The dipole tag has no wiki summary.
10
votes
1answer
236 views
In the Lennard-Jones potential, why does the attractive part (dispersion) have an $r^{-6}$ dependence?
The Lennard-Jones potential has the form:
$$U(r) = 4\epsilon\left[ \left(\frac{\sigma}{r}\right)^{12} - \left(\frac{\sigma}{r}\right)^{6} \right]$$
The (attractive) $r^{-6}$ term describes the ...
8
votes
1answer
227 views
Magnets arranged in a sphere
If I was to take a bunch of magnets and arrange them in a sphere (And keep them there with glue or plastic or something) so that the north pole faces the outside of the sphere and the south pole faces ...
7
votes
5answers
1k views
Direction of rotation of proton in magnetic field--opposite to a dipole
Chatroom created by @pcr for discussing this: http://chat.stackexchange.com/rooms/2824/direction-of-rotation-of-proton-in-magnetic-field
Here's a small paradoxical question I was asked a long ...
5
votes
1answer
177 views
What is the “direction” of the transition dipole moment? (Understanding Eq. 9.29, Charge and Energy Transfer 3rd Ed, May & Kuhn)
For a real vector $\mathbf{r}$, the direction is given by: $\hat{\mathbf{n}}=\mathbf{r}/\left|\mathbf{r}\right|$.
The transition dipole moment is a complex vector. How do you define its direction?
...
4
votes
2answers
333 views
Meaning of the phrase “dipole moment of the combination”
Here is a question I came across in a book:
Three point charges $-q$,$-q$ and $2q$ are placed on the vertices of an equilateral triangle of side length $d$ units.What is the dipole moment of the ...
3
votes
5answers
467 views
What is the origin of the Dirac delta term in the dipole electric field?
I am a bit lost how one has deduced the formula for electric field with electric dipole because of some inconsistency between different sources. The Wikipedia article contains a delta function in the ...
3
votes
2answers
124 views
Why is there a factor of 1/2 in the interaction energy of an induced dipole with the field that induces it?
In this paper, there's the following sentence:
...and the factor 1/2 takes into account that the dipole moment is an induced, not a permanent one.
Without any further explanation. I looked ...
3
votes
2answers
130 views
How do you fit a dipole in an electron?
Experiments used to observe particle spin properties (such as Stern-Gerlach) rely on a varied magnetic field and a dipole-like reaction in the particle, deflecting it in one direction or another.
In ...
3
votes
1answer
917 views
Force from point charge on perfect dipole
Have a point charge and a perfect dipole $\vec{p}$ a distance $r$ away. Angle between $\vec{p}$ and $\hat{r}$ is $\theta$. Want to find force on dipole.
I'm having more than a little difficulty ...
3
votes
4answers
2k views
What is the physical sense of the transition dipole moment?
So if the states are the same we achieve the expectation value of the dipole moment for a given state. I mean
$ \langle \mathbf{\mu} \rangle = \langle \psi \vert \hat{\mathbf{\mu}} \vert \psi ...
2
votes
1answer
108 views
Conservation of Angular momentum in the dipole selection rules
If the total angular momentum J of an atom is not changing during a dipole transition, where does the angular momentum for the photon come from?
2
votes
2answers
107 views
Power due to dipole radiation and time reversal symmetry in classical E&M
The dipole formula for the power loss emitted by a time varying electric dipole is (in natural units) $P = \frac{\dot d_i^2}{6 \pi}$. This is clearly even under time reversal symmetry $T$, but a ...
2
votes
1answer
151 views
Minimizing potential energy of a dipole in an electric field
My test paper asked me which way a dipole should be orientated in an electric field to minimize its potential energy. My answer was that the dipole should lie parallel to the electric field with the ...
1
vote
1answer
98 views
Why does the aligning of magnetic dipoles in a material cause its heat capacity to decrease?
This is with regards to adiabatic magnetisation.
1
vote
1answer
130 views
Explain the electric dipole moment vector
For a pure dipole situated at the origin, I don't understand why the dipole moment vector is
$$
\vec{p} = p\cos \theta \hat{r} - p\sin \theta \hat{\phi}
$$
Since the vector does not have any $r$ in ...
1
vote
1answer
259 views
Dielectric in a parallel plate capacitor
Uniform charge: each atom has charge $q$.
Magnitude of dipole moment is $q s$, where $s$ is the distance the nucleus is shifted.
According to my notes, the charge on the surface of a dielectric in ...
1
vote
1answer
65 views
Explanation for the next steps of chaplygin dipole
this post is the Chaplygin dipole, it's an interesting issue.
Can someone explain me these steps in other words please? any Explanation of any step will help me, I hope that together I will ...
1
vote
2answers
204 views
Does the intensity of dipole radiation fall as $1/r^2$ or $1/r^3$?
I have seen this derivation:
I want to estimate what is the intensity of the electrical field as
function of $r$ the distance from the radiated source ?
I think it is can modled as pointed source ...
0
votes
1answer
73 views
What is the $Q_y$ transition in a bacteriochlorophyll?
Bacteriochlorophyll (BChl) are pigments that occur in the photosynthetic mechanisms of bacteria. I am studying some papers on the excitonic properties of BChl's, and the term $Q_y$ transition comes up ...
0
votes
1answer
79 views
Explanation for the next steps of lamb-chaplygin dipole
Can someone explain me the steps please (I mean steps 2 and 3)? I didn't understand it.
1) Any flow field represented by a stream function $\psi$(x,r), defined as:
v = - $\frac{\partial ...
0
votes
1answer
284 views
Lamb-Chaplygin dipole
There is an interesting issue of hydrodynamics: whirlpools.
I want to learn about the Lamb-Chaplygin dipole.
Lamb-Chaplygin dipole corresponds to a steady solution of the two dimensional Euler ...
0
votes
1answer
204 views
Dipole moment of the electron
I've read that there are some restrictions on the value of a possible intrinsic electric dipole possessed by the electron, but isn't the dipole value dependent on the electron's wavefunction? Assuming ...
0
votes
0answers
44 views
Is this picture of the electron dipole moment correct?
It's the electron spinning on its axis, and a magnetic moment shoots up. The direction of the North-South is opposite what I thought it should be. Why is the vector arrow pointing from North to ...
0
votes
0answers
76 views
Electric potential due to an infinite polarized sheet
I have an infinite plane (no thickness) with a uniform dipole density $\mathbf p = p \mathbf n$, with $\mathbf n$ being the normal to the plane. So the surface charge density is $\sigma = \mathbf p ...
0
votes
0answers
67 views
How to determine field strength of a dipole embedded in a sphere?
I have a dipole which is embedded in a sphere.
Sections of the sphere may consist of materials of differing magnetic permeability.
I'd like to determine the strength of the magnetic field at ...
0
votes
1answer
456 views
Where will the electric field be zero in dipole [closed]
Lets say we have an electric dipole. I can't figure out where the location of net zero electric field will be.
Tnx
-1
votes
1answer
52 views
Electric dipole moment, which charge is the $q$ for?
Electric dipole moment says $p = qd$. Which charge does the $q$ equal to?
