An oersted is the standard unit of measurement used to quantify magnetic field strength. This term was adopted in 1932, in honor of the late Danish scientist Hans Christian Oersted, whose experiments significantly contributed to understanding electric currents, and who is credited with the discovery of electromagnetism.

One oersted measures the field strength that would cause a unit magnetic pole to experience a force of 1 dyne in a free space. It is equivalent to 79.58 amperes per meter.

(The above is information I found on many professional scientific websites, all of which seemed to know what they were talking about. But I am no expert, and there seems to be a wording problem, as user filoraene has been kind enough to point out: "It is simply not true that the Oersted is the unit of field strength in physics. This is the unit of field strength in the now-obsolete CGS unit system. In the CGS-system, the magnetic field (H-field) and the magnetic inductance (B-field) have different units, Oersted and Gauss respectively. I think just calling the H-field "the magnetic field strength" is highly misleading, if physically correct, as many people confuse the inducance and the field. BTW, the exact equivalency is 10^3/(4*pi) Ampere per meter.")


The first Danish satellite, the Oersted, was launched from the Vandenburg Air Force Base in California in 1999. Its objective was to help obtain a continuous measurement of the terrestrial magnetic field.


Oersted Technology produces magnetics equipment and instruments, including magnetizers, magnetizing fixtures, gaussmeters, fluxmeters, Helmholtz coils, and more. The front page of their website features a lovely photo of a rotting zombie finger pressing a big red button marked "MAGNETIZE." Futuristic.

If the name Oersted actually existed in Danish, which it doesn't, it is anybody's guess how it should be pronounced and what it would mean.

It would definitely be different from Ørsted, which is the name of several villages and, per derivation, a number of humans, some of whom have gained international fame: scientist Hans Christian Ørsted, jazz musician Niels-Henning Ørsted Pedersen, bicycle racer Hans-Henrik Ørsted.

Most likely it would be a three-syllable name: O-er-sted.

The measuring unit

There is one context where Oersted and Ørsted actually do serve as legitimate alternative spellings of the same word: the measuring unit for magnetic field strength.

The rationale most likely is that the ø is interpreted as a German umlaut, ö, which the Germans - unlike Danes - often write oe.

Oer"sted (?), n. [After Hans Christian Oersted, Danish physicist.] (Elec.)

The C.G.S. unit of magnetic reluctance or resistance, equal to the reluctance of a centimeter cube of air (or vacuum) between parallel faces. Also, a reluctance in which unit magnetomotive force sets up unit flux.


© Webster 1913.

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