All Questions
Tagged with electromagnetism homework-and-exercises
258
questions with no upvoted or accepted answers
2
votes
0
answers
1k
views
Hysteresis Curve and how to implement it using Preisach model or other models
As a homework I need to draw a hysteresis curve (preferably an interactive one) using Matlab or any other programming language. The problem is I have trouble finding a good algorithm to do so. I need ...
- 51
2
votes
0
answers
885
views
Finding the terminal velocity of a magnet dropped in a solenoid
We have to find proportionality of the terminal velocity with the factors of the system:
Plot: a small dipole(mass $m$) with dipole moment $\mu$ is dropped in a long solenoid (radius $r$, ...
- 2,479
2
votes
0
answers
886
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Solar wind and the Earth's magnetic field
I have again an old question from a comprehensive exam I took a couple of months ago. Lucky for me one could pick 5 out of 8 questions, because on some of the problems I didn't even know how to start. ...
- 14.9k
2
votes
0
answers
205
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Wave propagation in anisotropic media
I'm given a wave propagation in an anisotropic medium with the following properties:
$\epsilon=\left[\begin{array}{ccc} \epsilon_{11} & 0 & 0 \\
\epsilon_{21} & \epsilon_{22} & \...
- 2,897
1
vote
0
answers
60
views
Vector potential of Weird loop
I have to calculate the vectorpotential of a current flowing through the loop at the origin:
where the current is given by $I(t)=kt$ for some $k>0$.
Given equations
$$\mathbf{A} = \frac{\mu_0}{4\...
- 49
1
vote
1
answer
102
views
Perturbation of central field potential
i`d like to consider system with Coulomb potential: $U = -\frac{\alpha}{r}$ and constant magnetic field.It is easy to write Lagrangian function:
$$ L = \frac{m}{2}(\dot{\rho}^2 + \rho^2\dot{\phi}^2) + ...
1
vote
0
answers
132
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Coilgun projectile force calculation
Please excuse me if I am completely wrong because I am a 9th grader but I hopefully am able to explain briefly about my problem. I was trying to create a function to calculate the Force of an iron ...
- 11
1
vote
1
answer
49
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How can I estimate the force of an electromagnet?
I am doing an experiment on electromagnetism, basically I am just testing the pulling force of an electromagnet using a newton meter with a magnetic hook and seeing how the pulling force changes as i ...
- 11
1
vote
0
answers
92
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Relativistic equations of motion in uniform electric field through matrix exponentiation
For my undergraduate studies, I was faced with the problem of finding the equations of motion for a particle subject to a uniform electric field, in the relativistic case. I would like to follow the ...
- 25
1
vote
1
answer
97
views
Magnetic Scalar Potential of Infinite Wire
While working on a question about magnetic scalar potential, I encountered a challenge. The question posits that the magnetic scalar potential, denoted as $\phi$, takes the form $\phi = -\frac{I}{2\pi}...
1
vote
0
answers
55
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Finding the equation of motion for vector potential $A_{\mu}$ in topologically massive electrodynamics
Essentially I want to vary the action
$$
S_M = \int d^3x \sqrt{-g} \left[- \frac{1}{4} F^{\mu \nu} F_{\mu \nu} - \frac{\alpha}{2} \epsilon^{\mu \nu \rho} A_\mu F_{\nu \rho} \right]
$$
with respect to $...
- 21
1
vote
0
answers
74
views
Confusion regarding magnetic length
Consider the geometric length of a magnet to be $L$ and magnetic length to be $L'$.
Some sources claim that $L'$ = $(0.84)L$.
One such claim can be found here:-
I cannot find any good reason to be ...
user355398
1
vote
0
answers
72
views
Electromagnetic waves in medium with strange polarization vector
I have an exercise in Electromagnetic waves, basically to find the refractive index of a wave in a medium with polarization $\mathbf{P}=\alpha \nabla \times \mathbf{E}$. I used the Maxwell equations ...
- 147
1
vote
0
answers
63
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Help with local gauge transformation
I have to prove that the following Lagrangian is invariant under local gauge transformation ($\psi\to e^{-i\lambda(x)}\psi$ and $A_\mu\to A_\mu+\partial_\mu\lambda(x)$, where $\lambda$ is real): $$\...
1
vote
1
answer
160
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Showing that dirac delta point charge densities is covariant
Consider a point charge $Q$ with a trajectory of $\textbf{s}(t)$ in frame $O$. The densities are:
$$\rho(\textbf{x},t) = Q\delta^{(3)}(\textbf{x} - \textbf{s}(t))$$
$$\textbf{J}(\textbf{x},t) = Q\...
- 29