What is Dipole moment: Definition and 217 Discussions

The electric dipole moment is a measure of the separation of positive and negative electrical charges within a system, that is, a measure of the system's overall polarity. The SI units for electric dipole moment are coulomb-meter (C⋅m); however, a commonly used unit in atomic physics and chemistry is the debye (D).
Theoretically, an electric dipole is defined by the first-order term of the multipole expansion; it consists of two equal and opposite charges that are infinitesimally close together, although real dipoles have separated charge.

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  1. PhysicsRock

    Dipole moment of given charge distribution

    I have come up with a solution, however, I'm not sure whether I'm correct. A fellow student of mine has a different result. I'm gonna show my solution, and hopefully one of you can confirm my result or tell me what I did wrong. $$ \begin{align} p_z &= \int d^3x z \rho(\vec{x}) \notag \\ &=...
  2. the_fater

    Multipole Expansion for Two Charged Hemispheres

    My thought: First of all, I find the upper hemisphere (with a total charge +Q): ##ρ(\vec r)=\frac {V} {Q}## where V is the volume of the upper hemisphere = ## \frac {2} {3} \pi R^3##. Secondly, find the lower hemisphere (with a total charge −Q): ##ρ(\vec r)=\frac {V} {Q}## where V is the volume...
  3. H

    Why a particle with spin=0 can't posses a magnetic dipole moment?

    Hi, I would like to know why a particle with spin=0 can't posses a magnetic dipole moment? Using Wigner-Eckart theorem for ##\langle j,1,m,0|j,m \rangle## I get ##\langle j'|| \vec{J}|| j \rangle = \hbar \sqrt{j(j+1)} \delta_{jj'}## It seems like the right hand side is the magnetic dipole...
  4. B

    A Induced dipole moment (adiabatic) following the rotating E-field

    Hello! Assume I have a 2 level system, where the 2 levels have opposite parity. If I apply an electric field, I will get an induced dipole moment. For now I want to keep it general, so the induced dipole moment can be very large, too. Let's say that I start rotating this electric field in the...
  5. Harikesh_33

    I Question regarding how to interpret dipole moment for bound charges

    How do I interpret physically what dipole moment is ? The explanations that I received were "two charges seperated by a small distance " ,"it talks about ability of a dipole to rotate under the influence of an Electric Field " ,"Second term of the Multipole expansion" ,I get that these terms...
  6. Salmone

    I Two molecules with different polarizability in an EM field

    If I have two separated and non-interacting molecules with different constants polarizabilities ##\alpha_1## and ##\alpha_2## and I send an EM field of frequency ##\omega## first on the molecule no.##1## and then on the molecule no.##2## so that the two molecules will have a dipole moment...
  7. Ahmed1029

    I Dipole moment of a cylinder of uniform polarization

    If I want to calculate the dipole moment of a dielectric cylinder of uniform polarization perpendicular to its axis, I could multiply the polarization by the volume of the cylinder, which is okay. But another method is to consider the cylinder to be a superposition of two cylinders of equal and...
  8. A

    I Understanding the diagonal elements of the transition dipole moment

    Hey guys, I just numerically calculated the matrix elements for a superconducting qubit and I'm having some trouble to interpret the result. I will include a plot of the matrix I got below: I basically have "large" non zero elements on the main diagonal of this matrix. In previous courses I...
  9. Salmone

    I Derivative of the retarded vector potential

    In a problem of an oscillating electric dipole, under appropriate conditions, one can find, for the potential vector calculated at the point ##\vec{r}##, the expression ##\vec{A}=\hat{k}\frac{\mu_0I_0d}{4\pi}\frac{cos(\omega(t-r/c))}{r}## where: ##\hat{k}## is the direction of the ##z-axis##...
  10. Salmone

    I Something about retarded potentials for oscillating electric dipole

    In a problem of an oscillating electric dipole, under appropriate conditions, one can find, for the potential vector calculated at the point ##\vec{r}##, the expression ##\vec{A}=\hat{k}\frac{\mu_0I_0d}{4\pi}\frac{cos(\omega(t-r/c))}{r}## where: ##\hat{k}## is the direction of the ##z-axis##...
  11. A

    Magnetostatiscs: dipole moment and magnetic field

    Hello! I tried to solve a) see figure below, is it correct? b) so what I think I can do is to solve ## M_{12} ## from the equation of the magnetic flux then I will get ## \frac{\Phi}{I} = M_{12}## Then I can even use the equation får the magnetic flux and the magnetic field $$ \Phi = \int \vec...
  12. K

    I Dipole moment of Rydberg states

    Hello! Are there any experimental measurements or theoretical calculations of the electric dipole moment of any Rydberg state for CaF or BaF? Thank you!
  13. A

    I Orbital magnetic dipole moment of a proton

    hi every one what is the amount of orbital magnetic dipole moment of proton? this different with the intrinsic magnetic.
  14. VVS2000

    Dipole moment of a rotating disk

    I could do the first part of the question with ease but second part I am not sure how to proceed. Should we calculate the magnetic field at d(where the loop is) and infer something from that for it's motion?? Plz help me out Thanks in advance
  15. R

    I General Magnetic Dipole Moment For an Electron in an Atom

    On the first attached page ##\mu_z## is associated with orbital angular momentum (Eq. 41.34). On the following pages (Eq. 41.38) it is associated with spin angular momentum? Are these both part of the same thing? I tried to read further but the book does not address this. In example 41.6 it...
  16. patric44

    Why the Stern-Gerlach experiment didn't detect the L?

    i recently read about the stern-gerlach experiment and found out that they did it in the first place to verify the principle of the "space quantization " introduced by Bohr , and they thought they did detect the quantization of the orbital angular momentum of ( L = 1 , m = 1,-1 ) neglecting the...
  17. H

    Electric dipole moment vs electric current dipole moment

    I have to estimate the electric dipole moment of an NV center in units of Am. I know that for a regular electric dipole moment it can be estimated using p=ed. With e=1.6*10^-19 and d=0.1 nm (interatomic distance), this however is in units Cm. I don't know how to go to Am
  18. falconblade

    Changing the k constant in voltage potential equation?

    Summary:: What if you were calculating the voltage potential for a dipole, but underwater? I'm making a predictive model (in R programming) for the voltage potential at any point around a dipole. I need to be able to change parameters, one being the k constant. V=( kpcosѲ)/(r^2). Where V is...
  19. Elder1994

    Find the electric dipole moment for a water molecule

    The equation that we saw in class is for a continuous charge distribution, I think that for this exercise I need to treat the system as a discrete charge distribution but I'm not sure. Also, I don't know how I can calculate the intensity of the electric field needed to move this charge.
  20. I

    Dipole moment from electrostatic potential equation

    Hello to everyone. The question or debate here is how you obtain the commonly known equation of dipole electric moment: from the electrostatic potential equation for a multipole of order n: I understand it is related with Dirac delta functions but a step by step solution might be helpful.Thank...
  21. I

    How can I get help with my technical and schoolwork questions on the PF forum?

    I am a undergrad student dying slowly to solve few questions that came into my mind lately. Some help might be helpful.
  22. T

    I Electric dipole moment of the nucleus of an atom

    Summary: Why is the electric dipole moment of the nucleus of an atom equal zero? Summary: Why is the electric dipole moment of the nucleus of an atom equal zero? I read about the hyperfine interactions that cause the altering of the energy levels of the nuclues of an atom. Under the...
  23. P

    A Dipole moment operator and perterbations

    I am reading a PHD thesis online "A controlled quantum system of individual neutral atom" by Stefan Kuhr. In it on pg46, he has a Hamiltonian I am also reading a book by L. Allen "optical resonance and two level atoms" in it on page 34 he starts with a Hamiltonian where the perturbation is...
  24. dRic2

    Showing Charge & Currents in Vol: Proving $\mathbf{p}$ Dipole Moment

    Homework Statement For a configuration of charges and currents confined within a volume ##V##, show that $$\int_V \mathbf J d \tau = \frac {d \mathbf p}{dt}$$ where ##\mathbf p## is the total dipole moment. Homework Equations ... The Attempt at a Solution I have one question: since the...
  25. S

    A Dipole moment of an isolated quantum system

    How to prove the dipole moment of an isolated quantum system in isotropic space is identically equal to zero, unless there exists an accidental degeneracy. Thanks in advance
  26. A

    Magnetic Dipole Moment of a bar magnet

    A bar magnet will have a definite magnetic dipole moment, irrespective of the presence of an external field. Why is the moment, then, always defined in relation to the torque it would feel in an external field? Is there any other definition for the same?
  27. Navin

    Dipole moment carbon florides of isotopes of Hydrogen

    Homework Statement Compare Dipole moment of CH3F and and CD3F where D is deuterium. Homework Equations Theory questions The Attempt at a Solution Our sir had explained that to do this question we muat take into account the vibration of the atom in the respective molecule. That is that the...
  28. A

    What is the size of the magnetic dipole moment?

    Consider the magnetic field B generated by a magnetic dipole. The intensity of B measured along the axis of the dipole, at a distance of 10 cm from the dipole itself, is 1.0 10-5 T. What is the size of the magnetic dipole moment? (μ0 =4π10-7 mkg/C2) a) 0.050 Am2 b) 5 10 -4 Am2 c) 0,1 Am2 d) 1 10...
  29. S

    Potential due to a charged plate using the dipole approximation

    Homework Statement A plane z=0 is charged with density, changing periodically according to the law: σ = σ° sin(αx) sin (βy) where, σ°, α and β are constants. We have to find the potential of this system of charges. Homework EquationsThe Attempt at a Solution [/B] I...
  30. WeiShan Ng

    Deriving magnetic dipole moment from multipole expansion

    Homework Statement This is from Griffith's Introduction to Electrodynamics, where the book is deriving the magnetic dipole moment from multipole expansion of the vector potential The vector potential of a current loop can be written as $$\mathbf{A(r)}=\frac{\mu_0 I}{4\pi} \left[ \frac{1}{r}...
  31. G

    I Do Polarized Atoms Imply Shifted Electron Orbitals?

    When neutral atoms become polarized from ambient EM radiation, does this automatically imply that electrons have shifted orbitals,or do they remain in the same levels but become deformed? Thanks
  32. MrGenetic

    How change dipole moment of this N terminal?

    When the aminoacid environment were changed with adding OH or etc., Aminoacid N terminal were affected by H amount and in determined pKa, they loose hydrogen from N terminal. NH3 goes Nh2. My question is related to this. While this event occur, how change dipole moment of this terminal? Electron...
  33. G

    Why do neutron stars have such powerful magnetic fields?

    The sources I've looked at claim the magnetic field is present because there are still some electrons in the neutron star. Here is how I understand their reasoning: a star's radius significantly decreases when it collapses into a neutron star, ultimately decreasing its moment of inertia. In...
  34. L

    How to calculate the dipole moment of the spherical shell?

    Homework Statement A spherical shell of radius R has a surface charge distribution σ = k sinφ. Calculate the dipole moment of the spherical shell. Homework Equations P[/B]' = ∫r' σ(r') da' The Attempt at a Solution So I believe my dipole will be directed along the y axis, as the function...
  35. Philosophaie

    I Electric Dipole Moments: Sun, Earth, Planets, Minor Planets, Moons

    Is there a table of Electric Dipole Moments, ##\bar p##, for the Sun, Earth, Planets, Minor Planets and Moons?
  36. Philosophaie

    Electric Field and Electric Dipole Moment for a Dipole

    The Magnetic Dipole Moment for a Magnetic Field for a dipole oriented on the x-y axis is: ##\bar m = |m| \hat z## The Magnetic Field is: ##\bar B = \frac{\mhu_0}{4 * \pi * |\bar r|^5} * 3 * \bar r * (\bar m . \bar r) - \bar m * |\bar r|^2## Vector Potential is: ##\bar A = \frac{\mhu_0}{4 * \pi...
  37. arpon

    I Four-vector Dipole Moment: Electric & Magnetic

    What is the four-vector related to electric and magnetic dipole moment?
  38. D

    Could a distribution of magnetic Dipoles create an Energy minimum

    The think is that I would like to create a magnetic trap "minimum of magnetic potential energy in all 3 directions of space" using a distribution of magnetic dipoles as a field generator. In other words, I would like to know if setting in some way some magnetic dipoles is possible to create a...
  39. O

    I Calculate the Dipole Moment of an object

    How would I calculate the Dipole Moment of a piece of mild steel approximately 15cm in length?
  40. AdrianMachin

    The direction of electric dipole moment of water molecule

    I was watching a video explaining how microwave ovens work when I found that there is a difference between my physics textbook and online images of the electric dipole moment of the water molecule, as well as the one shown in the video. Why do they differ?
  41. D

    Interaction between a neutral atom and an external magnetic field

    Lets suppose that I have a magnetic dipole moment at (0,0,0) pointing to the Z axis, and in the position (X,Y,Z) in the space, I have a Hydrogen atom, I would like to know the exact interaction between the magnetic field created by the magnetic dipole moment in (0,0,0) and the magnetic fields of...
  42. Konte

    I Xt - Understanding Dipole Moment Components in Rigid and Non-Rigid Molecules

    Hi everybody, I want to ask a question about the dipole moment vector ##\vec{d}##, with components expressed in the molecule-fixed axis. By permuting identical nuclei that compose a rigid molecule, I know how ##d_x##, ##d_y##, ##d_z## change. But when dealing with non-rigid molecule, I no...
  43. Albi Mema

    Forces between the dipole and a point charge

    Homework Statement We have an electric dipole with moment P=2*[10][/-5] pointing in x direction. What is the force experieced by dipole at origin when a point charge Q=3*[10][/-4] is located at (0.014 m ,0,0) Homework Equations 1. [E][/dipole]=(1/4π[ε][/0])(2p/r3) 2. p=qs 3. F=qE 4. τ=pEsinϑ...
  44. Cocoleia

    Dipole moment, electric potential

    Homework Statement I am given this picture and I know that |q1|=2nC, |q2|=5nC, d=1mm I need to first find the total dipole moment of the system. Then I need to find an equation that represents the electric potential due to this net dipole moment for all (everywhere) Homework Equations p=qd...
  45. 1

    Force between 2 parallel magnetic dipole moments

    Homework Statement Find the force of attraction between 2 magnetic dipoles a distance r apart. Both dipoles point to the right. Homework EquationsThe Attempt at a Solution All I need help with is figuring out how to determine if the force is attractive or repulsive between the 2 dipole...
  46. D

    A Dipole moment at the sub atomic level

    The following mechanism leads me to wander that a moving neutral object (compose from atoms) in vacuum may generates electric filed due to very small dipole moment. I propose that when atoms force to move in a certain direction the force propagates within the atom. A retardation in movements...
  47. S

    Electric dipoles and a magnetic dipoles

    Is there any interaction between a perfect magnetic dipole and a perfect electric dipole, both at rest? What abut real dipoles? What does QED say about this?
  48. JulienB

    Direction of dipole moment in e-field of another dipole

    Homework Statement Hi everybody! I'm trying to solve a problem about dipoles, but there is something I don't quite get about it. Well, first here is the problem: An electric dipole ##\vec{p}_1## is placed at the zero-point and shows in the z-direction. A second electric dipole ##\vec{p}_2##...
  49. S Aditya

    About the Orbital Dipole Moment

    I was going through the chapter Chemical Bonding in one of the books and found something about orbital dipole due to lone pairs. In each diagram the orbital dipole due to lone pair was directed from the central atom to the end of the hybridized orbital (lone pair). Why is that so?
  50. AmKo3

    B Centre of Charges Coincide & Dipole Moment: Explained

    What does it mean when we say "centre of charges coincide"? What is the physical meaning of dipole moment?
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