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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7
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4answers
9k views

Rough, easy DIY method of measuring magnetic field strength

How to easily, using standard DIY equipment measure the strength of magnetic field generated by a permanent magnet? Narrowing down the "loose language" of the above: strength of magnetic field: ...
8
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1answer
266 views

Materials with different gravitomagnetic permeability?

If you start with general relativity, and assume small perturbations around a nearly flat metric, it is possible to obtain linearized equations of gravity that look a lot like Maxwell's equations, ...
5
votes
1answer
141 views

Order of magnetic phase transitions

Is there any phase transition occur in paramagnetism to diamagnetism transitions state. What should be the order and how will I calculate the order?
0
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1answer
197 views

What is the energy of interaction between two infinite charged wires?

This is related to my previous question. I assume that the two wires have the same charge density with the same sign ($\lambda_1 = \lambda_2 = \lambda$) If I want to take the same approach, the ...
3
votes
0answers
222 views

Theoretically speaking what are the limits for super-capacitors in terms of their storage capability?

According to wikipedia, commercially available super-capacitors in 2010 can store 30Wh/kg, with 85Wh/kg achieved in a lab in 2011. Have any theoretical calculations been done to show what can be ...
0
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0answers
675 views

Faraday law, third Maxwell's equation in Mathematica

Three question about this equation: $ \displaystyle\nabla\times\mathbf{E}=-\frac{\partial \mathbf{B}}{\partial t} $ 1 If I solve this equation with Mathematica, I find the magnetic field ...
2
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1answer
624 views

How does a magnet work?

I'm having trouble understanding how a magnet (not the field that is generated as a result but the material itself) work. The particles are aligned in a specific direction to give rise to force but I ...
2
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2answers
934 views

Tensor product notation [closed]

In the image there is a tensor product: $$F_{\mu\nu}F^{\mu\nu}=2(B^2-\frac{E^2}{c^2})$$ It's about how this operation on the co- and contravariant field strength tensors can give one of the ...
0
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1answer
387 views

Will I recieve a shock if I charged a capacitor then i touch the 2 poles in same time?

What happens if I charged a capacitor then i touch the 2 poles in same time?
0
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1answer
78 views

Can we transfer the charge on a plate of a capacitor elsewhere?

I know it is hard , but can we transfer the charge on a capacitor plate elsewhere?
5
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2answers
2k views

How to calculate required current and specifications for a “wet coil” to generate x Tesla of magnetic field?

A water management project requires a "wet coil" (coil will be submerged in aqueous media) designed to generate a steady-state electromagnetic field of adjustable magnetic magnetic flux density at the ...
9
votes
2answers
2k views

Would a gauss rifle based on generated magnetic fields have any kickback?

In the case of currently developing Gauss rifles, in which a slug is pulled down a line of electromagnets, facilitated by a micro-controller to achieve great speed in managing the switching of the ...
0
votes
1answer
659 views

What is the importance of electrodynamics and magnetism in physics as a whole? [closed]

At my university the second half of a year long sequence in basic calculus based physics focuses on electrodynamics and magnetism. I am wondering what is the significance of these topics to physics in ...
1
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2answers
150 views

A problem concerning the force between currents or moving electrons

Concerning two identical wires carrying the same current (same direction, speed and magnitude), they will be attracted because of the Ampere force. But when I was in the frame moving with the same ...
2
votes
1answer
420 views

If we have a current $I$ flowing down a wire, why must the net bound current be zero?

Say we are dealing with a wire that has a current $I$ flowing through it, i.e. $I$ is the free current. Why must it then hold that the net bound current, that is, the bound volume current, $J_b$, and ...
5
votes
2answers
862 views

Electromagnetism for Mathematician

I am trying to find a book on electromagnetism for mathematician (so it has to be rigorous). Preferably a book that extensively uses Stoke's theorem for Maxwell's equations (unlike other books that on ...
0
votes
1answer
4k views

Why isn't Hydrogen's electron pulled into the nucleus? [duplicate]

Possible Duplicate: Why do electrons occupy the space around nuclei, and not collide with them? Why don’t electrons crash into the nuclei they “orbit”? From what I learned in chemistry, ...
1
vote
1answer
91 views

Idea of precursors of the electro-magnetic waves

The idea of the material Maxwell equation is almost clear. But I'm curious about the idea that except for material equation the pure Maxwell equation should work, but in harder sense: more currents ...
2
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2answers
2k views

Artificial planetary magnetic field

I wonder how difficult it is to create an artificial planetary magnetic field with generators? What power they would need? The question is inspired by thinking about possible colonization of ...
5
votes
3answers
837 views

Why does the electric field dominate in light?

I read a book on the wave property of light where the author mentioned that the electric field, instead of magnetic field, dominates the light property. I don't understand why. In Maxwell's theory, a ...
2
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0answers
194 views

Where can I find a complete list of metamaterials up to today?

Where might I find a list of all the metamaterials up-to-date?
0
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2answers
237 views

Force on a bar magnet

A bar magnet is freely falling vertically inside a conducting ring placed in horizontal plane. Will it fall with an acceleration equal to g, less than g or greater than g?
4
votes
1answer
175 views

Using the monte carlo method to compute the magnetic field of a curent carrying loop

I have written a program in cpp that computes the magnetic field at a point from a current carrying loop. It uses the biot savart law and the monte carlo technique to carry out the integral. The ...
3
votes
2answers
3k views

Electric field and electric potential of a point charge in 2D and 1D

in 3D, electric field of a piont charge is inversely proportional to the square of distance while the potential is inversely proportional to distance. We can derive it from Coulomb's law. however, I ...
1
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1answer
541 views

Dipole moment of the electron

I've read that there are some restrictions on the value of a possible intrinsic electric dipole possessed by the electron, but isn't the dipole value dependent on the electron's wavefunction? Assuming ...
1
vote
1answer
189 views

Does a magnet's field become stronger or weaker in a vacuum?

This article seems to indicate that a magnet (atleast magnetite, it may not apply to rare earth magnets) weakens when subjected to extremes of pressure. This is purportedly the result of a decrease in ...
10
votes
4answers
3k views

Are the Maxwell's equations enough to derive the law of Coulomb?

Are the 8 Maxwell's equations enough to derive the formula for the electromagnetic field created by a stationary point charge, which is the same as the law of Coulomb? If I am not mistaken, due to ...
1
vote
1answer
316 views

Help: 3D visualization of magnetic field around moving point charge

The diagrams I'm able to find online only show the concentric field lines in the particle's plane, perpendicular to the motion, which of course generalizes to the cylindrical shape around a conductor. ...
7
votes
5answers
3k views

Can you put a magnetic ball into a hollow magnetic sphere?

if all magnets have to have two poles(one north one south), is it possible to construct a hollow sphere where the inside face of the sphere was one pole, and the outside face another pole? is it also ...
2
votes
1answer
83 views

Why does $H_2$ form on such a long time scale?

If we were trying to figure out the time scale for a gas-phase reaction between two hydrogen atoms in a molecular cloud (which has density $~10^4/$cm$^3$), apparently the reaction would happen on a ...
2
votes
1answer
666 views

Minimal coupling of an atom to the EM field

The Hamiltonian of an atom coupled to an EM field, both described quantum mechanically is: $$H = \frac{1}{2m}(\hat{p}-q\hat{A})^2 = \frac{\hat{p}^2}{2m} ...
2
votes
2answers
1k views

Poynting vector of a wire between capacitors

A capacitor made of two circular plates of radius $L$ separated by $d$, initially the plates carry $\pm$ Q charge. Then a wire of resistance R is placed between them, how do I go about deriving a ...
0
votes
3answers
534 views

What is voltage: strict but intuitive definition from accumulator's perspective

I know, that voltage is analogous to pressure for charge, but analogies lie. I don't see charge pressing anything and I don't understand definition of $U=A/q$ (voltage = work/charge), cause I can't ...
0
votes
2answers
1k views

Can electromagnetic fields be used to deconstruct and reconstruct atoms?

I was thinking one day and came up with a theory after reading about how scientists were studying anti-matter by using electro magnetic fields to separate matter from the anti-matter they made. It ...
1
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0answers
60 views

outward pressure in an confined electron gas

Suppose i have some electrons stored in a empty shell container with a negative ion layer in the inner surface so the electrons keep bouncing inside without being able to leave the inner cavity. I ...
4
votes
1answer
2k views

Force on Earth due to Sun's radiation pressure

I have been asked by my Classical Electrodynamics professor to calculate the force that the Sun exerts in the Earth's surface due to its radiation pressure supposing that all radiation is absorbed and ...
1
vote
1answer
141 views

Lorentz model and energy exchange

The Lorentz model, describing the electron of the atom as an harmonic oscillator forced by an oscillating electric field $\vec{E}$, shows that the dipole moment $\vec{D}$ obeys the following equation ...
1
vote
0answers
136 views

Can mu-metal reduce the negative effect of metal close to low frequency RFID antennas?

I have an 134.2 khz RFID antenna for sport events which is basically a 1x1 meter square sheet of rubber with 3 loops of antenna cable embedded. The problem is that the transponder recognition range is ...
1
vote
2answers
631 views

Proving the consistency of Faraday's law of electromagnetic induction

Here is a question which frequently occurs on my school exam paper: "Prove that Faraday's law of electromagnetic induction is consistent with the law of principle of conservation of energy." What ...
0
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1answer
2k views

Mutual Inductance and the Dot Convention

Can anyone please explain me, the dot convention in coil systems (Mutual and self inductance) with some related images to understand..?
8
votes
2answers
868 views

why dosen't a charged particle radiate energy in circular motion in a uniform magnetic field?

I have studied in my Physics course that one of the drawbacks of Rutherford's atomic model was that when an electron will revolve around the nucleus, it is undergoing acceleration and so it should ...
0
votes
3answers
1k views

Divergence equations (Maxwell)

Let $\mathbf{E}(r,t),\mathbf{B}(r,t)$ be two vector fields (in $\mathbb{R}^3$), s.t. they satisfy fot $t=0$ the equations: $\nabla \cdot \mathbf{B}(r,0)=0.$ $\nabla \cdot ...
-1
votes
1answer
89 views

Question about de Broglie Waves?

Is photon interaction , electrostatic interaction outside the nucleus and gravitational interaction is all due to electromagnetic waves ? and CAN be identified as with the de Broglie waves ? I ...
2
votes
2answers
155 views

What happens when a ferromagnetic object encounters a field too strong for it?

Just thinking aloud ... It is possible for a star to grow so large it collapses under it's own gravity. Along a parallel path (so to speak) when a conductor carries a current too large for it to ...
-1
votes
2answers
580 views

how do you destroy magnetic field - demagnetize?

And what happens with the magnetic field of a star that goes supernova? The magnetic radiation is scattered through the cosmos? Each particle will go away with its own magnetic radiation?
3
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2answers
68 views

heavy nuclei surface exposed to positron gas

Suppose there is a material with heavy nuclei attached on its surface, presumably binded by the outer shell electrons. Now, the surface is exposed to a cold positron gas, which annihilates against ...
4
votes
2answers
21k views

Why does electricity flowing through a copper coil generate a magnetic field?

Can some one please explain to me why electricity flowing though a copper coil generates a magnetic field or where I could possibly find that information? Are there other materials that produce a ...
0
votes
1answer
66 views

Reason for the convention about polarization states

I'd like to know if there is a special reason for limiting convention of polarization state to waves that can be split in just two components of equal frequency.
0
votes
1answer
4k views

Violation of Newton's 3rd law and momentum conservation [closed]

Why and when does Newton's 3rd law violate in relativistic mechanics? Check this link.
1
vote
1answer
897 views

In which of the above figures will the light bulb be glowing?

What is principle of solution behind this induction problem (problem 29)? The problem can be find in here (problem 29). Problem is: The five separate figures below involve a cylindrical magnet and ...