Oersted

 ( Centimetre–gram–second System Of Units ) 

The oersted (, "Oersted". Random House Webster's Unabridged Dictionary. symbol Oe) is the coherent derived unit of the auxiliary magnetic field H in the CGS-EMU and Gaussian units systems of units."as late as 1936 a subcommittee of the IEC International Electrotechnical Commission proposed the names 'maxwell', 'gauss' and 'oersted' for the cgs electromagnetic units of flux, induction and magnetic field strength, respectively". — John James Roche, The Mathematics of Measurement: A Critical History, The Athlone Press, London, 1998, , page 184 and John James Roche, " B and H, the intensity vectors of magnetism: A new approach to resolving a century-old controversy", American Journal of Physics, vol. 68, no. 5, 2000, doi: 10.1119/1.19459, p. 438; in both cases giving the reference as Claudio Egidi, editor, Giovanni Giorgi and his Contribution to Electrical Metrology: Proceedings of the meeting held in Turin (Italy) on 21 and 22, September 1988, Politecnico di Torino, Turin (IT), 1990, , pp. 53–56 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.Kaye, G. W. C, & Laby, T. H.: Table of Physical and Chemical Constants, page 14. Longman, 1973.

---

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.Hirst, A. W. Electricity and Magnetism For Engineering Students. Blackie & Son Limited, 1959, p. 411. The oersted corresponds to (≈) amperes per metre, in terms of SI units.

The H-field strength inside a long solenoid wound with 79.58 turns per metre of a wire carrying 1 ampere is approximately 1 oersted. The preceding statement is exactly correct if the solenoid considered is infinite in length with the current evenly distributed over its surface.

The oersted is closely related to the gauss (G), the CGS unit of magnetic flux density. In vacuum, if the magnetizing field strength is 1 Oe, then the magnetic field density is 1 G, whereas in a medium having permeability (relative to permeability of vacuum), their relation is

$B(\backslash text\{G\})\; =\; \backslash mu\_\backslash text\{r\}\; H(\backslash text\{Oe\}).$

Because oersteds are used to measure magnetizing field strength, they are also related to the magnetomotive force (mmf) of current in a single-winding wire-loop:

$1\backslash text\{\; Oe\}\; =\; \backslash frac\{1000\}\{4\; \backslash pi\}~\backslash text\{A\}/\backslash text\{m\}.$

---

Stored energy The stored energy in a magnet, called magnet performance or maximum energy product (often abbreviated BH_max), is typically measured in units of megagauss-oersteds (MG⋅Oe).

---

See also

• Centimetre–gram–second system of units
• Ampere's model of magnetization

Post Comment