All Questions
Tagged with electromagnetism homework-and-exercises
1,551
questions
2
votes
1
answer
6k
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Computing the Poynting vector?
Approaching the following problem:
A plane monochromatic electromagnetic wave with wavelength $\lambda = 2.0 cm$,
propagates through a vacuum. Its magnetic field is described by $
> \vec{B} = (...
- 387
4
votes
2
answers
511
views
About an electrostatics integral and a delta-function kernel
I'm having trouble with an integral and I would like some pointers on how to "take" it:
$$
\int \limits_{-\infty}^{\infty}\frac{3\gamma a^{2}d^{3}\mathbf r}{4 \pi \left( r^{2} + \frac{\gamma^{2}}{c^{...
user8817
4
votes
3
answers
12k
views
Rotational speed of a coil in a uniform magnetic field at equilibrium
I'm looking at the following problem from "Physics 3" by Halliday, Resnick and Krane (4th edition):
The armature of a motor has 97 turns each of area 190 cm² and rotates in a uniform magnetic field ...
- 91
0
votes
1
answer
941
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Solution to the Maxwell's equation
Question goes as
Show that the solutions to the Maxwell's equations
$$ \nabla \times \vec H = \frac 1 c \frac{\partial \vec E}{\partial t}+\frac {4\pi} c \vec J, \hspace{ 2 mm} \nabla \times \...
- 1,541
5
votes
2
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Make a semi transparent mirror with copper
The question:
How would you make a semi transparent mirror (50% reflection, 50% transmission) with glass with a layer of copper. For light $\lambda$ = 500nm Try to be as realistic as possible
What I'...
- 215
0
votes
1
answer
979
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Why does magnetic field lines go from plus to minus?
My question is why the magnetic field lines goes from plus to minus, if there was two charge. Is it true or isn't it true.
- 23
1
vote
2
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How do I relate the direction of a compass needle to the direction of a current?
A compass needle is placed above the wire points with its N-pole toward the east. In what direction is the current flowing?
If a compass is put underneath the wire, in which direction will the ...
- 19
1
vote
1
answer
2k
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Magnetic Permeability & Reluctance on old exam question
This is a past exam question from one of our lectures, and we have an issue with (i), I believe I need to use the equation $\rho=\frac{RA}{l}$, but I am not sure - could someone enlighten me on the ...
- 11
1
vote
1
answer
607
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Toroid with variable current and Ampere's Law
Say you have a current $I(t)$ (notice the time dependence) flowing through a Toroid with $N$ total loops and all the usual approximations: $(b-a) \ll r,\; B=0$ outside.
(source: gsu.edu)
You are ...
- 115
1
vote
1
answer
209
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Perpendicular Fields and Equations of Motion [closed]
I have the following problem to solve:
A particle of mass $m$ and charge $e$ moves in the laboratory in crossed, static, uniform, electric and magnetic fields. $\mathbf{E}$ is parallel to the $x$-...
- 3,320
2
votes
3
answers
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Maximize Magnetic Self-Inductance Through a Wire
You are given a long length W of copper wire. How would you arrange it to obtain the maximum self-inductance? Why?
I am trying to use the equation
$$L=\mu_o n^2 l A$$
I try to solve it using a ...
- 123
3
votes
1
answer
664
views
Unknown isotope
Problem description:
The most common isotope of a single nucleus stripped of its electrons is accelerated through a potential difference of 1225V and fired horizontally into a B-field directed ...
user1822
3
votes
2
answers
9k
views
Magnetic field in a cavity
We are given an infinitely long cylinder of radius $b$ with an empty cylinder (not coaxial) cut out of it, of radius $a$. The system carries a steady current (direction along the cylinders) of size $I$...
- 41
2
votes
1
answer
4k
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In what position can a current-carrying loop of wire be located in a magnetic field so that it doesn't tend to rotate?
I understand that if the wire is not aligned with the magnetic field, it won't rotate, but I'm still confused on how so.
Also, which direction is the current flowing?
- 21
1
vote
1
answer
122
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Formula for potential for 2 coaxial tubes
Could someone remind me of the formula for potential function for a system consisting of 2 coaxial tubes maintained at a fixed potential difference and the in between medium has uniform conductivity $...
- 13