2. Magnetism is a property of materials that respond to an
applied magnetic field. Permanent magnets have persistent
magnetic fields caused by ferromagnetism. That is the strongest
and most familiar type of magnetism. However, all materials are
influenced varyingly by the presence of a magnetic field.
3. STORY OF MAGNETISM
Aristotle attributed the first of what could be called a scientific discussion on magnetism
to Thales of Miletus, who lived from about 625 BC to about 545 BC.[1] Around the same
time, in ancient India, the Indian surgeon, Sushruta, was the first to make use of the magnet
for surgical purposes.[2]
In ancient China, the earliest literary reference to magnetism lies in a 4th century BC book
named after its author, The Master of Demon Valley (鬼谷子): "The lodestone makes iron come
or it attracts it."[3] The earliest mention of the attraction of a needle appears in a work composed
between AD 20 and 100 (Louen-heng): "A lodestone attracts a needle."[4]The ancient Chinese
scientist Shen Kuo (1031–1095) was the first person to write of the magnetic needle compass
and that it improved the accuracy of navigation by employing theastronomical concept of true
north (Dream Pool Essays, AD 1088), and by the 12th century the Chinese were known to use
the lodestone compass for navigation. They sculpted a directional spoon from lodestone in such
a way that the handle of the spoon always pointed south.
Alexander Neckham, by 1187, was the first in Europe to describe the compass and its use for
navigation. In 1269, Peter Peregrinus de Maricourt wrote the Epistola de magnete, the first
extant treatise describing the properties of magnets. In 1282, the properties of magnets and the
dry compass were discussed by Al-Ashraf, a Yemeni physicist, astronomer, and geographer
4. Sources of magnetism
Magnetism, at its root, arises from two sources:
Electric currents or more generally, moving electric
charges create magnetic fields (see Maxwell's Equations).
Many particles have nonzero "intrinsic" (or "spin") magnetic
moments. Just as each particle, by its nature, has a
certain mass and charge, each has a certain magnetic
moment, possibly zero.
5. How to preserve magnetism.
Many magnets can lose their power by being
stored incorrectly so it is important to understand
how to store magnets if you want to keep them in
maximum shape for as long as possible. If you get
permanent neodymium magnets they will keep their
strength on their own even if you store them less
appropriate. Still, the tips on how to store magnets in
this article are good to follow even when you get the
highest quality of magnets and magnetic products.
6. Holding notes to the refrigerator.
Hold refrigerator doors closed.
Used in fan motors that could recirculate air in the refrigerator.
Used in proximity switches that might monitor a window being closed
(security system).
Used in stepdown transformers that make house voltage from line
voltage.
Used in a compass.
Used in the little gyro toy that keep the gyro rolling along a track.
Used in a chaotic pendulum.
Used to determine the mass of a charge particle.
Used to create the image on a standard CRT picture tube.
Uses
