Class 6 Science Chapter 4 Notes Exploring Magnets
Playing with magnets is always fun. We see so many examples in our everyday life in which an object attracts some special materials like iron, such objects are known as magnets. Magnets can even attract or repel other magnets too. In this chapter, we will explore the interesting concepts related to it.
Magnet
The substances having the property of attracting iron are known as magnets. In our daily life observations, we have often seen certain stickers on the doors of refrigerators. The white iron boards in schools often have dusters that can be stuck to them. A pin holder has lots of pins stuck to it and a crane picks up pieces of iron from waste, etc. All these objects have a special substance called a magnet in them. Nowadays, magnets are used to make mobile devices, telephones, televisions, etc.
Natural Magnet and Artificial Magnet
A magnet that is found in nature is known as a natural magnet, e.g. magnetite and lodestone, whereas the magnet that can be made by magnetizing materials like iron, cobalt, nickel, etc., is known as an artificial magnet or man-made magnet.
Nowadays, artificial magnets are prepared in different shapes, e.g. bar magnets, horseshoe magnets, cylindrical magnets, ball-ended magnets, and U-Shaped magnets.
Magnetic and Non-Magnetic Materials
All the materials are not attracted by magnets. Magnets attract only certain materials. Those substances that get attracted by a magnet are called magnetic materials, e.g. iron, steel, nickel, and cobalt. Those substances that are not attracted by the magnet are called non-magnetic materials, e.g. rubber, plastic, stainless steel, feather, and leather. Magnets can make our tasks much easier, e.g. when a needle slips from our hand on the floor. To find it, we use a magnet. Since a needle is made of iron, it can be attracted by a magnet. Non-magnetic materials cannot be magnetized. It means that non-magnetic materials cannot be converted into magnets.
Poles of Magnet
When we bring a magnet close to iron filings, we see that iron filings get attracted toward a magnet. If we observe, we will find that most of the iron filings stick at the two free ends of a magnet. These free ends are called the poles of a magnet. Poles of the magnet are the regions of strongest magnetism. All magnets have two poles north pole and the south pole, irrespective of their shape. Usually, north (N) and south (S) poles are marked on the magnets.
The North and south poles of a magnet always exist in pairs. The north pole and south pole of a magnet can’t exist independently or cannot be separated. If a magnet is broken into two or more pieces, each of them will have a north pole and a south pole.
Finding Direction
An interesting property of a magnet is that a freely suspended bar magnet always comes to rest in a north-south direction. Based on this property, a small device called a magnetic compass was developed in the olden days for finding directions. The end of the magnet that points towards the north is called north seeking end or north pole of the magnet and the other end that points towards the south is called south seeking end or south pole of the magnet.
In the early centuries, this property of magnets was very useful for travelers. They used to suspend natural magnets with a thread to find directions. Other methods can help to find directions, e.g. By using the direction of the rising sun in the morning, we can find out the rough direction towards the east. If we stand facing east, then our left will be towards north. It may not be very exact but it will help to make out all the directions as shown in the figure.
Magnetic Compass
In the olden days, a magnetic compass was used for finding directions. A magnetic compass is a small circular box with a transparent cover on it. There is a magnet, in the shape of a needle, mounted on a pin standing on the bottom of the box. It is pivoted to rotate freely. The end of the needle which rests in the north direction is usually painted red. Below the needle, there is a dial with directions marked on it.
The Earth also behaves like a giant magnet. The magnetic compass aligns with the earth’s magnetic poles such that the north pole of the magnetic compass needle always points to the earth’s north pole and vice-versa. To find the directions using a compass
- The compass is placed at a place where we wish to know the direction.
- The compass needle points in the north-south direction, when it comes to rest.
- The dial of the compass is gently rotated and aligned with the north-south axis of the needle. This gives the north-south, direction.
Attraction and Repulsion between Magnets
When the north-north or south-south poles of two magnets are brought closer, they push each other away or they repel each other. It can be stated that poles repel each other.
On the other hand, when the north-south or south-north poles of two magnets come closer, then they attract each other. It can be stated that unlike poles attract each other. The attractive or repulsive force that is exerted between the poles of a magnet is also known as magnetic force.
In some magnets, the north and south poles are marked as N and S while in some other magnets, the north pole is indicated by a white dot, and in some cases, the north pole is painted red and the south pole is painted blue.
→ The compass needle is also a magnet. It shows the same behavior if a magnet is brought closer to it.
→ When the North pole of a magnet is brought closer to the North pole of the compass needle, it moves away.
→ When the South pole of the magnet is brought closer to the North pole of the compass needle, it moves closer.
→ The magnetic force can pass through thin sheets of non-magnetic objects such as paper, glass, or wood.
→ Generally, the north and south poles of a magnet are marked as N and S. In some magnets, the north pole is indicated by a white dot.
→ Sometimes, the north pole of a magnet is represented by red colour and the south pole by blue colour.
Maglev train works on the principle of attraction and repulsion between magnets. It contains two sets of magnets. One set of magnets is used to repel and push the train up off the track and another set is used to move the elevated train ahead.
How to keep magnets safe?
- Keep magnet in pairs with unlike poles on the same side.
- Keep a piece of wood in between while storing magnets.
- Place two pieces of soft iron across the ends.
- Do not heat, hammer, or drop the magnets from a height.
- Keep them away from mobiles, computers, televisions, music systems, etc.
Fun with Magnets!
Magnets can move some objects without touching them. Some of the fun experiments are given below.
→ We can make a magnetic garland by using a bar magnet which induces magnetism in the board pins, causing them to stick together.
→ We can create a maze by using cardboard and plastic straws (as shown in the figure) and try to take the steel balls out of the maze by moving a magnet below the cardboard tray.
→ We can also pick out a steel paper clip fallen in water by using a magnet, without making our fingers or the magnet wet.
→ Bar magnet: A bar magnet is a rectangular piece of an object, made up of magnetic materials, that shows permanent magnetic properties.
→ Magnetic materials: Materials that are attracted to a magnet are called magnetic materials. For example, iron, nickel, cobalt.
→ Non-magnetic materials: Materials that are not attracted to a magnet are called non-magnetic materials. For example, wood, plastic, and rubber.
→ Poles of a magnet: The two ends of a magnet where the magnetic force is strongest are considered the two poles of a magnet.
→ Magnetic compass: A device that contains a magnetic needle that rests itself in a north-south direction. It is used to find directions.
→ Attraction: Attraction is the force that attracts two bodies to move towards each other.
→ Repulsion: Repulsion is the force that keeps the bodies away from each other.