🧲 Magnetism: Magnets, Magnetic Fields and Electromagnets
Learn magnetic and non-magnetic substances, properties of magnets, magnetic fields, Earth’s magnetic field, electromagnets, storage and demagnetization with animated activities.
📌 Magnetism Learning Map
🎯 Learning Objectives
- Identify magnetic and non-magnetic substances.
- Understand characteristics and properties of magnets.
- Explain magnetic field and Earth’s magnetic field.
- Learn making, care, storage and demagnetization of magnets.
📊 Learning Outcomes
- Classifies materials as magnetic or non-magnetic.
- Explains poles, attraction and repulsion.
- Describes electromagnets and core material.
- Explains permanent and temporary magnets.
🧩 Competencies
- Observation Skills
- Classification Skills
- Scientific Reasoning
- Application Skills
🌈 5W-1H + 1U
🔴 What: Magnetism is the property by which a magnet attracts magnetic substances.
🟠 Why: Magnetism is useful in compasses, motors, speakers, cranes and electric devices.
🟡 When: Magnetism is observed when a magnet attracts iron, nickel, cobalt or steel.
🟢 Where: Magnets are used in homes, schools, hospitals, industries and navigation.
🔵 Who: Students, scientists, electricians, engineers and doctors use magnets.
🟣 How: A magnet produces a magnetic field around it and attracts magnetic substances.
⚫ 1U: Like poles repel and unlike poles attract.
🧲 Magnetic and Non-Magnetic Substances
Click a material
Iron Wood Steel Plastic Nickel Rubber Cobalt PaperQuick Rule
Magnetic substances are attracted by magnets. Examples include iron, nickel, cobalt and steel.
Non-magnetic substances are not attracted by magnets. Examples include wood, plastic, rubber and paper.
🧲 Magnetic Field Around a Magnet
A magnetic field is the region around a magnet where its magnetic force can be felt.
Animated Magnetic Field Lines
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Magnetic field lines emerge from the north pole and enter the south pole outside the magnet. They are strongest near the poles.
Characteristics of a Magnet
- Has two poles: north and south.
- Attracts magnetic substances.
- Freely suspended magnet points north-south.
- Magnetic force is strongest at poles.
Properties of Magnets
- Like poles repel.
- Unlike poles attract.
- Magnetic poles always occur in pairs.
- A magnet can induce magnetism in magnetic substances.
Earth’s Magnetic Field
- Earth behaves like a huge magnet.
- A compass works because of Earth’s magnetic field.
- Earth’s magnetic field helps in navigation.
⚡ Making Magnets and Electromagnets
Making of Magnets
- By stroking method.
- By electrical method.
- By induction method.
Permanent Magnets
- Retain magnetism for a long time.
- Usually made of steel or special alloys.
- Used in speakers, magnetic holders and compasses.
Temporary Magnets
- Lose magnetism quickly.
- Usually made of soft iron.
- Used in electromagnets, bells and cranes.
Animated Electromagnet
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An electromagnet is made by passing electric current through a coil wound around a soft iron core. Soft iron is chosen because it magnetizes and demagnetizes easily.
Care, Storage and Demagnetization
| Topic | Important Points |
|---|---|
| Care of Magnets | Do not drop, heat or hammer magnets. Keep them away from strong electric currents. |
| Storage of Magnets | Store bar magnets in pairs with unlike poles together and soft iron keepers at ends. |
| Demagnetization by Heating | Heating disturbs the magnetic arrangement and weakens magnetism. |
| Demagnetization by Hammering | Hammering disturbs magnetic domains and reduces magnetism. |
| Demagnetization by Electricity | Alternating current can demagnetize a magnet. |
📊 Permanent vs Temporary Magnets
| Basis | Permanent Magnet | Temporary Magnet |
|---|---|---|
| Magnetism | Retains magnetism for a long time | Loses magnetism quickly |
| Material | Steel or hard magnetic materials | Soft iron |
| Use | Compass, speaker, magnetic lock | Electric bell, crane, electromagnet |
| Demagnetization | Difficult | Easy |
Soft iron is preferred as the core of an electromagnet because it becomes magnetic quickly and loses magnetism quickly when current is switched off.
✅ Magnetism Quiz
🧠 HOTS Questions
1. Why is soft iron used as the core of an electromagnet?
Soft iron is used because it gets magnetized quickly and loses magnetism quickly when current is switched off.
2. Why should magnets not be heated?
Heating disturbs the arrangement of magnetic domains and may demagnetize the magnet.
3. Why does a compass point north-south?
A compass aligns itself with Earth’s magnetic field.
4. Why are electromagnets useful in cranes?
They can be switched on to lift magnetic materials and switched off to release them.
5. Why do magnetic poles always occur in pairs?
Even if a magnet is broken, each piece gets both north and south poles. A single isolated pole is not obtained.
