1. Write a note on the behaviour of magnets.

Magnets can attract or repel other magnets and can attract any magnetic material even if it is not magnetized. When suspended from a thread, a bar magnet aligns itself in a north-south direction.

2. Write a note on the behaviour of non magnets.

Non magnetic materials, such as wood, paper, plastic and most metals,  cannot be magnetized and so cannot attract or repel other magnets and cannot attract any magnetic material.  Some such as paper and water can let the force of magnetism pass through them while other materials, such as steel sheet, do not let the force of magnetism pass through them.

3. What is a magnet?

When a material is showing magnetic properties, it is said to be magnetized and is known as a magnet.  Magnets can attract or repel other magnets and can attract any magnetic material even if it is not magnetized.

4. What do you mean by the poles of a bar magnet?

At each end of a bar magnet is a place where the magnetic force is stronger than at other places in the magnet. These places where the magnetic force is strongest are called the poles of the magnet. The end of the magnet which points towards north when the magnet is free to move is called the north seeking pole or north pole. At the other end of the magnet is the south seeking pole or south pole.

5. Explain the phrase in magnetism- “different poles attract, similar poles repel”.

When the north pole of one magnet is brought close to the south pole of another magnet that is free to move, the south pole moves towards the north pole. Similarly, a north pole is attracted to a south pole.  However, two south poles repel each other, as do two north poles.

6. What will happen if a steel paper clip which is not magnetized is brought towards either pole of a magnet?

If a steel paper clip which is not magnetized, is brought towards either pole of a magnet, you will feel the pull of the magnetic force becomes stronger as the paper clip gets closer to the pole. As you move the paper clip away from the poles, you will feel the pull of the magnet become weaker.

7. What are the metals present in the alloy Alnico? Which ones are magnetic?

Alnico is an alloy of Aluminium, Nickel and Cobalt. Out of the three, aluminium is non magnetic, while cobalt and nickel are magnetic because they are ferro magnetic materials.

8. What is a domain?

Groups of particles from which a magnetic material is made from tiny regions called domains. Each domain behaves like a tiny magnet. If the domains are arranged at random, the material does not attract other magnetic materials to it although it can be attracted to a magnet. It also does not point north- south when it is free to move. Magnetic domains can be made to arrange themselves in line. Then all their north poles face in one direction and all their south poles face in the opposite direction. This arrangement produces a north and a south pole in the material as a whole. When the magnet is in this condition, it has been magnetized and is now a magnet.

9. What do you mean by magnetic field?

The region around a magnet in which the pull of the magnetic force acts on magnetic materials is called the magnetic field.

10. Explain the earth’s magnetic field.

At the centre of the earth is the earth’s core. It is made from iron and nickel and is divided into two parts- the inner core made of solid metal and the outer core made of liquid metal. As the earth spins, the two parts of the core move at different speeds and this is thought to generate the magnetic field around the earth and make the earth seem to have a large bar magnet inside it. The earth spins on its axis which is an imaginary line that runs through the centre of the planet. The ends of the line are called the geographic north and south poles. Their positions on the surface of the earth are fixed.