# Dipole

The Yird's magnetic field, approximatit as a magnetic dipole. Houever, the "N" and "S" (north an sooth) poles are labeled here geografically, which is the opposite o the convention for labelin the poles o a magnetic dipole moment.

In pheesics, thare are several kinds o dipole:

• An electric dipole is a separation o positive an negative charges. The simplest example of this is a pair o electric charges o equal magnitude but opposite sign, separated bi some (usually small) distance. A permanent electric dipole is ctied an electret.
• A magnetic dipole is a closed circulation o electric current. A simple example o this is a single luip o wire wi some constant current throu it.[1][2]
• A current dipole is a current frae a sink o current tae a soorce o current within a (uosually conductin) medium. Current dipoles are eften uised tae model neuronal soorces o electromagnetic fields that can be meisurt uisin MEG or EEG technologies.
• A flow dipole is a separation o a sink an a soorce. In a heichly viscous medium, a twa-beater kitchen mixer causes a dipole flow field.
• An acoustic dipole is a (teepically periodic) solution o the wave equation that is generatit bi twa close-thegither soorces o opposite sign. A simple example is a dipole speaker.
• Ony scalar or ither field mey hae a dipole moment.

## References

1. Brau, Charles A. (2004). Modern Problems in Classical Electrodynamics. Oxford University Press. ISBN 0-19-514665-4.
2. Griffiths, David J. (1999). Introduction to Electrodynamics (3rd ed.). Prentice Hall. ISBN 0-13-805326-X.