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. S

    How do I determine the dipole moment from given E-field and point charge?

    Homework Statement E-field at (2[m], 30⁰, 90⁰) is E = 4aѳ [V/m]. Find the magnitude and direction of the dipole moment p. Homework Equations I know that I need I need to solve for the equation: p = Qd, where Q is the point charge at the given point and the distance between +Q and -Q, which...
  2. R

    Electric Dipole Moment | Magnesium Atom

    Firstly, I apologise if this is in the wrong place as it's not a homework question as such, but it is part of coursework. I am modelling the trapping and cooling of an atom with a laser, and have an equation for the dipole moment which I think may be off. I am getting strange results (slowing...
  3. L

    Calculating Magnetic Dipole Moment & Torque of Coil in Magnetic Field

    Homework Statement A circular coil having 20 turns and a radius of R = 12.8 cm carries a current of 2.70 A. It is placed in a uniform magnetic field of 60.0 mT. The initial angle between the magnetic moment of the coil μ and the magnetic field B is 26.0o. 1)Calculate the magnetic dipole...
  4. G

    Understanding Dipole Neutrality, Wave Functions & Dipole Moment

    May anyone help me with these questions 1 why is a dipole neutral as it completely resembles a system of two charges 2 i know probably its very advanced, but can anyone give me out a scope on wave function and its relation to energy of an orbital 3 am not sure if this is the right forum...
  5. R

    Calculating Magnetic Dipole Moment of Spin-2 Point Particle with Proton Mass

    Homework Statement ..Is it possible to find the Magnetic Dipole Moment of a point particle with spin quantum number 2 and mass equal to that of a proton. I'm not sure how to start this question as there's nothing on it in the textbooks I have! Thanks
  6. K

    Electric Dipole Moment of copper and sulphate ions

    Homework Statement The electric dipole moment of a CuSO4 molecule is 3.2 * 10^-32 (i.e. 10 raised to the power of -32)C-m. Find the separation between the copper and sulphate ions. Homework Equations Electric deipole moment = 2aq where 2a=separation between the two charges q and -q...
  7. D

    Electric Dipole Moment and electric field

    Homework Statement Two dipoles are oriented as shown in the diagram below. Each dipole consists of two charges +q and -q, held apart by a rod of length s, and the center of each dipole is a distance d from location A. If q = 6 nC, s = 1 mm, and d = 6 cm, what is the electric field at location...
  8. K

    Electric Dipole Moment: Mechanics Counterpart Explained

    I know the definition of the electric dipole moment is given by \mu = -e x, where e is the charge of electron and x is the displacement. I am thinking a mechanics counterpart of the dipole moment. We note that in mechanics, the moment is defined as the force cross the position vector. Consider...
  9. N

    Magnitude of dipole moment

    Homework Statement A certain electric dipole is placed in a uniform electric field E of magnitude 20 N/C. Figure 22-59 gives the potential energy U of the dipole versus the angle θ between E and the dipole moment P. What is the magnitude of P? Homework Equations U=p(dot)E The...
  10. S

    How Is Torque Calculated on a Dipole in an Electric Field?

    Homework Statement A dipole of moment 0.50 e · nm is placed in a uniform electric field with a magnitude of 8.0 104 N/C. What is the magnitude of the torque on the dipole for each of the following situations? (a) the dipole is aligned with the electric field 0. N · m (this is correct)...
  11. S

    Calculating the Dipole Moment of LiBr

    Dipole Moment! Ok I'm very tired because I've spent the past 50 minutes trying to figure out a problem that should take only 5. Someone please just take 2 minutes of your time to save me 20 more minutes. THis is a simple problem yet I cannot do it on my own, without my textbook and with what...
  12. N

    Griffiths E&M 3.33 write e-field of dipole moment in coordinate free form

    Homework Statement Show that the electric field of a "pure" dipole can be written in the coordinate-free form E_{dip}(r)=\frac{1}{4\pi\epsilon_0}\frac{1}{r^3}[3(\vec p\cdot \hat r)\hat r-\vec p]. Homework Equations Starting from E_{dip}(r)=\frac{p}{4\pi\epsilon_0r^3}(2\cos \hat r+\sin\theta...
  13. D

    Change in orbital magnetic dipole moment of the electron due to unifrom B field

    Homework Statement Assume that an electron of mass m and charge magnitude e moves in a circular orbit of radius r about a nucleus. A uniform magnetic field B is then established perpendicular to the plane of the orbit. Assuming also that the radius of the orbit does not change and that the...
  14. J

    Calculating Electric Dipole Moment of Point Charges Along Z-Axis

    Hi I want to calculate the electric dipole moment of point charges along the z-axis with distances a and with the charge distribution \varrho (\vec{x}) = q \delta (\vec{x}) - 2q \delta (\vec{x} - \vec{a}) + q \delta (\vec{x} - 2 \vec{a}) and of course \vec{a} = a \vec{e}_{z} I...
  15. A

    Why is the direction of the dipole moment always taken from -q to +q?

    Homework Statement Can anyone explain why the direction of the dipole moment of an electric dipole is always taken as "from -q to +q" but not "from +q to -q"? In fact when we draw the electric lines of force we are only drawing in such a way that they start from +q and terminate at -q.Then...
  16. J

    Dipole moment of non-conducting spherical shell

    Homework Statement I'm trying to find the dipole moment of The surface charge distribution is: \sigma = \sigma_{0} sin 2 \theta Homework Equations The Attempt at a Solution p_z=\int_{0}^{\pi}{\sigma* z* dA } = \int_{0}^{\pi}{(\sigma_0 \sin{2...
  17. J

    Calculate Dipole Moment of Spherical Shell w/ Surface Charge Density

    Calculate the dipole moment of a spherical shell of radius 'a' whose surface charge density is σ=σ0(1+cos(θ)). The origin is at the center of the sphere. What I know: 1) p=∫r'*ρ*dV' I'm having trouble understanding how to transform this equation so that I can calculate the dipole moment...
  18. L

    Dipole Moment of Water: Understand 105 Degrees & Impingement

    I understand a little about dipole moment. Its like a compass which aligns itself when an external field is applied. But a little fuzzy when it comes to dipole moment of water. why is it 105 degrees. How does this come into play when they are impinged with microwaves or time varying E field.
  19. H

    Magnetic Moment of Electron: Intrinsic Spin & Dipole Moment

    hi I am student of graduate and want to clear the picture of MAGNETIC MOMENT of electron in my mind.can someone tell me that if an electron is moving in its orbit constituting its intrinsic spin(1/2) ho can it forms dipole moment(to poles) when place in magnetic field?and what is the difference...
  20. Useful nucleus

    Why is there a discrepancy in the calculated dipole moment of a water monomer?

    a water monomer has HOH angle of 104.5 and OH length of 0.98 , partial charges are +0.4 on H and -0.8 on O. The reported electric dipole moment for this monomer is 1.86D. I tried to calculate it and got 2.3 D. The way I do it is by multiplying the distance between the center of the H-H and the...
  21. I

    What does a molecule having dipole moment signify?

    Can someone give me a clear picture of it's physical meaning? What does a molecule having dipole moment signify? All the explanations I've seen are very hazy.
  22. K

    No Permanent Dipole Moment in Two-Level System w/External Field

    In two-level system, with external field applied, why there is no permant dipole moment? In classical point of view, dipole moment is coming from displacement of positive and negative charge. In quantum case, inside the atom, even no external field, there is certain probability for the electron...
  23. K

    Polarizaition and dipole moment?

    I am learning a simple model for two-level system in which the dipole moment is written as d = d_{12}|1\rangle\langle 2| + d_{21} |2\rangle\langle 1| where d is the dipole moment element, "1" stands for ground state and "2" stands for excited state. For a system has the particle density be...
  24. K

    Electric Dipole Moment Help: Prove Integration Equation

    Help me to sort out this problem:: Prove that, "integration over[J(r)dr]=del(p)/del(t)" ... where p is the electric dipole moment ... please as soon as possible, reply me ...
  25. A

    Calculating the Dipole Moment of Benzene Rings

    Hi , How to calculate the diploe vector of benzene ring?. what is the formula for calculating the diploe moment?. Thanks in advance Aneesh
  26. J

    Magnetic Dipole Moment of a Coil

    Homework Statement You have a coil of N turns, with current I through it. It is in a magnetic field B, which causes it to feel a torque. Give an expression for its magnetic dipole moment. Homework Equations The Attempt at a Solution Well, I know magnetic dipole moment is A...
  27. D

    Electric dipole moment question

    1. In an electric dipole moment, assume that both charges are positive and find the electric field "E" at point "P", assuming X>>d, where "d" is the distance between the two charges and "X" is the distance of point "P" from the center of the dipole. I have thought a lot about it but I am very...
  28. T

    Chemistry How to calculate the dipole moment of a molecule?

    how to calculate the dipole moment of a molecule?? using electronegative values of periodic table ??
  29. G

    Question about the magnetic dipole moment of the electron

    Let's say that an electron is moving with constant velocity through a magnetic field. If the magnitude of the field is the same everywhere in space and if it is perpendicular to the velocity of the particle everywhere, the electron will follow a circular path. We all know that. What I need to...
  30. K

    Finding Expectation Value of Electric Dipole Moment Matrix Form

    Homework Statement I we know the eigenstates of the system be |\psi_1\rangle and |\psi_2\rangle. Current state of the system is |\Psi\rangle = c_1 |\psi_1\rangle + c_2 |\psi_2\rangle Try to find the expectation value of electric dipole moment \mu (assume it is real) and write it in...
  31. F

    Dipole moment for a charge arrangement

    Homework Statement What is the dipole moment for the following charge arrangement? (Please view attachment) http://img378.imageshack.us/my.php?image=dipoleal6.jpg" http://img378.imageshack.us/my.php?image=dipoleal6.jpg Homework Equations p = \int r' \rho (r) d \tau '...
  32. J

    Dipole moment electric potential

    Homework Statement what is the potential 18 cm from a dipole moment 2.6nCm at a) 42 deg to axis b) on the perpendicular bisector note: dipole separation << 18cm Homework Equations electric dipole moment, p = qd where q is charge, d is distance electric potential for point...
  33. M

    Magnetic Field of Magnetic Dipole Moment

    I'm seeking some clarification on a topic found in Jackson 'Classical Electrodynamics' Chapter 5. This deals with the magnetic field of a localised current distribution, where the magnetic vector potential is given by \vec{A}(\vec{x}) = \frac{\mu_0}{4\pi}...
  34. N

    Do Transition Dipole Moments Have Different Signs? Resolving a Contradiction

    Hi, Is dipole operator symmetric or antisimmetric? Or, in other words, do the transition dipole moments from state 1 to the state 2, and from the state 2 to the state 1 have different sign? I.e. mu_12 = - mu_21. As far as I understand, the diagonal elements for the dipole operator...
  35. I

    Needle suspended from string - dipole moment?

    Homework Statement A needle suspended from a string hangs horizontally. The electrical field at the needle's location is horizontal with magnitude 3.7 x 10^3 N/C and it's at an angle of 30 degrees with the needle. There is no net electrical force acting on the needle, but the string exerts...
  36. R

    How Do You Calculate the Potential Energy Between Two Dipoles?

    Homework Statement Consider two dipoles with moments u1 and u2 arranged as in the following diagram. Each dipole is depicted as two charges of equal magnitude separated by a distance d. The centre-to-centre separation of the two dipoles is the distance r. The line joining the two dipole...
  37. S

    Magnetic Dipole Moment - Vector Orientation

    Guys, I don't quite understand the concept of magnetic dipole moment as a vector. Suppose we have a magnet (like a rod) in 3 dimensional space. North pole at (0, 0, 0) and South pole at (0, 1, 0). How would the magnetic dipole vector \vec{m} be oriented? Thanks.
  38. E

    Calculating Magnetic Dipole Moment of a Sphere

    [SOLVED] Griffiths 5.58 Homework Statement A uniformly charged solid sphere of radius R carries a total charge Q, and is set spinning with angular velocity \omega. What is the magnetic dipole moment of the sphere.Homework Equations The Attempt at a Solution The magnetic dipole moment of a...
  39. E

    Griffiths dipole moment

    [SOLVED] Griffiths dipole moment Homework Statement On page 244 of Griffiths E and M book, Griffiths defines the magnetic dipole moment as \vec{m} = I \int d\vec{a} . Then in problem 5.58, he asks us to calculate the dipole moment of a uniformly charged spinning solid sphere. How is that...
  40. M

    Magnetic Dipole Moment and Angular momentum

    Homework Statement Show that the magnetic dipole moment M of an electron orbiting a proton nucleus of a hydrogen atom is related to the orbital angular momentum M=(e/2m)L Homework Equations M=NIA, Torque =MB, F=qvB=v^2/r, L=Iw=mrv=rp (where p=mv) N=1 in this case I assume? The...
  41. P

    Electric fields - dipole moment

    Homework Statement An electric dipole, consisting of charges of magnitude 2.60 nC separated by 7.20 µm, is in an electric field of strength 1400 N/C. (a) What is the magnitude of the electric dipole moment? (b) What is the difference in potential energy corresponding to dipole...
  42. G

    Need Help with Calculating Dipole Moment Ratio

    I am having some trouble starting this one. http://img301.imageshack.us/img301/8080/79432817ke4.jpg Im not sure if I am supposed to replace the psi(v) with some ground state harmonic oscialltor function or not. If so, do I then just take the integrals and then divide 1 to 2 by 0 to 1 to...
  43. tony873004

    What is the needle’s dipole moment?

    A needle suspended from a string hangs horizontally. The electric field at the needle’s location is horizontal with a magnitude 3.7*103 N/C and is at an angle of 30° with the needle. There is no net electrical force acting on the needle, but the string exerts a torque of 3.7*10-3 to hold the...
  44. J

    Calculating Electric Field & Dipole Moment of Electron in Hydrogen Atom

    Homework Statement OK I really would appreciate some help on this - just a point in the right direction would be great: The potential due to the electron in a hydrogen atom at distance r from the nucleus is V = kq[(exp(-2r/a) - 1)/r + (exp(-2r/a)/a] Where k=1/(4pie0) where e0 is the...
  45. G

    Electric Field and dipole moment

    There is a dipole moment that is symmetric along a y-axis and is along an x-axis. A charge -q is placed a distance a along the -x direction and a charge +q is placed a distance a along the +x direction, making the distance between the 2 charges 2a. I'm supposed to show that the electric field...
  46. J

    Finding the Magnitude of a Dipole Moment

    [SOLVED] Finding the Magnitude of a Dipole Moment Hi there, I'm new to posting, but I've used this forum many times to help me with my homework :) I went the "take a photo of the textbook" route (there is a picture with the problem), so I hope that's acceptable. Homework Statement A...
  47. malawi_glenn

    What Is the Atomic Electric Dipole Moment and Its Role in Van der Waals Binding?

    Hi I was wondering if anyone could give me info about atomic electric dipole moment at a very fundamental level (fenomenological, basic quantum), I do not seem to find it when I google =( My Aim is just to understand van der Waals binding in solids a little bit more.
  48. S

    What is the magnetic dipole moment of the sphere?

    Homework Statement A uniformly charged solid sphere of radius R carries a total charge Q, and is set spinning with angular velocity \omega about the z axis. (a) What is the magnetic dipole moment of the sphere? Homework Equations \vec{m} = I \int d\vec{a} The Attempt at a...
  49. S

    Transition Dipole Moment and Electron Transfer

    Well I am doing a project suffice to say on electron transfer. In protein complexes it has been shown that förster equation gives pretty good results, so I am trying to understand this equation. But there seems to be not much resource on that (I think I will be buying Förster's own book...
  50. B

    Average effective dipole moment?

    Hi , I crashes myself with this problem about diploe. Please can I have some suggestions. Assume that the density of water is 1000 [kg/m3] and that there are 3.34 × 1025 molecules per kg of water. (One mole of water weighs 18.0[g] since atomic weight of water is 18.0. A mole contains a...
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