Magnets and its characteristicsCopy

Learning Objectives

• Describe the forces between magnets, and between magnets and magnetic materials
• Explain that magnetic forces are due to interactions between magnetic fields
• Give an account of induced magnetism
• Distinguish between magnetic and non-magnetic materials
• Draw the pattern of magnetic field lines around a bar magnet
• Describe an experiment to identify the pattern of magnetic field lines, including the direction
• Distinguish between the magnetic properties of soft iron and steel

Contents to learn

Magnets

A magnet can attract magnetic materials such as iron, steel, cobalt, and nickel and it has two poles (i.e. North pole and South pole). Like poles repel and unlike poles attract each other

A freely suspended magnet always points in a fixed direction. This fixed direction is towards the geographical north pole of Earth, which is the magnetic south pole. This is also the phenomenon based on which the needle of a compass works.

Magnetic Materials

Magnetic materials can be attracted by the magnet, for example, iron, cobalt, nickel, alnico, and steel. “Strongly magnetic metals are called ferromagnetic materials”. Non-magnetic materials cannot be attracted by magnets, for example, cork, glass, plastic, rubber, and wood.

Magnetic materials are classified as hard or soft. Hard magnetic materials include steel, which retains magnetism well but is difficult to bend or magnetize in the first place. It is used in the making of permanent magnets, compass needles, and loudspeaker magnets. Soft magnetic materials include soft iron, which is easy to magnetize but loses its magnetism very quickly. It is used in the core of electromagnets, transformers, and radio aerials.