Oersted
unit of magnetic field strength in the CGS system of units
The oersted (, symbol Oe) is the coherent derived unit of the auxiliary magnetic field H in the CGS-EMU and Gaussian systems of units. It is equivalent to 1 dyne per maxwell.
Difference between Gaussian and SI systems
In the Gaussian system, the unit of the H-field is the oersted and the unit of the B-field is the gauss. In the SI, the unit ampere per metre (A/m), which is equivalent to newton per weber, is used for the H-field and the unit tesla is used for the B-field.
History
The unit was established by the IEC in the 1930s in honour of Danish physicist Hans Christian Ørsted. Ørsted discovered the connection between magnetism and electric current when a magnetic field produced by a current-carrying copper bar deflected a magnetised needle during a lecture demonstration.
Definition
The oersted is defined as a dyne per unit pole. The oersted corresponds to 1000/4π (≈79.5775) amperes per metre, in terms of the pre-2019 SI units.
The H-field strength inside a long solenoid wound with 79.58 turns per metre of a wire carrying 1 A is approximately 1 oersted. The preceding statement is exactly correct under the pre-2019 definition of the ampere if the solenoid considered is infinite in length with the current evenly distributed over its surface, and has exactly 1000/4π turns per metre.
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This entry incorporates text from “Oersted” on English Wikipedia. Contributors are listed in the page history. Text is available under the Creative Commons Attribution-ShareAlike 4.0 License. Selected authority identifiers and statements are retrieved from Wikidata under CC0; their references and qualifiers remain part of the verification path.