Fields Definition and 1000 Threads

Every conservative vector field is irrotational? Every irrotational vector field is conservative? Every solenoidal vector field is incompressible? Every incompressible vector field is solenoidal?

Why aren't force fields such as magnetic, electric and gravitational fields considered as a violation to law of conversation of energy?? :confused:

What field would you say is the most exciting in engineering/physics? I'm defining engineering/physics very loosely, so don't worry if your field is more biology than physics or whatever. So anyway; Which has the most potential for financial profit and entrepreneurship? Which has the most...

Homework Statement Which one of the following statements best explains why it is possible to define an electrostatic potential in a region of space that contains an electrostatic field? A) Work must be done to bring two positive charges closer together. B) Like charges repel one another...

This is something that has bothered me a lot since I tend to overanalyze and worry alot. In college, I studied physics and math, but decided that I wanted to get into engineering, so I applied and got a job at a defense contractor. However, I was terminated quickly because I was unable to get an...

Hi, please help me .. How can I derivative covariant and contravariant fields? as in the attached picture Thanks.. http://www.gulfup.com/?tNXcaN w.r.t alpha

why all EM waves are sinusoidal ? or this is not true at all, i.e., EM waves of other waveforms do exist ? the above 2 questions are among the most vague in classical EM theory, of which i studied many topics in collage as an electrical engineering student, and i liked the subject so i kept...

I believe I understand the basics of some fields, but I am unsure about the correctness of all of my knowledge. - All particles are excitations of their field (If it's a fermion) and the field they mediate (If it's a boson) - Electron repulsion is created by the exhcnage of virtual photons...

Left invariant fields on a group G satisfies a lie algebra; say we have an n-dimensional Lie algebra for which the fields ##{X_1, \ldots , X_n}## is a basis. Let these satisfy the algebra ##[X_a, X_b] = c_{ab}^c X_c##. Suppose now that we have a Riemannian manifold with killing vectors...

Hi folks! I'll start by admiting that I'm a cockroach compared to Einstein or Hawking, and I think that due to Hawking's great mind, maybe he wrote the book in a way he found conspicuous. But I don't have Hawking's IQ, and for me is definitely harder to understand the concept of "Time...

Homework Statement Experiments show that a steady current I in a long wire produces a magnetic field B that is tangent to any circle in the plane perpendicular to the wire and whose center is the axis of the wire. Ampere's Law relates the electric current to its magnetic effects and states...

Capacitors are popular candidates for explaining electric fields. The phenomenon becomes really apparent with the aid of a leiden jar ...which is really just a capacitor. Anyways, as long as you're cranking the handle on the electrostatic machine, the charge is going to build and build until I...

Electric fields vs magnetic fields? Ok, so in class last week, I had asked my professor about using the Lorentz Force Law to solve a particular problem. When he responded with "we only have a magnetic force from the current in the wire, so we don't have to worry about an electric field," that...

This isn't a homework question, however I'm curious if displacement fields can simply be added to find the total displacement field at some point. My instinct tells me this should be true. For linear media, D=εE. Since electric fields can be superimposed upon each other, shouldn't the same be...

Homework Statement Question 1. General Plane Waves. We may represent a general electromagnetic plane wave by (real part of the complex exponentials) E=E_{0}*e^(i*k*r-iwt) B=B_{0}*e^(i*k*r-iwt) Show that Faraday's Law becomes iwB0=-ik x Eo Homework Equations dB/dt=- curl of E The...

Hello! Well, I guess it's all in the title, really. I was reading about k-essence, and it was described as a scalar field having a non-canonical kinetic term. I did a bit of browsing and couldn't find a clear explanation of what, exactly, a non-canonical kinetic term is. Any help would be...

I'm currently taking Physics II and had a question. I'd ask my professor, but he's out of town until Monday and this is driving me crazy. Anyway, we recently started learning about magnetic fields. So far, I'm grasping most of it no problem. One thing that is throwing me off though is how...

I have an idea for a research project in neurobiology but I have only a limited background in these fields (I currently work in web development). Is there any way to gain the necessary skills and have access to the right equipment to carry out the experiments I want to do without going back to...

Conceptual question help--Electric fields, potentials, etc. Homework Statement 1) Assume that the electric field E is equal to zero at a given point. Does it mean the electric potential V must also be equal to zero at this point? If not, provide an example to prove your answer. if you think...

I just though of this and though "it's abstract math meeting physics, so probably not". After looking up fields in several abstract algebra books I thought that maybe fields in physics were called as such in physics because they share something with the mathematical structure of fields in group...

Homework Statement Consider a line of length L=0.950 m and uniform positive charge per unit length λ=2.9 μC. Point A is a distance x=0.23 m from the center of the line, while B is the same distance from the line but a distance y=0.28 m farther along the line; point C is a distance z=0.050 m...

My class hasn't delved into Gauss's Law much besides describing conductors at electrostatic equilibrium to have no net electric field or force within itself. For the picture, the question is: What are the magnitudes of the electric fields at: 1) r = a 2) r = 3/2 a 3) r = b...

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...