Skip to main content

Questions tagged [dipole-moment]

Dipole moment is the electrostatic moment generated by two opposite charges taken together, far away from the charge's locations

Filter by
Sorted by
Tagged with
-3 votes
0 answers
22 views

Molecular polarizability equation check [closed]

ChatGPT gave me an equation to calculate the molecular polarizability using the fluctuation of the dipole moment components, but I can't verify its validity because it gives me a made up reference. I'...
cadena's user avatar
  • 9
0 votes
0 answers
38 views

Linear approximation of the magnetic dipole field

Summary: using 3 angles to represent a magnetic dipole's orientation is redundant because the rotation around the $z$-axis of the dipole does not change the magnetic field, there are only 2 DOFs for ...
William Lin's user avatar
0 votes
0 answers
29 views

Magnetic energy associated with an intrinsic dipole

Generally for an Amperian dipole we have: Magnetic energy when it is placed in a uniform magnetic field is $\vec m \cdot \vec B$. We can define "a fake kind of energy" [Feynman] that can ...
MATHS MOD's user avatar
  • 182
0 votes
1 answer
34 views

Dipole moment in an electric system when the charges are not symmetrically distributed

Suppose we have two -q charges and +2q charge ate the corners of an equilateral triangle. Now to calculate the dipole moment suppose we assume that the +2q charge is 2 charges of +q magnitude. My ...
Pushkar Kumar's user avatar
0 votes
1 answer
26 views

Subsequent motion (time evolution) of angled dipoles in electric field

Suppose we have a system of two dipoles, each with dipole moment $\mathbf{p}=2aq$ each aligned at angles $\theta$ and $-\theta$ with the horizontal. I’m thinking of an angle bracket shape, essentially....
zxayn's user avatar
  • 73
1 vote
1 answer
46 views

Net dipole moment of identical-particle system [closed]

Let $N$ identical electric charges be arranged arbitrarily in space, in such a way that each of them has a fixed position $\vec{r}_i$, a charge $q$ and a mass $m$. If I were to calculate the total ...
Lagrangiano's user avatar
  • 1,616
1 vote
0 answers
25 views

Direction of dipole after spontaneous emission

Consider a simple $J'= 1$ to $J = 0$ transition for an atom. If the magnetic field set the quantization along the z-direction, I am wondering what is the direction of the dipole moment after the atom ...
Lufter Rice's user avatar
1 vote
2 answers
40 views

Angular velocity vs Angular frequency

Are these two omega same? (angular frequency of a current oscillating loop and angular velocity of a rotating body)
Shreyansh Kabir's user avatar
0 votes
0 answers
15 views

Forward voltage of LEDs from quantum mechanics perspective

I have a very elementary understanding of LEDs and semiconductors altogether, but a more solid understanding of QM, and I was wondering if there was a way to explain (preferably mathematically) ...
JBatswani's user avatar
  • 187
0 votes
0 answers
32 views

Charge density arising due to a moving electric dipole should be time-dependent

Recently, I was reading an article that was trying to refute Fisher's claim regarding the expression for the magnetic moment developed due to a moving electric dipole. According to Fisher, the value ...
Abhinav Tahlani's user avatar
0 votes
2 answers
38 views

Calculating the discontinuity in the scalar potential in a dipole layer

Calculating the discontinuity in the scalar potential in a dipole layer, as can be seen here, we get the following equation (1.89): $$\Phi_{-}=-\frac{D}{4\pi\varepsilon_{0}}\int_{disk}d\Omega=-\frac{D}...
Jhordan Silveira de Borba's user avatar
2 votes
1 answer
53 views

When is the time derivative of the electric dipole moment 0?

While reading Introduction to Electrodynamics by David J. Griffiths I encountered a problem regarding the time derivative of the electric dipole moment. I wanted to find the conditions when the time ...
Tomasz P's user avatar
0 votes
0 answers
30 views

Electric dipole transitions: why is $\langle \vec{d} \rangle$ for stationary states 0 but not for superpositions?

We've learned in lecture about electric dipole transitions for hydrogenic atoms, and our professor claimed that $\langle\vec{d}\rangle=0$ for stationary states, but not for superpositions of states. ...
JBatswani's user avatar
  • 187
0 votes
1 answer
54 views

Coexistence of a static electric and magnetic dipole

I have been trying to construct a charged object (not a conductor carrying any current) that can behave simultaneously as an electric and magnetic dipole and then calculate the electric and magnetic ...
Cognoscenti's user avatar
2 votes
1 answer
72 views

What's the origin of van der waals force between atoms?

What does it mean the Van der Waals force comes from the fluctuating dipoles of the atoms? Why is the dipole moment fluctuating? Is it because the vacuum EM field is fluctuating then it stimulates the ...
user74750's user avatar
  • 195
1 vote
1 answer
126 views

Dipole moments of elementary particles

Reading T violation from Perkins High Energy Physics, 4th ed, pp 82. Here I don't understand the definition of last 4 quantities, magnetic and electric dipole moments, longitudinal and transverse ...
Sagar K. Biswal's user avatar
4 votes
1 answer
734 views

Modeling a pure dipole as a function similar to a Dirac delta function

I am taking an undergraduate course in E&M following Griffiths. I was wondering if there is a good way to embed the information of a dipole into the charge distribution (and if it would be of any ...
Pallav Pant's user avatar
1 vote
0 answers
115 views

Is there an intuitive way to understand the Lagrangian for magnetic and electric dipole moment?

From the textbook I learned that the electric dipole moment (EDM) and magnetic dipole moment (MDM) has the following Lagrangian: $$\mathcal{L}_{EDM}=F_{\nu\mu}\bar{\psi}\gamma^{5}\left[ \gamma^{\nu},\...
Bababeluma's user avatar
1 vote
0 answers
23 views

Absorption Cross Section for Two-Level Spin System in an AC Magnetic Field - Photon Picture

For a two-level spin with a energy difference of $E = h f$, where the two levels have zero dipole electric coupling and can only be driven by a magnetic field, how do I calculate the absorption cross ...
SpinSensor's user avatar
0 votes
1 answer
36 views

Meaning of electric dipole moment

what is the meaning of electric dipole moment? Or why do we need to define electric dipole moment?
Physics Ed's user avatar
1 vote
3 answers
344 views

Intuition for magnetic dipole moment

The definition of the electric dipole moment of a system of charges makes sense intuitively - $$\boldsymbol {\bf p} = \int_{V} \boldsymbol {\bf r} \rho (\boldsymbol {\bf r})dV$$ describes the overall ...
Aadhaar Murty's user avatar
0 votes
1 answer
78 views

Multipole expansion, same charges

I know dipole is defined with 2 opposite charges. That's why in EM dipoles exist, while in gravity they do not. However, I view multipole expansion as a way to describe how the distribution of charges ...
Matteo's user avatar
  • 77
2 votes
1 answer
104 views

Understanding polarization and magnetization intuitively?

I am trying to develop a more intuitive understanding of the field produced by magnetization and polarization. I have the following image, and I can derive it from Maxwell's equations what the fields ...
reesespieces's user avatar
0 votes
0 answers
19 views

Dipole moment and Branching ratio relation

I am looking for a good derivation of relation between dipole moment of transition and Branching ratio of the transition, is there a good textbook for this?
I'm Batman's user avatar
0 votes
0 answers
45 views

Larmor precession with an oscillating field?

With a non-polar molecule like CO2, presumably Larmor precession doesn't apply. However, CO2 has a mode of vibration that induces an oscillating dipole moment. Could something similar to Larmor ...
Dr Xorile's user avatar
  • 1,552
1 vote
1 answer
70 views

What does centre of mass of charge mean?

I am unable to understand what does this centre of mass of positive charge and centre of mass of negative charge mean??
Physics student's user avatar
0 votes
0 answers
37 views

What does centre of positive and negative charge separated by a small distance mean? [duplicate]

I dont understand the meaning of this statement that centre of positive and negative charge is separated by a small distance??
Physics student's user avatar
1 vote
4 answers
122 views

Why do we make a dipole a ideal dipole?

My question is that why do we make a dipole a ideal dipole ($q\to\infty$ and $d\to 0$) …i mean i want the reason behind to take this and what is the problem of taking a charge with some magnitude (not ...
Physics student's user avatar
0 votes
1 answer
62 views

Density of current in a Elementary Dipole

I can't understand this formula from my textbook, I'm trying to understand why the Density of Current is I*ΔZ(ΔZ is the lenght of the dipole) i mean a density of current would be I/Δs (with Δs the ...
Martino Pistis's user avatar
0 votes
0 answers
82 views

How do i determine the dipole moment of a charged conducting sphere in a uniform electric field?

What bugs me the most is that since there is net charge, i dont know two things, how would that charge distribute across the surface (even though my intuition says that one of the sides will have more ...
jfinizolas's user avatar
0 votes
1 answer
62 views

How do degenerate states affect molecular absorption?

Molecular absorption of light is related to the transition dipole moment according to the equation from Hilborn, 1982: $$\sigma(\omega)=\frac{\pi \omega}{3\epsilon_0\hbar c} \frac{g_2}{g_1}\mu^2\rho(\...
ChaSta's user avatar
  • 101
0 votes
1 answer
73 views

Does this basic example of two bar magnets preserve angular momentum conservation?

Let's say I hold two bar magnets side by side both vertically aligned ($z$-axis). I don't want to worry about their shapes, so let's approximate them as dipoles. I will use the dipole formula rather ...
Maximal Ideal's user avatar
0 votes
1 answer
96 views

Why does spin break time reversal symmetry but electric dipole moment does not break time reversal symmetry?

I wasn't able to get a proper reason behind this and the only thing I could find were classical analogies for spin which (when I asked my prof) were not to be relied upon.
Harshdeep Chhabra's user avatar
1 vote
2 answers
150 views

Can ideal dipoles be associated to a covariant four-current?

I am trying to check if the classical electromagnetic sources from a point electric/magnetic dipole do form a true four-current. In this SE post, it is shown that a point electric charge do transform ...
Woe's user avatar
  • 388
0 votes
1 answer
42 views

Dipole operator in a lattice model

If I have a lattice Hamiltonian, say for example the Hubbard model $$H = \sum_{j,k, \sigma} t_{j,k} \hat{c}^\dagger_{j \sigma}\hat{c}_{k \sigma} + U\sum_{j} \hat{n}_{j \uparrow}\hat{n}_{j \downarrow},$...
Qwertuy's user avatar
  • 1,262
0 votes
0 answers
19 views

Why in an isotropic, linear and homogeneous dielectric, the average electric moment can be expanded as a series of electric field $\mathbf{E}$? [duplicate]

As I was reading this classic 1939 document by Kirkwood The Dielectric Polarization of Polar Liquids. It is stated in the text that the average electric moment in an isotropic liquid can be expanded ...
Zhao Dazhuang's user avatar
0 votes
2 answers
78 views

Confused by validity of torque on a magnetic dipole

I'm not quite understanding the concept of a magnetic dipole. From what I've seen, we can treat a given conducting loop as a magnetic dipole ONLY in the approximation where we consider its potential (...
David's user avatar
  • 113
1 vote
0 answers
73 views

How does the the Landé g-factor change?

In my statistical physics book, it is said that, when a particle with total angular momentum $\vec J$ is placed in a weak external magnetic field, it has a dipole magnetic moment equal to $$\hat {\vec ...
SimoBartz's user avatar
  • 1,904
1 vote
1 answer
150 views

Dipole moment operator for many a electrons wave function

From textbooks (such as Optical Spectroscopy of Inorganic, Henderson, 2006) I know that the electric dipole moment operator is defined for one electron as: $$ \hat{\mu} = e \hat{r} $$ But then suppose ...
WIP's user avatar
  • 123
6 votes
1 answer
298 views

What is the covariant version of the dipole moment?

Magnetic dipoles in a rest frame behave as a mixture of dielectric dipoles and magnetic dipoles in another moving frame. However this is sometimes controversial due to Mansuripur's paradox (see ...
Mauricio's user avatar
  • 5,588
0 votes
2 answers
99 views

When deriving work from an uniform electric field and dipole why do we need to integrate it?

If the force is constant in a uniform field wouldn't that mean you dont need to integrate to find work?
user avatar
2 votes
2 answers
2k views

What is the difference between paramagnetic and ferromagnetic?

What is the difference between paramagnetism and ferromagnetism? Before answering, I want to note my difference between the rest of the similar questions on this website: from what I think I know, ...
Jausg Svashsh's user avatar
8 votes
1 answer
193 views

Why does a transition between 2 $s$-orbitals work for cesium's clock transition?

I have a small question about the cesium's clock transition. According to the information on the Wiki: https://en.wikipedia.org/wiki/Caesium_standard, the chosen transitions are two hyperfine ground ...
Hsu Bill's user avatar
  • 388
0 votes
1 answer
383 views

Coupling of electrc field with electric dipole moment in the hamiltonian

I'm studying linear response theory from "Fundamentals of many body physics" by Nolting. We want to study electrical AC conductivity, so what happens when we apply a spatially homogeneous ...
Rhino's user avatar
  • 693
1 vote
0 answers
43 views

Shouldn't the electric dipoles (and thus dielectrics) increase the net electric field?

We know that the magnetic field is almost always greater in a medium, apart from diamagnetic media, than in vacuum. And the reason is, of course, that the magnetic dipoles align with the external ...
Shibasish's user avatar
2 votes
1 answer
96 views

Infinite integrals in calculation of dipole potential

The Situation Assume that a point dipole is positioned at $z=D$ and is pointing in an arbitrary direction so that its dipole moment is $\textbf{p} = p \cos \alpha \, \mathbf{\hat{r}} + p \sin \alpha \,...
sbaginski's user avatar
  • 188
0 votes
1 answer
79 views

How to get electric dipole moment formula from a unbalanced dipole?

The potential due to the electric dipole moment is given $$ \Phi_{dipole}(\vec{x}) = \frac{1}{4 \pi \epsilon_0} \frac{(\vec{x} - \vec{x'}) \cdot \iiint_V \rho(\vec{x'}) \vec{x'}\, d^3 x'}{|\vec{x} - \...
IvanaGyro's user avatar
  • 277
1 vote
0 answers
46 views

Earth magnetic field, WMM/IGRF

I am studying about World Magnetic Model (WMM) and International Geomagnetic Reference Field (IGRF) models. It is well known that, to a first approximation, earth magnetic field is a field of dipole. ...
Emma Anderson's user avatar
3 votes
1 answer
289 views

What does electric dipole moment really mean? [duplicate]

Electric dipole moment is mathematically defined as, $p = q\cdot d$, where $q$ is the magnitude of the charge and $d$ is the separation distance between the charges. I was introduced the term "...
Akshai Christy Jacob's user avatar
3 votes
2 answers
251 views

Dipole matrix elements for Bloch wavefunctions?

Suppose we have a one-dimensional periodic system with lattice constant $a_0$. From Bloch's theorem, we can express the wavefunction for an electron in band $m$ with crystal momentum $k$ $\left\langle ...
user139632's user avatar

1
2 3 4 5
7