What Is a Wire Dipole?

A dipole generally refers to a pair of charges or "magnetic charges" with opposite signs that are very close together. For example, the electric field lines of an electric dipole composed of positive and negative charges are shown in the figure. The Earth's magnetic field can be approximated as a magnetic dipole field. In geophysical exploration, it is important to study the dipole field. Because theoretical calculations show that the excited polarized secondary field of a spherical ore body in a uniform primary field is equivalent to the current field of a current dipole, some magnetic anomalies can also be studied using the magnetic dipole field. Equivalent dipole fields are used to replace the corresponding electric and magnetic fields. The spatial distribution of the field and the basic quantitative concepts can be obtained simply and clearly, which is also convenient for model experiments.

Definition: In the principle of automatic control,

Many molecules have electric dipole moments. This is due to the uneven distribution of positive and negative charges inside the molecule. E.g:

(Positive value) H-Cl (negative value) Molecules with permanent electric dipole moment are called polarized molecules . If a molecule has an induced electric dipole, the molecule is said to be polarized . Peter Debye was the first physical chemist to study the electric dipoles of molecules. To commemorate his contribution, the unit of measurement of the electric dipole moment is named debye, and the symbol is D.

The electric dipole of a molecule is divided into the following three types (see Intermolecular forces):

Permanent electric dipole : If the electronegativity of several atoms in a molecule is very different, the more electronegative atom will attract the electron closer to itself, thus making the occupied area more negative; in addition Regions of less electronegative atoms become more positive. In this way, a permanent electric dipole is formed.

Instantaneous electric dipole : Sometimes, electrons happen to be more concentrated in a certain area of the molecule, and this accidental situation will produce a temporary electric dipole.

Induction electric dipole : When an external electric field is applied to a molecule, the shape of the normal electron cloud inside the molecule will be changed by inducing the effect of this external electric field, thereby generating an electric dipole. Its accompanying electric dipole moment is equal to the product of the external electric field and polarization.

The following table shows the electric dipole moments of common compounds in the gaseous state, using Debye units:

substance	Electric dipole moment p / D
carbon dioxide	0
Carbon monoxide	0.112
ozone	0.53
Phosgene	1.17
water vapor	1.85
Hydrogen cyanide	2.98
Cyanamide	4.27
Potassium bromide	10.41

These values can be calculated from the measurement of the relative permittivity _r . When the molecule cancels the net electric dipole moment due to the symmetry, the electric dipole moment is set to 0. The maximum electric dipole moment is in the range of 10 to 11. Knowing the electric dipole moment, scientists can deduce the corresponding molecular structure. For example, the data shows that carbon dioxide is a linear molecule; ozone is not. ^[5]