Study Notes: Fun with Magnets - Science Class 6

WHAT ARE MAGNETS?
(i) Definition: Magnets are pieces of iron or other materials which exhibit the properties of magnetism i.e. the ability to attract other objects that contain iron. Compass needles, fridge magnets and MRI scanners are some common examples of magnets.

(ii) History: It is said that magnets were discovered after a shepherd named Magnes accidentally got his iron stick stuck to a rock. It was later discovered that the said rock had magnetic properties and was called Magnetite, named so after the shepherd.

(iii) Greece: A Greek shepherd named Magnes discovered magnets 4,000 years ago in Magnesia, Greece. The name magnetite has been derived from Magnesia or Magnes. Magnets are named after Magnetite.

TYPES OF ARTIFICIAL MAGNET
These days magnets come in different shapes and forms such as: horseshoe magnet, bar magnet, cylindrical or a ball-ended magnet, needle magnet etc.

Magnets attract magnetic materials. Natural rocks that have the property of attracting iron, nickel and cobalt are called natural magnets. Magnes discovered a natural magnetic rock, called the lodestone. In the form of a bar, it was used to find directions on the earth, and so the name, 'lodestone,' which means the stone that leads. Lodestone has a compound of iron called magnetite. These natural magnets have the magnetic property of attracting materials like iron, nickel and cobalt. "Archimedes", the ancient Greek scientist, is believed to have used lodestone to pull nails from enemy ships. Taking the nails out made the ships sink.

Magnetic and Non-Magnetic Materials

We can include differences between natural and artificial magnets

PROPERTIES OF A MAGNET

• Magnets attract objects of iron, cobalt and nickel.
• Magnets have two poles, the north pole (N) and the south pole (S).
• Poles always exist in pairs. They cannot be separated. The force of attraction     of a magnet is greater at its poles than in the middle.
• Opposite poles of two magnets attract each other.
• Like poles of two magnets repel each other.
• If a bar magnet is suspended freely by a thread, it aligns itself in the north-south direction.

Types of magnets

MAGNETIC COMPASS
Definition: A compass is an instrument that is used to find the directions.
Construction: It has a thin magnetic needle supported from a pivot so that it can rotate freely. The needle is placed over a dial with the directions marked. The entire assembly is placed inside an airtight box.
The north pole of the magnetic needle is painted red. The magnetic needle in the compass points in the north-south direction. By aligning the dial properly, the directions can be found. In the ancient days, an old pointing device, called the south pointing fish, was used to know the directions. The head of the fish pointed towards the south.

Alignment of a compass: Take a compass and make sure that the magnetic needle comes to rest.
Rotate the box so that the red tip of the magnetic needle coincides with the north mark of the dial.
The compass is now aligned. Next, select any object around you.
Then, with the help of the compass, identify the direction in which the object lies relative to you.

Law of magnets: Unlike poles attract each other Like poles repel each other.

Artificial magnets: Magnets can be made artificially, too. A rectangular iron bar, an iron needle, a blade or an iron nail can be turned into a magnet by rubbing a bar magnet over it.
Take a rectangular piece of iron. Place it on the table. Now take a bar magnet and place one of its poles near one edge of the bar of iron. Without lifting the bar magnet, move it along the length of the iron bar till you reach the other end. Now, lift the magnet and bring the pole (the same pole you started with) to the same point of the iron bar from which you began. Move the magnet again along the iron bar in the same direction as you did before. Repeat this process about 30-40 times.
Bring a pin or some iron filings near the iron bar to check whether it has become a magnet

Precautions to protect magnets from losing their magnetic properties

• Never drop magnets from heights.
• Never heat a magnet.
• Do not hammer a magnet.
• Certain items such as CD's, DVD's, debit cards, credit cards or ATM cards, audio and video cassettes, and mobile phones contain magnetic material. Keep them away from magnets to prevent damage.