Magnetism – JSS1 Intermediate Science Lesson Note (Third Term)

WHAT IS A MAGNET?

Have you ever played with a small piece of metal that can pull a needle or a nail toward itself without even touching it? That special object is a Magnet.

The Meaning of Magnetism

Magnetism is an invisible force that can pull (attract) or push away (repel) certain materials. We call materials that are attracted to magnets Magnetic Materials (like Iron, Steel, Nickel, and Cobalt).

Types of Magnets

1. Natural Magnets: These are found in nature inside rocks.
   1. The most famous natural magnet is a rock called Lodestone (or Magnetite). Thousands of years ago, people discovered that these rocks could pull small bits of iron.
2. Artificial Magnets: These are made by humans in factories. They are much stronger than natural magnets. They come in different shapes:
   1. Bar Magnets: Shaped like a rectangular brick.
   2. Horse-shoe Magnets: Shaped like the letter “U”.
   3. Ring/Disc Magnets: Round like a coin or a doughnut.
   4. Needle Magnets: Used in compasses.

PROPERTIES OF MAGNETS

Every magnet has “rules” that it follows. These are called its properties.

1. The Two Poles

Every magnet has two ends called Poles.

• One end is the North Pole (N).
• The other end is the South Pole (S). Even if you break a magnet in half, each new piece will still have a North and a South pole!

2. The Law of Magnetism

This is the most important rule of magnets:

• Like Poles Repel: If you try to push a North pole against another North pole, they will push each other away.
• Unlike Poles Attract: If you put a North pole near a South pole, they will snap together tightly.

Simple Catchphrase: “Opposites attract, Likes repel!”

3. The Magnetic Field

Around every magnet, there is an invisible “zone” where its power works. If a nail is inside this zone, it gets pulled. If it is too far away, nothing happens. This zone is called the Magnetic Field.

[Image showing the magnetic field lines around a bar magnet]

HOW TO CARE FOR MAGNETS

Magnets can actually “lose” their power if they are not treated well. This is called Demagnetization.

How a magnet loses its power:

1. Dropping it: Banging a magnet on the floor many times weakens it.
2. Heating it: Putting a magnet in fire will make it lose its pull.
3. Hammering it: Hitting it with a heavy object.

How to store them:

To keep magnets strong, we use small pieces of soft iron called Keepers to bridge the poles when we put them away in the lab.

USES OF MAGNETS

Magnets are not just toys; we use them in many important ways:

1. In the Kitchen: Many refrigerators have magnetic strips in the door to keep them tightly closed.
2. In Navigation: A Compass uses a tiny magnetic needle that always points North. This helps sailors and pilots find their way.
3. In Electronics: Computers, speakers, and microphones all have magnets inside them to help them work.
4. In Recycling: Huge magnets are used in scrap yards to pick up heavy pieces of iron and steel from piles of rubbish.
5. In ATM Cards: That black stripe on the back of a bank card is magnetic and stores your information.

Class Activity

Let’s go on a “Magnetic Treasure Hunt”!

1. Take a small magnet and touch different things in the classroom (your pencil, a paperclip, a plastic ruler, the window frame).
2. Make two lists:
   1. Magnetic: Things the magnet stuck to.
   2. Non-Magnetic: Things the magnet ignored.

Revision Questions

1. Name the natural rock that acts as a magnet.
2. What happens when you bring the North pole of one magnet near the North pole of another?
3. Why does a compass needle always point in a North-South direction?
4. Mention two ways a magnet can lose its magnetism.

Homework

Go home and find three places where magnets are used in your house. Write them down and explain what the magnet is doing in each place.