Electromagnetism Definition and 853 Threads

I am searching information about the interplanetary magnetic field,e.g, what is its strength? Does it vary with time? (I guess so) Are there statistical model to predict its variation in space and time? ... At the moment I have not a specific question in my mind, but I am looking for some...

My question might sound stupid to you but please clear my confusions. I'm taking an circular arc like element on the plate. That arc has a radius of 'r' (AB) and the radius is inclined at an angle 'θ' with OA (∠OAB). The area between arc of radius r and r+dr is dA. dA = 2θr.dr The charge on...

So I'm kinda stumped. I'm assuming that since ##\vec{m}||\vec{B}##, the x and y components of both are zero. But I'm unsure how to take this further.

I tried to solve it by removing the voltmeter and simplifying it to just one resistor, then calculate the individual volts and then the deltaV, but still didn't found the answer, can you guys help me?

So I was able to do out the curl in the i and j direction and got 3xz/r5 and 3yz/r5 as expected. However, when I do out the last curl, I do not get 3z2-3r2. I get the following \frac{\partial}{\partial x} \frac{x}{(x^2+y^2+z^2)^\frac{3}{2}} = \frac{-2x^2+y^2+z^2}{(x^2+y^2+z^2)^\frac{5}{2}}...

Hi all, I am an undergraduate junior majoring in materials science who would like some advice with respect to which courses to take for the fall semester of my senior year. Some background: I am a materials science student and I intend to study spintronics and topological insulators for my...

Hey, i have several questions about electromagnetism, i hope you will be able to solve these haha : 1) how to define the electric field? i mean without saying E = F/q because a field causes the electric force and not the reverse so we can't use the force yet right? 2) how to snap a capacitor...

Homework Statement Imagine having a conducting sphere with free charge ##Q## surrounded by a spherical shell filled with a dielectric and then a conducting spherical shell with no free net charge. I want to find out the charge induced on the spherical conducting shell by the sphere or by the...

Homework Statement Consider the following system: which consists of a conducting sphere with free charge , a dielectric shell with permittivity ##\epsilon_1##, another dielectric shell with permittivity ##\epsilon_2## and finally a conducting spherical shell with no free charge. Homework...

My elementary school had its first annual science fair a few weeks ago, so me and my friend signed up and we decided to do it on wireless electricity. So naturally, we built a tesla coil. It took a couple of tries, but we eventually got it to barely illuminate a portion of a fluorescent light...

I've wondered this for a while but not known how to ask the question, If light is a transverse wave, then what is it transverse to? To elaborate, light travels in three-dimensions, radially. To me, this seems analogous to the sound wave, with pulses of pressure moving longitudinally to the...

1. Problem statement A very long straight solenoid has a diameter of 3cm, 40 turns per cm, and a current of .275 A. A second solenoid is with larger diameter is slipped over it with N turns per cm, and the current is ramped down to zero over 0.2 s. a) What is the emf induced in the second...

Assuming the point charge lies at the origin, what is the electric field at the origin? Zero or undefined?

I was wondering if the [Feynman-Heaviside formula](http://www.feynmanlectures.caltech.edu/II_21.html) for the electric field of a moving charge could be used to write down the force/reaction force between charges ##q_1## and ##q_2## in a Machian purely relational way. The retarded electric...

my current skills in math are differential eq and linear algebra... and I am about to start reading Feynman lectures of physics and planning to read all John Baez's recommended books.. after reading Feynman's, what would be the next best thing to do? learn more math? or jump already to core...

In superconducting state, If the superconductor and the guide line are stationary, will the force between the the guide line and the superconductor change when they are close to or far away from the magnet?

As shown in the figure, the aircraft includes a geomagnetic field convergence layer, which is a superconductor material. The geomagnetic field convergence layer repels the direction of changing the geomagnetic field, so that the geomagnetic field passes between the upper and lower converging...

Hello! I'm working on an online assignment and am on my last chance to submit the right answer, so I figured I'd ask here for some help to see where my reasoning is wrong. Problem: For each of the five questions, I can choose one of four responses: Positive, Negative, Neutral, or Cannot Tell...

Consider an electric dipole consisting of charges ##q## and ##-q##, both of mass ##m##, separated by a distance ##d##. If the dipole is given an acceleration ##a## perpendicular to its moment the total electric force on it, due to each charge acting on the other, is given approximately by...

Particles follows accordingly the general equation: $$ m*\overrightarrow{a}=q*\overrightarrow{E}+q*\overrightarrow{v}\wedge \overrightarrow{B} $$ But in the case of two coupled coils the time varying current at primary coil (and its magnetic field variation) creates corresponding varying...

I am contemplating writing a science fiction story involving flexible barriers that can be erected in a very short time. Force fields are pervasive in science fiction, but from what little I've read, they're not very plausible. Is there a flexible material, or class of materials, that...

Homework Statement Hi everyone! My name is Alexandra, and I'm new in this forum. I am trying to determine the mentionated tensor without the assumption of linear media or vacuum ( ## \textbf{D} = \epsilon \textbf{E} ## and ## \textbf{B} = \mu \textbf{H} ##). What I want to obtain is the...

Homework Statement A charged particle has an electric field at ##\langle -0.13, 0.14, 0 \rangle## m is ##\langle 6.48\times10^3, -8.64\times10^3, 0 \rangle## N/C. The charged particle is -3nC. Where is the particle located? Homework Equations ##\vec E=\frac 1 {4π\varepsilon_0} \frac q {|\vec...

I'm studying for an exam (so this is existential) and I never really got how to write the limit conditions for an interface. In my problem, there is an incident electric field, and there are two cases: 1) the field is polasised perpendicularly to the incidence plane (TE) 2) polarised in the...

Hi everyone, I have a question that can't solve. Does exist a lagrangian for the relativistic angular momentum (AM)? I can't even understand the question because it has no sense for me... I mean, the lagrangian is a scalar function of the system(particle,field,...), it isn't a function FOR the...

How can it be easily shown that it's a bad idea to develop relativistic gravitational theory in full analogy with electromagnetism? I.e. why not to introduce 4-potential for gravitation in analogy with 4-potential in covariant form of Maxwell equations and get something fully analogous to...

Greg Bernhardt submitted a new blog post Are Magnetic Field Lines Real? Continue reading the Original Blog Post.

I was studying Feynman Lectures on Physics Volume 1 chapter 29. In there he proves that electric field propagates like a wave. Here is my attempt (in image), please tell me my mistake. Thank you

Homework Statement So I'm really confused with mutual inductors and dot convention. If your answer is going to be a link to any website I can assure you I read them all and that only left me more confused. So here are my questions: Homework Equations 3. The Attempt at a Solution [/B] ->...

Homework Statement I'm working through an example with motional EMF and I'm having trouble understanding the directions of vectors so that I can apply induction law. The magnetic circuit seems complex because the circuit is used to analyze other situations but the air gap 3, the coil 3 and the...

Homework Statement I'm currently studying induction law and circuits with inductors. I came however with the following circuit: [1]: https://i.stack.imgur.com/ghaiE.png Homework Equations 3. The Attempt at a Solution [/B] Now my text says the following: "Unlike what your intuition might...

(Hope I posted in the right section) Hi, starting from next semester I will have to attend classes that require a "decent" understanding of electromagnetism. I know very little about it though (it's a very long story...) so I started to study Griffith's book. At least I know the mathematics...

Hello, There is a common setup used when describing the intimate relationship between electricity and magnetism. I have a question about the setup. Setup: There is some long current-carrying wire. Outside of that wire, there is some test charge. In the first situation, the test charge is...

Homework Statement It is clear that SOMETHING exerts a force on the conducting wire in a downwards direction. By Newton's 3rd law, the (field of) this conducting wire also exerts a force on something. Homework Equations Could the magnet be said to move upwards (and hence reading decrease)...

Hello, I just had a quick question. Does anyone have links to online lectures for Upper-Division Electromagnetism? I so far haven’t been able to find much other than a few isolated videos here and there. I’m looking for something that covers Legendre polynomials, spherical harmonics, maxwell’s...

Hello To develop one interesting idea I need to be able to do calculations on (1) scattering of light from bodies in arbitrary motion, possibly at relativistic speeds; (2) Propagation of light in electromagnetic media that are in arbitrary motion (possibly relativistic). For example, I would...

Homework Statement Consider an infinitely long cylindrical rod with radius a carrying a uniform charge density ##\rho##. The rod is surrounded by a co-axial cylindrical metal-sheet with radius b that is connected to ground. The volume between the sheet and the rod is filled with a dielectric...

Homework Statement Homework Equations The Attempt at a Solution The textbook says that the electric field on a surface of a conductor is: . So, I guess since the sphere is metallic I can assume that what I have written there is true?

Homework Statement Two magnetic materials are separated by a planar boundary. The first magnetic material has a relative permeability μr2=2; the second material has a relative permeability μr2=3. A magnetic field of magnitude B1= 4 T exists within the first material. The boundary is...

Recently ( due to me moving forward with my undergraduate studies in electrical engineering ) I purchased a plethora of books, aimed at self study, in an attempt to try and understand the concepts behind electrostatics, electrodynamics, and magnetostatics etc. I read reviews on books that would...

Homework Statement A straight wire of length 0.20m moves at a steady speed of 3.0m/s at right angles to a magnetic filed of flux density 0.10T. Use Faraday's law to determine the e.m.f. induced across the ends of a wire. Homework Equations E= Nd Φ/dt but N=1 so E= dΦ/dt The Attempt at a...

I would very much appreciate a clarification on what is meant by a changing electric field in the context of statements such as 'a changing electric field creates a changing magnetic field'. My question is does the electric field actually need to reverse as a lot of examples show where two...

Greg Bernhardt submitted a new PF Insights post A New Interpretation of Dr. Walter Lewin's Paradox Continue reading the Original PF Insights Post.

Homework Statement Griffiths' Introduction to Electrodynamics problem 2.10, Homework Equations Gauss' Law, ##\int_{S} \textbf{E}\cdot \textbf{dS} = \frac{Q_{\text{enc}}}{\epsilon_0}##[/B]The Attempt at a Solution It seems reasonable that the flux through the shaded surface and the front...

Homework Statement Suppose we have a regular n-gon with identical charges at each vertex. What force would a charge ##Q## at the centre feel? What would the force on the charge ##Q## be if one of the charges at the vertices were removed? [/B]Homework Equations Principle of Superposition, the...

I have just finished my first semester of third year undergraduate physics, and have a 3-4 week break before my next semester, in which I will be taking a third course in electromagnetism (classical electrodynamics). It is my second course with a full focus on electromagnetism, since in first...

Homework Statement Consider a cylinder of thickness a=1 mm and radius R = 1 cm that is uniformly magnetized across z axis being its magnetization M= 10^5 A./m. Calculate the bound currents on the cylinder and, doing convenient approximations, the B field on the axis of the cylinder for z=0...

I know that the right hand rule applies for induced currents, and the left hand rule is for motors, but why? It doesn't seem to connect with any other physics laws and is very counter-intuitive that the current will flow in one direction rather than the opposite direction if both are...

Homework Statement A plane z=0 is charged with density, changing periodically according to the law: σ = σ° sin(αx) sin (βy) where, σ°, α and β are constants. We have to find the potential of this system of charges. Homework EquationsThe Attempt at a Solution [/B] I...

Hello all, I have a question regarding Maxwell's Equations and Faraday's unipolar induction equation. If we study the case of a cylindrical magnet with a radius of r which is rotating about its axis with angular velocity w. The electrons within the magnet collide with the moving atoms, causing...