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. N

    Help with Magnetic Dipole Moment

    Im looking to find the resultant magnetic moment of a permanent magnet inside of a steel housing. Some of the remnant flux density is absorbed by the magnet and the field is altered. I want to figure out the total magnetic dipole including the presence of the steel housing. I've been using...
  2. Curieuse

    Potential Energy for dipole in Electric Field

    Homework Statement To derive Potential Energy for dipole p in Electric Field E. 2. Homework Equations Potential Energy is the work done by the external agent in turning the angle of the dipole from the U=0 position to another position against the influence of the electric field applied...
  3. S

    Dipole moment arrows confusion

    My teacher posted on his website, Lewis structures of different compounds. One of them were N3- Why isn't there a dipole moment arrow pointing from the central atom to the other Nitrogen? Does the arrow only point from neutral atom to negatively charged atom?
  4. S

    Thin rod w/linear charge density, dipole moment

    Homework Statement A thin rod of length 2L has a linear charge density that isλ0 at the left end but decreases linearly with distance going from left to right in such a way that the charge on the entire rod is zero. Given E = −kλ0/L(d/(L−d)−ln(d−L)+d/(L+d)+ln(L+d)) for a point P that is...
  5. N

    A Transition dipole moment - polarized absorption

    Hi everyone, I am interested how is polarized light absorbed by a molecule or an atom. Unfortunately, I come to a problem in the derivation where a complex vector in a real space appears. This is something I never seen before and I do not know how to interpret it. Therefore I would like to ask...
  6. K

    Magnetic dipole moment derivation

    (2) Hi. I am having a problem with understanding how to approximate 1/R in the forms of equations written above. I took this equations from a blog, and it tells that I can use talyor polynomial. but I don't get there somehow.
  7. puggleboy

    Finding dipole moment / Electric Field Problem

    Homework Statement Problem 3 from the attached photo Homework Equations p = qd The Attempt at a Solution I know the magnitude of the dipole moment is p = qd, where d is the distance between the 2 oppositely charged particles. I know the direction of the dipole moment vector is from - to +. My...
  8. K

    Why is the concept of dipole moment significant in physics?

    Hi, I was wondering why dipoles are singled out as a separate section in my physics textbook. For instance, after discussing electric fields the textbook specifies what a dipole is, dipole moment, and the electric field for a dipole. Finding the e-field for a dipole would be the same as finding...
  9. A

    Understanding Dipole Moment: The Measure of Electric Strength Explained"

    Dipole moment is the measure of strength of electric dipole and is equal to product of either charge and distance between two charges. P=ql but as we know when charges are close the force b/w them is strong n when they are far away force decrease. But in above equation strength increases with...
  10. I

    Electric field of dipole moment

    Homework Statement A solid sphere, radius ##R##,is centered at the origin. The "northern" hemisphere carries a uniform charge density ##\rho_0## and the "southern" hemisphere a uniform charge density ##-\rho_0##. Find the approximate field ##\mathbf E(r,\theta)## for points far from the sphere...
  11. B

    Why does not dipole moment depend on coordinates system?

    Homework Statement This is problem 6.5 in Griffiths EM. I can't understand why dipole moment does not depend on coordinate systems. Homework EquationsThe Attempt at a Solution
  12. M

    Transition dipole moment: cause or result of interaction?

    According to the wikipedia article about the transition dipole moment: When an atom or molecule interacts with an electromagnetic wave of frequency , it can undergo a transition from an initial to a final state of energy difference through the coupling of the electromagnetic field to the...
  13. gracy

    Electric dipole moment problem

    Homework Statement find the electric dipole moment of the system shown in figure Homework Equations In the simple case of two point charges, one with charge +q and the other one with charge −q, the electric dipole moment p is: where d is the displacement vector pointing from the negative...
  14. D

    Atomic dipole moment for a superposition state

    Hi all, I'm trying to understand how to calculate the time dependent expectation value of the atomic dipole moment for a superposition state, and I have a good guess to check with you. Say we have \psi = \frac{1}{\sqrt{2}} \left[ \psi _{100} + \psi _{310} \right] at t = 0. Then, for t > 0: \Psi...
  15. Jimbob999

    Find magnetic dipole moment of coiled wire

    Homework Statement A 45-m long wire is coiled so that it makes a coil containing 100 circular loops, one on top of the other. If the wire carries a current of 13 A, what is the magnetic dipole moment of the coil? 21 A·m2 6.7 A·m2 3.3 A·m2 2.6 A·m2 1.2 A·m2 Homework Equations B(z) = u0/2pi...
  16. fricke

    Do Mono-nuclear Molecules Exhibit Dipole Moment and Why?

    Do mono-nuclear molecules have dipole moment? If yes then, what type of dipole moment? why do they have (or do not have) dipole moment?
  17. S

    Finding energy from dipole moment - Helmholtz pair?

    Firstly apologies for not typing this out - but I need the diagram. And I have no idea where to start. I 'think' most of it is correct. BUT - I have no idea what to do with the last part of c. I thought I could just double the energy. But I'm going to get a negative energy for the system...
  18. S

    Electric dipole moment and Electric field

    Hello everyone, I would like to ask a couple of questions which are related to electric dipole moment and electric field. First one: Let us assume that we have somehow a constant electric field. The obvious thing to say is that any material that contains a Net Charge ( moving one or not moving...
  19. A

    Mathematical relation between dipole moment and frequency?

    how can we relate innermost stable circular orbits, keplerian, epicyclic, frame dragging precession frequency with dipole moment.
  20. T

    Do ionic crystals have total electric dipole moment?

    I have come up with a paradox: Ionic crystals, in which cations and anions form a lattice, seems to have total electric dipole moment! For example, consider a one dimensional example: ##+ - + - + - ... + - + -## In the above picture, a ##+## represents a cation and a ##-## represents an anion...
  21. sams

    Transition dipole moment of diatomic molecules

    Hello Everyone, A little question regarding the TDMs between two different electronic states of a diatomic molecule. If I am calculating the TDM from state A to state B, is it the same if we are calculating the TDM from state B to state A? Are these two transitions the same? Thank you so much...
  22. A

    Dipole moment of a specific charge distribution

    A negative charge cloud distribute as a ellipsoid and a positive point charge situated at the centre of the ellipsoid.What should be the dipole moment of charge distribution.I mean, if the negative charge distribution is spherical and positive point charge at the centre then surely dipole moment...
  23. fhc6791

    Dipole moment of small circular antenna - only magnetic?

    When making an extension from linear dipole antennas to small circular antennas, I am only coming across expressions for a magnetic dipole moment (as opposed to having just an electric dipole moment for a linear dipole antenna). The expression being: m = πr2I at its peak The above expression...
  24. F

    Electric dipole moment for a uniformly charged ring

    Homework Statement Text description: Let V(z) be the potential of a ring of charge on the axis of symmetry at distance z from the center. Obtain the first two non-vanishing terms of the multipole expansion for V(z) with z>>a where a is the radius of the ring. Can you see by symmetry that the...
  25. S

    What is Chromoelectric dipole moment?

    Basically, I wonder what Chromoelectric dipole moment is and how it is formed...
  26. J

    Determining Compound Dipole Moment for Finals

    Can someone explain how to determine if a compound has a dipole moment and how to determine how big or small it is (possibly numerical value)? I have a final tomorrow and I've looked this up on multiple website and cannot find any good explanation.
  27. M

    Why does a hydroquinone has a non zero dipole moment?

    Why does hydroquinone possesses non zero dipole moment? The OH groups present at para positions on the benzene ring should cancel the effect of each other...if there is a plane change then exactly in which cases molecules do change planes?
  28. P

    Finding the Dipole Moment of a Cylinder

    Homework Statement I am trying to calculate the dipole moment of a cylinder of volume charge density ##\rho_0## of radius ##R## and height ##H## with is center coinciding with the origin. My guess is that it should be 0 because of the symmetry but I am not able to show it. Below is my...
  29. J

    Potential Energy/ dipole moment curves

    Hi, I wasn't sure if this is more Physics/Astro or chemistry because its actually all 3. i've got some conceptual issues with some tasks at hands, and was wondering if anyone could clear that up for me. (These questions are all regarding molecules) 1) How do you create a potential energy...
  30. L

    Finding the dipole moment of a molecule in an electric field

    Homework Statement "A molecule has its dipole moment aligned with a 1.8 kN/C electric field. If it takes 3.5x10^(-27) J to reverse the molecule's orientation, what is its dipole moment?" Homework Equations Potential energy of dipole in an electric field U = -p*E = -p*E*cos(theta) U...
  31. I

    Calculating change in Magnetic Dipole Moment

    In one moment in time you have a charge going about in a circle of radius r. in another moment in time the charge goes in the same circle but faster, where Δv is the difference in speed. i want to find the change in the magnetic dipole moment Δm.if magnetic dipole moment m=IA (assuming uniform...
  32. S

    Need help regarding transition dipole moment

    Hi, I have been trying to get the expression for the transition dipole moment of hydrogen but I am not able to get the expression. Hope someone can help me with that. I want to evaluate \vec{d}(v)=<v|\hat{r}|0> where v is the free state and 0 is the 1s wave function for hydrogen...
  33. C

    Free electrons and intrinsic spin magnetic dipole moment orientation?

    Are there any experiments or theories about the relation between magnetic dipole moment orientation and velocity vector of free electrons?
  34. K

    Dipole moment of given charge distribution

    So, I've got a charge distribution given by: \begin{equation} \rho(r,\phi,z)=\frac{q}{2\pi R}\delta(r-R)\delta(z)\cos(2\phi) \end{equation} This, if I'm not mistaken, translates into a circular charge distribution located in the z-plane, a distance R from origo. Thus \begin{equation}...
  35. P

    Zero dipole moment in stationary state?

    P.W. Anderson in his essay "more is different" said that: "no stationary state of a system has an electric dipole moment". He used an example of NH3 to illustrate that. I then checked online and found that, Chemists said there is dipole moment in NH3 molecule, but (nuclear) physicists claim...
  36. majormaaz

    Earth's Magnetic Dipole Moment

    Homework Statement The Earth's magnetic dipole moment is 8.0 x 1022 A m2. (a) What is the magnetic field strength on the surface of the Earth at the Earth's north magnetic pole? You can assume that the current loop is deep inside the earth. 6.17e-5 T (b)How does this compare to 5.0 x...
  37. W

    Dipole Moment Integration Question

    In "An Introduction to Electrodynamics", Griffiths gives the following equation for the dipole moment: p=\int r' \rho(r') d\tau'. My question is, in general, what volume am I integrating over? It seems a bit arbitrary to me. I assume I'm integrating over whatever volume is enclosing the charge...
  38. K

    How Do You Transform Electromagnetic Dipole Moments When Boosting Orthogonally?

    I just wondered how I transform electromagnetic dipole moments. For example assuming I have magnetic dipole moment μ in a frame without E dipole moment. Then I boost orthogonal to μ. Now I would like to determine the electric dipole moment. I could use the magnetic potential and transform...
  39. V

    Energy of a magnetic dipole moment

    Homework Statement The z component of the magnetic dipole moment due to the spin of an electron about its axis is μz = +/- eh/4∏m, where h = 6.63 x 10-34 J s is Planck's constant. A) If μz is parallel to a magnetic field of 10 T, how much energy in electron volts must be supplied to reverse...
  40. B

    What is the difference between magnetic dipole moment and torque ?

    imagine a door shaped circuit in the between a south and north pole such that the long sides are perpendicular to the magnetic field created by the magnet , now in my physics book , it says that the torque that rotates the door is equal to B * Md where Md is the magnetic dipole moment which...
  41. I

    What does q x d represent in dipole moment calculations?

    i have an intuition of electric field lines, and force. All quantities yielded from an operation between two quantities should hold meaning. what meaning does the value "q x d" hold? I'm looking for intuition/ an intuitive grasp of the dipole moment.
  42. G

    Mie scattering for sphere with constant dipole moment

    Hi does anybody here know whether there already exists a theory that describe Mie scattering for spheres that have a constant dipole moment?
  43. G

    Error in dipole moment calculation

    I am calculating the dipole moment of a metal sphere in a uniform electric field E_0 in z-direction. From here I know that the charge density [look at page 15][1] [URL="[PLAIN]http://www.phy.iitb.ac.in/~dkg/PH-102/conductors.pdf"]http://www.phy.iitb.ac.in/~dkg/PH-102/conductors.pdf[/PLAIN]...
  44. O

    How do scientists know the direction of Magnetic dipole moment?

    How they know, how to see the spin of electron>?? Without external field applied, there is random dipole in the paramagnet. for diamagnet, without external field , there will be no dipole exist. Thanks.
  45. Z

    Electric Dipole Moment, Potential, and Field of contiuous charge

    Homework Statement There are three charged line segments, each with linear charge density λ, extending from the origin to (a,0,0), from the origin to (0,b,0), and from the origin to (0,0,c). a) Find the dipole moment of this charge distribution. b) Find the first two terms in the...
  46. P

    How to calculate the magnetic dipole moment?

    How to calculate the magnetic dipole moment?? Does anyone out there know how I can calculate the magnetic dipole moment of a simple bar magnet? Or any kind of magnet? Without using this formula: \tau = μ x B
  47. HelloCthulhu

    Calculating Net Dipole Moment for Water - What Am I Doing Wrong?

    Greeting PF! http://chemwiki.ucdavis.edu/Physical_Chemistry/Atomic_Theory/Dipole_Moments On the website above, I found an equation for the dipole moment of water: "...the net dipole moment =2(1.5)xcos(104.5/2)=1.84 D." I understand how to calculate the bond dipole. But after...
  48. L

    Does the concept of dipole moment of charged molecule exist or not?

    Generally the concept of dipole moment is used in neutral system, ie the total positive charge equals to the total negtive charge. Could the concept and also the calculation be used in charged system? For example, NaOH, (Na+)(O-2)(H+), we can calculate its dipole moment. Could I calculate...
  49. X

    Average Effective Dipole moment

    Homework Statement Water relative permitivity is about 81. If the electric field E=x[V/m] (x unit vector) is inside the water, what is the vector P(dipole polarization per unit volume)? Then Assume that the density of water is 1000 [kg/m3] and that there are 3.34 × 1025 molecules per...
  50. L

    Electric potential of a dipole moment

    Homework Statement The dipole moment of a water molecule is 6.29E-30Cm. What is the electric potential's magnitude 1.43nm from a water molecule along the axis of the dipole? Homework Equations p = qr The Attempt at a Solution I don't have values for q or r. I just know the...
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