Field Definition and 1000 Threads

I'm trying to conduct an experiment where I calculate the magnetic field strength of a magnet, by comparing the levitation distances between two magnets. My experiment involves using different masses to anchor down magnetic repulsion between 2 magnets. Fg = Fm. The formula I am using for this...

Sorry, I guess I should have remembered all of this from my school days, but right now I have forgotten so much that I need some help. I am developing some simple experiments for school children (age ca. 12). This one involving magnets. I am not asking for detailed calculations, that is way...

I'd like to hear your professional opinion on and experience with using Quantum Field Theory for the Gifted Amateur by Tom Lancaster and Stephen J. Blundell as a self-study textbook. Thank you.

I am not sure why latex is not rendering, but here is the question. The answer is ##\frac{a^2}{8}## and for the love of my life, I don't know how. Can you please help me with this?

I've no idea how to solve this problem. The sign of the charge is not mentioned, so I'm assuming the charge is "+". The charge exerts an outward electric field. Since two lengths of the right-angle triangle are given, I use the Pythagorean to find the hypotenuse, which is the distance between q...

There are two identical spheres with the same charge that are the vertices of an equilateral triangle. ##+3 \mu C## will exert an outward electric field, which is drawn in the FBD below (see the attached pic), Since the horizontal force components (1x and 2x) are equal and opposite at point P...

First, my ignorance... I know there are classes of equations: Laplace, Poisson, Wave, Diffusion, etc. (I suppose Laplace is a subset of Poisson, but that is not the issue). Into what category of mathematical equations would you place the field equations of elasticity (stress/strain/displacement)?

I've been working on developing infinitesimal recursion (what I call continuous hierarchy), but I ended up arriving at "field series" instead. My searches didn't seem to come up with anything reasonable (battlefield the video game series), so I'm wondering what the official name for a field...

I have a simulated data of charged particles in a magnetic field. I have selected clusters, each cluster contains a set of points(x,z) and I want to perform RK4 between the first and second clusters and fill the positions in a histogram. I have selected the clusters with the initial...

from the partition function - am trying to show that ##\langle \mu \rangle = \beta^{-1} (\partial \log Z / \partial B)## where ##Z## is the canonical partition function for one atom, i.e. ##Z = \sum_{m=-j}^{j} \mathrm{exp}(\mu_0 \beta B m)##, and ##\mu = \mu_0 m##. The average...

For this, From the work kinetic energy theorem, if we assume that the book and the earth is the system, and that the finial and inital speed of the system is zero, then is the work KE theorem there is no net work done on the system. However, clearly there is work done on the system is shown by...

Hi, I am confused about whether decreasing the magnetic field used for a generator could increase the generator's power output. I used four equations: 1. Torque = Force x radius 2. Torque = NIAB (N = number of turns, I = current, A = area of armature, B = magnetic field). 3. emf =...

Hi, I am trying to learn relativistic classical field theory as a preparation for studying quantum field theory. I am currently reading chapter 13 i Herbert Goldstein's Classical Mechanics edition 3, but I think that this book is a bit too brief and does not fully derive and explain the...

How does an electric field of a moving charge, for example a moving electron, inside a wire looks like? Does it looks like this with distorted circular radial lines?

Why doesn't this work if the field is strong? Or does it work as long as there are no singularities? Mentor's Note: Original thread title was, "Calculating rest mass by integrating T_{00} over a 3 volume for static metric"

My question is specifically with calculating the intensity. The book solution is I=P/(4*pi*r^2) but would this not give me a weaker electrical amplitude in the final calculation after plugging it in to I=(1/2)*√(ε0/μ0)*(E02) ?

(a) ##\vec G=24xy\hat a_x+12(x^2+2)\hat a_y+18z^2\hat a_z## @ ##P(1,2-1)## ##\vec G=24(1)(2)\hat a_x+12(1^2+2)\hat a_y+18(-1)^2\hat a_z## ##\vec G=48\hat a_x+36\hat a_y+18\hat a_z## (b) I am not sure how to get this part started. Could someone point me in the right direction?

Assume there is a force (vector field) on the space .....does the effect of this field on the particle(the change of momentum) at some position depend on the speed at that position? And is it related to the time interval dt the particle experiences this force ? Can i say dt=dx/v? And is that...

Problem: Solution part a) where formula 6.14 is just M x n. We need to do part b without seperation of variables, I'm quite stuck. Will B just be the magnetic field inside a solenoid? How can I find the other fields.

After watching this clip Electric Field Lines Lab I wonder if it is possible to see both electric field lines and magnetic field lines at the same time by swapping the two nails in the video with two bar magnets, as the conductors as we understand bar magnets are metals and metals are good...

TL;DR Summary: Find acceleration of electron in dB/dt >0 Hello. Here is a problem that i'm not so sure about: Inside a solenoid there is a time-dipendent magnetic field B, so we have dB/dt = b (constant). We want to know the acceleration of an electron: a) placed in the center of the solenoid...

If a mass is moving it has a wavelength - my question is, is the gravitational field of the mass then modulated accordingly ?

The problem of bound states of an electron trapped in a dipole field is being studied by Alhaidari and company. (See, for example, https://arxiv.org/ftp/arxiv/papers/0707/0707.3510.pdf). It is not clear to me why the point dipole approximation is used everywhere in such calculations. Can't an...

I would like to discuss the nature of the following effect. At whatever angle and with whatever initial speed the particle fly into a uniform potential field, over time the directions of the instantaneous velocity and field strength converge. The kinematics and dynamics here are trivial, but I...

Hi, unfortunately, I am not sure if I have calculated the task correctly The electric field of a point charge looks like this ##\vec{E}(\vec{r})=\frac{Q}{4 \pi \epsilon_0}\frac{\vec{r}}{|\vec{r}|^3}## I have now simply divided the electric field into its components i.e. #E_x , E-y, E_z#...

Dear Experts, When a thin conducting sheet with no charge on is placed at a certain distance from a point charge, does it shield the electric field caused due to the point charge from reaching the other side of the sheet. As an extension of that idea, when a conducting sheet or slab is placed...

Exercise: Solution: The result is correct, but I'm unsure about equation from 29 to 30 where right-hand side became just the covariant dual field tensor. I assumed that I could interchange the covariant dual- and normal covariant field tensor, but don't think it's possible since matrices...

I need help with a Baldor dc motor, 15kw 240 volt armature and 150 volt field, I don't need the 15kw and so want to feed it with 150 volts to both field and armature, does anyone know the effect this will have on the motor, can I cause damage, what would be the approximate power output, I know...

I am learning QFT rn, so the question that I naturaly ask myself often is why do we have to use field operators in relativistic quantumn theory instead of operators with finite number of degrees of freedom which are used in non-relativistic quantumn mechanics? One of the reasons that I came...

There are a couple of problems with the same setup. On plugging in the values and solving for the integral, I am not getting the expected values of the force. Is there something wrong in the solution attached?

Hello! I have a 2 level system with a dipole moment d. I want to simulate numerically the evolution of the system under an external sinusoidal electric field (far off resonant). This is straightforward using SE. However I also have on top of that another electric field, created by a coupling of...

I have this Lagrangian for a free massless left Weyl spinor, so it’s just the kinetic term, that can be written embedding the field into a larger Dirac spinor and then taking the left projector in this way: $$i \bar{\psi} \cancel{\partial} P_L \psi$$ Srednicki says that the momentum space...

I am facing a problem while wanting ##\phi## dynamics in a cubic potential; ##g\phi^{3}##. The equation of motion I get for my case is(this follows from the usual Euler-Lagrange equations for ##\phi## in cosmology--Briefly discussed in Carol's Spacetime Geometry, inflation chapter)...

So I thought I knew how to do this problem but I've run into some issues that make the algebra feel impossible and I am beginning to feel like I'm taking the wrong approach, I ended up rewriting it in a doc because I was concerned maybe my handwriting was the cause of my error so the work is...

Griffith's E&M problem 4.7 asks to calculate the energy of a dipole in a uniform electric field and I ended up getting a different answer than the one given. I thought that calculating the energy/work done to construct the dipole is the same as dragging two point charges where one is d apart...

I am recently reading "Introduction to Electrodynamics, Forth Edition, David J. Griffiths " and have a problem with the derive of the curl of a magnetic field from Biot-Savart law. The images of pages (p.232~p233) are in the following: The second term in 5.55(page 233) is 0. I had known...

Quick and possibly stupid question, but in the equation for calculating the electric field: ##{\mathbf E} = \frac{1}{4πe_0}\frac{q}{r^2} \hat {\mathbf r}## What unit is ##q## in? Coulombs? Although now that I think more on it I suppose it also depends on the units you're using to calculate the...

I can't find the answer anywhere here's my question. can a centrifuge exist outside a field of gravity. More specifically, in a theoretical void of nothing without stars in view or any point of reference for comparison how could motion like spinning or acceleration exist?

Question: Eq. 12.109: My solution: We’ll first use the configuration from figure 12.35 in the book Griffiths. Where the only difference is that v_0 is in the z-direction. The electric field in the y-direction will be the same. $$E_y = \frac{\sigma}{\epsilon _0}$$ Now we're going to derive the...

Hey all, I am encountering an issue reconciling the choice of prefactors in the canonical quantization of the scalar field between Srednicki and Peskin's books. In Peskin's book (see equation (2.47)), there is a prefactor of ##\frac{1}{\sqrt{2E_{p}}}## whereas in Srednicki's book (see equation...

Hello! I have the following Hamiltonian: $$ \begin{pmatrix} 0 & -\Omega\sin(\omega t) \\ -\Omega\sin(\omega t) & \Delta \end{pmatrix} $$ where ##\Delta## is the energy splitting between the 2 levels, ##\Omega## is the Rabi frequency of the driving field and ##\omega## is the frequency of the...

The formula we are given is E=(1/2r)(alpha)R^2(muo)Ioe^-(alpha)t. However, I am struggling to figure out what each of the symbols stands for in the formula...can someone help me out? Like super confused on what alpha is in this case.

Does the magnetic field caused by moving particles depend on the particle spin value? Eg a stream of say protons spin 1/2 is creating a magnetic field. If the particles are (say) lithium nuclei spin 3/2 instead, does that create the same strength field ? (same conditions of course)

I've found the distance from each point to the center, which is equal to r=20x1.732/3 = 11.55 cm. I find out that E2 and E3 due to -4µEyC on x-direction canceled each other. The E2y = E3Y = EY = E2Ycos60 = E2/2 = [(KQ2)/r^2]/2 So the net E-field: E = E1 +E2y+E3Y =kQ1/r^2 + [(KQ2)/r^2]/2 +...

A minimally coupled scalar field can model a cosmological fluid model where And where the equation of state can be the standard ## \omega = \frac {p} {\rho}## I can see how this does a fine job modeling matter, because as the scale factor increases, the density will go as ##\frac {1} {a^3}##...

Of the classical books about EM, I found that Jackson's is the only one that touches with some rigour the subject of deriving the macroscopic field from the microscopic one. Unfortunately, I am quite disappointed by the derivation of Jackson. In the reference he gives, he says that a couple of...

I integrated B within the limits of a (from 0 to 0.007) teh result was 3.64E-10 T and it was wrong. the correcto one would be 5.8 E-4 T and it is a major diference (aprox 1 million times ) Waht shoud I have done? Regards

Hello, This question, which I found in various electricitiy and magnetism books (e.g. Introduction to electrodynamics grif.). There are many variations of this question, I am mainly interested in the following setup of it: -Suppose there is a charged disk of radius R lying in the xy-plane, and...

Question: My answer: What it looks like for an electric charge: Am I correct? If you want I can hand out my Latex on how I got to it, it will refer to the book Griffiths a lot.

TL;DR Summary: A (nonconservative electric field is induced in any region in which) A. there is a changing magnetic flux B. there is a changing magnetic field C. the inductive time constant is large D. the electrical resistance is small E. there is electrical current there can be more than one...