Fields Definition and 1000 Threads

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...

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?

I am reading Dummit and Foote Section 13.4 Splitting Fields and Algebraic Closures In particular, I am trying to understand D&F's example on page 541 - namely "Splitting Field of x^p - 2, p a prime - see attached. I follow the example down to the following statement: " ... ... ... so...

The photon field has two physical degrees of freedom (dof): its two transverse polarization directions. But what about non-abelian gauge theories? What about N massless spin-1 particles that transfom under SU(N), how do I count their degrees of freedom? Gluons, for example, are massless spin-1...

Dummit and Foote Exercise 1 on page 545 reads as follows: Determine the splitting field and its degree over \mathbb{Q} for x^4 - 2 . ------------------------------------------------------------------------------------------------------ I have started on the solution to this exercise as...

Homework Statement The permittivity of a given medium is given by the equation ε = \begin{pmatrix} ε_1 & 0 & 0\\ 0 & ε_1 & 0\\ 0 & 0 & ε_2 \end{pmatrix} A wave is traveling in the \hat{k} direction in this medium where the unit vector \hat{k} is defined as \hat{k} =...

Homework Statement The differential equation is y' = y^2 Draw a direction field for the given differential equation. Based on the direction field, determine the behavior of y as t →∞. If this behavior depends on the initial value of y at t =0, describe this dependency.Homework Equations The...

Homework Statement Let K be the closure of Qu{i}, that is, K is the set of all numbers that can be obtained by (repeatedly) adding and multiplying rational numbers and i, where i is the complex square root of 1. Show that K is a Field. Homework Equations The Attempt at a...

Hi, upon studying vector calculus and more precisely about the curl I stumbled upon a question : why is it that there is always a potential function of a vector field when the curl of this vector field is equal to 0?

Hi folks! I've considered a career as a technical writer for the mechatronics/electronics fields for a while now (yes I have engineering education), but I'm wondering if I'd want to work in a European country like Netherlands, Germany...do they need technical writers in English? Or, do they...

Can an electromagnetic wave be deflected by electric or magnetic field.

reading this page : http://hyperphysics.phy-astr.gsu.edu/hbase/electric/potsph.html it says "The electric field inside a conducting sphere is zero, so the potential remains constant at the value it reaches at the surface:" if the electric field inside the sphere is 0, then wouldn't that...

Homework Statement Consider two “circulating” electric field configurations. Expressed in polar coordinates (s,φ,z) they are: (these expressions are not dimensionally correct) 1. E = (0,s,0) 2. E = (0,1/s,0) a. Calculate ∇×E for both configurations. b. Note that ∫E⋅dl≠ 0 in either...

Homework Statement An infinitely long, uniformly charged straight line has linear charge density λ1 coul/m. A straight rod of length 'b' lies in the plane of the straight line and perpendicular to it, with its enared end at distance 'a' from the line. The charge density on the rod varies...

Hi guys! I need help on a problem from one of my GR texts. Suppose that ##\xi^a## is a killing vector field and consider its twist ##\omega_a = \epsilon_{abcd}\xi^b \nabla^c \xi^d##. I must show that ##\omega_a = \nabla_a \omega## for some scalar field ##\omega##, which is equivalent to showing...

I wasn't sure where to post this question, so I posted it here. As the title suggests, I want to know how to calculate (at least roughly) the electric field induced by excitation and ionization of a material (such as a metal) using a high intensity laser. My final goal is to compare the...

I started working for a multinational FMCG after graduating in Mechanical Engineering. With one year as of now in it, I somehow feel this is not a path to take for lifetime. I am paid well and my work is mix of management and engineering (Since it's the maintenance and I am the process owner)...

Whenever I ask someone what an electromagnetic field is exactly, they say that science does how questions, not why questions (which doesn't really make sense in this context, maybe i worded my question differently). We say that there are four fundamental forces that create the universe we live...

hi i know what is coherent state, but i read this text in an article and i don't understand this " if we wish to describe long range macroscopic forces, only bosonic fields will do, since fermionic fields cannot build up classical coherent states. " can you explain it for me, how...

In the absence of external forces, the electric field inside a conductor is supposed to go to zero. This is because if any field were to exist, then the charges in the conductor would experience force and continue moving until they canceled the field. However, is it true that for any system a...

To keep it simpler let take the electromagnetic (EM) field. A photon, in one perspective, can be described as an excitation of the EM field. Is the EM field omnipresent in all (time-space) the universe? or Does the photon creates/emit an EM field around it?

Basically my question is this: could we, in principle, formulate all of classical electromagnetic theory purely in terms of the force one charge exerts on another, or do we need to include the electromagnetic fields in order to arrive at a complete theory? ("complete" as in equivalent to...

It is well known that all sorts of systems tend towards minimal potential energy. I was wondering if this applies to static electric fields also, i.e. is an electric field such that it's energy integrated over all space is minimal? For example if we have a bounded source free region and if the...

So I've been simulating a really simple geometry using ANSYS Maxwell. It is a cylinder only and I am looking at the \overrightarrow{B} and \overrightarrow{H} fields in order to see their relationship between them when the material is magnetized in the circumferential direction. I used a...

when we say , electron acts like a wave ,does we mean to say that it produces electric and magnetic field or em waves varying with distance and time

In Srednicki's textbook (chpt 5) he has an expression: \int d^3k f(k) \int d^4x (\partial^2 e^{ikx}) \phi(x) and he wants to integrate by parts in order put the Laplacian on the field \int d^3k f(k) \int d^4x (e^{ikx})\partial^2 \phi(x) instead of the the exponential. He says that...

Hi. I am researching magnetic fields and getting no where. I am writing a computer programs to calculate Magnetic force between 2 magnets that can act both + to + and + to -. Given the movement of the magnets, the program will be calculating minute movements and compensating for changes in...

I did some research on Wikipedia, and I quote from the write up on Real Particles: "The term(Virtual Particles) is somewhat loose and vaguely defined, in that it refers to the view that the world is made up of "real particles": it is not; rather, "real particles" are better understood to be...

If a body was between two gravitational fields, would it feel a tension force like the two gravitational forces were pulling it apart, or would the two fields cancel each other out and the body wouldn't feel anything? I'm assuming in this scenario that both fields are big enough so that there...

Homework Statement Let w be a primitive n-th root of unity in some finite field. Let 0 < k < n. My question is how to rationalize [\tex]\dfrac{1}{1 + w^k}[\tex]. That is, can we get rid of the denominator somehow? I know what to do in the case of complex numbers but here I'm at a loss...

Homework Statement A,B,C,D are four 'thin',similar metallic parallel plates,equally separated by distance d,and connected to a cell of potential difference(V) as shown in the attachement. Write the potentials of A,B,C,D. If B and C be connected by a wire,then what will be the potentials...

What impact will a extremely high frequency of ultrasound have on a electromagnet? Will the magnetic field also oscillate at that frequency? What about a conductive wire transmitting electrical current? Will ultrasound on the wire cause the magnetic field to oscillate?