| oersted | |
|---|---|
| Unit system | Gaussian units |
| Unit of | magnetic field strength |
| Symbol | Oe |
| Named after | Hans Christian Ørsted |
| Derivation | 1 dyn/Mx |
| Conversions | |
| 1 Oein ... | ... is equal to ... |
| Gaussian base units | 1 cm−1/2⋅g1/2⋅s−1 |
| SI units | (4π)−1×103 A/m ≈ 79.57747 A/m |
Theoersted (/ˈɜːrstɛd/,;[1] symbolOe) is thecoherent derived unit of theauxiliary magnetic fieldH in thecentimetre–gram–second system of units (CGS).[2] It is equivalent to 1dyne permaxwell.
In the CGS system, the unit of theH-field is the oersted and the unit of theB-field is thegauss. In the SI system, the unit ampere per meter (A/m), which is equivalent tonewton perweber, is used for the H-field and the unit oftesla is used for the B-field.[3]
The unit was established by theIEC in the 1930s[4] in honour of Danish physicistHans 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.[5]
The oersted is defined as adyne perunit pole.[clarification needed][6] The oersted is1000/4π (≈79.5775) amperes per meter, in terms ofSI units.[7][8][9][10]
The H-field strength inside a longsolenoid wound with 79.58 turns per meter 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 thegauss (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 havingpermeabilityμr (relative to permeability of vacuum), their relation is
Because oersteds are used to measure magnetizing field strength, they are also related to themagnetomotive force (mmf) of current in a single-winding wire-loop:[11]
The stored energy in a magnet, calledmagnet performance ormaximum energy product[12] (often abbreviated BHmax), is typically measured in units of megagauss-oersteds (MG⋅Oe).
