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 The dyne (symbol: dyn; ) is a derived units of measurement, unit of force (physics), force specified in the centimetre–gram–second system of units, centimetre–gram–second (CGS) system of units, a predecessor of the modern International S ...

per

maxwell Maxwell may refer to: People * Maxwell (surname), including a list of people and fictional characters with the name ** James Clerk Maxwell, mathematician and physicist * Justice Maxwell (disambiguation) * Maxwell baronets, in the Baronetage of N ...

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 Johann Carl Friedrich Gauss (; ; ; 30 April 177723 February 1855) was a German mathematician, astronomer, Geodesy, geodesist, and physicist, who contributed to many fields in mathematics and science. He was director of the Göttingen Observat ...

. 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 Hans Christian Ørsted (; 14 August 1777 – 9 March 1851), sometimes Transliteration, transliterated as Oersted ( ), was a Danish chemist and physicist who discovered that electric currents create magnetic fields. This phenomenon is known as ...

. 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

TDK AM Pro cassette - wrapper detail with magneric specs

The oersted is defined as a

per unit pole. The oersted corresponds to (≈) amperes per metre, in terms of

SI units The International System of Units, internationally known by the abbreviation SI (from French ), is the modern form of the metric system and the world's most widely used system of measurement. It is the only system of measurement with official st ...

. The H-field strength inside a long

solenoid upright=1.20, An illustration of a solenoid upright=1.20, Magnetic field created by a seven-loop solenoid (cross-sectional view) described using field lines A solenoid () is a type of electromagnet formed by a helix, helical coil of wire whos ...

wound with 79.58 turns per metre of a wire carrying 1 A 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

(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(\text) = \mu_\text H(\text).

Because oersteds are used to measure magnetizing field strength, they are also related to the

magnetomotive force In physics, the magnetomotive force (abbreviated mmf or MMF, symbol \mathcal F) is a quantity appearing in the equation for the magnetic flux in a magnetic circuit, Hopkinson's law. It is the property of certain substances or phenomena that give ...

(mmf) of current in a single-winding wire-loop: :

1\text = \frac~\text/\text.

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).

References

{{CGS units Centimetre–gram–second system of units Units of magnetic induction

Difference between Gaussian and SI systems

History

Definition

Stored energy

See also

References