Fields Definition and 1000 Threads

Hi. Given a one-parameter family of maps such as Φt : ( x , y ) → ( xet + 2et -2 , ye2t ) the velocity vector field at t=0 is given by d(Φt)/dt = (x+2) ∂/∂x + 2y ∂/∂y My question is ; how does differentiating a vector function Φt with respect to t result in a scalar function ? Thanks

Homework Statement We were asked to use a Hall probe (in units of Guass) to measure the magnetic field strength in 0.5 cm increments away from a wire carrying 4 A of current. As we got further and further away from the wire our B value got smaller and smaller. Eventually they became negative...

This is a continuation of a previous thread in which I was informed my TA was mistaken on an aspect of magnetism. This thread is just to verify another problem within the homework is correct. Other threads will be posted to continue. 1. Homework Statement A) What is the magnetic flux...

So the main reason I'm posting about this problem is that one of the teaching assistants helped me with this problem, but a buddy of mine got something different on part A and part B (Assess). So I wanted to post up here and see what you guys say. 1. Homework Statement The loop in the...

If fields fill all of space, how do they have room to move? Those tile games we had as kids always required one empty space to slide the tile into.

My question is, how does one get a wave function for a 'combined' spin-1 and a spin-0 field? How is this possible? I have only been able to find combined states for equal spin identical particles. If you don't understand my question, I'll be glad to reword it.

Using the electric field as an example: Does modern physics see the electric field as one universal field covering the entire universe or because of the vast distances involved it can be several?

In the srednicki notes he goes from $$H = \int d^{3}x a^{\dagger}(x)\left( \frac{- \nabla^{2}}{2m}\right) a(x) $$ to $$H = \int d^{3}p\frac{1}{2m}P^{2}\tilde{a}^{\dagger}(p)\tilde{a}(p) $$ Where $$\tilde{a}(p) = \int \frac{d^{3}x}{(2\pi)^{\frac{3}{2}}}e^{-ipx}a(x)$$ Is this as simple as...

How do you detect a very weak electric field? What kind of measurement devices are out there? What are the most sensitive devices used for measuring electric fields? I'm looking for something comparable to how SQUIDs or quartz resonators can be used to detect magnetic fields.

Homework Statement I need a pointer to a proof of the following items: if div X =0 then X = curl Y for some field Y. if curl X = 0 then X = grad Y for some field Y. Can anyone provide a pointer to a proof? Thanks. Bob Kolker Homework EquationsThe Attempt at a Solution

Homework Statement A proton is accelerated from a rest position into a uniform electric field and magnetic field that are perpindicular to each other, as shown, The proton passes through the parralel plates without being deflected, at a constant velocity. When the proton leaves the plates, it...

For each of the four fundamental forces (or fields), must one always specify the Lagrangian and Hamiltonian? What else must one specify for other fields (like the Higgs Fields)?

Hi Everyone. There is an equation which I have known for a long time but quite never used really. Now I have doubts I really understand it. Consider the unitary operator implementing a Lorentz transformation. Many books show the following equation for vector fields: U(\Lambda)^{-1}A^\mu...

is it correct that if free floating electrons enter a magnetic field @ a right angle to the field they will take a circular orbit around such field?

Hi, as part of my physics assignment, I have the following question: As a spacecraft approaches a planet, the following measurements of velocity and radius were taken. From these values, a graph of v2 (y axis) and 1/r (x axis) was plotted. Use this graph to obtain a value for the mass of the...

I hesitate to ask this but what are electric and magnetic fields? We are told that the electromagnetic force is carried by the photon (which consists of oscillating electric and magnetic fields) but the photon does not cause (?) or interact with external magnetic and electic fields. Presumably...

I'm looking for introductory references to the topic of time of tunnelling decay when besides the potential barrier there is also a magnetic field present. I have found a couple of articles about the topic but they treat complicated cases in condensed matter, I'm more interested in the basic of...

How can we align all the input fields of form vertically in justified position.For example like this form:

Hi all! I'm super lost on this homework question. I tried asking the professor but was kind of brushed to the side. My vector calculus knowledge is pretty limited (I had an unfortunately experience in that class). Anybody have any ideas on how to go about solving for this? It's a problem out of...

I've been given a copy of my friend's midterm exam from this same class from last term, and decided to take a crack at it to help study. One question type in particular really messes me up and it looks like the following. How would I go about solving these in the future? A solid insulating...

I am currently doing a PhD in theoretical physics (let's for simplicity say gravity and black holes). However, I have also in my free time been working a bit in a more applied field (let's say cold atom physics), and have been reasonably successful (in the sense that I have some publications...

My question is about Force Free fields in the study of plasma stability (in MHD regime): Consider an isolated ideal plasma in an equilibrium state (where the effect of selfgravity is negligible), from the Navier-Stokes equation we get that: $$\vec{\nabla} P = \frac{1}{c} \vec{J} \times...

Homework Statement Two large parallel plates are 0.8 m apart and generate an electric field of 12 N/C between them. At 0, 1/4, 1/2, 3/4, and full distance (0.8m), how much kinetic energy does a +0.25 C charge gain as it passes through each location? Homework Equations V = PE/q The Attempt...

Disclaimer: I'm not sure if this is the correct forum. An ideal conductor (ideal = no resistance) is essentially taking the electric field at one terminal and connecting it to the other terminal. Charge moves when it is in an electric field, electric field strength is in Volts per meter, or...

Are there any theories that have mixing between fields and space? For instance, a theory with mixing between two fields might look like: L_{int} = k \phi(x) \psi(x) Where mixing between a field and space might look like: L_{int} = k \phi(x) x What are the consequences of something like this?

Can someone please explain to me why, a changing magnetic field can produce an electric field and a changing electrical field can produce a magnetic field. Also how do magnetic fields originate, what causes them?

Are the E and M components of an E-M wave (at a given frequency) necessarily in phase in free space? A conductor? A dielectric material?

Homework Statement Hello. I am having trouble understanding this particular statement found in one of my textbooks. " Work done to move a charge along a line perpendicular to the field is zero" The Attempt at a Solution Field is a space around a charge where if we place any other charge...

Homework Statement Hi this is my first post I hope that my explanation is good. Now this is the explanation. Now I will provide the known values. So I start looking literature and some formulas to solve this and I found two different propagation constants. Gama and Beta. Homework...

I know Zwitterions contain both a positive and negative charge. As such, I know that the zwitterions will not migrate towards either pole of the field. My question is: will the zwitterions align with the electric field lines?

So I was thinking, if the body has its own electrical currents... especially in the brain, then the brain must have an electrical field that extends infinitely. If that is the case can the brains electrical field interact with the real world and influence it. So for example if the field was...

After the success of QM. They want to extend it to fields like electric field, electromagnetic field.. hence the initial attempt at quantum field theory (QED).. next they think particles like electrons can be treated the same.. hence the so called second quantization. Besides fields.. what else...

Homework Statement Define a structure VEHICLE which contains producer, model and chassis number. Store the content of a structure in binary search tree such that the key for storing contains all fields of a structure (producer has the highest priority, and chassis number has the lowest). Print...

Separate questions: 1. What is the mathematical formalism where one can transform between field and geometry or they both being emergence? 2. What is the mathematical formalism that can describe QFT but not using the concept of fields nor particles. What are they called and current attempts at...

Suppose I have electric field of the form ##\mathbf{E} = 3x\mathbf{i} + 3y\mathbf{j}##. Calculating the charge density gives me ##\rho = \epsilon_0 \nabla\cdot\mathbf{E} = 6\epsilon_0##. But now if I turn one of the components of the field in the opposite direction, for example ##\mathbf{E} =...

Does a superconductor experience any forces acting upon it when it is passed through a magnetic field?

In my electromagnetic theory book, there is a classification of vector fields, one of the 4 different type vector fields is "solenoidal and irrotational vector field" (both divergence-free and curl-free). If solenoidal and rotational vector fields are same thing, then it means the vector field...

In QFT particles are described by fields, but AFAIK these fields are mathematical since we don't measure values of fields at a particular spacetime. So what does it mean to say a higgs field exist! I mean it is one thing to say Higgs particle exists (in LHC), but I have not seen anybody measure...

Are electric and magnetic fields real or are they just mathematical manipulations? Of course, one could say that we do not care about whether they are real or not, the only thing which matters is that they are useful in describing various things. But we assign quantities like energy, momentum...

In a source-free, isotropic, linear medium, Maxwell's equations can be rewritten as follows: \nabla \cdot \mathbf{E} = 0 \nabla \cdot \mathbf{H} = 0 \nabla \times \mathbf{E} = -j \omega \mu \mathbf{H} \nabla \times \mathbf{E} = j \omega \epsilon \mathbf{E} If we are looking for a wave...

Consider a Majorana spinor $$ \Phi=\left(\begin{array}{c}\phi\\\phi^\dagger\end{array}\right) $$ and an pseudoscalar current ##\bar\Phi\gamma^5\Phi##. This term is invariant under hermitian conjugation: $$ \bar\Phi\gamma^5\Phi\to\bar\Phi\gamma^5\Phi $$ but if I exploit the two component...

Hi, In general relativity we have no general conservation of energy and momentum. But if there exists a Killing-field we can show that this leads to a symmetry in spacetime and so to a conserved quantity. Thats what the mathematic tells us. But I don't understand what's the meaning of an...

There is a recent article (Optics July 2015) claiming violation of Bell inequalities for classical fields: "Shifting the quantum-classical boundary: theory and experiment for statistically classical optical fields" https://www.osapublishing.org/optica/abstract.cfm?URI=optica-2-7-611...

I am a Mechanical engineering student planning to do masters in physics next year. I am interested in astrophysics and astronomy, but classical and quantum mechanics also interests me.If I take admission into a masters degree program in physics, would I be able to specialize in these fields?What...

I think the equation for the relationship of the E (electrical) and B (magnetic) fields in electromagnetic (EM) radiation is E=Bc, where c is the speed of light. I think this is correct, but what does it tell us? On it's face, it looks as though the B field (of a photon, say) is...

1. The magnetic field at point P due to a magnetic source S1 is represented by ==>. Can a bar magnet S2 be brought close to P so that the total magnetic field at P due to S1 and S2 is zero? Explain your answer.2. None3. Yes, this is possible if both fields at point P have the same magnitude but...

Recently I've had some discussions about time in GR. I've always read in different places that people usually want a spacetime to have a hypersurface-orthogonal timelike Killing vector field so that they can assign a time dimension to that spacetime. But Why is this needed? I can understand it...

In the absence of a sense of scale, will the gravitational fields of large objects be indistinguishable, one from the other?

Homework Statement Consider the ring of polynomails in two variables over a field K: R=K[x,y] a)Show the elements x and y are relatively prime b) Show that it is not possible to write 1=p(x,y)x+q(x,y)y with p,q \in R c) Show R is not a principle ideal domain Homework Equations None The...

As I understand it, you can create a concentrated magnetic field at a specific point by having two electromagnets in a cone shape, both pointed at each other. The cone effectively condenses the field, and is strongest at the region between the points of two cones. Is this understanding even...