Oersted (unit)

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Physical unit
Unit name Oersted
Unit symbol
Physical quantity (s) Magnetic field strength
system Electromagnetic CGS unit system , Gaussian CGS unit system
In SI units
In CGS units
Named after Hans Christian Ørsted

Oersted (unit symbol  Oe ; after the Danish physicist Hans Christian Ørsted ) is the unit of magnetic field strength in the Gaussian and electromagnetic CGS system of units . It has not been an official unit since 1970 .

An oersted was defined as the magnetic field strength at which the forcedyn acts on a unit pole .

Full definition

In magnetostatics, a unit pole is the analogue of the electric charge in electrostatics. In a magnetostatic quantity system, "Coulomb's law for magnetic poles" applies


Two uniform poles of the same kind have a pole strength if they repel each other with a force at a distance in a vacuum . At one point of a magnetic field has the field strength

the value of one oersted when a unit pole experiences a force from one dyn.


The unit Oersted has no equivalent in the SI system of units , because the magnetic field strength in the associated international size system has a different dimension . A field strength in Oersted corresponds to a field strength in amperes per meter of:

By multiplying by the magnetic field constant , a magnetic flux density of 1  Gs in the Gaussian CGS system of units or of 100  µ T in the SI system of units is obtained in a vacuum (where, since the new definition of the SI units in 2019, the relationship μ 0  = 4π · 10 - 7  Vs / Am only approximately applies):

The energy product of permanent magnets is often given in M G · Oe.


  • L. Ruppert: History of the International Electrotechnical Commission . Buereau Central de la Commission Electrotechnique Internationale, Geneva 1956 ( Online (PDF; 977 kB)).

Individual evidence

  1. Ludwig Bergmann, Clemens Schaefer: Electricity . Walter de Gruyter, 1966, ISBN 978-3-11-144188-7 , p. 175.
  2. ^ Wilhelm H. Westphal: Physics: A textbook . Springer-Verlag, 2013, ISBN 3-662-30391-4 , pp. 364 ( limited preview in Google Book search).
  3. Ludwig Bergmann, Clemens Schaefer: Electricity . Walter de Gruyter, 2013, ISBN 3111441873 , p. 95.
  4. ^ Müller / Krauss, Handbuch für die Schiffsführung, 8th edition from 1983, ISBN 3-540-12100-5 , p. 67