Electric dipole moment

The electric dipole moment characterizes a spatial charge separation. Has a body, such as a molecule, at different locations, an electric charge of opposite signs, so that the focus of the negative charges (electrons) and the center of positive charge ( atomic nucleus ) do not coincide, then this body has an electrical dipole moment.

In chemistry, the dipole moment is a measure of the strength of a Dipolmoleküls.

, Other dipoles ( for example magnetic dipoles ) are possible, thus forming the other dipole moments.

Calculation

If there is a negative charge -q at a distance a positive charge q, and these charges are mutually rigidly connected, so this structure has a dipole moment of greatness:

The greater the load Q, the greater the dipole moment. Even if the charges move further apart (directed from the negative to positive charge distance L), the dipole moment is larger.

Located at a discrete charge distribution n charges at the locations relative to the center of gravity of the charge distribution, then the total dipole moment of the Einzeldipolmomenten sets together:

In the general case of a continuous distribution of charge, the dipole moment is calculated from the charge density:

The discrete case is apparent from the general when one represents the charge density of the individual loads, and the delta function:

The volume integral then gives only contributions to the locations of the charges, so that

Results.

Generally, a potential of a constant part and multipole including just the dipole moment are developed.

Unit

Despite the conversion to the SI system, the cgs unit Debye is still used as a unit of the dipole moment, named after the Dutch physicist Peter Debye. The reason for this is that one would have to deal with the use of the SI unit coulomb meters with very small numbers:

For molecules the dipole moment is usually in the range from 0 to 12 Debye.

The dipole moment can be determined using the Debye equation by measuring the dielectric constant. Also provide measurements of the Stark effect on the dipole moment of the substance information.