Fields Definition and 1000 Threads

Homework Statement The Question is here: imgur link: http://i.imgur.com/wIlUZMM.jpg Homework Equations U_c = \frac{\kappa \epsilon_0 A d E^2}{2} U_c = C \Delta V_c \kappa: dielectric constant \epsilon_0: permittivity of free space C: capacitance The Attempt at a Solution [/B] I...

Urs Schreiber submitted a new PF Insights post Examples of Prequantum Field Theories II: Higher Gauge Fields Continue reading the Original PF Insights Post.

Urs Schreiber submitted a new PF Insights post Examples of Prequantum Field Theories I: Gauge Fields Continue reading the Original PF Insights Post.

I assume that all the fundamental physics known - as of today - can be reduced to quantum general covariant fields (including spacetime itself to be seen as a field of those...). Now, sorry if my question is quite abstract and based on tomorrow's hypothetical new physics, but would it be against...

Hi guys! Sorry for all the questions on electromagnetism. My understanding is that an electric field exists in electric monopoles and dipoles, as well as moving magnetic dipoles, and magnetic fields only exist in magnetic dipoles and moving electric dipoles. Is this correct? There are 2 parts...

Does the (assumption of) ubiquitousness of EM fields explain single particle interference well/better? Below is a rough logic, however it maybe need modifications. The double slit or the mach-zehnder or any object changes the configuration of time-space and EM fields. The photon may not know...

Homework Statement http://postimg.org/image/vzhqi8er5/ Homework EquationsThe Attempt at a Solution I understand all the calculations here - http://www.physicspages.com/2012/10/18/coaxial-cable-with-dielectric/ I have one issue that is bugging me though - if λ charge density is distributed over...

I'm Indian and I've heard stuff that it is difficult to get into a good PhD program in the US/UK for string theory because the competition is more fierce than other fields. Furthermore,the likelihood for getting academic positions is even tougher(added to the fact that I'm from a different...

Hi all :) I am about to finish the chapter of electromagnetic induction in my class. And I taught my students that the electric field induced due to changing magnetic flux is different that the electrostatic field due to stationary charges(Now I am wondering would it be wrong if I used the...

Hello. There is one thing I can not find the answer to, so I try here. For instance, writing a general superfield on component form, one of the terms appearing is: \theta \sigma^\mu \bar{\theta} V_\mu My question is if one could have written this as \theta \bar{\theta} \sigma^\mu V_\mu ...

Hi. In GR , covariant differentiation is used because the basis vectors are not constant. But , what about in SR ? If the basis vectors are not Cartesian then they are not constant. Does covariant differentiation exist in SR ? And are for example spherical polar basis vectors which are not...

Hi all, This is for SQL queries, sorry ran out of space in the title. Say we are doing a query that includes a null field/attribute. Must we always use either an " Is null" or " Is not null" statement? Thanks.

I'm in my first semester at a JC and I'm trying to figure out what kind of physics I might want to pursue as a career. I know I love space, and I want to be able to apply my math towards it. What initially sparked my interest in physics was theoretical physics, however, I soon realized the job...

Homework Statement The problem deals with a charged (Q) rotating sphere around its axis (Ω_0) z^^ (z hat) of radius a. I'm asked to find the total angular momentum of the EM fields. 2. The attempt at a solution There is a solution posted to this question and I was just wondering why my...

Hi everyone, First, sorry if the question is stupid, I do not have any background in Physics. Just very curious. Potential energy due to gravity is: m * g * h Joules Now, suppose I lift a weight on Moon at a given height. I will have: 1.6 * m * h Joules I maintain it at that height and go to...

number of fields line originating from 1 C charge is it infinity as per the following video or 1/epsilon according to http://www.topperlearning.com/forums/ask-experts-19/calculate-the-no-of-field-lines-originated-from-a-charge-of-physics-electric-charges-and-fields-81114/reply My textbook...

Can a cylinder with 1 side open act as a faredey cage (which do not allow passage of magnetic field) when magnetic field are only coming parallel to the curved part

This is more of a QFT question, so the moderator may want to move it to another forum. The simplest example of a QFT that I learned was the scalar field; in Sakurai's 1967 textbook. I know the Higgs is a J=0 particle. Is it described by the simple scalar field discussed in Sakurai's text? I ask...

Homework Statement four point charges are placed at the corners of a square as shown in the figure having side 10 cm.If q is 1μC then what will be electric field intensity at the centre of the square? Homework Equations 3. The Attempt at a Solution [/B] Half of diagonal a/√2 0.1/√2...

I have no idea how lethal/strong space radiation is, but i do have an idea that most of it is from the sun perhaps? I also know that the prime factor to deflect this radiation is magnetic field and the ozone layer. I think the magnetic field handles only particle radiation and atmosphere handles...

¿How is possible deduce the Lagrangian of the fields of a theory knowing only his Feynman Diagrams?

I need help explaining that this assumption is not correct or correct: A product uses Radio waves to turn on a LED. Radio waves can be a form of electromagnetic fields therefore, a Hall Effect sensor could be used in this device to turn on that LED.

My professor in Classical Electrodynamics is great and all, but sometimes he has trouble understanding what it is that I don't understand. So here I am. Let's say we have the some sort of (monochromatic) radiating system generating a electric field with Fourier amplitude Eω(x) and want to...

As fields ##\phi ## are ill defined at precise time and position i read that fields have to be smeared. So we have test functions f in bounded regions in space time. We have a Hilbert space and ##\phi (f) ## is an operator which acts on H. Maybe we can retrieved the usual wave function when it...

Homework Statement A satellite is designed to orbit Earth at an altitude above its surface that will place it in a gravitational field with a strength of 4.5 N/kg. a) Calculate the distance above the surface of Earth at which the satellite must orbit b) Assuming the orbit is circular...

Most threads discussing this subject have only confused me further, gone offtopic and later been locked. I have a basic yes/no question, which is the following: is there one single electromagnetic field in the universe that is excited locally (creating fields, in apparent plural, although...

Homework Statement I was just studying the Klein Gordon equation with fields. In particular I was reviewing the continuity equation. In the derivation for it, the usual approach is to take the klein-gordon equation (I'm using 4-vector covariant notation), multuply by the complex conjugate of...

Does anyone know if they have considered using ultra high efficiency magnets to create an oscillating pulse into the energy of the electron orbital shells? This may in turn break the Coulomb barrier.

I've read that matter and energy fields occupy all of space, and that space is integral with time, so I'm wondering whether it might be consistent with contemporary physics for undetectably small proportions of the mass of matter and / or energy to occupy arbitrarily large proportions of an...

Homework Statement Explain the circumstances that enable a particle to move un-deflected with uniform motion through an electric field if it is given an initial velocity perpendicular to the electric field. Assume the electric field is the only field present.[/B] Homework EquationsThe Attempt...

Hi all! I am a 13-year-old that is very interested in physics. I am currently studying fields, and I have gotten into some advanced parts of field theory. With that, I have 3 big questions: 1. In vector and higher order tensor fields, what does it mean to "observe the field from point...

How does an electric charge produce an electric field? How is this field maintained over time without the input of energy? When the charge moves, why is or isn't there any remnant of the field left behind in space?

Homework Statement 1) Describe and explain what happens to the electron beam on the screen of a teltron tube as the EHT(electrical high tension) voltage increases from 3000V to 3500V. 2)What is the effect of E field on light waves? Homework EquationsThe Attempt at a Solution 1) The beam...

Homework Statement In a book I find the following derivation: \int (J \cdot \nabla ) \frac{\bf{r} - \bf{r}'}{|\bf{r} - \bf{r}'|^3} d^3\mathbf{r'}= -\sum_{i=1}^3 \int J_i \frac{\partial}{\partial r_i'} \frac{\bf{r} - \bf{r}'}{|\bf{r} - \bf{r}'|^3} d^3\mathbf{r'} \\ = -\sum_{i=1}^3 \int J_i...

A disk with a uniform positive surface charge density lies in the x-y plane, centered on the origin. The disk contains 2.5 x 10-6 C/m2 of charge, and is 7.5 cm in radius. What is the electric field at z = 15 cm? I have used the formula...

Hello, I am in a calc 1 general physics 2 summer session class and missed the lectures on this due to sickness. I'm really confused on applying coulomb's and gauss's laws to find the electrical field of a sphere or outside a sphere. This is of both variable and constant charge densities. I've...

Can someone correct my understanding on electromagnetic waves please; I've clearly got the wrong end of a stick somewhere, but can't figure out where my misunderstanding is! Thanks. If I draw a classic EM wave with the electric field on the up and down axis and the magnetic field at right...

Homework Statement A ring with radius R has a constant current and is rotating around a diameter with constant angular velocity omega. 1)Calculate the radiation fields far from the ring. 2)What's the direction of the polarization for an observer along the axis of rotation? 3)What are the...

I'm just trying to think of a qualititive solution to the following thought experiment: I have an RF source of very large voltage driving a signal towards point A (say, a capacitor or a dipole antenna). The source itself is not really part of this experiment, but I just want a sinusoidal...

What is the interaction Lagrangian of matter and graviton fields?So(on the answer)we can say about the nonrenormalization.Why is the divergence of two gravitons diagram able to be the limit of the coincidence of the verties.So we can say about the nonrenormalization.

Please forgive me if I am posting in the wrong forum. Also the board limits the length of the title. I wanted to ask about Effect of high intensity electric and magnetic fields on spacetime. To begin, 15 years ago this was published...

Please forgive me if I am posting in the wrong forum. Also the board limits the length of the title. I wanted to ask about Effect of high intensity electric and magnetic fields on gravity. To begin, 15 years ago this was published...

**Not a homework question. In my professor note, it says that: "If a material causes magnetic field (in parallel direction to the surface charge) below a boundary is not the same as the boundary (in parallel direction to the surface charge) above the boundary, then a surface current is...

I want to understand the 'vertex factor' of 3-bosons field and 4-bosons field but get confused. (I know the lagrangian and have computed the interaction vertices already) only need to understand the vertex factor. In other words, I want to learn how 3-boson vertex and 4-boson vertex are...

I'm trying to work up some examples to help me understand this concept. Would the periodic flow on a solid torus be transverse to it's boundary?

I have a question that I can't figure out , there is a toroidal transformer , and the core has an attached part on which another coil is wound. the main coil of the toroidal transformer is connected to a DC source. which creates a static magnetic field in the torus core. the other coil at the...

It could be that I'm misinformed, but I heard electrons at rest have magnetic fields. I thought that magnetic fields required a charge to be traveling at velocity before a magnetic field would arise. If this is the case could someone help me out? If an electron has a magnetic field at rest what...

When we start by postulating local SU(2) gauge invariance for our weak isospin doublets \begin{align} \psi &= \begin{pmatrix} \nu_{e} \\ e^{-} \end{pmatrix}_{L} \end{align} etc., we have to introduce massless gauge fields to preserve the Lagrangian's invariance. For SU(2) this demands 3...

Since Mars doesn't have a magnetic field of its own due to the cooling of it's core, what if you took a strong magnet from Earth say a superconductive magnet or electromagnet, will the small magnetic field (relative to mars) repel solar radiation, solar flares and other background radiation form...

This started with me trying to read up how static electric/magnetic fields are described with photons, but it quickly evolved into the realization that I don't really know how the photonic viewpoint describes *any* changing EM field that isn't a neat monochromatic wave. Some sites mention...