All Questions
Tagged with electromagnetism homework-and-exercises
1,552
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Dirac Delta Magnetic field
Suppose, we are given a magnetic field $\vec{B}$ as:
$$\vec{B} = \phi \delta(x)\delta(y)\hat{e}_z$$
where $\phi$ is some constant and $\delta$ is dirac delta function.
How do we find the corresponding ...
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How do we deduce the vector potential for a constant magnetic field?
How do we show that for a constant magnetic field $\vec B = const$, the vector potential is $\vec A = \frac12 \vec r \times \vec B$?
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What property of light allows it to propagate in space? [closed]
I got this question in a university entrance exam; I'm not sure what could've been the answer. I've scoured the web and could hardly find a decent answer. The question and choices were:
What property ...
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Is this a Lorentz-scalar? How do I tell?
I'm struggling to identify whether a scalar is a Lorentz-scalar. E.g:
$$\partial_i A^i \quad i \in {1,2,3}.$$
How do I determine if this is a Lorentz-scalar or not?
If got the same problem with ...
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Derivation of Ampere's Law in Jackson
The derivation of Ampere's Law in Jackson E&M from the Biot Savart law is for the most part fairly traditional, using the $\nabla\times(\nabla\times A)$ identity on the vector potential:
$$\nabla\...
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Pressure experienced due to magnetic force?
A current $I$ flows in a long thin walled cylinder(parallel to the axis) of radius $R$. What pressure do the walls experience?
This is the 263rd problem in Section III from the book 'Problems In ...
- 4,023
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Physics olympiad question about a charge capacitor
This is problem 1463 from the Russian magazine Quant.
Unfortunately my Russian is not good enough, so I apologize if the translation of the problem contains errors.
Problem. Inside a flat charge ...
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Induced current using a reference system bound with a moving charge
Suppose we have a charge moving at velocity $\mathbf{v}$ in the same plane of a square wire.
If I sit in a reference frame where the square wire is still, since the charge is moving with velocity $...
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What would it take to cause lightning to jump between the Moon and the Earth?
This question comes from @Floris' speculation at the end of his excellent answer about what it would take to kill everyone on the Earth with electricity.
Doing all this in 1/10th of a second requires ...
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Calculating the electrostatic energy per unit length of a cylindrical shell surrounded by a coaxial cable
Suppose an infinitely long cylindrical shell of radius $a$ carries a surface charge density $\sigma_0$ and is surrounded by a coaxial cable of inner radius $b$ and outer radius $c$ with uniform charge ...
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Can we explicitly solve the Hamilton–Jacobi equation for a particle in a uniform magnetic field?
HJE for nonrelativistic charged particle in an electromagnetic field is
$$\frac{1}{2m}\left(\nabla S - q\mathbf{A}\right)^2 + q\phi + \frac{\partial S}{\partial t} = 0.$$
For a uniform magnetic ...
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Why is there no induced current in this loop? [closed]
This problem comes from Barron's SAT Subject Test Physics book.
A loop of wire and a bar magnet are moving relative to one another. Which motion in the diagrams shown below will NOT induce a ...
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3
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How to see $\mathbf{E}\cdot\mathbf{B}$ is a total derivative?
Since $\mathbf{E}\cdot\mathbf{B}$ is a Lorentz invariant of the electromagnetic fields it seems like an interesting thing to plug into a Lagrangian to see what happens. However, this ends up ...
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Why do planets not radiate EM waves in their orbits?
Despite being overall near-netural, I would expect the individual electrons and proton to radiate long EM waves as we accelerate around the Sun or rotate around our poles. Is the acceleration so small ...
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