Oersted

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Oersted (symbol: Oe) is a unit of magnetic field strength or magnetic H-field. It is named after the Danish physicist Hans Christian Ørsted who, in 1820, discovered that electric currents create magnetic fields, an important step in understanding the relationship between electricity and magnetism. This discovery laid the foundation for the theory of electromagnetism, making Ørsted a central figure in the development of modern physics.

Definition

One oersted is defined as the amount of magnetic field strength that is necessary to produce a magnetic flux density of one gauss (G) in a vacuum. In the Centimeter-Gram-Second (CGS) system of units, the oersted is expressed as 1000/(4π) amperes per meter in the International System of Units (SI). This relationship illustrates the connection between the magnetic field (H-field) and the magnetic flux density (B-field) in a vacuum, where the permeability of free space (\( \mu_0 \)) is \( 4\pi \times 10^{-7} \) H/m (henries per meter).

Historical Context

Hans Christian Ørsted's discovery in 1820 that a current-carrying wire could deflect a magnetic compass needle was groundbreaking. It demonstrated for the first time that electricity and magnetism were related phenomena. This experiment led to further research in the field of electromagnetism, notably by scientists such as André-Marie Ampère, Michael Faraday, and James Clerk Maxwell. Ørsted's work not only changed the way scientists understood electricity and magnetism but also had a profound impact on the technological advancements that followed.

Applications and Importance

The oersted plays a crucial role in the fields of electromagnetism and magnetic materials. It is used to measure the strength of the magnetic field produced by magnetic materials, as well as by electrical currents and electromagnetic devices. Understanding and measuring the magnetic field strength is essential in designing and operating a wide range of electrical and electronic devices, including electric motors, generators, transformers, and magnetic storage devices.

Conversion to Other Units

The oersted is part of the CGS system, which has largely been superseded by the SI system. In SI units, magnetic field strength is measured in amperes per meter (A/m). The conversion factor between oersted and amperes per meter is direct, with 1 Oe being equivalent to approximately 79.577 A/m. This conversion is important for scientists and engineers who work across systems that use different units of measurement.

See Also

• Magnetic field
• Gauss (unit)
• Centimeter-Gram-Second (CGS) system
• International System of Units (SI)
• Electromagnetism
• Hans Christian Ørsted