Almost 20 centuries ago, an ore called magnetite was found and was called “lodestone” or leading stone. Name magnetism derived from the name of the place from where these type of rocks were found. The lodestone later was given name of magnet.
Lodestone & Magnet:
For along time magnet was merely regarded as point of curiosity, that it attracts iorn and do repultion against other similar stones. Then it was found that if a elongated piece of lodestone was suspended horizontally, it turned and pointed towards north. Later was it was understood that earth itself was a huge magnet, reasons of lodestone stabilizing in north was justified. Earth’s natural south magnetic pole is placed at geographical north pole.
Magnetism is a form of energy:
Magnetic energy can not be seen, heard or tasted, touched or nor has a smell. This energy can do work for us. It can magnetize other material, lift material and can produce electricity by applying mechanical movements.
Magnetic & non-magnetic materials:
Iron is a good magnetizing material. Soft steel, nickel, cobalt and newly developed ceramic has excellent magnetic properties. Temporary magnets are made from iron, they hold magnetic properties only till magnetic force is within. Permanent magnets means which holds the magnetic property indefinitely.
Glass, paper, wood, rubber. plastic, cotton etc are called non-magnetic material and they can not be magnetized. Although these materials do not get magnetized, they are transparent to these energy means, magnetic line of force can pass through these substances.
Bases of magnetism is that explained in atom structure we learned earlier these atoms are believed to be tiny magnets (Magnetic dipoles) with a north and a south pole.
Faraday visualized the magnetic field as being made up of imaginary, magnetic lines of force. Such lines of force leaves at North pole and completes elliptical path outside the magnet to the South pole then reenters the magnet and advance to North pole from within the magnet. The magnetic field is flowing from north to south, externally.
Magnetic field can be “seen” by doing a small experiment. A magnet is placed with a white paper over it, covering entire magnet. Then a powder of iron (Saw dust) is sprayed over it. The iron dust settles to show us the magnetic field and proves its existence in a visual way
Now if we take a non-magnetic object, such as a glass rod, and place it within the path of a magnetic field, the lines of force produced by the field would pass right through the object.
If, however, we wrap a magnetically conductive layer around the object, such as a soft iron, the iron will cause the lines of force to bend, and go around the object instead of through it. This is called a SHIELDING effect.
