the field has to be zero for the field to be a possible electric field, but is this the sole determining factor? What about if the potential is some wonky function that doesn't seem plausible, and...

Homework Statement An ink drop with charge q = 3 ✕ 10-9 C is moving in a region containing both an electric field and a magnetic field. The strength of the electric field is 8E5 N/C and the strength of the magnetic field is 1.3 T. At what speed must the particle be moving perpendicular to...

Problem: You can make an electromagnet by wrapping wire around a wire and connecting the ends to a battery. If the battery is connected so that current wraps up in the front and down in the back, which direction will the magnetic field of the nail point? Answer: the magnetic field of the nail...

Homework Statement What is the centripetal acceleration of a satellite orbiting Saturn at the location exactly one Saturn radius above the surface of Saturn Homework Equations Ac=v^2/r In the previous question found out that the fg at that location is 1/4 of 36.0 N The Attempt at...

\HugeHomework Statement Consider a state of the EM field which satisfies \left\langle \textbf{E}_x(\vec{r})\right\rangle =f(\vec{r}) Find a coherent state which satises these expectation values.Homework Equations \textbf{E}(\textbf{r})=\frac{i}{\sqrt{2 V}}\sum _{\textbf{k},\lambda }...

Homework Statement A single isolated proton is fixed on a surface. Where must another proton be located in relation to the first in order that the electrostatic force of repulsion would just support its weight? 2)Two identical objects have charges from +6.0*10^-6 and -2.0*10^-6...

Hi guys! So I just need help in one tiny thing. Does anyone know a good book that can thoroughly explain physically and mathematically diamagnetism in plasmas within magnetic fields? I would really appreciate the help guys! Also, I am very much familiar with vector calculus (also tensor calculus...

If we know that the Polarization P in LIH dielectrics is proportional to the net field inside the dielectric according to: P = ε0χeE...(1) And we know that D = εE...(2) Does it not follow that we can ascertain the polarization directly from the applied (free charge) field, since we...

Homework Statement 5. An alpha particle ( 2 protons and 2 neutrons) is placed between two stationary, charged objects. It is 0.0030 m to the right of the object carrying a +1.0 X 10-12 C charge, and 0.0020 m to the left of the object carrying a -2.0 X 10-12 C charge. Draw a picture and...

Do moving charges 'create' or 'induce' magnetic field around them? I believe that induction is a phenomenon in which the behavior of one object depends on the behavior of another object provided they interact with each other. In this case, the moving charge is just surrounded by air or vacuum...

I would like to know whether there is any difference in Electromagnetic field and Magnetic field. I know their source but I'm curious to know whether they are different in nature? I also wants to know whether Magnetic Shield Material works same way on Electromagnetic or Electrical field...

I have an enigmatic problem that I cannot explain. I have on video the results of this experiment at particular location where I believe bio-electromagnetic weapons testing is occurring. Does anyone have theories of why the following occurs? I have several sized physical compasses that...

Homework Statement This isn't homework or coursework as such, but i thought it may be the best place to ask this question. The last time i posted in the other section it was deleted! Im considering the case of an electrode of finite width L in the x direction. The y direction is...

Homework Statement The electric field on the x-axis due to a point charge fixed at the origin is given by E=(a/x2)i, where a = 6.00 kVm and x is not equal to zero. a) Find the magnitude and sign of the point charge b) Find the potential difference between the points on the x-axis at x=1...

ability to feel electrical/magnetic fields? are there anyone here who has worked in a manufactoring environment? I have found that when stepping out into areas with higher amplitude electrical fields, I get a strange feel where my chest feels heavy and breathing becomes more difficult. Any...

A piece of iron is placed in exterior magnetic field(+B1,"Going right"), with H = 100 Oe At the same time, there is another opposite magnetic field acting on that same iron (-B2,"Going Left") with H = 10 Oe They oppose each other, the iron is magnetized initially by B1, what happens when the...

The vector field F=<y,x> looks exactly like the the direction field for the system dY/dt = {dx/dt = y} {dy/dt = x} A few questions on this: Are the direction field of a system of ODE's the same as a vector field of calculus? In vector calc we take the line integral of a vector field...

Homework Statement Consider a region of space containing static free charge density ρ(r) and current density j(r). What two physical laws determine the electric and magnetic field in this region? State the integral form of each law, showing the explicit dependence of each on ρ(r) and j(r)...

Electron is a charge, what means concrete configuration of electric field, growing to infinity in the center (if it would be a point particle). It is also a magnetic dipole moment - concrete configuration of magnetic field growing to infinity. And a mass - concrete configuration of gravitational...

Homework Statement The unit of magnetic flux is named for Wilhelm Weber. A practical-size unit of magnetic field is named for Johann Karl Friedrich Gauss. Along with their individual accomplishments, Weber and Gauss built a telegraph in 1833 that consisted of a battery and switch, at one end...

This is probably a minor point, but I have seen in some QFT texts the Euler-Lagrange equation for a scalar field, \partial_{\mu} \left(\frac{\delta \cal{L}}{\delta (\partial_{\mu}\phi)}\right) - \frac{\delta \cal L}{\delta \phi }=0 i.e. \cal L is treated like a functional (seen from the...

Hi again: I'm curious as to someone understands well the difference between a Reeb Vector Field and a general Contact field; a Contact field is one whose flow (even when only defined locally, i.e., in non-complete manifolds) preserves the contact structure, but not the form, i.e., if C is a...

Greetings PFers, Can someone help explain to me the difficulties of designing a device which utilizes static electric fields to map an objects’ internals and externals? My understanding is that as a electric field propagates through matter, it encounters absorption. I envision a device...

Hello, I am having a lot of trouble in determining the difference between an electromagnetic field and electromagnetic radiation. Is an electromagnetic field caused by electromagnetic radiation within the space of which the field acts over? However if I am right a point charge that is not...

Hi, All: Let w be a contact form , say in ℝ3, or in some 3-manifold M i.e., a smooth, nowhere-integrable 2-plane subbundle of TM. I'm trying to see how to find the Reeb field Rw associated with w. My ideas are: i) Using the actual definition of the Reeb field associated with a contact...

I am reading Nicholson: Introduction to Abstract Algebra, Section 6.3 Splitting Fields. Example 1 reads as follows: (see attachment) -------------------------------------------------------------------------------------------------- Example 1. Find an extension E \supseteq \mathbb{Z}_2 in...

Homework Statement The diagram shows the magnetic field between like magnetic poles Homework Equations Point C is the exact middle of the region between the poles. Explain why the strength of the magnetic field at point C is zero? The Attempt at a Solution The like poles repel each...

If there's a point charge Q at the center of a spherical surface(of radius a) made of conducting material that is connected to earth, why is the electric field past r>a zero ? Doesn't it imply that the spherical surface becomes charged with -Q ? And why is that? What would be the...

Just need someone to tell me if I'm doing this right. If I have accelerated a particle in which the mean free path is 50nm and I need the collision to be 5eV would this be correct in determining the required electric field strength? 5/.00000005 = 100MV/m

Hi, I'm reading www.phys.ethz.ch/~babis/Teaching/QFTI/qft1.pdf and trying to understand the canonical quantization of the Schrodinger field. In particular, the Lagrangian: \begin{equation} \mathcal{L} = \frac{i}{2}\psi^* \partial_0 \psi - \frac{i}{2}\psi \partial_0 \psi^* +...

Hello all, thanks for reading. I'm in the process of designing a machine that will move a hall effect sensor in 3 dimensions through a magnetic field and record readings. Before I started the design however, I wanted to see if there would be huge problems in how I envision this machine...

Homework Statement The electric field E1 is constant over the whole of one surface of parallelepiped and directed out of the surface. On the opposite surface is field E2 constant over the surface and is directed into the surface. the two surfaces forming an angle of 30 ° with the...

According to my textbook, the electrical field is defined as E = F/q where q --> 0, because we want the test charge to affect the other charges around it in the least possible way. It then goes on to say that qE = F is true for charges not strong enough to move the other charges. Why is that, if...

This isn't really isn't strictly a homework question; there wouldn't be solutions provided. I know the answer -- if anything it follows from other electrostatic results. I would like to make sure what I have written down as steps are legitimate. I will also skip ahead some steps because typing...

Problem #1 A slab of thickness 2a (extending infinitely in the y and z directions) with non-uniform charge density is parallel to the yz-plane. The charge density is given by ρ(x) = γx2, -a < x < a where γ is a constant. 0, a < |x|. (a) Use Gauss's law plus symmetry to find...

What determines if a ligand will have a strong electrical field?