Electromagnetism Definition and 853 Threads

dH=dl/dt dB=dl/dx dE/dB=-dx/dt dD=dl/dx dH/dD=-dx/dt H - magnetic field strength; B - magnetic flux density; E - irradiance; D - electric displacement field. Please, have a look at these equations. Are they correct? I can't grasp the idea. Any explanations? I need some intuitive understanding...

Hi everyone! I've been reading about these topics (Feynman lectures and more on the internet and some books) but I still have a doubt, maybe because I haven't understood the whole of it. This is my doubt: Think of an imaginary situation in which we have an accelerating charge. The...

Hello everyone, I read on WIKIPEDIA, that: In 1953 Einstein wrote to the Cleveland Society of Physics on the occasion of the commemoration of Michelson-Morley's experience that "what brought me more and less Directly to the theory of special relativity was the conviction that the electromotive...

Homework Statement q=1.602*10^-19 point 1 L=1mm=r1 v=1.1*10^6 at point 2 F=1.44*10^-12 at point 1 Homework Equations E=(1/4πε)*(q/r) ΔV=∫E*dr=(1/4πε)*q∫(1/r)=(1/4πε)*q*ln (r2/r1) ΔU=ΔK=mv^2/2 ΔK=mv^2/2=ΔV*q=q*(1/4πε)*Q*(ln(r2/r1))...

Homework Statement So I want to know the distance to 2. The proton is at v=0 at the 1. We know that: q=1.602*10^-19 point 1 L=1mm v=1.1*10^6 at point 2 F=1.44*10^-12 at point 1 Homework Equations [/B] E=(1/4πε)*(q/r2) ΔV=∫E*dr=(1/4πε)*q∫(1/r2)=(1/4πε)*q*(1/r2-1/r1) ΔU=ΔK=mv2/2...

Homework Statement [/B] A proton is accelerated from rest at the positive plate of two charged parallel plates with a potential difference of 2000 v. After leaving the plates through a small hole in the negative plate, it enters a uniform magnetic field of 0.50 T in a direction perpendicular to...

I guess it is a trivial fact that field must be ##(\phi_1 - \phi_2)/s## but I don't get how ? is there a derivation for it ?

First off, I am new here, so please don't tear me apart too hard if I miss or misinterpret something, I'll cotton on eventually :D As I understand it, when a permanent magnet repels an oppositely charged object, such as another oppositely charged permanent magnet, no energy is technically being...

Hello, and thanks in advance for taking a look at my question. Generally, I am trying to make a railgun force model. Since railguns depend on the magnetic field created around the rails (and the resulting Lorentz force) I need to model the magnetic field created by the current that flows...

Hi I'm thinking about making an instrument to show the force on a wire carrying electric current for students in lab. A normal wire which levitates from ground after it has current flowing in it. We have the following equations F = ILBsin(a) W = ALg 'A' being the mass of unit length of the...

Homework Statement trying to do question C Homework Equations I know my answer to C cannot be right because it's worth six marks, any help or tips would be greatly appreciated. :) The Attempt at a Solution

Homework Statement The current in coil P is constant. An iron rod is inserted into coil P. Coil Q is placed next to P with a voltmeter connected to it. Explain why, during the time that the rod is moving, there is a reading on the voltmeter connected to coil Q Homework Equations emf=-Dphi/dt...

Homework Statement Consider a plane monochromatic wave incident on a flat conducting surface. The incidence angle is ##θ##. The wave is polarized perpendicular to the plane of incidence. Find the radiation pressure (time-averaged force per unit area) exerted on the surface. Homework Equations...

Homework Statement ##l/l_0=100## ##S=3 (cm)^2## ##B_r=200μ_0H_c=2mT## ##R=10Ω## No current runs through the feromagnetic core. Calculate the charge ##q## that goes through ##R## from the moment in the diagram to the moment it is removed from the core. Homework Equations 3. The Attempt at a...

[Moderator's note: posts from several threads on the same topic have been merged into this thread.] When we measure the EM field of a charged particle, what exactly are we measuring? Are we measuring the position of the EM field, the strength of it, what? Does a penning trap measure the EM...

Homework Statement Consider a glass plate of refraction index n and thickness ## \Delta x ## placed between a point monochromatic source S and an observer O, as in picture. (a) Prove that, if absorption from the plate is neglegible, then the effect on the wave received by O is the add of a...

Homework Statement The problem statement is simply to find the vector potential inside and outside an infinite wire of radius R, current I and constant current density j using the Poisson equation. Homework Equations The Poisson law can be written A = μ0 /4π *∫(I/r*dl) or A = μ0 /4π *∫(i/r*dV)...

The magnetic force is defined as ## \rm F_e = Bqvsin\theta## and the magentic flux is defined as## \rm \phi = BAcos\theta## My question is since we are multiplying the two vectors, why is ##sin\theta## used in one equation and ##cos\theta## in second given that ##\theta## is the angle between...

Hi does the quantum mechanic play a role in the intrinsic nature of electromagnetic fields and its propagation? massi

hi i was wonder as to why when an solonid is placed with a current within and magnet there's a an rotational force. why is it that he difrence in strength of magnetic field created results in an rotation many thanks Ewen

Okay, so in Griffith's introduction to electrodynamics, Griffith clearly defines surface current density as follows: "when charge flows over a surface, we describe it by the surface current density, K. Consider a 'ribbon' of infinitesimal width dL running parallel to the current flow. If the...

Hi, I want to find an equation for the force generated by a solenoid on a moving steel ball bearing given current, number of loops, area of the solenoid for a lab project. I've tried looking through many sources, but was unable to find anything. I also tried looking at this previous discussion...

So i have learned about the ability of Faraday Cage for blocking an external electric field. But is the thickness of the conductor effect the ability? Is there any limit of its thickness so that the cage won't be able to block external electric field anymore? I have read and searched about this...

Hello! I have a question about a GRE problem. It is problem 55 in the attached file. So the answer seems to be (A) but I am a bit confused. Isn't this basically interference, so the right answer would be (C)?

Let's say I have a charge q which is viewed from its rest frame. So it's velocity v is 0. So the so-called magnetic component of its Lorentz force, which is q v x B, is 0. But I can have a magnet moving in this frame of reference. Let's say the velocity of this magnet according to the charge's...

In Purcell- Electricty and Magnetism book, in the chapter on electromagnetic induction, I found the following explanation regarding the magnetic flux through a circuit of area ##S##. Consider the circuit in figure, moving in a time ##dt## in a magnetic field ##B##, constant in time (but not...

I have a doubt on this calculation of magnetic field in presence of displacement current. Consider a capacitor of radius ##R## and with plates at distance ##d## being charged: there is a displacement current in it. Suppose that I want to calculate the magnetic field ##B## at a distance ##r <...

Hey all, I am working my way through a couple of emag books (Griffiths, Jackson, and Schwinger) and I was wondering if any of y'all have suggestions for problems that you thought were particularly physically insightful or useful. Cheers, IR

It has been demonstrated that it is possible to make humans hear sounds using waves. Abstract From Journal of Applied Physiology Is there a practical method for shielding? I mean using materials for simple attenuation, and/or altering characteristics of waves (frequency, phase and/or amplitude).

https://postimg.org/image/lg27z8ngn/ 1. Homework Statement in the first one. I need to find the electrical force in the second one. Lorentz force which exerts the wire on the other element third. Magnetization (M) for Nickel quarter. Electromotive force induced on the dipstick Translate...

Homework Statement An infinite line of charge with charge density λ is parallel to and a distance d above an infinite grounded conducting plate. What is the charge density σ that is induced in the plate? For simplicity, consider the line of charge to lie along the line x = 0. Homework...

I'm trying to understand how the various EM tensors work in General Relativity. The only source I've found is https://en.wikipedia.org/wiki/Maxwell%27s_equations_in_curved_spacetime, but there are two things I don't get. Why do they use ordinary partial derivatives instead of covariant ones...

Homework Statement Loop of current ##I## sitting in the xy plane. Current goes in counter clockwise direction as seen from positive z axis. Find: a) the magnetic dipole moment b) the approximate magnetic field at points far from the origin c) show that, for points on the z axis, your answer is...

Homework Statement A long solenoid has a radius of 3 cm, 3000 turn per meter, and carries a current I = IOcos(ωt), where Io is 0.25 A and ω is 628 s−1 . It is placed through a circular loop of wire, radius 5 cm, which has resistance 100 Ω. The magnetic field in a solenoid is B = µonI. (a) Find...

Hello. I want to study electromagnetism so I can understand it in circuits and for electrical engineering as well. Are there any good introducotry books? I have done basic mechanics (kinematics motion in a straight line, work, energy, power , ideal pulleys and motion in two dimensions, calculus...

Hello, friends! My textbook, Gettys's Physics, says that the Lorenz gauge choice uses the magnetic vector potential $$\mathbf{A}(\mathbf{x},t):=\frac{\mu_0}{4\pi}\int \frac{\mathbf{J}(\mathbf{y},t-c^{-1}\|\mathbf{x}-\mathbf{y}\|)}{\|\mathbf{x}-\mathbf{y}\|}d^3y $$and the electric potential...

This is not a specific homework problem. It is a lack of understanding in theory relating to a lab report I have to write. We (my group and I) wrapped a 40 cm PVC pipe in copper wire (very densely and for almost the entire length), applied a current to it, and dropped a permanent magnet...

Homework Statement Hi everybody! I'm preparing for an exam of electromagnetism, and I am struggling with the last question of this problem (hopefully the two first ones are correctly solved): Given potential: ##\phi(\vec{r}) = k \frac{q}{r} e^{-r/R}## with ##r=\sqrt{x^2 + y^2 + z^2}## and ##R...

(I'm sorry for my poor English.) In GR the explanation for the bending of light by gravity is that gravity is a curvature in space (and time) and thus light follows the curved space. I was reading about the (undiscovered) graviton. It would have spin 2. Does it mean a graviton would interact...

Electricity flowing through a wire creates it's own magnetic field. So when the electricity is flowing through a wire, it's magnetic field works AGAINST the generator, slowing it down. So is there is any way to stop slowing down process without increasing amount of current ??

Okay, so we learn in basic physics that electric fields are created by charges and that magnetic fields are created by moving charges. After that, we learn that those two are just two faces of the same coin: the electromagnetic field. Also, we know that electromagnetic waves travel trough the...

Hi! I am one class away from graduating with a degree in geology from my university. I have a specific interest in geophysics and spent my summer in Ecuador (and spent some time at their Geophysics institute) and in New Mexico working with Los Alamos National Lab using geophysical techniques...

Why do people ignore polerization and magnetization when rewriting maxwells equations for different fields? Thanks!

If an insurer were to offer a policy against data loss from a catastrophic event such as an electromagnetic pulse, the insurer would be in no position to pay when the contingency occurs, the reason being that all of his own bank account will have been wiped clean by the same EMP. Therefore I...

So the potential inside a conductor is constant. Does this mean that if there were a conductor, B, inside another conductor, A, the charges of A/B would redistribute such that the electric field inside would be zero (hence constant potential)? This seems logical but a bit too easy? Also, if it...

I have a confusion regarding Faraday's law of electromagnetism. Consider this diagram At this instant, the velocity of the rotor is parallel to the field lines, hence, no emf is induced in the rotor. Altetnatively, we can say that the rate of change of flux associated with the rotor is 0 at...

I have to say first that I found quite a similar question under https://www.physicsforums.com/threads/poynting-vector-dilemma.331375/ However those thread ended without real answer.There shall be the following simple setup: A battery, and quite at a distance a light bulb. They are connected by...

So, I'm working with a DC shunt wound motor and I want to calculate the actual voltage production on paper mathematically before building. I have been studying the biot-savart law and understand it to a fair degree. One of my questions is after you get your measurements in Teslas from said law...

hi, nowadays I try to get involved electromagnetic waves equations, and I came across that $$ \nabla $$ is treated like $$ ik $$ and $$ \frac {\partial } {\partial t} $$ is treated like $$ -iw $$ And if you look at the part painted with orange in my attachment, afterwards you can see that $$...

Hi I would like to ask you guys something a little basic but is itching my mind, the question is : do electrons have net movement when dealing with ac currents? Suposing we have a sine wave for voltage and current. Thanks in advance ! PD:please excuse any grammar mistake.