Electric dipole is two equal but different signsPoint chargeSystem composed of.The characteristic of electric dipole uses electric dipole momentp=qlDescription, wherelIs the distance between two charges,landpThe direction of is specified by-qPointing+q。
If the external electric field is uneven, in addition to the torque, the electric dipole will also be subjected to the translation effect.The electric field generated by an electric dipole is the vector sum of the electric field generated by the positive and negative point charges constituting it.
MicrophysicsThe common unit in is debye, and the symbol is D;
, which is equivalent to one tenth of the distance between nuclei within a typical molecule (about
）Charge of the same electron
The product of.
Electric field generated by electric dipole
Center atCoordinate systemThe electric potential generated by the electric dipole at the origin in the distance is:[1]
Far away means
。
Electric field generated by electric dipole
The gradient obtained by this formula is that the electric dipole located at the origin is generated at a distanceelectric field intensity：
Electric dipole in external electric field
The electric dipole only receives non-zero resultant force in the non-uniform external electric field.The resultant force is[1]
In the external field, the electric dipole will also be subjected to torque,[2]
In the above two equationselectric field intensityBoth refer to the residual electric field after removing the electric dipole's own field strength.
As can be seen from the second equation,
Is the value that the electric dipole may be subjected to under the unit external electric fieldMaximum torque, so the electric dipole moment is also calledElectric moment。
The electric potential energy of, that is, the interaction energy, is
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Schematic diagram of electric dipole radiation
The common electric dipole system in real life isdipole momentDielectric molecules of.There is one kinddielectricPositivenegative chargeThe centers do not coincide and form electric dipole, which is calledPolar molecule；The positive and negative charge centers of another kind of dielectric molecule coincide, which is calledNonpolar moleculeHowever, under the action of an external electric field, the two charge centers will shift from each other, thus forming an electric dipole.[2]
Electric dipole is a combination of dielectric theory andAtomic physicsFrom stability to X-ray frequencyelectromagnetic fieldDielectricdispersionAnd absorption, as well as antenna radiation and other phenomena, all use dipoles (such as oscillating dipoles
）The concept of.
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takedipoleWhen the concept is generalized, there can be multipoles, which contain
Equal sizePoint charge, of which half are positive and half are negative, arranged into a regular lattice.In the multipole sub series,n=When 0, it isPoint charge；n=1, electric dipole;n=2, calledQuadrupole；n≥ 2, collectively referred to as high-order multipole.High order multipole model applied tonuclear physicsThe most important one is the quadrupole.If any point charge set or any distributed charge can be surrounded by a sphere, the potential outside the sphere can be concentrated onBall centerThe sum of the potential of the point multipole series ofMultipole expansion。
