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1st century AD – Pliny in his Natural History records the story of a shepherd Magnes who discovered the magnetic properties of some iron stones, "it is said, made this discovery, when, upon taking his herds to pasture, he found that the nails of his shoes and the iron ferrel of his staff adhered to the ground". [6]
RCA developed for the first apparatus for recording video signals on magnetic tapes. 22 km magnetic tape are needed per hour. By 1956, succeeds the company Ampex through the use of multiple tracks, the tape speed to more practicable 38.1 cm / s lower. The European Broadcasting Union is founded "Euro Vision".
In the late 1920s, Gregory Breit and Merle Tuve at the Bureau of Terrestrial Magnetism constructed a working device that used varying magnetic fields to accelerate electrons. Their device placed two solenoidal magnets next to one another and fired electrons from a gun at the outer edge of the magnetic field. As the field was increased, the ...
This discovery gave a clue to the subsequently proved intimate relationship between electricity and magnetism which was promptly followed up by Ampère who some months later, in September 1820, presented the first elements of his new theory, which he developed in the following years culminating with the publication in his 1827 "Mémoire sur la ...
'Magnet' is derived from the legend of Magnes, or from the territory of Magnesia. Pliny states that Magnes, the shepherd, discovered it, and the legend told of him is that while carrying a message over Mount Ida he felt his feet clinging to the earth, to the iron ore which lay thickly upon the hill. Hence the name of the Magnet.
Authors usually derive magnetism from electrostatics when special relativity and charge invariance are taken into account. The Feynman Lectures on Physics (vol. 2, ch. 13–6) uses this method to derive the magnetic force on charge in parallel motion next to a current-carrying wire.
The unit was established by the IEC in the 1930s [4] in honour of Danish physicist Hans 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.
Magnetofossils are the fossil remains of magnetic particles produced by magnetotactic bacteria (magnetobacteria) and preserved in the geologic record. The oldest definitive magnetofossils formed of the mineral magnetite come from the Cretaceous chalk beds of southern England, while magnetofossil reports, not considered to be robust, extend on Earth to the 1.9-billion-year-old Gunflint Chert ...