Magnetic poles, fields, induced magnetism, and the difference between magnetically hard and soft materials. The base layer for electromagnetism.
What you’ll learn
Mapped to the Cambridge IGCSE 0625 syllabus (2026-2028).
4.1 — Describe attraction and repulsion between magnetic poles.
4.1 — Define magnetic field and represent it with field lines.
4.1 — Describe induced magnetism.
4.1 — Distinguish between magnetically hard and soft materials.
Magnetic poles
Like poles repel; unlike poles attract. Two poles per magnet — never one alone.
Two magnetic poles: north (N) and south (S). They are at the ENDS of bar magnets where the magnetic effect is strongest.
Force rule.
N near N → repel.
S near S → repel.
N near S → attract.
Repulsion is the test for a magnet. Magnetic materials (like iron) are ATTRACTED by both poles. Only another MAGNET will REPEL.
Red poles are north, grey poles are south — like poles push apart, unlike poles pull together.
Cutting a magnet. Cut a bar magnet in half: you don't get one N and one S, you get two new bar magnets, each with its own N and S. Magnetic monopoles don't exist (in classical physics).
Like poles: repel.
Unlike poles: attract.
Repulsion is the only definitive test for a magnet.
Cutting a magnet creates two smaller magnets.
Magnetic fields and field lines
Field lines run from N to S outside the magnet. Closer lines = stronger field.
Magnetic field. A region where a magnetic force is exerted on another magnet or magnetic material.
Field lines.
Outside the magnet: from N to S.
Inside the magnet: from S to N (closing the loop).
Never cross.
Closer together = stronger field.
Field lines emerge from the north pole and curve round to the south pole; they bunch tightest near the poles.
Plotting a field. Use a small plotting compass. Place it near a bar magnet; the compass needle aligns with the field at that point. Mark the direction. Move the compass and repeat. Connecting the directions traces out the field lines.
Iron filings method. Sprinkle iron filings on paper over a magnet. Tap gently; filings line up along the field, revealing the pattern. Doesn't show direction (just the lines).
Earth's magnetic field. Earth itself acts like a giant bar magnet — that's why a compass needle points roughly north. The geographic North Pole is actually a MAGNETIC south pole (which is why a compass north points there — opposites attract).
Forces come from interacting fields (Supplement). When two magnets are brought together, the magnetic force between them is due to the interaction of their magnetic fields. Each magnet has its own field; where the two fields overlap they interact. If the fields link up (unlike poles facing) the magnets attract; if the fields oppose (like poles facing) the magnets repel. So 'like poles repel, unlike attract' is really a statement about how the magnets' fields interact.
Field lines: N to S outside.
Don't cross.
Closer = stronger.
Plot with compass or iron filings.
Magnetic forces are due to interactions between magnetic fields.
Induced magnetism
A magnetic material near a magnet becomes a temporary magnet too.
Induced magnetism. When a piece of magnetic material (e.g. iron) is brought near a permanent magnet, the magnet's field re-aligns the magnetic domains in the iron. The iron itself becomes a temporary magnet.
That's why a paper clip sticks to a magnet — the magnet induces magnetism in the paper clip, which then attracts to the magnet. A chain of paper clips works the same way: each one becomes a temporary magnet that holds the next one.
Removing the magnet.
Magnetically soft material (e.g. pure iron): loses magnetism almost immediately.
Magnetically hard material (e.g. steel): keeps magnetism for a long time.
Worked qualitative. Why does an iron nail picked up by a magnet pick up other iron nails? It's been temporarily magnetised by induced magnetism — and now acts as a magnet itself.
Used in: electromagnets, transformer cores, relay cores.
Magnetically hard.
Examples: steel, alnico, neodymium alloys.
Magnetises slowly.
RETAINS magnetism after the field is removed.
Used in: permanent magnets (compasses, fridge magnets, motors).
An external field re-aligns the domains; soft materials let them spring back, hard materials lock them.
Why it matters. Electromagnet cores need to switch on and off quickly — that's why they use soft iron. Permanent magnets need to STAY magnetised — that's why they use hard steel or specialised alloys.
Worked. A relay (electromechanical switch) has a soft iron armature that gets pulled toward an electromagnet when current flows. Why soft iron? So that as soon as the current is removed, the armature DEMAGNETISES instantly and snaps back — fast switching.
Magnetism appears every Paper 2 (3-4 marks: pole rules, field-line drawing, hard vs soft) and many Paper 4s as a setup for electromagnetic effects. Examiner reports flag attraction-only as a test for magnets — it's not, because magnetic materials are also attracted. Only REPULSION proves both objects are magnets.
Worked examples, formulae, definitions and the mistakes examiners flag — everything you need to push from a pass to an A*.
Take this whole topic with you
Download a branded revision sheet — worked examples, formulae, definitions and common mistakes for Simple Phenomena of Magnetism, ready to print or save as PDF.
Step-by-step worked examples — Simple Phenomena of Magnetism
Step-by-step solutions to past-paper-style questions on simple phenomena of magnetism, written exactly the way a tutor would explain them at the board.
1Predict force between two bar magnets
Core• poles
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Question
Two bar magnets are placed end-to-end: north pole of one near south pole of the other. State the force between them.
Step-by-step solution
Step 1
Unlike poles attract, like poles repel.
Answer
Attractive force.
2Test for a magnet
Core• Adapted from 0625/22 May/Jun 2024 Q15• test
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Question
How can you tell if an iron bar is a magnet or just a magnetic material?
Step-by-step solution
Step 1
Bring an end of the unknown bar to the SOUTH pole of a known magnet.
Step 2
If the unknown REPELS at any orientation, it is a magnet. Magnetic material would only attract.
Answer
REPULSION is the only conclusive test for a magnet.
Examiner tip
Attraction occurs for both magnets and magnetic materials. Only repulsion proves both are magnets.
3Field around a bar magnet
Core• field lines
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Question
Sketch the magnetic field of a bar magnet and state the direction of arrows.
Step-by-step solution
Step 1
Field lines emerge from N and curve round to enter S.
Step 2
Closer lines = stronger field; lines never cross.
Answer
Lines from N → S externally; concentrated near the poles.
4Induced magnetism
Extended• induction
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Question
Explain why a paperclip is attracted to a strong magnet even though the paperclip is not itself a magnet.
Step-by-step solution
Step 1
The strong field temporarily aligns small magnetic regions (domains) in the paperclip.
Step 2
The end nearest the magnet becomes the OPPOSITE pole → attraction.
Answer
Induced magnetism: domains align so the end facing the magnet becomes opposite-polarity → attraction.
5Identify N pole with a known compass
Core• compass, poles
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Question
A bar magnet is placed on a bench. A plotting compass is brought near one end and the red (N-seeking) needle points TOWARDS that end. Which pole of the bar magnet is this?
Step-by-step solution
Step 1
The red end of a plotting compass is its NORTH pole.
Step 2
Unlike poles attract. If the compass NORTH is pulled towards the bar magnet's end, that end must be a SOUTH pole.
Answer
The end is the SOUTH pole.
Examiner tip
The examiner report flags candidates often calling the attracting end 'north' — remember the compass needle's red tip is itself a NORTH pole, so it is attracted to a SOUTH.
6Sketch the field between two bar magnets
Extended• Adapted from 0625/42 May/Jun 2023 Q9• field lines, two magnets
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Question
Two bar magnets are placed in a line with the N pole of one facing the S pole of the other. Describe the magnetic field pattern in the gap between them.
Step-by-step solution
Step 1
Field lines leave the N pole on the left and enter the S pole on the right.
Step 2
Between the poles the lines are straight, parallel and evenly spaced — a uniform field.
Step 3
Arrows point from N (left) → S (right). Lines do not cross.
Answer
A nearly uniform field in the gap: straight parallel lines from the N pole on the left to the S pole on the right.
7Why two magnets exert forces — interacting fields
Extended• magnetic field, forces
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Question
Two bar magnets are brought close together. Explain, in terms of magnetic fields, why a force acts between them, and why this force can be either attractive or repulsive.
Step-by-step solution
Step 1
Each magnet produces its own magnetic field in the space around it.
Step 2
When the magnets are brought together, the two fields overlap and interact. The magnetic force between the magnets is due to the interaction of these two magnetic fields.
Step 3
When unlike poles face each other the fields link up (lines run smoothly from one magnet into the other) and the magnets are pulled together — attraction. When like poles face each other the fields are pushed apart and the magnets are forced apart — repulsion.
Answer
Each magnet has its own field; the force arises from the interaction of the two overlapping magnetic fields. Linking fields (unlike poles) give attraction; opposing fields (like poles) give repulsion.
Examiner tip
The 2026 syllabus §4.1 Supplement requires you to explain that magnetic forces are due to interactions between magnetic fields — not just to state 'like poles repel'.
8Beyond 0625 — Magnetic shielding with soft iron
Extended• shielding, soft iron
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Question
A small compass is placed inside a hollow soft-iron ring near a strong magnet. Explain why the compass needle barely responds to the external magnet.
Step-by-step solution
Step 1
Soft iron is easily magnetised and acts as a 'concentrator' of field lines.
Step 2
Almost all the field lines from the external magnet pass through the iron ring rather than crossing the hollow interior.
Step 3
Inside the cavity the field is therefore very weak — the region is shielded.
Answer
The soft-iron ring redirects field lines around (through itself), so the field inside the cavity is greatly reduced → the compass barely deflects.
Examiner tip
Enrichment beyond Cambridge IGCSE 0625 — magnetic shielding and the term 'reluctance' are NOT in the 0625 syllabus. §4.1 covers magnets, magnetic materials, induced magnetism and field-line patterns only. Magnetic shielding/reluctance belong to AS/A-level (and other-board) physics. This example is kept as enrichment; it will not be examined on 0625.
9Soft iron vs steel cores
Extended• induction, soft iron, steel
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Question
A soft-iron bar and a steel bar are each placed in turn near a strong magnet, then the magnet is removed. Compare what happens to their induced magnetism.
Step-by-step solution
Step 1
Both bars are magnetic materials — domains line up with the external field, so both are attracted while the magnet is near.
Step 2
Soft iron: domains return to random arrangements when the magnet is removed → bar loses magnetism almost immediately.
Step 3
Steel: domains stay aligned → bar retains its induced magnetism and behaves as a weak permanent magnet.
Answer
Soft iron loses its induced magnetism quickly; steel retains it. Soft iron suits electromagnets; steel suits permanent magnets.
10Identify magnetic vs non-magnetic materials
Core• materials
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Question
A student is given four small bars: copper, aluminium, iron and brass. Describe a single experiment to identify the magnetic bar.
Step-by-step solution
Step 1
Bring a strong permanent magnet close to each bar in turn (no contact needed).
Step 2
The bar that is ATTRACTED is the magnetic one. The other three (copper, aluminium, brass) are non-magnetic.
Answer
Only the IRON bar is attracted to the magnet; the others (copper, aluminium, brass) are non-magnetic.
11Beyond 0625 — Field of a bar magnet near a current-carrying wire (neutral points)
Challenge• combined fields, synoptic
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Question
A long straight wire carries a current vertically upwards. A bar magnet lies on the bench with its N pole pointing AT the wire. Sketch-describe the combined field in the horizontal plane near the wire.
Step-by-step solution
Step 1
Field of the wire alone: concentric circles around the wire (right-hand grip rule). Looking down, the circles go anticlockwise.
Step 2
Field of the bar magnet alone in this region: roughly straight lines pointing away from N towards the wire.
Step 3
Where the two fields add (same direction), the resultant is stronger and field lines bunch up. Where they OPPOSE (directly between N and wire, on the side where the wire's circular field runs back towards N), they partially cancel — a NEUTRAL point (zero field) can form here.
Answer
Combined field = vector sum. A NEUTRAL POINT can form between the wire and the magnet where the wire's circular field exactly cancels the bar magnet's field.
Examiner tip
Enrichment beyond Cambridge IGCSE 0625 — the combined field of a bar magnet plus a current-carrying wire, and the term 'neutral point', are NOT in the 0625 syllabus. §4.1 covers field-line patterns of a bar magnet only; combining fields by vector addition and locating neutral points is AS/A-level (and other-board) content. This example is kept as enrichment; it will not be examined on 0625.
Key Formulae — Simple Phenomena of Magnetism
The formulae you need to memorise for simple phenomena of magnetism on the Cambridge IGCSE 0625 paper, with every variable defined in plain English and a note on when to use it.
Pole interaction
Like poles repel;unlike poles attract
When to use
Any two-magnet interaction.
Key Definitions and Keywords — Simple Phenomena of Magnetism
Definitions to memorise and the exact keywords mark schemes credit for simple phenomena of magnetism answers — sharpened from recent examiner reports for the 2026 0625 sitting.
Magnetic material
Examiner keyword
A material that can be attracted by a magnet (e.g. iron, steel, nickel, cobalt). Itself is not necessarily a magnet.
Permanent magnet
Examiner keyword
A material that retains its magnetism, with two poles (N and S) that produce a magnetic field.
Soft vs hard magnetic materials
Examiner keyword
Soft (e.g. iron): magnetises and demagnetises easily. Hard (e.g. steel): retains magnetism longer.
Magnetic field line
Examiner keyword
Imaginary line whose direction at each point gives the direction of the force on a north pole. Lines emerge from N and enter S.
Induced magnetism
Examiner keyword
A piece of magnetic material becoming magnetised because of a nearby magnetic field.
Common Mistakes and Misconceptions — Simple Phenomena of Magnetism
The traps other students keep falling into on simple phenomena of magnetism questions — taken from recent Cambridge IGCSE 0625 examiner reports and mark schemes — and how to avoid them.
✕Using attraction as the test for a magnet
0625/42 — recurring
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Why it happens
Magnets attract magnetic materials too.
How to avoid it
Only REPULSION proves an object is a magnet.
✕Drawing crossing field lines
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Why it happens
Sketch carelessness.
How to avoid it
Field lines never cross — at any point the field has only ONE direction.
✕Drawing field-line arrows from S to N
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Why it happens
Confusing with current.
How to avoid it
Outside a magnet, field lines run N → S. Memorise: 'North → South outside'.
✕Saying steel is the best core material for an electromagnet
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Why it happens
Confusing 'strong' with 'easy to magnetise'.
How to avoid it
Electromagnets need SOFT iron (easy to magnetise AND lose magnetism quickly when current stops).
Practice questions
Exam-style questions with step-by-step worked solutions. Try one before checking the method.
Past paper style quiz
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4. Exam Quiz
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Video lesson
Short walkthrough of the concepts students most often get stuck on.
Simple Phenomena of Magnetism — frequently asked questions
The things students keep getting wrong in this sub-topic, answered.