Dipole

A single charge that emits an electric field is called a monopoly. In contrast, a dipole is understood to mean the physical arrangement of two opposite charges (positive and negative). This is not a two-pole system - this name in turn stands for a certain group of electrical circuits. A dipole itself does not carry an electrical charge because the two opposite charges neutralize each other. Each dipole is characterized by a so-called dipole moment. This vectorial quantity can be calculated using the following formula:

While stands for the distance between the two opposite charges, indicates q their amount. Depending on the area and form in which dipoles occur, a distinction is further made between electrical and magnetic dipoles. The following overview summarizes the most important features.

Dipoles and magnetic fields

Basically, all complex magnetic structures can be assembled from dipoles. Examples of dipoles are magnets with a south pole and a north pole. As soon as there are several charge distributions, multipoles are mentioned. In principle, this term encompasses all structures of magnetic and electrical fields that result from the charge distribution. A magnetic field always consists of at least one dipole field. Even if you break apart a magnet in the middle, you cannot separate the opposite charges. This is because a new north and south pole is created at the interface, so that both fragments in turn form a new dipole.

Dipoles and electric fields

Since electrical dipoles are created by the separation of charges, they tend to be rare on a macroscopic level. In contrast, electrical dipoles are often found at the microscopic level. Among other things, they are created by asymmetric molecules in water. Muscle and nerve fibers in the human body also cause electrical dipole moments. This can be measured using an electrocardiogram, for example, using electrical voltages.

Which molecules are dipoles?

If the center of gravity of negative charges (electrons) and positive charges (atomic nuclei) does not coincide within a body, then this body has an electrical dipole moment. This is why we speak of a dipole molecule as soon as a molecule has both a positive and a negative pole. In chemistry, the dipole moment serves as a measure to measure the strength of a corresponding molecule. In principle, a dipole molecule must contain at least one polar atom bond. That is why dipoles can be found, for example, in:

  • Ammonia (NH3)
  • Hydrogen chloride (HCI)
  • Water (H2O)

By contrast, chemical compounds such as carbon dioxide (CO2) or methane (CH4) have no dipole molecules. It is important to distinguish between polar substances in general and dipoles in particular. Polarity generally refers to the formation of separate charge centers, which means that an atomic group is no longer electrically neutral. Under certain circumstances, a dipole moment can arise from polar bonds. This means that a polar molecule (e.g. methane) does not necessarily have to be a dipole molecule.


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