Hello, young learners! Welcome to today's physics lesson. Today, we are going to explore a fascinating world — the world of magnetism. Have you ever played with magnets and watched how they mysteriously pull certain objects toward them? Or perhaps you've used a compass to find directions? All of this happens because of magnetism. In this lesson, we will learn what makes a substance magnetic, how magnets behave, how we can make magnets, and even how electricity can create magnetism. Let us begin our journey into this invisible force that surrounds us every day.
Let us start with the basics. A magnet is any substance that has the special property of attracting iron. The story of magnets began long ago, around 800 B.C., when people discovered a strange mineral that could pull iron objects toward it. This mineral was called magnetite. There is a charming legend about a shepherd named Magnes, whose iron shoe nails and the iron tip of his walking stick got stuck to a rock containing this mineral. The rock was found near a town called Magnesia in Asia Minor, and that is how the word "magnet" came into use. Because this rock always pointed in a fixed direction when freely suspended, it was also called the lodestone, which means "leading stone."
Now, magnets can be classified into two types. First, natural magnets. These are pieces of magnetite or lodestone found in nature. They come in irregular shapes and are rather weak, so they are not very useful for practical purposes. Second, artificial magnets. These are made by us from iron or steel, and they can be shaped as we need them. They are much stronger than natural magnets. You might have seen bar magnets, cylindrical magnets, U-shaped magnets, horse-shoe magnets, magnetic needles, and the magnetic compass used to find directions.
Let us now understand which materials are attracted by magnets and which are not. The substances that get attracted by a magnet are called magnetic substances. Iron, steel, cobalt, and nickel are all magnetic substances. These are also known as ferromagnetic substances. On the other hand, substances that do not get attracted by a magnet are called non-magnetic substances. Wood, plastic, copper, paper, aluminium, rubber, glass, gold, silver, and brass are all examples of non-magnetic materials. So, if you bring a magnet near a wooden pencil, nothing happens. But if you bring it near an iron nail, the nail jumps toward the magnet!
Now, let us look at the special characteristics of a magnet. Every magnet has two important characteristics. First, when a magnet is suspended freely so that it can swing, it always comes to rest in a specific direction — the north-south direction. The end that points toward the north is called the north pole, or north-seeking pole. The end that points toward the south is called the south pole, or south-seeking pole. We mark them with the letters N and S. Sometimes, a red dot is placed at the north pole to help us identify it. This property is incredibly useful — it is what makes the magnetic compass work for finding directions.
The second characteristic is that a magnet attracts small pieces of iron. But here is something interesting — the attraction is not the same everywhere on the magnet. If you bring a bar magnet near iron nails, you will notice that most nails cling to the ends of the magnet, while very few stick to the middle. This tells us that the attractive property is strongest at the ends and weakest at the center. These ends where the attraction is maximum are called the poles of the magnet. Remember, the poles are actually located slightly inside the ends, not exactly at the very tips.
Let us now discuss the four fundamental properties of magnets. First, a magnet attracts small pieces of iron. Second, a freely suspended magnet always rests in the north-south direction. Third, and this is very important — like poles repel each other, and unlike poles attract each other. If you bring two north poles together, they push away from each other. The same happens with two south poles. But if you bring a north pole near a south pole, they pull toward each other. Fourth, poles always exist in pairs. You cannot have a magnet with just one pole. Even if you break a magnet into pieces, each piece becomes a complete magnet with both a north and a south pole. Break it again and again — still, every tiny piece has two poles.
Now, let us explore the invisible region around a magnet. The space surrounding a magnet in which magnetic substances experience a force of attraction is called the magnetic field. You cannot see this field, but you can detect it. Here is a simple way to visualize it. Place a bar magnet under a stiff sheet of paper and sprinkle iron filings on top. Gently tap the paper, and watch what happens. The iron filings arrange themselves in a beautiful pattern of curved lines. These lines show the magnetic field, running from the north pole to the south pole of the magnet. The field is stronger near the magnet and becomes weaker as you move farther away.
First, let us understand magnetic induction, which explains how a magnet can attract iron without touching it.
Now, let us understand Earth's own magnetism.
Here is something remarkable — the Earth itself behaves like a giant magnet. When you suspend a magnet freely, its north pole points toward geographic north because it is actually being attracted to the magnetic south pole of the Earth, which lies near geographic north. Similarly, the south pole of your magnet points toward geographic south because it is attracted to the magnetic north pole of the Earth, which lies near geographic south. This is because unlike poles attract each other. Although Earth behaves like a huge magnet, there is no actual magnet inside it. You can recognize Earth's magnetic field by this behavior of a freely suspended magnet. Another way to observe Earth's magnetic field is to bury a soft iron bar in the north-south direction — after some days, it becomes magnetized with the end toward geographic north becoming a north pole.
There are four ways to make a magnet. Let us explore them one by one. Iron, cobalt and nickel are ferromagnetic substances that can easily be converted into magnets and can also be demagnetised quite easily.
The first method is magnetic induction. When you bring iron near a magnet, it temporarily becomes magnetic. The end near the magnet's north pole becomes a south pole, and the far end becomes a north pole. This is why a magnet can attract a piece of iron — the unlike poles attract each other. Remove the magnet, and the iron loses its magnetism. This temporary magnetism is called magnetic induction.
The second method is the single touch method. Place an iron bar on a table and stroke it with a bar magnet from one end to the other. Lift the magnet and repeat about twenty times. Then turn the bar over and stroke again twenty times. The end touched last gets opposite polarity to the striking pole.
The third method is the double touch method. Use two magnets with opposite poles touching the center of the iron bar, with a cork between them. Move them together toward one end, then back to the center without lifting. Repeat about twenty times, then turn the bar and repeat. This method is faster than single touch.
The fourth method, and the most powerful, is the electrical method. Wrap insulated copper wire around an iron bar and connect it to a battery through a switch. When current flows, the bar becomes a magnet. The end where current enters clockwise becomes the south pole, and the other end becomes the north pole. Reverse the current to reverse the poles. When switched off, the bar loses its magnetism. In 1820, a Danish physicist named Hans Christian Oersted discovered the connection between electricity and magnetism, showing that a current-carrying wire creates a magnetic field around it.
A temporary magnet is one that loses its magnetism quickly. It is made of soft iron. It shows magnetic properties only while current passes through a coil around it. Its strength and polarity can be changed. It is easily demagnetised. A permanent magnet, made of steel, retains its magnetism for a long time. Its strength and polarity cannot be changed. It is not easily demagnetised.
An electromagnet is a coil carrying current with a soft iron core inside. For temporary electromagnets, the core is soft iron. For permanent electromagnets, the core is steel. The strength of an electromagnet can be increased by increasing the current or by increasing the number of turns in the coil. Electromagnets are useful because their strength can be varied and they can be turned off and on as desired.
Electromagnets have countless uses in our daily lives. They are used in electric bells, telephones, and magnetic toys. Strong electromagnets are used in industries to load and unload heavy iron and steel scrap. Permanent magnets are used in electrical measuring instruments like galvanometers, ammeters, and voltmeters. You will also find magnets in electric motors, dynamos, loudspeakers, computers, and many other devices. The magnetic compass, which uses a small magnetic needle, helps sailors and pilots find geographic directions by pointing north and south.
Let us learn how to store magnets properly. A magnet has a tendency to lose its magnetic properties if left alone, so we should never leave a magnet by itself. To prevent magnets from losing their strength, we use magnetic keepers. These are small pieces of soft iron placed across the poles of a magnet. By magnetic induction, opposite poles develop at the ends of the keepers, creating a closed loop that preserves the magnet's strength. For bar magnets, two keepers are used with opposite poles facing each other, with a piece of wood in between. For horse-shoe magnets, a single keeper is placed across both poles.
So, to keep your magnets strong, handle them gently, store them with keepers, and keep them away from heat. Magnets can be demagnetised by rough handling, hammering repeatedly, dropping on hard surfaces, heating to high temperature, or passing alternating current through a coil around them while keeping the magnet in east-west direction.
Let us recap what we have learned today.
First, magnets are substances that attract iron, and they can be natural or artificial. Natural magnets like lodestone are weak and irregular, while artificial magnets made of iron or steel are strong and shaped for practical use.
Second, magnetic substances like iron, steel, nickel, and cobalt are attracted to magnets, while non-magnetic substances like wood, plastic, glass, copper, and aluminium are not.
Third, every magnet has two poles — north and south — and poles always exist in pairs.
Fourth, like poles repel and unlike poles attract.
Fifth, a freely suspended magnet always rests in the north-south direction.
Sixth, the space around a magnet where magnetic force acts is called the magnetic field.
Seventh, Earth itself behaves like a magnet with its magnetic south near geographic north and magnetic north near geographic south.
Eighth, we can make magnets by magnetic induction, single touch, double touch, or electrical methods.
Ninth, temporary magnets made of soft iron lose magnetism easily, while permanent magnets made of steel retain it.
Tenth, electromagnets are coils with soft iron cores that become magnetic when current flows, and their strength can be increased by increasing current or number of turns.
Eleventh, magnets need proper care — store them with keepers, avoid heat, rough handling, repeated hammering, and dropping on hard surfaces.
Magnetism is truly one of nature's most fascinating phenomena. I hope you enjoyed learning about this invisible force today. Keep exploring, keep questioning, and see you in the next lesson!