- Magnetic Innovations
A compas is an instrument containing
a freely suspended magnetic element which displays the direction of the
horizontal component of the Earth's magnetic field at the point of observation.
The magnetic compass is an old Chinese
invention, probaly first made in China during the Qin dynasty (221-206
B.C.). Chinese fortune tellers used lodestones (a mineral composed of an
iron oxide which aligns itself in a north-south direction) to construct
their fortune telling boards.
Eventually someone noticed that the
lodestones were better at pointing out real directions, leading to the
first compasses. They designed the compass on a square slab which had markings
for the cardinal points and the constellations. The pointing needle was
a lodestone spoon-shaped device, with a handle that would always point
south. Magnetized needles used as direction pointers instead of the spoon-shaped
lodestones appeared in the 8th century AD, again in China, and between
850 and 1050 they seem to have become common as navigational devices on
ships. The first person recorded to have used the compass as a navigational
aid was Zheng He (1371-1435), from the Yunnan province in China, who made
seven ocean voyages between 1405 and 1433.
See also Gyroscopes
- Biography on the gyroscope compass inventor Elmer Sperry and the history
Ferrites or magnetic oxides are
stones that attract iron and other metals. These are natural magnets and
are not inventions. However, the machines that we make with magnets are
Ferrites were first discovered thousands
of year ago. Large deposits were found in the district of Magnesia in Asia
Minor, giving the mineral's name of magnetite (Fe3O4).
was nicknamed lodestone and used by early navigators to locate the magnetic
North Pole. William Gilbert published
De Magnete, a paper on magnetism
in 1600, about the use and properties of Magnetite. In 1819, Hans
Christian Oersted reported that when an electric current in a wire
was applied to a magnetic compass needle, the magnet was affected - this
is called electromagnetism.
In 1825, British inventor William
Sturgeon (1783-1850) exhibited a device that laid the foundations for large-scale
communications: the electromagnet.
Sturgeon displayed its power by lifting nine pounds with a seven-ounce
piece of iron wrapped with wires through which the current of a single
cell battery was sent.
of a History of Classical Electromagnetism
U.S. patent # 3,005,458 is the first
patent issued for a cow magnet issued to Louis Paul Longo, the inventor
of the Magnetrol Magnet, for prevention of hardware disease in cows.
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