Force And Motion – Session 8

You might have probably played with magnets before. If you tried moving them near each other, sometimes they stick to each other. Sometimes they do not want to be anywhere near each other. They repel each other. Have you ever wondered why these magnets repel or attract each other?.

Magnets repel or attract each other due to magnetic force. Magnetic force is like an invisible hand between particular objects. It can make things pull together or push apart. This magnetic force is there in magnets.

Every magnet has two special ends. These ends are called poles. One end of the magnet is called north pole. The ther end is called the south pole. These poles decide if the magnets will pull together or push away.

When the north pole of a magnet gets near the south pole of another magnet, they are attracted to each other. If you put the same types of poles near each other, they will repel. For example, if you put the north pole of the magnet near north pole of the other magnet, they will repel each other. Simlarly, if you put the south pole of the magnet near the south pole of the other magnet, they will also repel each other.

The area around a magnet where the magnetic force is felt is called the magnetic field. This field is invisible, but its effects are very much real and can be observed. Let us do a simple experiment to observe a magnetic field. Take a strong magnet, like a bar-magnet or horseshoe-magnet, some iron filings, and a piece of paper.

Start by placing the paper over the magnet. Then, gently sprinkle the iron filings onto the paper, right-above the magnet. As you do, you will see that the iron filings begin to move and arrange themselves. If you vibrate the paper a bit by flicking the paper, they will start showing a clear pattern. They will form lines and curves around the magnet, tracing the paths of the magnetic force.

These patterns you see are the iron filings lining up along the magnetic field lines. Magnetic field lines represent the presence and direction of magnetic field. They create a visible representation of how the magnetic force spreads around the magnet. These lines flow from the North pole of the magnet to the South pole. Essentially, the invisible force of magnet is pulling these tiny bits of iron into place.

The closeness of the lines indicates the strength of the magnetic force. The magnetic force is strongest in the area where the lines are densely packed. In some areas, there are gaps between the lines. In these areas, the magnetic force is weak.

The magnetic field lines originate or in other words begin, at the north pole of the magnet. Imagine them as arrows coming out of the north pole. These lines then flow around the magnet towards the south pole. They enter the south pole, creating a continuous loop. Outside the magnet, the lines run from north pole to the south pole. Inside the magnet, the lines run from the South pole to the North pole. They create a continuously loop in this way.

Now we can clearly understand why the north pole of one magnet attracts the south pole of another magnet. The magnetic field lines originates from the north pole of one magnet and travel into the south pole of the other magnet.We can see magnetic field lines are in one direction here. As a result the north pole of one magnet attracts the south pole of the other magnet.

Let us say the north pole of one magnet is near the north pole of the other magnet. The magnetic field lines are in opposite direction between two north poles. As a result the magnets will repel each other.

You might have seen a compass. It is a device used for navigation. The compass is like a little guide that always knows where the north is. Inside the compass, there is a tiny magnetic needle that can spin around. This needle points to the north direction. How does this compass knows the direction of north?.

The Earth is like a huge magnet with its own magnetic field. You can see that one end of the earth is the north pole and the other end is the south pole similar to a simple magnet. This magnetic field of earth starts at the north pole. It flows towards the south pole.

The needle inside the compass is magnetic. It naturally aligns itself with the magnetic field of the earth. The north seeking end of the needle is marked in red. This end of needle is attracted to the north pole of the earth. This causes the needle to point towards north pole of the earth.

Do you know how some birds navigate to reach their home? Some birds can detect the magnetic field of the earth. By sensing the magnetic field of the earth, these birds can determine direction and their precise location. Not only birds but sea turtles, bats and pigeons also have this ability.