Learning Objectives
- Understand what magnets are and how they were discovered
- Learn about magnetic and non-magnetic materials
- Identify the poles of a magnet and their properties
- Understand attraction and repulsion between magnets
- Learn how a compass works
Key Concepts
Discovery of Magnets
Magnets were discovered in ancient times in a place called Magnesia (in present-day Turkey). A shepherd named Magnes found that a natural rock (called magnetite or lodestone) attracted iron nails in his shoes. This natural magnetic rock led to the development of magnets as we know them today.
Magnetic and Non-magnetic Materials
Magnetic materials: Materials that are attracted by a magnet. Examples: iron, cobalt, nickel, steel. These are mostly metals.
Non-magnetic materials: Materials that are NOT attracted by a magnet. Examples: wood, plastic, rubber, glass, copper, aluminium, gold, silver. Note that not all metals are magnetic.
Poles of a Magnet
Every magnet has two poles: the North Pole (N) and the South Pole (S). The magnetic force is strongest at the poles. When a bar magnet is suspended freely, it always points in the north-south direction — the end pointing north is the North Pole and the end pointing south is the South Pole.
Properties of Magnets
Attraction: A magnet attracts magnetic materials like iron, cobalt, and nickel.
Directive Property: A freely suspended magnet always rests in the north-south direction.
Like poles repel: North repels North; South repels South.
Unlike poles attract: North attracts South and South attracts North.
Pair of poles: If a magnet is broken into pieces, each piece will still have both a North and South pole. You cannot get a single pole.
Magnetic Compass
A magnetic compass is a small device with a magnetised needle that can rotate freely. The needle always points towards the geographic north. Compasses are used by travellers, sailors, and hikers to find direction. The compass was invented in China.
Making a Magnet
We can make a magnet by rubbing an iron bar with a magnet in the same direction repeatedly. The iron bar becomes a temporary magnet. This is called magnetisation. Magnets lose their magnetism if they are heated, dropped, or hit hard.
Storing Magnets
Magnets should be stored in pairs with unlike poles together, with a wooden or iron piece across their ends. Keep magnets away from electronic devices like mobile phones, TVs, and computers as magnets can damage them.
Summary
Magnets attract magnetic materials and have two poles — North and South. Like poles repel and unlike poles attract. A freely hanging magnet points north-south. Compasses use this property to find direction. Magnets can be made by rubbing iron with a magnet. Proper care must be taken to store magnets correctly.
Important Terms
- Magnet: An object that attracts materials made of iron, cobalt, and nickel
- Magnetic Material: A material attracted by a magnet (iron, cobalt, nickel, steel)
- Non-magnetic Material: A material not attracted by a magnet (wood, plastic, copper)
- North Pole: The end of a magnet that points towards geographic north
- South Pole: The end of a magnet that points towards geographic south
- Compass: A device with a magnetic needle used to find direction
- Magnetite: A naturally occurring magnetic rock (lodestone)
Quick Revision
- Magnets attract iron, cobalt, nickel, and steel
- Every magnet has a North Pole and a South Pole
- Like poles repel; unlike poles attract
- A freely suspended magnet points north-south
- The magnetic force is strongest at the poles
- A compass needle is a small magnet that points north
- Not all metals are magnetic (copper, gold, silver are non-magnetic)
- Magnets lose magnetism when heated, dropped, or hammered