Fun With Magnet: science class six
Matsya Yantra
In ancient India compass was known as Matsya Yantra. The Matsya Yantra was also known as fish apparatus because the magnet used was in it was in the shape of fish.
Figure6: Matsya Yantra, used in India
The reference of using of Matsya Yantra has been written in the Rig Veda. And it is also referenced in the work "Merchants Treasure" written at Cairo by Baylak Al Kiljaki, in which it is written that the magnetic needle as being in use in the Indian Ocean.
Concentration of Magnetic Property
Magnetic property is concentrated at the poles of the magnet. This means force of attraction of a magnet are more at its pole. A magnet can pull a magnetic material more strongly at its pole.
Figure7: A bar magnet with iron fillings stuck with it
When iron fillings are sprinkled over a magnet, more iron fillings get stuck at the poles. Along with this some of the iron fillings stuck on its body also. This happens because magnet is stronger at its poles. The strength of magnet gradually decreases towards the centre of the magnet, it is weakest at its centre.
Field Lines of a Magnet
When iron fillings are sprinkled over a magnet, iron fillings get stuck with it in a special pattern. The sticking of iron filling is more at the poles of a magnet and gradually becomes lesser at its center.
Figure8: Field Lines of a Magnet
The special patter in which iron fillings are stuck with a magnet can be drawn using lines. The lines or pattern in which iron fillings are stuck with magnet is called the Field Lines of a magnet.
Figure9: Field Lines of a Magnet
Figure10: Field Lines of a Magnet
The Field Lines of a bar magnet can be drawn on paper.
Figure11: Field Lines of a Magnet
Repulsion and Attraction between Magnets
There is attraction between opposite poles and repulsion between the same poles of the two magnet.
This means south pole of a magnet repulses south pole of other magnet. And south pole of a magnet attracts north pole of other magnet.
Isolation of Magnetic Poles of a Magnet
A magnet has two poles and they cannot be isolated.
If a bar magnet is broken into two pieces. The both pieces, which are also magnets, has two own poles. If these further cut into four pieces, all have their own separate poles.
It is found that if you cut a magnet into more pieces, its poles cannot be isolated.
So a magnet cannot have isolated north or south poles. Poles always exist in pairs.
Make Your Own Magnet
A magnet can easily be made.
A magnet when rubbed continuously on a piece of iron in certain fashion i.e. in one direction only, the piece of iron gets the magnetic property, and becomes a magnet.
Figure12: Making of a magnet
Making a Magnet Using Electricity: An Electromagnet
A piece of iron can turn into magnet using electricity.
When electricity passed through a coil wrapped over a piece of iron, then during the passing of electricity, that very piece of iron acts like a magnet. Such magnets are known as Electromagnet.
Electromagnets are stronger than natural magnets.
Electromagnet is used in fan, motor, electric generator, etc.
Some Common Uses of Magnets
(a) Magnetic tape is used in recording media, such as in audio tapes.
(b) Magnetic tape is used in credit and debit card. The black strip over a credit and debit card is a magnetic tape. This contains information about the debit or credit card.
(c) Magnet is used in lids of purse to close it firmly and easily.
(d) Magnet is used in the door of refrigerator, almirah, etc.
(e) In computer hard disc, information are recorded over magnetic disc.
(f) Magnet is used in microphone and loudspeakers.
(g) Electromagnet is used in electric motors and electric generators.
(h) There are many toys in which magnet is used.
(i) Magnet is used in screw driver to hold the screw easily.
(j) Magnets are used to treat many diseases.
A Few Cautions
A magnet should be kept with some precautions, because it can loose its magnetic properties in the following cases:
(a) If a magnet is heated, it looses its magnetic property.
(b) If a magnet is hammered, it can loose its magnetic properties.
(c) If a magnet is dropped from some height, it can loose its magnetic properties.
A magnet becomes weak it is not stored properly, so they should be kept safe.
Tips to keep a magnet safe
(a) Bar magnets should be kept in pair with their opposite poles on the same side.
(b) A piece of wood should be kept between two bar magnets to separate them while two pieces of soft iron should be place across a bar magnet.
(c) A horse shoe magnet should be kept with a piece of iron across the poles.
Summary
(1) The word Magnet came from a Greek name "Manges".
(2) Natural magnets are made from magnetite which a rock mineral.
(3) Magnetite contains iron and attracts iron, nickel, cobalt and other magnetic materials.
(4) Materials which are attracted towards magnet are called magnetic materials, such as iron, cobalt, nickel, etc.
(5) Materials which are not attracted towards magnet are called non-magnetic materials, such as wood, plastic, etc.
(6) A magnet has two poles.
(7) Pole of a magnet which indicates north direction is called north pole and that points to the south direction is called south pole.
(8) When a magnet suspended freely its pole always indicates towards north and south direction.
(9) There is attraction between opposite poles and repulsion between similar poles of two magnets. This means north pole of a magnet attracts south pole of other magnet. While north pole of a magnet repulses north pole of other magnet.
(10) The poles of a magnet cannot be isolated. If a bar magnet is broken into two pieces, both new pieces has two poles, i.e. north and south pole.
(11) Magnets are used in toys, speakers, microphones, motor, dynamo, audio and video tapes, credit card, debit card etc.
(12) Magnet is used to treat some diseases also.
Some Keywords and Their Definition
(a) Compass
A compass is a small device which is used to find direction. A compass contains a small needle like magnet pivoted over a pin, which facilitates free rotation of magnetic needle.
(b) Magnet
A piece of iron which has a property to attract article made of iron or other magnetic materials towards it, is called magnet.
(c) Magnetic Materials
Materials which attract towards a magnet are called magnetic materials, such as iron, cobalt and nickel.
(d) Non-magnetic Materials
Materials which do not attract towards a magnet are called non-magnetic materials, such as rubber, plastic, etc.
(e) Magnetite
A rock mineral which has property to attract magnetic materials towards it, is called Magnetite. Magnetite is a natural magnet.
(f) North Pole of a magnet
End of a magnet which points towards north direction when suspended freely is called north pole of a magnet.
(f) South Pole of a magnet
End of a magnet which points towards south direction when suspended freely is called south pole of a magnet.
Reference:
Figure6 : Krishna Chaitanya Velaga / CC BY-SA, Link
.jpg){kind=link}
Figure7: Fun With magnet, NCERT Book, Science class 6 page number 128
Figure8: By Newton Henry Black - Newton Henry Black, Harvey N. Davis (1913) Practical Physics, The MacMillan Co., USA, p. 242, fig. 200, Public Domain, Link
Figure9: By Geek3 - Own work, CC BY-SA 4.0, Link
Figure10: By Geek3 - Own work, CC BY-SA 4.0, Link
Figure11: By Geek3 - Own work, CC BY-SA 3.0, Link
Figure12: Fun With magnet, NCERT Book, class 6 science, page number: 131