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🧲 CIE IGCSE Physics – Simple Phenomena of Magnetism

1️⃣ Magnetic Poles and Forces Between Them​

🔹 Magnetic Poles​

Every magnet has two ends called poles:

  • North pole (N pole)
  • South pole (S pole)

Poles always exist in pairs — you cannot have a single isolated pole.

🔹 Forces Between Poles​

PolesForce
N and NRepulsion
S and SRepulsion
N and SAttraction

Key Terms

  • Attraction → Force pulling objects together
  • Repulsion → Force pushing objects apart

👉 Rule to remember:
Like poles repel, unlike poles attract.

🔹 Magnets and Magnetic Materials​

Magnets attract certain materials:

  • Iron
  • Steel
  • Nickel
  • Cobalt

These are called magnetic materials.

They do NOT attract:

  • Plastic
  • Wood
  • Glass
  • Copper
  • Aluminium (in IGCSE context)

🔹 Magnetised vs Unmagnetised​

  • Magnetised material → Acts like a magnet and has poles.
  • Unmagnetised material → No overall magnetic effect.

Example:
A steel nail normally is unmagnetised. After stroking it with a magnet, it can become magnetised.

2️⃣ Induced Magnetism​

🔹 Definition​

Induced magnetism occurs when a magnetic material becomes temporarily magnetised when placed in a magnetic field.

Example:
If a bar magnet is brought near an iron nail:

  • The end closest to the magnet becomes the opposite pole.
  • The nail becomes temporarily magnetised.

Important:

  • When the magnet is removed, the iron usually loses its magnetism

3️⃣ Temporary vs Permanent Magnets​

PropertyTemporary Magnet (Soft Iron)Permanent Magnet (Steel)
Easily magnetised?YesHarder
Easily demagnetised?YesNo
Used forElectromagnetsBar magnets

🔹 Soft Iron​

  • Magnetises easily
  • Loses magnetism quickly
  • Used in electromagnets

🔹 Steel​

  • Harder to magnetise
  • Retains magnetism
  • Used for permanent magnets

4️⃣ Magnetic vs Non-Magnetic Materials​

🔹 Magnetic Materials​

Attracted by magnets.
Examples:

  • Iron
  • Steel
  • Nickel
  • Cobalt

🔹 Non-Magnetic Materials​

Not attracted by magnets.
Examples:

  • Plastic
  • Wood
  • Glass
  • Copper
  • Aluminium

⚠️ Exam Tip: Aluminium is technically weakly magnetic (paramagnetic), but at IGCSE level it is considered non-magnetic.

5️⃣ Magnetic Field​

🔹 Definition​

A magnetic field is a region in which a magnetic pole experiences a force.

You cannot see a magnetic field, but you can show it using:

  • Iron filings
  • A plotting compass

6️⃣ Magnetic Field Lines Around a Bar Magnet​

🔹 Pattern​

  • Field lines leave the North pole
  • Curve around
  • Enter the South pole
  • Inside the magnet, they go from South to North

👉 The field forms closed loops.

🔹 Important Properties of Field Lines​

  1. They never cross.
  2. They go from N → S outside the magnet.
  3. Closer lines = stronger field.
  4. They are most concentrated at the poles.

7️⃣ Direction of Magnetic Field​

The direction of a magnetic field at a point is:

The direction of the force on the North pole placed at that point.

That means:
If you put a small compass at a point, the needle’s north end shows the field direction.

8️⃣ Plotting Magnetic Field Lines​

🔹 Using Iron Filings​

  1. Place paper over a magnet.
  2. Sprinkle iron filings.
  3. Tap gently.
  4. Filings form a pattern showing the field.

⚠️ Shows shape, not direction.

🔹 Using a Compass​

  1. Place the compass near the magnet.
  2. Mark direction of needle.
  3. Move the compass step-by-step.
  4. Join arrows to form field lines.

This method shows:
✔ Shape
✔ Direction

9️⃣ Uses of Permanent Magnets and Electromagnets​

🔹 Permanent Magnets (Steel)​

Used in:

  • Compasses
  • Fridge magnets
  • Door catches
  • Speakers
  • Small motors

🔹 Electromagnets (Soft Iron Core + Current)​

Used in:

  • Scrap yard cranes
  • Electric bells
  • Relays
  • Circuit breakers
  • MRI machines (advanced)

Why electromagnets are useful:

  • Can be switched on/off
  • Strength can be changed
  • Polarity can be reversed

🔟 Magnetic Forces and Fields​

Magnetic forces are caused by:

Interactions between magnetic fields.

Example:
Two magnets repel because their magnetic fields interact.

A magnet attracts iron because:

  • The magnet’s field induces magnetism in the iron.
  • Opposite poles are created.
  • Attraction occurs.

1️⃣1️⃣ Field Strength and Spacing​

Magnetic field strength depends on spacing:

  • Closer field lines → Stronger field
  • Wider spacing → Weaker field

Strongest field is at:
✔ The poles of a magnet

🔥 Common Exam Questions & Tips

🧠 Frequently Tested Ideas​

✔ Define magnetic field.
✔ State rule for attraction and repulsion.
✔ Compare soft iron and steel.
✔ Explain induced magnetism.
✔ Draw field lines correctly.
✔ State field direction.

✏️ Drawing Tips (Very Important!)​

When drawing field lines:

  • Start from the North pole.
  • Arrows must point N → S (outside magnet).
  • Lines must curve smoothly.
  • Lines must never cross.
  • Lines should be denser at poles.

Examiners deduct marks for:
❌ Arrows missing
❌ Lines crossing
❌ Straight lines only
❌ Wrong direction

🧲 Important Definitions (Memorise These)

Magnetic field:
A region in which a magnetic pole experiences a force.

Induced magnetism:
Magnetism produced in a material when it is placed in a magnetic field.

Temporary magnet:
A magnet that is easily magnetised and demagnetised.

Permanent magnet:
A magnet that retains its magnetism.

Magnetic material:
A material that can be magnetised and is attracted by a magnet.

⚡ Quick Summary Checklist

Make sure you can:

☐ State N and S poles
☐ Describe attraction and repulsion
☐ Explain induced magnetism
☐ Compare soft iron and steel
☐ Define magnetic field
☐ Draw correct field lines
☐ Explain field direction
☐ Explain field strength using spacing
☐ Give uses of magnets