Electrodynamics Definition and 404 Threads

In Classical Electromagnetic Radiation, Heald and Marion take the divergence of Faraday's and Ampere-Maxwell's laws and state: $$-\vec\nabla\cdot\frac{\partial\vec B}{\partial t}=\vec\nabla\cdot\vec\nabla\times\vec E=0$$ If we assume that all the derivatives of B are continuous, we may...

The bound surface current is $$\mathbf{K}_b = \mathbf{M} \times \hat{n}$$ which gives $$\mathbf{K}_b = {M} \hat{x}$$ Applying ampere's law: ##\oint \mathbf{B} \cdot d\mathbf{l} = \mu_0 I_{\text{enc}}## to the top surface, which encloses the bound surface current yields: ##\mathbf{B} = \mu_0...

I continue my reading of Griffiths electrodynamics (chapter 9, electromagnetic waves) and I got stuck on this: Author tries to prove a stretched string supports wave motion and I found it very difficult to grasp. In the second equation, why can we replace sin function with a tangents really...

I posted the table of contents a couple of years ago. https://www.physicsforums.com/threads/advancing-to-higher-level-electromagnetism-is-purcell-morin-the-solution.1045237/#post-6797112 An ex-library book. It was printed in Poland, so it is not the highest quality paper. I could only find a...

I am trying to understand the solution to exercise 12.71 in the document linked below which accompanies Griffith's book on electrodynamics. The problem states that we are to use the Larmor formula and relativity to derive the Lienard formula. $$Larmor \ {} formula: P = \frac{\mu_0q^2a^2}{6\pi c}...

we know that, using the Green's identity ##\iiint\limits_V (\varphi \Delta\psi -\psi \Delta\varphi)\ dV =\iint_{\partial V} (\varphi \frac {\partial \psi}{\partial n}-\psi \frac {\partial\varphi}{\partial n})\ da## and substituting ##\varphi=\phi## and ##\psi=G## here, we can write the potential...

In my electrodynamcis assignment I'm being asked to derive the wavelength of the normally polarised wave transmitted through a glass/air interface as a function of ##n_1## (the refractive index of the first medium) using the concept of phase continuity and the fact that maxima should be equal at...

Hey, What is meant by Coulomb gauge not being Lorenz invariant? The Coulomb gauge is just a constraint on \mathbf{A} and \phi and thus it is independent of inertial frame. I posted the question in the wrong section. This question is in the context of QFT. The notes says: A disadvantage of...

I'm looking to brush up on my knowledge of electrodynamics and am trying to decide between Jackson and Griffiths. I have a fairly advanced math background and am comfortable with differential geometry, special and general relativity. I'm leaning toward Jackson but wanted to get input from...

Why is electrical field bent like that rather than following a straight line across to the relevant point over there?

Can someone explain what exactly happens at (4) ? I do not clearly follow, except that there is some cosine law going on? I also do not really understand why at (3), r' doesnt have a z hat component, but I can live with that.

Okay I’m assuming I have to use √1- v^2/c^2 multiplied by some coefficient of length but I don’t understand any of this and could really use help understanding the process and/or reference material that might point me in the right direction

I've been doing some research on the topic of radiation reaction force/self force in classical electrodynamics and although there are some discussions on the internet I would like direct answers to these following questions: Is there a rigorous and universally accepted treatment of radiation...

In https://www.physicsforums.com/threads/what-assumptions-underly-the-lorentz-transformation.1015982/post-6657920 a discussion evolved from the basic assumptions of the Lorentz transformations, to a paper M. LeBellac, J. M. Levy-Leblond, Galilean electromagnetism, Nuovo Cim. 14B, 217 (1973)...

I'm currently studying Griffiths electrodynamics on my own and I want to be done with it once and for all. I however don't know if all the chapters are important for the rest of physics and which ones can be skipped without loss of continuity. Can someone give me some insight?

Hello PhysicsForums community, I have been reading through Zangwill's Modern Electrodynamics all on my own, and I've just joined here hoping I can post some questions that come up for me. To start, I am confused about something in section 6.7.1, concerning the variation of total energy U of a...

Summary:: Courses in electrodynamics Any online lectures or courses keyed to this book? Thanks very much

I'm currently studying quantum mechanics from MIT opencourseware, just about to finish 8.05, quantum physics 2. I have little knowledge of electrodynamics, but I want to learn enough to be comfortable studying quantum electrodynamics in the future. My math background is pretty strong, so I've...

As human beings, we tend to act and observe and think over time periods spanning a few milliseconds to several decades (or even centuries.) Essentially all phenomena that we directly engage with in everyday life are electrodynamical (with quantum electrodynamics over reasonably short time and...

Hi! I tried to solve it by using the equation of the electric potential above and as we see it requires the electric field, but the electric field at the center of the ring is zero. Then I tried by using the equation [text] V = \frac{1}{4\pi\epsilon_0r} \int \lamda dl [\text] and I got [text] V...

I tried solving the problem using the force formula, so what I have known is the magnetic field B and E. I also have a motion in the x-axis, that means that the velocity will be pointed at the x-axis. Inserting this in the formula I will be having something like this: $$\mathbf{F} = q(\mathbf{E}...

I am unsure how to solve the problem and would appreciate any suggestens on how to start solving the problem.

I was trying to solve it using the formula for polaresation P = ε E - ε0 E. Then I tried to solve for E which is D/ε and D= ρf/ε. So at the end, I will have something as P = pf- (ε0ε). ρb = -∇ * P = 0 so σb = P * n = ...? I am unsure what the direction for the polaresation should be? I need...

While I was doing a problems of chapter 9 of DJ griffith electrodynamics I came across this problem 4 Problem statement Obtain eq 20(show in the below picture) Directly from the waves equation by separation of variable Could I have a straight solution in your word Thank you

Hello everyone, I recently completed kleppner and kolenkow classical mechanics book. Next I am going to learn Electrodynamics. My brother is a EE major and he gave me his copy of "principles of electromagnetics" Matthew Sadiku 4th edition. But a lot of people here recommend Griffiths. So, 1.)...

https://arxiv.org/abs/2010.10345 My question is, Has the Feynman Diagram IIc been published or not? Did Kroll & Karplus lie or not? https://vixra.org/abs/2002.0011 Are these critics valid?

I was reading in the Book: Introduction to Quantum Mechanics by David J. Griffiths. In chapter Time-independent Perturbation Theory, Section: Spin -Orbit Coupling. I understood that the spin–orbit coupling in Hydrogen atom arises from the interaction between the electron’s spin magnetic moment...

Hey guys! Sorry if this is a stupid question but I'm having some trouble to express this charge distribution as dirac delta functions. I know that the charge distribution of a circular disc in the ##x-y##-plane with radius ##a## and charge ##q## is given by $$\rho(r,\theta)=qC_a...

Maybe this will help.

The problem is shown above, the hint to solve the problem is below. See the hint if it is difficult for you to imagine what is going on. I am assuming the diagram in the hint shows what's happening when the mass is falling at terminal velocity. I have quite a few questions. 1. How do the wheels...

So this is more of an intuitive question rather than a mathematical one. I present the problem. Assume I have 2 charges of charge +q at a distance r from each other on the z axis. Position of two charges is (0,0,r/2) and (0,0,-r/2). Assume now that I want to calculate the force these two...

Consider two massive charged objects at rest with a large horizontal distance ##d## between them (object ##1##: mass ##m_1##, charge ##q_1## and object ##2##: mass ##m_2##, charge ##q_2##). I apply a constant vertical force ##\vec{f_1}## upwards to object ##1## so that it gains an acceleration...

In my opinion the field momentum is the field's intrinsic momentum which it will give to charges(if any present)...

A return path for the current was provided by the ocean itself. Given that the resistivity of seawater is about 0.25 ohm-meter, see if you can show that the resistance of the ocean return would have been much smaller than that of the cable. (Assume that the electrodes immersed in the water were...

In this explanation we need to involve the Dirac delta functions(maybe) but I clearly have a difficulty in understanding it can some one explain me the whole concept of constant or non constant volume charge density.

Hi, so the four-dimensional generalization of $$\vec{B}=\mu\vec{H}$$ is $$F_{\lambda \mu}u_{\nu} + F_{\mu \nu}u_{\lambda} + F_{\nu \lambda}u_{\mu} = \mu (H_{\lambda \mu}u_{\nu} + H_{\mu \nu}u_{\lambda} + H_{\nu \lambda}u_{\mu})$$ From these four-tensors and four-vector I should be able to...

I'm having troubles setting up this problem. I know we are to use boundary conditions to determine An and Bn since in this case (a<r<b) neither can be set to 0. I don't know how the given potentials translate into boundary conditions, especially the V3 disk.

I don't really know how to find it mathematically as I am really confused in finding the normal vector and finding the electric field as well. pls help

If I understand correctly, the concept of electric and magnetic fields originated with Faraday and was developed by reconceptualizing forces acting at-a-distance. For example, the electric field concept was developed by looking at the force on a test charge in the presence of a source charge...

Could anyone explain how did Jackson obtain the Taylor distribution of charge distribution at the end of section 1.7 (version 3)?

Summary:: So this is a question from Griffiths' book on electrodynamics. The topic is on electircal potential. I have come up with a solution to a problem; the solution is wrong but I cannot spot the mistake. So here is the question: My answer to this question is: $$\sigma( θ ) = \frac...

Summary:: Not entirely sure if this is the appropriate board, if I'm mistaken feel free to move it somewhere better. I decided to slowly go through Jackson's infamous Classical Electrodynamics book as a challenge to myself, solving as many exercises as possible. I will document my progress...

Hi folks, Electricity and magnetism have always been my favorite subjects, and I am just getting to learn the basics of quantum theory and it is absolutely terrific going. I was always fascinated by the story of Feynman, Schwinger, and Tomonaga tackling QED from the books Genius by James Gleick...

In order to find force( and hence the Acceleration) on the Pentagonal plate,we must find the Resistance of the plate.But to find the resistance we must know how the current is flowing through the given plate(see attached figure). My question is how is the current flowing through the Pentagonal...

I've just found a recent very interesting and very modern textbook on classical electrodynamics. It starts with special relativity (rather than electrostatics) and contains a lot of high-energy topics, including renormalization (within classical realm), massive vector fields, gravitational...

Thanks in advance!

So I've been trying to figure out how EMF shielding works. More specifically, I've seen videos where placing a metal conductor in front of a circular coil (with AC running through at radio frequencies) apparently shielded anything behind it. After searching online, I repeatedly saw Eddy...

In his Nobel lecture (https://www.nobelprize.org/prizes/physics/1965/feynman/lecture/) Richard Feynman states that by varying the Schwarzschild-Tetrode-Fokker direct interparticle action $$A=-\sum_i m_i\int\big(\mathbf{\dot X_i}\cdot\mathbf{\dot X_i}\big)^{1/2}d\alpha_i+\frac{1}{2}\sum_{i\ne...