Electromagnetism Definition and 853 Threads

Good afternoon, I am carrying out a practical magnetism project which involves 2 small (2mm x 2mm - 0.6kg) neodymium magnets attached together, and an electromagnet to create a push-pull force from below in order to part them. For those that also build model railway/railroads, this will be a...

Hi I just saw this video . Here it's said that that electromagnetic force is just a consequence of special relativity, but I don't get the explanation. According to the video the electromagnetic force is generated by relative motion of charges, so it is essentially an electric force. It doesn't...

Hello. I have an assignment to submit and I really want to get full marks/know where I went wrong If anyone has a tiny bit of free time would you mind please checking my homework? Even if you just check 1 page I will be so grateful. Thanks again https://imgur.com/a/rHVdjzn

Homework Statement I have a simple problem relating to the superposition of plane EM waves that I'd to try out using complex notation. Could anyone run through the work to see if my understanding is right? Many thanks in advance! The incident E bit of the wave is $$\vec{E}_I = E_0 \sin(ky -...

Homework Statement A cylinder with radius ##R## and height ##h## which has a distributed charge on its surface with density ##\sigma## spins over its axis with angular velocity ##\omega##. If the cylinder has a mass density ##\rho##, find the relationship between magnetic momentum and angular...

Homework Statement Let’s say I have got a charge density $\rho (x,y,z) = \cfrac{C}{x^2}$ with C a specific constant. I want to know the potential on every point in space. How can I get an expression of the electric potential in terms of position? Homework Equations Gauss law/coulomb's law...

Homework Statement Determine the B-field inside the middle of a circular loop of current. Homework Equations Attempt at using Ampere's law: ##\oint \vec{B} \cdot d \vec{l} = \mu_0 i## The Attempt at a Solution ##\oint B \cdot R d \theta = \mu_0 i \Rightarrow BR(2 \pi) = \mu_0 i \Rightarrow B...

Homework Statement Example 5.9 in Griffiths's Introduction to Electrodynamics 4th shows us how to find B of a very long solenoid, consisting of n closely wound turns per unit length on a cylinder of radius R, each carrying a steady current I. In the solution, he goes on to explain why we don't...

Homework Statement In an electromagnetic filed, the elctric field ##\vec{E}## forms an angle ##\theta## with the magnetic field ##\vec{B}##, and ##\theta## is invariant for all inertial observers. Finding the value of ##\theta##. Homework Equations Tranformations of fields perpendicular to the...

Homework Statement Given an electromagnetic tensor ##F^{\mu\nu}##, showing that: $$\det{F^{\mu}}_\nu=-(\vec{B}\cdot\vec{E})^2$$ Homework Equations The Attempt at a Solution I had only the (stupid) idea of writing explictly the matrix associated with the electromagnetic tensor and calculating...

I started studying the book "A Student's Guide to Maxwell's Equations" by Daniel Fleisch some time back. It is an excellent book, giving a very good idea about the main laws of electromagnetism. I will soon finish the book. Now I need some book(s) which has problems on all the laws in classical...

Homework Statement Homework EquationsThe Attempt at a Solution [/B] I got the first 2 parts, but I'm having trouble with the last one. For the time the switch S1 is closed, I derived ##q(t) = CE(1 - \cos(\frac{t}{\sqrt{LC}}))##, by writing the loop equation ##\frac{E}{L} - \frac{1}{LC}q =...

I wrote and solved this problem but am having serious doubts about the answer I obtained. Homework Statement Two point charges \pm q move along the z-axis with velocity \pm v. If they are at the origin when t=0, what is the electric field magnitude a distance r from the z-axis? Homework...

Some background info: I am an international student that is currently studying at a supposedly prestigious university (Top 20 in QS and Times Higher Education ranking). As part of my major requirement, I am taking an EM module. The problem is, my forte is not really physics (I am an IBO...

Homework Statement A straight copper wire that carries a sinusoidal current with an alternating frequency of 50 Hz and a maximum amplitude of 0.5 A passes through the centre of a circular ring of a second copper wire, with the two wires orientated perpendicularly to each other. The radius of...

Homework Statement You’ve decided to protect your house by placing a 5.0 m tall iron lightning rod next to the house. The top is sharpened to a point and the bottom is in good contact with the ground. From your research, you’ve learned that lightning bolts can carry up to 50 kA of current and...

Homework Statement I only need help with part C and D Homework Equations Curl of B = mu0 J J = J free + J bound H = B/mu0 - M The Attempt at a Solution For C i, I said they're the same because free current is the same at both points. My argument is that because curl of B (at L) = mu0 Jfree...

Homework Statement Currently I am taking a course that teaches half the material and let's you figure out/ guess the other half. I have been pretty good at succeeding in this so far, but this one has me stumped. It is on my practice test. What in the world does this diagram mean?Homework...

Why does current produce a static magnetic field, but a static magnetic field doesn't produce current? Specifically, why is one true, but the inverse not true? I can accept that each rule individually is just how the universe works... but it sounds so contradictory when I examine both together...

Homework Statement Problem 1.24 (this is unimportant; it's just a different way of calculating the potential energy of a solid cylinder) gives one way of calculating the energy per unit length stored in a solid cylinder with radius a and uniform volume charge density ##\rho##. Calculate the...

Homework Statement Two charges 2q and -q are located at x = 0 and x = a respectively. There are field lines extending from the positive charge and lines going inwards to the negative charge. Some of these lines go from the positive charge to the negative, but some go off to infinity from the...

Homework Statement Find the distribution of charge giving rise to an electric field whose potential is $$\Phi (x,y) = 2~tan^{-1}(\frac{1+x}{y}) + 2~tan^{-1}(\frac{1-x}{y})$$where x and y are Cartesian coordinates. Such a distribution is called a two-dimensional one since it does not depend on...

Hi at everyone, why on wiki there is written: " According to modern understanding, the electron is a point particle with a point charge and no spatial extent. Attempts to model the electron as a non-point particle are considered ill-conceived and counter-pedagogic " I don't understand this...

That is, a field that accelerates charges in opposite directions on each side of an axis. I was thinking about interference of similarly polarized waves traveling in opposite directions (so that electric field peaks and valleys overlap but magnetic field adds constructively) - would there be an...

I was watching this video of veritasium today and was wondering why the aluminum plate doesn't oscillate when there is a changing magnetic flux. When the flux is increasing, the induced magnetic field (by the induced current) is against the magnetic field of the coil and this acts like 2 north...

Hi everyone, Lately I have been studying the Poynting Flux and I am familiar with the classic examples of how it can be used to describe the power being dissipated by a resistor and the energy flowing into a capacitor, but I have never come across a similar analog for how the Poynting flux...

In this page https://en.wikipedia.org/wiki/Matrix_mechanics I don't understand this statement : "When a classical particle is weakly coupled to a https://en.wikipedia.org/w/index.php?title=Radiation_field&action=edit&redlink=1, so that the radiative damping can be neglected, it will emit...

I have just covered the electricity unit in my advanced higher physics course, and have happily accepted that a force is created between charged particles. I understand that coulombs law can be used to calculate this force, but here is my question. What actually is this force between the charged...

Superconducting Ring In a superconducting ring does the contraction of space between electrons cause them to move inwards? Like in this animation. Force Between Parallel Wires With Current In the proton frame of two parallel wires with identical current, I've been told they attract and this...

In my experiment, I intended to find out how the change in the bar magnet drop height from solenoid affected the emf induced in the solenoid, however, I am unable to come up with an equation that shows a relationship between the two variables. I have thought of Biot-Savart law, but I do not...

Homework Statement An infinitely long cylinder of radius R carries a "frozen-in" magnetization, parallel to the axis, ## \vec M = ks \hat z ##. There are no free currents. Find the magnetic field inside and outside the cylinder by two different methods: (a) Locate all the bound currents and...

Homework Statement An electric doorbell requires a 12 V 60Hz ac supply a)What turn ratio is required on a transformer to operate from a 120V 60Hz ac supply? b)Step-up or step-down? c)If the transformer is connected the wrong way around the circuit what voltage is supplied to the...

https://phys.org/news/2017-10-effect-electromagnetism-years.html This was in my FB feed, was wondering how big this is

Good Afternoon Is it correct to calculate the force of a point charge by relating the force to the kinetic energy and this with its derivative? I have the graphic V/r (Velocity Vs Space), want to calculate force, relate work with force in this way: W=ΔEk, in my case the kinetic energy initial is...

Homework Statement I've completed an experiment where the dependence of magnetic field strength ##B## on current ##I## is measured at the midpoint along the axis between two Helmholtz coils (separation distance = coil radius ##r##). I got the expected linear relationship from the data but am...

It is a well known fact that, in electromagnetic units, strength of a shell and strength of current flowing through its boundary are same. See here. \begin{equation} \begin{matrix} \text{i.e.}\: i \text{(biot)} = \phi \text{(biot) } \end{matrix} \tag{1} \end{equation} (a) While converting to...

Hi guys, Disclaimer: not a physicist (I wish I was that brainy) Quick question regarding a speculative architecture project I am undertaking; In the completely hypothetical event of a huge, otherworldly solar flare super-charging the Earth's ionosphere beyond anything we have ever recorded...

I am computing force between two magnetic poles each of one unit pole (in emu) and situated one centimeter apart. In electromagnetic units: ##F_{dyne}=\dfrac{p^2}{r_{cm}^2}=\dfrac{1^2}{1^2}=1 dyne## where ##p## is pole strength in emu In SI units: ##F_{N}=k_A \dfrac{P^2}{r_m^2}=10^{-7}...

Hi, Could you please help me with the queries below? Thank you. Question 1: Please have a look on this attachment. In the given attachment, the disk is mounted vertically and only a part of the disk passes thru the magnetic field at any instant. If entire surface of the disk was rotating in a...

Let's assume that a and b charges are moving. now in our lab frame there will be a electric+magnetic force whereas in a rest frame of either of the charges, there will be only an electric force. So, two inertial observers will measure different forces?

Hello everyone, I'm currently doing a CSE bachelor (europe) in which I'll focus on physics. Now, I'd like to also put in some extra work to strengthen my focus on physics. This will put me ahead of others but it might also give me the chance of doing a masters in physics. Anyway, currently...

I try to learn electrodynamics as theoretical physicist, Now I study from Griffiths, I find it very good book and do the job! but the problem I need to learn electrodynamic to do future topics like Quantum Electrodynamics, and Pollack I find it good and modern, so my question is what is the best...

HI, initially I would like to put into words that there are sufficient resources, books or lecture videos on YouTube related to finite element analysis especially for structural dynamics (for instance JURGEN BATHE in MIT). But I would like to make you sure that there NO lecture videos or other...

Lenz's law shows that dropping a magnet through an aluminum pole will cause an induced current that slows down its fall drastically. I found a website that talks about this a little: https://www.lhup.edu/~dsimanek/TTT-slowfall/slowfall.htm It has the following question: I don't see any...

Homework Statement A uniformly magnetized and conducting sphere of radius R and total magnetic moment m = 4\pi MR^3/3 rotates about its magnetization axis with angular speed \omega. In the steady state no current flows in the conductor. The motion is nonrelativistic; the sphere has no excess...

Why does an increased electrical permittivity reduce the phase velocity of light in a medium? Furthermore, what interactions do we see on an atomic level? I am aware of the equation that defines the speed of light in terms of the electrical permittivity and magnetic permeability, but I do not...

I heard that you can never really touch anything. I also heard from an article that the reason why your butt doesn't fall through your chair is due to forces. Here is a short excerpt: "Cracking like lightning through the void, all the specks of electrons and the specks of nuclei are constantly...

This is an interesting question that popped through my mind. Some of us should know what is meant by „gauge transformations”, „gauge invariance/symmetry” and are used to seeing these terms whenever lectures on quantum field theory are read. But the electromagnetic field in vacuum (described in a...

I am an engineering major at Los Angeles Pierce community college. I have been for the last years working 40 hours a week in order to sustain and put myself through community college. After I transfer, I don't plan on working. Now, each semester due to my work schedule and life happening, I can...

https://arxiv.org/pdf/1705.07188.pdf Equation 5 in this paper states that $$\frac{\partial F}{\partial p_i} = 2Re\left\lbrace\frac{\partial F}{\partial x}\frac{\partial x}{\partial p_i}\right\rbrace$$ Here, p_i stands for the i'th element of a vector of 'design parameters' \mathbf{p}. These...