File:Barkhausen effect apparatus.jpg
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Summary
| Description |
English: A replica of the experimental apparatus used by German physicist Heinrich Barkhausen in 1919 to detect the Barkhausen effect. This is a hissing or series of crackling sounds heard in an earphone attached to a coil of wire around an iron core when the magnetic field through it changes. When a magnet is brought near a piece of iron, the domain walls of the magnetic domains move, reorienting the domains so the , The sound is caused by the domain walls getting hung up on defects in the crystal lattice and then "snapping" past them. This effect is responsible for the magnetization hysteresis curve of the magnetic material. The apparatus consists of a coil of wire wound around an iron core (center) with the coil attached to a vacuum tube amplifier and a pair of earphones. A horseshoe magnet (right) that can be rotated by a knob is next to the iron. When the magnet is rotated by 180°, its magnetic field which passes through the iron core changes from one direction to the opposite direction. The Barkhausen noise is heard in the earphone while the magnet is being turned. |
| Date | |
| Source | Retrieved September 21, 2015 from Irving J. Saxl, "Fundamentals of Electricity" in Radio News magazine, Teck Publications, New York, Vol. 18, No. 2, August 1936, p. 94, fig. 7 on Google Books |
| Author | Irving J. Saxl |
| Permission (Reusing this file) |
This 1936 issue of Radio News magazine would have the copyright renewed in 1964. Online page scans of the Catalog of Copyright Entries, published by the US Copyright Office can be found here. Search of the Renewals for Periodicals for 1963, 1964, and 1965 show no renewal entries for Radio News. Therefore the copyright was not renewed and it is in the public domain. |
Licensing
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This work is in the public domain because it was published in the United States between 1929 and 1963, and although there may or may not have been a copyright notice, the copyright was not renewed. For further explanation, see Commons:Hirtle chart and the copyright renewal logs. Note that it may still be copyrighted in jurisdictions that do not apply the rule of the shorter term for US works (depending on the date of the author's death), such as Canada (70 years p.m.a.), Mainland China (50 years p.m.a., not Hong Kong or Macao), Germany (70 years p.m.a.), Mexico (100 years p.m.a.), Switzerland (70 years p.m.a.), and other countries with individual treaties.
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| Date/Time | Thumbnail | Dimensions | User | Comment | |
|---|---|---|---|---|---|
| current | 09:40, 22 September 2015 | | 553 × 227 (33 KB) | Chetvorno | User created page with UploadWizard |
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