Magnetism Study Guide
1. Magnetic Fields Basics
• Magnetic Field:
The area around a magnet where magnetic forces can be detected.
• How to Detect a Magnetic Field:
Use a compass or iron filings.
• Magnetic Field Lines Around a Magnet:
- Lines go from the north pole to the south pole.
- Lines are closer together where the field is stronger.
- They never cross.
• Field Between Two Magnets:
- Like poles repel (lines push away).
- Opposite poles attract (lines connect).
2. Earth’s Magnetic Field
• Earth acts like a giant bar magnet.
• The magnetic north is actually near geographic south.
• Earth’s magnetic field is caused by molten iron in the core.
• Field lines go out of the south magnetic pole and into the north.
3. Making Magnets
• Rub a magnetic material with a magnet or use electricity.
• Make a Compass:
- Magnetise a needle.
- Float it on water using cork or foam.
4. Electromagnets vs Permanent Magnets
Feature
Electromagnet
Permanent Magnet
Magnetic Field
Only when current flows
Always present
Can be Turned Off
Yes
No
Strength Adjustable
Yes
No
5. How to Make an Electromagnet
• Wrap insulated copper wire around an iron nail.
• Connect the wire to a battery.
6. Uses of Electromagnets
• MRI machines
• Electric bells
• Scrap yard magnets
• Magnetic cranes
• Speakers and motors
7. Factors Affecting Electromagnet Strength
1. Number of coils – more = stronger.
2. Current – more = stronger.
3. Core material – soft iron is best.
4. Tightly wrapped coils – better field.
Predicting Effects:
•
More current = stronger
•
Fewer coils = weaker
•
Soft iron = stronger
•
No core = very weak
🧪 Practice Tasks
• Draw field lines for a bar magnet and Earth.
• Build a mini compass at home.
• Change one factor in an electromagnet and record what happens.