Fun with Magnets — Class 6 Physical Science
'Magnets are invisible forces in action — they pull, push, and point the way without ever touching.'
1. Introduction
A magnet is an object that can attract (pull) certain materials like iron, nickel, and cobalt. The power of a magnet is invisible — it acts through a magnetic field.
Why This Chapter Matters
- Understand magnetism — a fundamental force of nature
- Navigate using a compass
- Maglev trains, speakers, MRI machines use magnets
- Foundation for physics
2. Magnetic and Non-Magnetic Materials
Magnetic Materials
Materials that are attracted to a magnet.
| Material | Attracted to Magnet? |
|---|---|
| Iron | YES (strongly) |
| Nickel | YES |
| Cobalt | YES |
| Steel | YES (iron + carbon) |
| Aluminium | NO |
| Copper | NO |
| Gold | NO |
| Silver | NO |
| Plastic | NO |
| Wood | NO |
| Glass | NO |
'Only IRON, NICKEL, COBALT, and their alloys (like steel) are magnetic. All other common materials are non-magnetic.'
Testing Magnetic Property
Hold a magnet near different objects:
- Paper clip (iron) → Attracted → Magnetic
- Copper coin → Not attracted → Non-magnetic
- Steel spoon → Attracted → Magnetic
3. Poles of a Magnet
Every magnet has two poles — North Pole (N) and South Pole (S).
Properties of Poles
- Maximum attraction: The poles are where the magnet is strongest
- Inseparability: You cannot isolate a single pole. Cut a magnet in half → each piece has its own N and S pole
- Opposite poles attract, like poles repel
Finding Poles
- Suspended magnet: A freely suspended magnet ALWAYS points North-South
- The end pointing NORTH is the North Pole
- The end pointing SOUTH is the **South Pole'
4. Attraction and Repulsion
The fundamental rule of magnetism:
| Combination | Result |
|---|---|
| N + N | REPEL (push away) |
| S + S | REPEL (push away) |
| N + S | ATTRACT (pull together) |
'Opposite poles attract. Like poles repel.'
Demonstration
- Take two bar magnets
- Bring North of one near North of other → they push apart (repel)
- Bring North near South → they snap together (attract)
Why Repulsion Matters
Repulsion is the only real test of whether something is a magnet:
- Attraction can happen between a magnet and a magnetic material (like iron)
- Repulsion only happens between TWO magnets (like poles)
- 'If two things repel, BOTH are magnets. If they attract, one might just be magnetic material.'
5. Earth as a Magnet
The Earth itself behaves like a giant magnet with a north and south pole.
Magnetic Compass
A compass is a device that uses a tiny magnet (needle) to show direction.
N
↑
┌──┼──┐
W ─┤ │ ├─ E
└──┼──┘
↓
S
- The compass needle is a small magnet
- It always points North-South
- Used by sailors, hikers, and pilots for navigation
Interesting Fact
The Earth's magnetic south pole is near the geographic north pole. That's why the north pole of a compass needle points north — opposite poles attract!
History of Compass
- First used by Chinese around 200 BCE
- Lodestone (natural magnet) was used
- Revolutionised navigation — ships could sail even when stars were not visible
6. Types of Magnets
Natural Magnets
- Lodestone (magnetite, Fe₃O₄) — a naturally occurring magnetic rock
- Found in nature, though weakly magnetic
Artificial Magnets
Made by humans in various shapes:
| Type | Shape | Uses |
|---|---|---|
| Bar magnet | Rectangular bar | Labs, teaching |
| Horseshoe magnet | U-shaped | Stronger, used in old speakers |
| Cylindrical magnet | Rod-shaped | Various applications |
| Ring magnet | Donut-shaped | Speakers, sensors |
| Disc magnet | Flat disc | Small motors, fridge magnets |
Making a Magnet
Method: Stroking
- Take a steel bar (iron nail, knife blade)
- Stroke it repeatedly with a magnet in ONE direction (not back and forth)
- After many strokes, the steel becomes magnetised
Method: Electric current
- Wrapping a current-carrying wire around an iron core creates an electromagnet
- Electromagnets can be turned ON and OFF!
7. Uses of Magnets
| Use | How Magnet Is Used |
|---|---|
| Compass | Direction finding |
| Fridge magnets | Holding notes on metal surface |
| Speakers/headphones | Converting electrical signals to sound |
| Electric motors | Fans, mixers, washing machines |
| MRI machines | Medical imaging (very strong magnets) |
| Maglev trains | Floating trains using magnetic levitation |
| Cranes | Lifting heavy iron/steel objects (scrap yards) |
| Credit/debit cards | Magnetic strip stores data |
| Toys | Magnetic building sets, puzzles |
Electromagnets
- An electromagnet is made by coiling wire around iron and passing current
- Can be turned ON/OFF by controlling current
- Used in cranes, doorbells, telephone receivers
- 'Electromagnets are temporary magnets — you control when they work'
8. Common Mistakes — Fix Them Now
| # | Mistake | Correction |
|---|---|---|
| 1 | Thinking all metals are magnetic | Only iron, nickel, cobalt, and steel are magnetic. Copper, aluminium, gold are NOT. |
| 2 | Believing you can have a single pole | Every magnet ALWAYS has both N and S poles — they cannot be separated. |
| 3 | Confusing repulsion with attraction | Repulsion = like poles (N-N, S-S). Attraction = unlike poles (N-S). |
| 4 | Calling a compass needle 'just a needle' | The compass needle IS a small magnet that aligns with Earth's magnetic field. |
| 5 | Stroking a magnet back and forth to make a magnet | Always stroke in ONE direction only (not back and forth). |
9. Exam Focus
Marks Blueprint
| Question Type | Marks | Topic |
|---|---|---|
| MCQ | 1 | Magnetic / non-magnetic identification |
| Short answer | 2 | Attraction vs repulsion |
| Short answer | 2 | Earth as magnet / compass |
| Long answer | 3 | Properties of magnets / uses |
| Activity | 2 | Making a magnet by stroking |
Quick Self-Test (5 Questions)
Q1: Name three magnetic materials.
<details><summary>Answer</summary>Iron, nickel, cobalt (also steel).</details>Q2: What happens when you bring two north poles of magnets together?
<details><summary>Answer</summary>They REPEL each other (like poles repel).</details>Q3: How does a compass work?
<details><summary>Answer</summary>The compass needle is a small magnet that aligns with Earth's magnetic field, always pointing North-South.</details>Q4: Can you get a magnet with only one pole?
<details><summary>Answer</summary>No. If you cut a magnet in half, each piece becomes a new magnet with its own N and S poles.</details>Q5: Name two uses of magnets in daily life.
<details><summary>Answer</summary>Compass (navigation), fridge magnets, speakers, electric motors, MRI machines (any two).</details>10. Chapter Summary
- Magnetic materials: iron, nickel, cobalt, steel (not all metals!)
- Poles: Every magnet has North and South poles
- Attraction/Repulsion: Opposite poles attract; like poles repel
- Earth as magnet: Earth has a magnetic field; compass uses this
- Types: bar, horseshoe, ring, disc magnets; natural (lodestone) and artificial
- Uses: compass, motors, speakers, MRI, maglev trains, cranes
- Electromagnet: magnet made using electric current (can be turned ON/OFF)
'Magnets are fascinating — they work invisibly and connect us to the Earth's own magnetic field!'
