What is Dipoles: Definition and 106 Discussions

In electromagnetism, there are two kinds of dipoles:

An electric dipole deals with the separation of the positive and negative charges found in any electromagnetic system. A simple example of this system is a pair of electric charges of equal magnitude but opposite sign separated by some typically small distance. (A permanent electric dipole is called an electret.)
A magnetic dipole is the closed circulation of an electric current system. A simple example is a single loop of wire with constant current through it. A bar magnet is an example of a magnet with a permanent magnetic dipole moment.Dipoles, whether electric or magnetic, can be characterized by their dipole moment, a vector quantity. For the simple electric dipole, the electric dipole moment points from the negative charge towards the positive charge, and has a magnitude equal to the strength of each charge times the separation between the charges. (To be precise: for the definition of the dipole moment, one should always consider the "dipole limit", where, for example, the distance of the generating charges should converge to 0 while simultaneously, the charge strength should diverge to infinity in such a way that the product remains a positive constant.)
For the magnetic (dipole) current loop, the magnetic dipole moment points through the loop (according to the right hand grip rule), with a magnitude equal to the current in the loop times the area of the loop.
Similar to magnetic current loops, the electron particle and some other fundamental particles have magnetic dipole moments, as an electron generates a magnetic field identical to that generated by a very small current loop. However, an electron's magnetic dipole moment is not due to a current loop, but to an intrinsic property of the electron. The electron may also have an electric dipole moment though such has yet to be observed (see electron electric dipole moment).

A permanent magnet, such as a bar magnet, owes its magnetism to the intrinsic magnetic dipole moment of the electron. The two ends of a bar magnet are referred to as poles—not to be confused with monopoles, see Classification below)—and may be labeled "north" and "south". In terms of the Earth's magnetic field, they are respectively "north-seeking" and "south-seeking" poles: if the magnet were freely suspended in the Earth's magnetic field, the north-seeking pole would point towards the north and the south-seeking pole would point towards the south. The dipole moment of the bar magnet points from its magnetic south to its magnetic north pole. In a magnetic compass, the north pole of a bar magnet points north. However, that means that Earth's geomagnetic north pole is the south pole (south-seeking pole) of its dipole moment and vice versa.
The only known mechanisms for the creation of magnetic dipoles are by current loops or quantum-mechanical spin since the existence of magnetic monopoles has never been experimentally demonstrated.
The term comes from the Greek δίς (dis), "twice" and πόλος (polos), "axis".

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  1. milkism

    Oscillating dipoles, energy and brightness

    Problem: Attempt at solution: So "energy passing through per unit area per unit time" is equal to $$I = \frac{E_i}{A t}$$ So for a the graph will be in the form of ##y=1/x##? For b) do we have to solve the differential equation $$dI = \frac{E_i}{A dt}$$?
  2. tbn032

    Limits of Partial Charges in Dipoles

    In my book it is written "Ends of dipole possesses partial charges. Partial charges are always less than the unit electronic charge (1.6×10−19 C)". Suppose in a double bond(two electron is shared by each atom) or triple bond(three electrons are shared by each atom), can the electronegative atom...
  3. LCSphysicist

    Understanding the Radial Attraction Force between Two Electric Dipoles

    I am extremelly confused with this question: Basically suppose we have two electric dipoles, parallel to each other, as follows in the figure: I am supposed to show that the force is attractive and radial. But I am not getting how it can be radial (pointing toward each other)! See, the force...
  4. W

    I Magnetization inside a diamagnetic material antiparallel to ##B_{ext}##

    Let's say I have a constant magnetic field and I dive into it a diamagnetic material. Griffiths says that in the presence of a magnetic field, matter becomes magnetized and it will be found to contain many tiny dipoles with a net alignment along some direction. However, what's exactly the link...
  5. P

    Interactions Between 2 Dipoles

    Draw graphs showing how interaction energy depends upon the relative orientation of two dipoles if (i) p1 is parallel to r, (ii) p1 is perpendicular to r. I've done the first part and found the interaction energy as UInt = 1/(4*pi*epsilon0*r^3)*[p1.p2-3(p1.r^)(p2.r^)] which I know is correct...
  6. snoopies622

    Deflection of magnetic dipoles by a magnetic field

    I'm reading about the Stern–Gerlach experiment and the only part that confuses me is how a magnetic field would deflect particles with magnetic dipoles instead of just rotating them. In this case the magnetic field is non-uniform, but it still seems intuitively strange to me since magnetic...
  7. P

    Babinet's Principle: Effective Aperture Dipoles (Matlab)

    For clarification on "normal incidence" without drawing a picture. I'm going to assume the incoming wave has the electric field in the z-direction, the magnetic B / Auxillary H-field in the x-direction, and the Poynting Vector in the y-direction (i.e. normal to the plane of the aperture). That...
  8. Philip Koeck

    A Dipoles on a clean surface in vacuum

    Assuming a completely clean and flat solid surface (metal and amorphous carbon as examples). The surrounding vacuum is contaminated with water vapour at very low pressure. In what orientation would the water molecules adsorb to the solid surface?
  9. 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...
  10. G

    Electric Dipoles: Convention & Field Lines

    What is the convention? Because the field lines leave the positive charges and enter the negative ones, do not they?
  11. K

    I Are magnetic Ising-like dipoles advanced territory? [in Portugese]

    I was looking at some works by the members of my university physics departament and I found this one <Mod edit> Besides this abstract, the paper is in Portuguese. <\Mod edit> http://lilith.fisica.ufmg.br/posgrad/Dissertacoes_Mestrado/decada2010/denis-oliveira/DenisDaMataOliveira-diss.pdf...
  12. Minish

    Finding the probabilities of macrostates for paramagnetic dipoles

    Homework Statement Hi! So I am given two different microstates of a system with 10 dipoles in a magnetic field B. I am asked to find the microstate that belongs to the macrostate with the highest probability, and to give that probability. I am also asked to find the same but with the highest...
  13. P

    I EM Radiation of "Permanent" Molecular Electric Dipoles

    Suppose I were to subject a polar molecule to a high-frequency electric field. The polar molecule responds to the high-frequency electric field and thus it has a time-varying electric dipole moment vector. If we treated this as a classical electric dipole, it would be expected to radiate some of...
  14. P

    I How does a magnetic field affect the aggregation of nonpolar molecules in water?

    I'm an undergrad biochemistry major at a state university in NY (I've tried the chemistry forums already) trying to understand more about interactions between polar and non-polar molecules. Say I have a thin wax in water, we are taught that the entropy of the reordering of water contributes...
  15. 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...
  16. T

    I Is there dipoles in mono crystaline Si?

    How to model the electromagnetic behavior of mono-Si in room temperature? Shall we consider electron/hole only? Or shall we also take dipoles into account? If so, how are these dipoles generate? THX! Z.J.
  17. A

    How do you calculate the force between two magnetic dipoles?

    I've seen a couple of equations on Wikipedia and other sites and all of them are different. I need an equation as I want to specifically calculate the force between a magnet and a steel ball. The equations I've seen is this one here...
  18. D

    Electrostatic polarization of an axially symmetric conductor

    Homework Statement A grounded Z-axis symmetric closed conductor has a single point charge at the origin within it, inducing negative charge onto its inner surface. Given the induced charge density from the unit point charge, find the surface charge induced instead by a unit dipole at the...
  19. NihalRi

    Force between electric dipoles along the dipole axis

    Homework Statement Compute the force between two identical dipoles. See Problem P63 on page 544 to set up the problem. Explain why this result makes sense by comparing it to the force between two point charges and the force between a point charge and a dipole, in terms of the relationship to...
  20. mikemartinlfs

    Four Electric Dipoles = What level of electric flux?

    Homework Statement A circle, centered on the origin, has a radius of 1 mm. At each "pole" (1,0), (0,-1), (-1,0), (0,1) is an electric dipole. The positive charge of +10 microCoulombs is inside the circle, the negative charge of -10 microCoulombs is just outside the circle. What is the...
  21. 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?
  22. J

    Input Impedance of off center fed dipoles

    My name is Jackson Richter. I am retired from Rockwell-Collins and worked in the engineering lab for 31 years. Since my retirement my interested have peaked in radio communications. Especially in antenna design. Thanks to anyone here that would give me a little more insight with my...
  23. N

    Calculating Electric Field from a Dipole: Is This Equation Accurate?

    Is this the correct equation to find the electric field at point p from a dipole?
  24. U

    Electric charges and fields: Crossed dipoles

    Homework Statement Two short dipoles each of dipole moment p are placed art origin. The dipole moment of one dipole is along x-axis while that of other is along y axis. Then what will be the electric field at a point (a, 0)?Homework Equations The direction of electric field due to axial dipole...
  25. Kara386

    Are EM waves reflected by inducing Hertzian dipoles?

    A comment a lab script for a recent experiment I did noted that the mechanism by which reflection of EM waves occurs is through the induction of Hertzian dipoles in a material. Having read up on Hertzian dipoles, I have found nothing which discusses them in the context of reflection. I read...
  26. K

    Maximum Torque in Dipoles (electrostatics)

    In a --specifically uniform electric field-- (I may be wrong here) my understanding is that the dipoles will result in no net dipole force (due to cancelling out) but there will actually be a net torque experienced about the center. This torque will be trying to turn the dipole so the moment, p...
  27. rolotomassi

    Statistical physics for system of dipoles

    There is a project I'm working on to model the phase transition of 2 polymers with and without an external E-field. The approach I am taking is first to consider 2 types of dipoles, with a constant external field in the 'up' direction. I'm thinking in two dimensions for now. The dipoles can...
  28. Ghost117

    Calculating E Field of Dipoles at Distance r: Griffiths 4.5 Solution

    This is part of a question from Griffiths 4.5 (electrodynamics, 4th edition) Homework Statement p1 and p2 are (perfect) dipoles a distance r apart (Their alignment is such that p1 is perpendicular to the line separating them (pointing upwards) and p2 is parallel to the line separating them...
  29. J

    Exploring Current Dipoles: ECG, EEG, MCG and MEG

    Hi all, new user here. I did a search on Google for "current dipole" during an idle moment, and discovered this forum and joined. There was an old, closed thread concerning "current dipole", started by basheersubei and including tiny-tim, sophiecentaur, and madness, which closed 3.5 years ago...
  30. Isaac0427

    Types of dipoles and their fields

    Hi guys! Sorry for all the questions on electromagnetism. My understanding is that an electric field exists in electric monopoles and dipoles, as well as moving magnetic dipoles, and magnetic fields only exist in magnetic dipoles and moving electric dipoles. Is this correct? There are 2 parts...
  31. It's me

    What is the equilibrium angle - dipoles?

    Homework Statement Two coplanar dipoles are oriented as shown below. If θ is fixed, what is the equilibrium angle θ' ? Homework Equations The torque exerted by dipole P on dipole P' is given by $$\vec{N'}=\vec{P'}\times\vec{E}$$ where vector E is the electric field. The Attempt at a...
  32. gracy

    Unstable equilibrium in case of dipoles

    I know in case of unstable equilibrium of dipoles when dipole makes zero angle with electric field intensity ,But how we decide that this is unstable equilibrium I know in case of unstable equilibrium dipole returns to it's place after the small displacement ,I want to know why or how?why/how...
  33. Priyadarshini

    Van der Waals' Forces and Hydrogen Bonding

    Induced dipoles result in Van der Waals' forces and permanent dipoles in hydrogen bonds, right? But how do you know is a compound has formed hydrogen bonds or Van der Waals' forces? For example, HF forms hydrogen bonds while HCl forms Van der Waals' forces and not hydrogen bonds. But in HCl, H...
  34. C

    Total power radiated from two dipoles (electrodynamics)

    Homework Statement The retarded vector potential ##\mathbf{A}(\mathbf{r}, t)## in Lorenz gauge due to a current density ##\mathbf{J}(\mathbf{r}, t)## contained entirely within a bounded region of size d is $$\mathbf{A}(\mathbf{r},t) = \frac{1}{4\pi c}\int_V' \frac{\mathbf{J}(\mathbf r'...
  35. H

    Why can we assume dielectric induced dipoles are pure dipoles?

    Homework Statement Griffiths was trying to prove that when calculating the electric field inside a dielectric, we may assume the dipoles induced in it are "pure" dipoles, although they are in fact "physical" dipoles, as long as we view the field as a macroscopic field, one that is averaged over...
  36. J

    Coloumb's Law and Electric Dipoles question

    Homework Statement 1)HCl consists of one H and Cl atom separated by 0.127 nm, the bond length. The Cl atom has a partial charge of -0.177e and the H atom has a partial charge of +0.177e, where e = 1.602x10-19 C is the electron charge. 2)Now the HCl molecule is placed near a sodium ion Na+ with...
  37. R

    Why is the y-component of the electric field in a dipole cancelled out?

    Hi everybody. I noticed that I don't understand dipoles correctly. I just calculated the field of a dipole. There are two charges, one positive the other negative, in the distance of d. I got for the electric field: E=\frac{q}{4 \pi \epsilon} \binom{d}{0} The problem is, that there is only the...
  38. Roodles01

    Permanent dipoles in molecules

    As I understand, when an electric field is applied to an atom then the nucleus and electron cloud will be shifted out of balance giving rise to an electric dipole moment. Some molecules have permanent dipole moments though, e.g. Hydrogen Chloride, ". . . when a hydrogen chloride molecule is...
  39. WannabeNewton

    Average force between electric dipoles

    Homework Statement Consider a pair of electric dipoles ##\mu## and ##\mu'##, oriented in the directions ##(\theta,\phi)## and ##(\theta',\phi')## respectively; the distance ##R## between their centers is assumed to be fixed. The potential energy in this orientation is given by ##\varepsilon =...
  40. S

    Coulomb's force in atoms and effect on dipoles

    Hi! I've had this question for awhile. I asked my ochem professor and he didn't know how to answer it. My physics professor answered it but still left me with questions. In physics, the force of two charged particles is shows by Coulombs eq: F= k* q1 * q2/ r^2. My question is, why do...
  41. M

    Exploring Dipoles: Understanding the Charge Separation Phenomenon

    Question about dipoles... I read somewhere that a dipole is a separation of two equal but opposite charges. Is this true or can the two charges of a dipole have a different amount of charge?
  42. M

    What is the significance of dipoles in condensed matter physics?

    Question about dipoles... What is the difference between a dipole in physics and a dipole in chemistry?
  43. M

    How Do Magnetic Field Lines Form Between Two Pairs of Magnetic Dipoles?

    Hi , I am interested to know how would the magnetic field lines be formed and what effect each one of them would have to the one next to the other in such a configuration. I have two pairs of magnets. Distance between each magnet in a pair , numbered 2, is 2 mm. the distance between the two...
  44. F

    Why do greenhouses gases need to have dipoles?

    Greenhouse gases absorb and then re-emit the heat energy of infrared rays which have been partially absorbed and then reflected off the Earth from the sun, which is how the greenhouse effect works. I have heard, however, that in order for a gas in the atmosphere to be considered a greenhouse gas...
  45. A

    Current loops and electric dipoles

    Hello Physics enthusiasts Imagine an infinitesimal small current loop where the current can run clockwise or counterclockwise at frequency v. I am trying to find a linear combination of the two(current loops) which creates the same electric field pattern (far from the dipole) as a very small...
  46. T

    Torque of Dipoles: Problem 4.5 (Griffiths)

    "Problem 4.5 In Fig. 4.6 ##p_{1}## and ##p_{2}## are (perfect) dipoles a distance r apart. What is the torque on ##p_{1}## due to ##p_{2}##? What is the torque on ##p_{2}## due to ##p_{1}##? [In each case I want the toruqe on the dipole about its own centre. If it bothers you that the answers...
  47. T

    Does Electric Field Heat Up Conductors? Investigating Dipoles & Heat

    If we put a neutral conducting sphere in an electric field, it will become polarized. A force per unit area will be experienced on the surface according to: \vec{f} = \frac{1}{2\epsilon_0}\sigma^2\hat{n} My question is, does this process heat up the conductor? And if so, where is that...
  48. S

    Direction of magnetic force for magnetic dipoles

    A charged particle in a magnetic field experiences a magnetic force that is perpendicular to it. But is that the case with magnetic dipoles? There was this section in my textbook describing Torque on a Bar magnet in a uniform magnetic field which states that the magnetic force m.B on one pole...
  49. P

    Magnetic Dipoles: Understanding Attraction and Repulsion in Magnetism

    What is the key reason? I mean if you think about it, poles are just something we create to distinct the magnetic field. But they don't exist. Why do magnets attract/repel? Is it because of the dipoles? They want to aline themselves? Btw, are the dipoles in ceramic magnets equally the...
  50. M

    Understanding Atomic Dipoles and Spontaneous Emission

    Hi, In quantum optics, the interaction between light and atoms is described by a Hamiltonian of the form d.E where d is the dipole moment of the atom. The picture given is basically that this is a vector and we take the the dot product with this and the electric field vector (whose direction...