All Questions
Tagged with magnetic-fields dipole
51
questions
15
votes
3
answers
2k
views
Electromagnetic field energy "paradox"
The starting point is the energy density in electromagnetic fields:
$$ u = \frac{1}{2} \left( \epsilon_0 |\mathbf{E}|^2 + \frac{1}{\mu_0} |\mathbf{B}|^2 \right) \tag{1}$$
The "paradox" is if we use ...
- 1,289
7
votes
1
answer
10k
views
Why is the geomagnetic north pole at a different location from the magnetic north pole?
According to this site
Magnetic North, Geomagnetic and Magnetic Poles
The Geomagnetic poles (dipole poles) are the intersections of the Earth's surface and the axis of a bar magnet hypothetically ...
- 171
5
votes
3
answers
4k
views
Why does magnetic force vary in proportion to the cube of the distance instead of the square?
Magnetic forces vary from gravity and electromagnetic radiation (such as light) in that gravity and radiation diminish by the square of the distance from the source, but magnetism diminishes by the ...
- 4,494
4
votes
2
answers
734
views
Formula for force on a magnetic dipole
Using the magnetic current model, the force on a magnetic dipole, commonly derived in textbooks, is found to be:
$$
\mathbf{F} = \nabla(\mathbf{m} \cdot \mathbf{B}) \tag{1}
$$
If the magnetic pole (&...
- 602
4
votes
1
answer
344
views
A Classical model for diamagnetism
I'm trying to derive a classical model to describe diamagnetism, and I'd like to understand if it is possible to understand the basic properties of diamagnetic materials with it i.e.:
''A diamagnetic ...
- 307
3
votes
2
answers
418
views
Is the vector potential component $A_\phi$ for a dipole necessarily 0 due to symmetry about the $z$-axis?
Consider an electric dipole (+$q(t)$, -$q(t)$) [where say $q(t)=q_0\cos\omega t$] is placed along the $\hat z$ axis. In the spherical polar coordinates, its vector potential $$\vec{A} = A_r \hat r + ...
user199113
3
votes
3
answers
6k
views
Determining North and South pole of magnet
If I have an irregularly shaped magnetic material and want to find which way is the north and south. How do I do it?
And more importantly, why are the north and south poles of a magnet situated where ...
- 478
3
votes
2
answers
2k
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What happens when an electric dipole is placed in a uniform magnetic field?
I am currently trying to understand the classical consequences of more than one charged particles in a magnetic field. So a thought experiment which came to mind was an electric dipole being placed in ...
- 620
3
votes
1
answer
3k
views
How do I graph a magnetic field?
For a school project, I'm trying to graph a magnetic field. I found this page on the NASA website with spherical coordinate equations for a dipole field, but I'm having trouble interpreting the page.
...
- 33
3
votes
1
answer
780
views
Point particle with a magnetic dipole?
I have read these questions:
Are contravariant basis vectors and basis 1-forms identical?
Where John Rennie's answer says that electrons do have an electric dipole moment and we imagine that in math ...
- 29k
2
votes
2
answers
191
views
Can we understand a moving charge as a dipole?
I work as a physics teacher at a high school and I have to explain these days the magnetic field of a curreny carrying wire. Of course I may just give the formulae and describe how the field $\vec{B}$ ...
2
votes
1
answer
526
views
Why are domains formed as separate units?
I was reading about exchange coupling and domain formation in ferromagnetic materials. As far as I can understand, some of the dipoles in the ferromagnetic material align themselves in a group called ...
- 1,375
2
votes
1
answer
494
views
The force on a magnetic dipole in a non-uniform magnetic field
Let's say there is a non-uniform magnetic field $B=(0,0,z)$ (i.e. the field is parallel to $z$-axis and the amplitude is linearly changing along $z$-axis). If there is a current loop (=magnetic dipole)...
- 23
2
votes
1
answer
2k
views
Magnetic field of dipole derivation
How can we derive the following formula:
$$\vec{B}(\vec{r})=\frac{\mu_0}{4\pi}\left[ \frac{3(\vec{m}\cdot\vec{r})\vec{r}}{r^5} - \frac{\vec{m}}{r^3}\right]\; ,$$
I want to derive it as a limit of a ...
2
votes
1
answer
1k
views
Magnetic dipole in gradient magnetic field
I know that a magnetic dipole in a uniform magnetic field will precess.
What happens qualitatively (or quantitatively) to a magnetic dipole in a gradient magnetic field? According to Wikipedia, "...
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