The classical theory of electric and magnetic fields, both in the static and dynamic case. Also covers general questions about magnets, electric attraction/repulsion etc. Distinct from electrical-engineering.

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47 views

What is the relation between retarded potential and the Lorentz transformation of EM fields?

In Griffiths' ED book he derives the field of a moving charge by two ways: LW retarded potential. Lorentz transformation of EM fields. (eq10.68 and eq12.92 and the discussion that follows,3rd ...
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60 views

Boundary conditions for 2D helical waveguide

I'm interested in looking at standing wave solutions for the wave equation on a 2D annulus, with the twist that the annulus is "streched" in to a helix in 3D, but so that the rings themselves are ...
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61 views

Can I generate electricity through superconductors?

Can a superconductor produce electricity in any condition or in any state? OR can it be used to produce electricity with the help of any other components?
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14 views

Where can get channel waveguide dimension data ny nx na ns

I need channel waveguide dimension to test my waveguide mode solver. Can someone help me?
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97 views

Variation of electric field and current flowing

Theoretically, a change in either electric or magnetic field will cause a current to flow , I am already familiar to Faraday's law of electromagnetic induction, so I tried to search about producing a ...
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207 views

Rate of change of magnetic flux and the speed of the magnet

The faradays law is $-N*A* \frac{\Delta B} {\Delta T}$ which is the rate of change of magnetic flux times area. How to find out the voltage induced when the magnet moves through the coil and exits ...
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15 views

Is imperative magnetic flux the capacity of individual atoms, or the constituent valency of chemically-bonded molecules within a vacuum?

If magnetic energy depends on the electron poles within two-fields within a permanent magnets void, how do invidiual atoms react within the attraction or repulsion of poles, and what incurrence does ...
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109 views

Comparing sensitivity of flat spiral coils with regular solenoids

I'm attempting to compare the sensitivity that can be gained by using flat spiral coils against regular solenoid coils. A nice paper here gives reasonably accurate expressions for the inductance of ...
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91 views

Force of a magnet in a magnetic field?

Let's assume you have a simple bar magnet in a magnetic field. I know that the tendency is for the magnet to line up with the magnetic field. I'm trying to figure out how much force that actually ...
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160 views

Current Carrying Wire Loop near Current Carrying Long Wire

A rectangular wire loop of (width $a$ and height $b$) carrying clockwise current $I_1$ is a distance $d$ below a horizontal infinitely long wire carrying a current $I_2$ to the right. What is the ...
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36 views

What is the agent that does work in case of friction due to eddy currents?

In light of the well known fact that magnetic forces do no work, In every such case that nature presents us, it is possible to find some agent which does the work while magnetic forces just give ...
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50 views

Where can I find how to do data analysis for a magnetic hysteresis loop?

I am given a data set that has a hysteresis loop but there's a diamagnetic signal that I understand needs to be subtracted, but I don't know the how this is done. I remember finding the slope of the ...
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48 views

The electron and classical dynamics

Can I use Newtonian laws of dynamics and kinematics applied to electrons (like $F = ma$ and $s = s_0 + v_0 t + at^2/2$)? If not, why not? I know that everything in principle behaves in a quantum ...
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31 views

Uniform distribution of charge on a plane and on a bar: conditions to have no motion of the bar

On the plane z=0 there is a superficial charge distribution such that $\sigma$ is constant. Near to the plane, there is a bar, charged uniform with total charge q. At the extremities the bar has two ...
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188 views

Infinite long current carrying wire inside a infinite long solenoid

The magnetic field due to a long infinite solenoid is zero outside the solenoid. If there is a long infinite current carrying wire at the axis of this solenoid then The field is non-zero outside the ...
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131 views

Particle inside a charged shell

Imagine that I have a particle of charge $q$ at the center of a spherical insulating shell of charge $Q$ and radius $R$. Both the particle and shell are initially at rest. Now I apply a force ...
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84 views

What is the meaning of negative permitivity or negative permeability?

We say that when we force a field on the media the electrons change their positions and a save energy. How much a media can store energy is called permitivity, in this position how we can have ...
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44 views

Does the Blackett effect exist?

From Wikipedia: The Blackett effect, also called gravitational magnetism, is the hypothetical generation of a magnetic field by an uncharged, rotating body. This effect has never been observed. ...
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86 views

Solving the source free Maxwell equations for plane waves

I've been trying to solve the maxwell equations: $$\nabla\cdot\vec{D}=0,\quad \nabla\cdot\vec{B}=0$$ $$\nabla\times\vec{E}=-\frac{\partial \vec{B}}{\partial t},\quad \nabla\times\vec{H}=\frac{\partial ...
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164 views

Power Delivered By An Electromagnetic Wave Versus Power Delivered By A Transmission Line

Background Electromagnetic Waves As I understand it, an electromagnetic wave, like any other wave, is capable of delivering power from a source to a destination. To quantify how much power is ...
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35 views

Isotropic capacitance

I understand isotropic capacitance as the limit of a mathematical equation. Is that the only explanation that physics has? It seems to lack a more complete interpretation.
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54 views

Can modern times physics explain Hutchison phenomenon?

I saw this video and trying to understand the phenomenon. But as you can see the electro-magnetical device lifts the non-polar material.(1:35~2:00) How can it be possible?
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79 views

Angular momentum contained in E&M fields

I am trying to do this question as a prep for my quals and find my solution too simplistic. I fear I am missing something important. "Iron atoms (atomic mass 56) contain two free electron spins that ...
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66 views

Determining the Action of the Electromagnetic Field - Examples

In Landau Volume 2 (page 71) an expression for determining the entire electromagnetic Lagrangian is given. What would be an explicit numerical examples of working this idea out along the lines Landau ...
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41 views

Physical and dynamical components the four potential

I have a question regarding the four-potential and its gauge symmetry. We have a gauge freedom: $A_{\mu} \rightarrow A_{\mu} + \partial_{\mu}\chi$ Such a transformation does not alter the EM field. ...
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93 views

Most efficient (superconductive) coil design for generating inductance

What is the most efficient coil geometry for a magnet. I am assuming that toroidal coil are ultimately the most efficient as they are mechanically less susceptible to becoming destroyed. Are any sort ...
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89 views

Potential energy: Electric field two spherical charges

I want to determine the potential energy of two equally charged spherical charges by using the equation: $V_{pot}= \int_V \frac{1}{2} \epsilon_0 E^2 dV$ and therefore I was wondering what I has to ...
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61 views

Ideal metallic sphere in electric field

Assuming that you have a metallic sphere that is in an electric field $E=(E_r,E_\theta,E_\phi)^T$, $E_r,E_\theta=0$ and $E_\phi$ is some constant. Now I was wondering what the dipole moment in the ...
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39 views

Intensity change in reflected light for transverse magnetooptical Kerr effect?

I want to do some simple calculations for the (transverse) magneto-optical Kerr effect, to calculate what the change in intensity would be in the light reflected off of a magnetic medium. (I'm ...
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69 views

Mu-metal electromagnetic core?

Is it possibile to use Mu-metal as an core for a electromagnet? Considering thats is has a very high relative permeability? Low coercive force, and low hysteresis losses. And a very very low magnetic ...
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62 views

What is the physical property of metal nanoparticles?

I am a Math student but now I have to deal with gold nanoparticles in aqueous solution. Now I was wondering whether the physical properties of gold nanoparticles are the same as the properties of gold ...
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55 views

What can be done to increase the strength of a given electromagnet?

There's a lot of information online about increasing the strength of an electromagnet with more turns, different cores, etc, but not much about factors in the power supply that affect the strength of ...
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30 views

recharge magnet strength again

I have a speaker that have lost magnet strength. So I want to know is there any way can I recharge magnet strength again to this speaker. Truly, I don't have physics knowledge much therefore please ...
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35 views

Viscous force in a conductor

I was told that in a conductor there is a dissipative force and if Ohm's Law is valid for a component, the component has to be dissipative. I'm trying to prove it, but I have some problems. I know ...
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49 views

Blocking electro-magnetic waves between two near field antennas

Its been a while since I studied physics, so pardon my ignorance. I have two near field antennas. The range of the antennas is about 2-3 cm. I am looking for a way where I can block and unblock the ...
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63 views

Electrical properties of molten gallium arsenide

I'm looking for the resistivity and magnetic permeability of molten gallium arsenide, but can only seem to find the values for the solid material at room temperature (e.g., Wikpedia). Not even ...
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41 views

Electric Field of Electret

I've read that a method to measure Radon, is to use an Electret Ion Chamber. In particular here can be seen that, a voltage drop can be $2V$ in a single day. I believe this very much, yet I don't ...
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97 views

What is the “relative permeability” of Neodymium?

I am currently interested in finding a high "relative permeable" material to put into the core of a solenoid. However many sources quote Neodymium's recoil realtive permeability ($\mu_{rec}$) to be ...
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14 views

Potential E alternation

Considering a permanent magnet moving in a trajectory perpendicular to a straight wire of a given lenght, in a way that the magnet expose always the north face towards the wire, no matter the ...
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73 views

Is this picture of the electron dipole moment correct?

It's the electron spinning on its axis, and a magnetic moment shoots up. The direction of the North-South is opposite what I thought it should be. Why is the vector arrow pointing from North to ...
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84 views

Energy or Work done to pull an Iron cyclinder into a Solenoid

RadiI have been following the calcuations from these lecture slides here (slide 11). Where the slides attempt to approximate how much a solenoid pulls, by working out the energy required to pull an ...
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530 views

Could Space Travel be achieved using a very strong magnetic field to warp space?

An Alcubierre Warp Drive could theoretically achieve faster than light space travel but requires exotic matter or negative energy to compress space in front of the spaceship and expand space behind ...
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128 views

reflected wave in the transmission line

I am reading a book about the telegraph equations on the transmission line, which is illustrated as follow where the input impedance is $Z_0$ and the impedance of the load is $Z_L$, we setup the ...
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82 views

Cause a change in the magnetic field detectable by a smartphone Magnetometer

I hope someone can shed some light or point me in the right direction. I have a smartphone that has a Magnetometer built into it. I'm exploring some ideas of how I might be able to use it. I want to ...
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69 views

equilibrium intensity Helmoltz equation

Helmoltz equation describes the evolution of the bulk electromagnetic field, even when doing scalar optics as an approximation. Beam Propagation Method is a common approximation that assumes certain ...
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185 views

Solution of Maxwell's equation for simple, time-harmonic wire

I would like to compute the electric field $\boldsymbol{E}$ in the time-harmonic case for a (thick) wire parallel to the $z$-axis, but I can't quite get to it. What I've got so far: The current ...
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84 views

Curie's principle in electromagnetic field theory

I am looking for some explanation and if possible also some references about the applications of Curie's principle in electromagnetic field Theory, precisely in the computation of magnetic (resp. ...
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299 views

Equation of motion of charged particle under effect of magnetic field

A charged particle with specific charge q/m diverges from the origin [to the first quadrant] by angle X with x axis and with velocity v. To bring the particle back to the x axis, a magnetic field B is ...
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219 views

covarient derivative of electromagnetic field tensor

I'm trying to prove the energy momentum tensor in curved spacetime for Electromagnetic field is Divergence-less directly(Without using general lie derivative method which can prove any energy momentum ...
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98 views

cgs Gauss' system of units

I had never seen this system until today, and I'm really confused. I've read the wikipedia article about it but I still don't know how to change between this and the international system. For example, ...