All Questions
259
questions
1
vote
0
answers
261
views
Magnetic field due to circular surface current density
I am trying to find the magnetic field between two coaxial cylindrical shells of radius $a$ and $b$ respectively. They have a surface current density of $K = K_0cos(\theta)\hat{\theta}$ and $K=-K_0cos(...
- 324
0
votes
1
answer
488
views
Griffiths E&M questions about example 6.1 [closed]
I understand why $K_b = M\mbox{sin}\theta \hat{\phi}$ but when I try to use this to calculate the magnetic field, I keep coming up with an integral that cancels itself out and I don't understand how ...
- 324
0
votes
2
answers
49
views
Validating Basic Laws of Magnetostatics [closed]
I am having trouble with the following problem, although with similar problems I run into the same issue when it comes to validation. The example problem below is a problem for Amperes Law.
The ...
3
votes
1
answer
731
views
When can we use Ampère's Law methods to find $\mathbf{H}$ field?
I was reading David J. Griffiths Introduction to Electrodynamics and came across this question today.
Part (b) of the question can be solved by realising that $\mathbf{H}$ (the auxiliary field), by ...
- 323
0
votes
0
answers
363
views
Magnet layout to maximize magnetic attraction along entire surface
We want to use permanent magnets to attract iron filings. For this, we have several neodynium magnets shaped as disks and we would like to lay them out to have the highest possible attraction along ...
- 25
4
votes
2
answers
497
views
Helical motion on non-uniform magnetic field
I understand that when a charged particle enters a magnetic field with a velocity $v$, with a angle $\theta$ within the field lines, its perpendicular and parallel velocity components generate, ...
- 487
3
votes
1
answer
123
views
Confusion in the guiding center of gyrating particles
In Chen's Introduction to Plasma Physics and Controlled Fusion, while discussing magnetic mirrors, it's considered a magnetic field pointing in the $\hat{z}$ direction as shown below:
Going further, ...
2
votes
3
answers
141
views
Find the magnetic field of an infinite wire at distance $2R$, given the field at distance $R$ [closed]
If the magnetic field of an infinite wire at a distance $R$ is is $0.4 \;\text{T}$, find the field at a distance $2R$.
The approach suggested by internet is as follows:
Magnetic field due to an ...
- 817
6
votes
2
answers
1k
views
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 ...
- 132
1
vote
1
answer
100
views
Electric field in a rod rotating in a magnetic field [closed]
Recently I came across a problem:
A metal rod of length $L$, connected to a vertical shaft is rotating in a horizontal plane with a constant angular velocity $\omega$ (anticlockwise as seen from ...
- 23
3
votes
1
answer
2k
views
Magnetic field due to a finite-length straight wire carrying a constant current [closed]
My question: I want to find an expression at any point in space for the magnetic field $\mathbf B$ produced by a straight wire of finite length $L$ carrying a constant current $I$.
I think that we can ...
- 344
0
votes
1
answer
501
views
Magnetization of a cylinder
Suppose we have a short circular cylinder of radius $a$ and length $L$ carrying a uniform frozen-in’ magnetization $\mathbf{M}$ parallel to its axis.
Why is there no bound surface current on the two ...
- 78
0
votes
1
answer
132
views
The equation of motion(EOM) of rotation of couple moment of magnet bar which rotation axis is fixed at middle and placed in uniform magnetic fields
The magnet bar which rotation axis itself is fixed at the middle of the bar and the magnet bar is placed in the uniform magnetic fields.
$$ I \left[ \text{kg} \cdot \text{m}^{2} \right] :=\text{...
0
votes
1
answer
89
views
Induced emf of a moving rod with certain velocity
I am calculating the emf of a moving rod with velocity $v$, given $v$.
My approach is to multiply
$$Blv$$
Where $l$ is the width and $v$ is the rate of change of the length.
But then I found out ...
- 103
3
votes
0
answers
309
views
Force exerted by one current carrying wire loop on another [closed]
I am training for my physics exam and I stumbled upon this question:
We are given two current carrying wire loops with radii $R_1 \ll R_2 $
who are coaxial. The distance between them is $X$. Both ...
- 143