5
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What would an alternative to the Lorenz gauge mean? Difference vs Sum
Choice of gauge condition doesn't change the physics and doesn't change the measured E- and B-fields.
Mathematically, it will just make life more difficult. The Lorenz gauge is chosen for its ...
- 137k
5
votes
Accepted
Physical interpretation of selection rules for different multipole orders
One way to understand dipole or multipole fields are through the multipolar expansion. The idea is simple: Consider that you have a distribution of charges in space. Of course it produces some ...
- 3,349
3
votes
According to Maxwell Equations, how does the light travel straight line?
The electromagnetic wave equation allows for plane wave solutions in the form of
$$ \vec{u}=\vec{u_0}\exp(i\vec{k}\cdot\vec{r}-\omega t), $$
and since the wave vector can always be chosen to travel in ...
- 3,603
3
votes
According to Maxwell Equations, how does the light travel straight line?
From the Maxwell's equation you can derive the wave equation, whose solutions are a propagating wave. Next, we need to define what is meant by propagation direction of the wave, and then look to see ...
- 1,894
3
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What would an alternative to the Lorenz gauge mean? Difference vs Sum
Nothing would change in terms of $\mathbf{E}$ and $\mathbf{B}$ fields, but there is a reason why the generally the Lorenz gauge is preferred: it is Lorentz (with a t) invariant! In other words, if you ...
- 606
2
votes
According to Maxwell Equations, how does the light travel straight line?
With the setup as shown in the figure the light does not propagate in a straight line - the setup is cylindrically symmetric, and the resulting wave is a cylidnrical wave... looking rather different ...
- 65k
2
votes
Faraday's cage, but for Magnetism
Yes, for static fields
Magnetic shielding can be achieved by placing high magnetic permeability around the volume of interest. This doesn't block the external magnetic field, but it does draw it into ...
- 485
2
votes
Can we say induced emf depends on the path considered?
can I say that we can associate value to induced emf between any two points over some arbitrary path?
Yes.
Can we conclude induced emf over any imagined path does not depend on whether there is some ...
- 41.4k
2
votes
Accepted
Does $\vec F=I\int\mathrm d\vec{l}\times \vec{B}$ give the force on a current carrying wire when it is in motion?
You are correct; although the usual simple derivation works only for stationary conductor, the result is more general and holds for moving conductor as well.
One way to see it is the argument you gave ...
- 41.4k
2
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Is there any radiation similar to Bremsstrahlung in electron-electron or electron-positron scattering?
You are comparing apples and oranges. You show the tree diagram, but there are also radiative diagrams:
which are higher order, and hence fall under "radiative corrections".
In practice, ...
- 39.6k
2
votes
Fourier Optics of lenses and free space translations in terms of wave vectors
You just need to use your Fourier theorems. The Fourier transform of the product of two functions is the convolution of their spectra. Likewise, the Fourier transform of the convolution of two ...
- 15.8k
2
votes
What kind of tensor is the electromagnetic field tensor (Faraday tensor)
Fundamentally, as is the case with gauge fields in general, it's a second degree differential form, $F = ½ F_{μν} dx^μ ∧ dx^ν$, so that its components are those of an anti-symmetric rank two covariant ...
- 2,383
2
votes
Accepted
Some doubts on the derivation of $\partial_\mu T^{\mu\nu}=+\frac{1}{c}F^{\nu\sigma}J_\sigma$ for particles
First, consider the definition of the particle energy-momentum tensor, $T^{\mu\nu}_{\text{part}}(x)$. You're right to be a bit puzzled; it's not a given, but rather a construction representing the ...
- 196
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vote
Magnetic Flux in presence of variable magnetic field
You are correct that your magnetic field does not have zero flux through some closed surfaces. In terms of the differential forms of Maxwell's equations, this can be seen as a failure of $\vec{B}$ to ...
- 51.6k
1
vote
How is the emf in a transformer related to voltage of power supply?
It should only depend on the geometry of the primary coil, the number of turns and the rate of change of the current … How does the maximum AC voltage have anything to do with the maximum voltage in ...
- 109k
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