Electromagnetism Definition and 829 Threads

This has been helping me throughout my semester in an intermediate level EM course, so I thought I'd post it here: http://www.youtube.com/view_play_list?p=C2CEECFD938FD494"

Hi. I'm doing an experiment and I'm kinda stuck. I know that a current produces a magnetic field. In this experiment there is a current carrying wire (copper) and a permanent magnet suspended above it. Deflection is being measured as the current is varied. I know that both magnetic...

Homework Statement Show that the force caused by external electric field on a charge distribution is given by: F=qE(0)+(p\cdot \nabla)E(0)+... (it's enough to show the first two terms), where E(0) is the electric field in the origin which we choose to develop the expression around it. p is...

DC doesn't cause electromagnetism? That is what our teacher says. Can anyone explain why it doesn't? As far I remember I made an electromagnet from a nail by passing current through it from a battery cell about 6 years ago.

urgent electromagnetism help Homework Statement Assume that dust particle in the solar system are spherical, black and have a density of 2000kg/m^3. Use the total luminosity of the sun to calculate the time average poynting vector of the radiation at a distance r from the Sun. Hence...

1.Calculate the electric field of a quadrupole in spherical coordinates. 2.Calculate the electric field of a octupole in spherical coordinates.

Homework Statement 1. In a dilectric sphere with radius a and polarization vector P= P0 r (r is the spherical radial vector) where P0>0. find D,E and the polarization charge volume density and area density. 2. A chagrge q is displaced at the centre of a hollow dilectric sphere (with a,b as...

Homework Statement Use Gauss’s law to obtain a vector expression for the electric field produced by an infinte sheet of charge with a surface density of 1 C m−2 , confined to the xy plane. Hence show that the divergence of this electric field is zero for all points not in the xy plane...

A long straight horizontal wire carries a current of 70 amperes towards the east. The wire is placed in a uniform magnetic field of intensity 0.15 T towards the north. Find the magnitude and direction of the resulting force on a 25m length of this wire F=ILB sin \theta F =...

Hi, Apologies an advance for any general ignorance (not a physics student - just happen to have an interest and no background!) Is there generally a strong electromagnetic field associated with any mass demonstrating a strong gravitational field? Are there exceptions? I've heard that...

Is there a defined distance at which Electromagnetism starts exerting more force than the strong nuclear force? So far I have Gluons have <20MeV (32.04×10-13J) of energy. Using the uncertainty principle: t=h/(4×pi×E) and distance = t×c Therefore t = (6.6×10^-34)/(4×pi×<32.04×10^-13)...

Homework Statement We learned in E&M about the Dirac Delta function and its applications to representing the densities of point charges in space. For example, the charge density of space with a point charge q at the origin is given by q*delta(r). How does this density representation work with...

Homework Statement Any sites you recommend that can really supplement my understanding of Vector Calculus applied to Electromagnetis? Thanks

Homework Statement Two infinite long straight conductors and a rectangular circuit lies in the same plane. The straight conductors is parallel and got the distance 2a from each other. There runs a constant current of I1 and I2 in both of them, and the current is pointed downwards. The...

Find a pair of fields having equal and divergences in some region, having the same values on the boundary of that region, and yet having different curls. I really have no idea on where to start for this. Would making up 2 arbitrary fields in spherical co-ordinates work? a(theta) + b\phi +...

Hi, Just out of curiosity, what should I know if I am going to take upper-division electromagnetism course. The text for the course is Griffiths' Introduction to Electrodynamics. I am not a physics major (I am a math major), but I have taken the first-year, calc-based physics sequence...

Homework Statement A square loop of wire C, with side length 2a lies in a plane P and carries a steady electic current I. By using the Biot-Savart law show that the magnetic field B(r) at any point r in P but not in C is perpendicular to the plane P. Calculate the magnetic field at the...

This isn't exactly homework, but I felt that I had too much to ask that it wouldn't be right to put this in the regular section. Anyway, I've been reading the original paper on the design of a cyclotron (Lawrence & Livingstone) and there were two parts which didn't agree with what I knew... and...

Recently I read that gravitation and electromagnetism is unified by Kaluza-Klein theory. Can someone tell me in depth how they are unified

1. The problem statement, all given/known data A bar magnet is positioned at the mouth of a solenoid. The current indicated in the solenoid is then turned on. (Assume the solenoid is a lot bigger than the bar magnet.) Gravity and friction can be ignored. Describe what would happen, and...

Can anyone recommend supplementary texts books for Electromagnetism and Thermodynamics? I'm looking for some alternatives to my recommended textbooks. The first class is an electromagnetics class. This class is heavily calculus based and consists of building up concepts that culminate to...

I am studying for my junior level EM final that is a few weeks from now, we are using Griffiths' Introduction to electrodynamics. To prep for the test I am already planning on working through all of our homework problems, and examples in relevant sections, as well as a few problems we didn't do...

A "galilean puzzle" in electromagnetism Well, I still didn't managed to find the answer, since the puzzle seems a little bit more involved than I first tought...to perform the computations, you only need to know a little bit about lagrangian/hamiltonian dynamics in electromagnetism. Consider...

1. An electron is traveling in the +ve x-direction of an inertial frame T. An acceleration is given to the electron in the +ve y-direction with as large as magnitude as possible. How do I specify directions of the electric and magnetic fields that will achieve this? Why are the choice...

I thought I understood this matter, but the more I think about it the more confused I am becoming. Suppose I have a very long wire which has a uniform negative charge per unit length ρ. I hold near it a particle with charge -q. Due to the electrical field around the wire there is a force...

Feynman's "apparent" paradox - Electromagnetism This is the paradox discussed in chapter 17 of "Feynman Lectures on Physics - Vol II" http://www.flickr.com/photos/37453425@N07/3447068420/ Say suppose the battery drains out or somehow you stop the current outta the battery. By...

Is there any evidence that electromagnetism has played a role in the formation of galaxies, galactic clusters, and super cluster filaments?

Maxwell's equations in integral form are not obviously local. Faraday's Law, a good enough example, in differental form is \partial_i B_j - \partial _t E_k = J_k where (i,j,k) are cyclic permutations of (x,y,z). In integral form, \frac{d\Phi}{dt} = \oint E \cdot dl The...

I believe classical electrodynamics can be reduced to: 1) Lorentz force 2) Existance of a Lorentz invariant vector field of real entries, V=V^\mu \hat{e}_\mu 3) Charge is always associated with mass Maxwell's equations are obtained by associatating elements of the vector field with...

A amssive charged particle moves under the influence of a time varying magnetic field \mathbf{B}=B(r,t)\mathbf{\hat{z}}, where r is the distance from the z axis. Show that the particle can move in a circular orbit in a plane perpendicular to the field, accelerating and decelerating under the...

Correct me if I am wrong, but, if electromagnetism is relative then in a frame where charges have relative motion between the observer, the observer would detect electromagnetic radiation being emitted from the charge, and that to an observer moving alongside the charge at the same speed, no...

1. "A wire segment carries a current of 1.8A from a to b. There is a uniform magnetic field of 1.2T acting in the z-direction. Find the total force on the wire and show that the total force is the same as if the wire were a straight segment from a to b". I've attached the diagram showing what...

A sphere of radius R has a unifromly distributed charge Ze inside it (essentially it's a model of a nucleus) now my tutor worked through the first part of the question with me and we established that the potential inside the sphere was \varphi(\mathbf{r})=-\frac{Zer^2}{8 \pi \epsilon_0...

Ok this book is very common. It's the question number 6.5 A dielectric object that has a quasi-permanent polarization when the applied field is 0 is called an electret. Consider a uniformly polarized electret in the shape of a cylinder of height h and radius 10h. The polarization in the...

Homework Statement When a uniform electric field is applied to diamond, the induced dipole moment per unit volume (ie. polarisation) is P_{0} = 1.5 \times 10^{-7} \text{C m}^{-2}. Given that the density of diamond is 3500 \text{kg m}^{-3}, 1 kmole of diamond has a mass of 12kg. Avogadro's...

Dunno whether this is the right place for this question! but As it is related to subatomic particles, I think it is! We know that magnetism arises due to rotation of an electron around its own axis in metals, but after all what happens due the moving electric current? Will the same...

Hi I have tried the question below. However I am failing at the first hurdle part a! Some help and advice would certaintly be appretiated. Thanks Taking a simple model of the hydrogen atom as an electron rotating around the nucleus in a circle or radius 0.53ee-10m at a frequency of...

Hey i was wondering about a paticular problem i found in a textbook. Specifically just one little niggle i have with it. i am given that the electrostatic potential energy in a region of space is given by v(r) = ((q*n)/(epsilon-0))(x^2+y^2) (where n is a constant of dimensions m^-3)...

Hello everybody. I would like to ask anyone who have taken graduate electrodynamics with jackson. What do you think is the best way to prepare yourself to graduate electromagnetism by Jackson, if only electromagnetism by Griffith is covered during undergrad. In particular, what...

Is \vec{\nabla^{2}} \vec{E} a dot or a vector product?

Hi, got some homework to do in electromagnetism and one of the problems is: Homework Statement Consider a Cartesian coordinate system with charges Q (Q = 15μC) at x = + and – 1.3cm, and at y = + 1.7cm and – 0.7cm and at z = + 2cm and -0.5cm. Calculate the flux of the electrostatic field...

does the difference in charge play a role in electromagnetism such as a +8 charge pulling a -1 being stronger because of the difference in numbers or does that even matter i mean would that mean that that is stronger compared to a + 1 charge pulling a -1 charge. Thanks in advance.

Hi, just out of curiosity... Ampere's Law describes that an electric current produces a magnetic field. When corrected with Maxwell's displacement current, it describes that a magnetic field is also created by a time-varying electric field. Does this mean that an electric current produces...

Homework Statement An airplane with a wingspan W = 30 m is flying due north at v = 672 km/h. The Earth's field is 1.210-4 T, due north and inclined q = 42 below horizontal. What is the magnitude of the potential difference between the ends of the wings...

Hello, I'm new on this forum :) I seriously need help with this problem. It has to be perfect if I want to pass the course, so I will really appreciate any solution to check my results. ---- An electrical current of 100[A] runs through a cilindrical conductor (radius 0.01[m], infinite...

[SOLVED] Electromagnetism, calculate electron charge/mass ratio I've spent all day writing a post and now I can't post a link to my picture due to your rules. Solved the problem anyway

[SOLVED] Monstrous electromagnetism question. Homework Statement A slope variable: thèta Amount of coils: 10. Cilinder: Diameter D Length L Massa M Magnetic field B. The cilinder has 10 coils wrapped around it, in rectangular form (over the top and bottom of the cilinder). It is...

Homework Statement An electric dipole is located at a certain distance from a grounded plane. What force does the dipole exert on the plane? (The answer is to be expressed as an equation. No data were given, only the above text) Homework Equations I am not sure about this, but the course is...

I know I'm suppose to use the equation F = (kq1q2)/r^2 I tried doing [.1/sq. root (2)] m for two of the forces and just .1 m for one. I plug all the numbers into the equation and add up the 3 but it doesn't work. I really have no clue what to do with this. Please help.

1. Feynman says all of electromagnetism follows from Maxwell equations. 2. Somebody (Pointing to a Feynman diagram of a photon/electron reaction) said all of electromagnetism is in that one diagram. So, can anyone help me with these two questions: how does point 1 come from point 2. And, how...