Poles: like repel, unlike attract
Every magnet has a north (N) pole and a south (S) pole. Like poles repel (N-N or S-S); unlike poles attract (N-S). A magnet also attracts unmagnetised magnetic material at either pole. A magnetised object behaves as a magnet -- it has poles and can repel. An unmagnetised object has no overall poles, so it can be attracted but can never repel. The examiner keywords are N pole, S pole, attraction, repulsion, magnetised and unmagnetised.
Soft iron is temporary, steel is permanent
Soft iron = a soft magnetic material: easily magnetised but it loses its magnetism easily -- a temporary magnet, ideal for an electromagnet core. Steel = a hard one: harder to magnetise but it keeps its magnetism -- a permanent magnet. An electromagnet (a coil on a soft-iron core) is magnetic only while current flows, so it can be switched on/off, made stronger (more current or turns) and reversed (reverse the current).
(Extended) Magnetic field and induced magnetism
A magnetic field is a region in which a magnetic pole experiences a force. Its direction at a point is that of the force on a N pole there, so field lines run N to S outside the magnet. Induced magnetism: unmagnetised magnetic material in a field becomes a magnet, its end nearest the pole becoming an opposite pole, so it is attracted. Hence iron nails hang in a chain, each magnetising the next; soft iron loses it once out of the field.
Drawn from real examiner reports.
Attraction does not prove a magnet
A magnet attracts both another magnet and any unmagnetised magnetic material, so attraction proves nothing -- the bar could be unmagnetised iron. Only repulsion is a definite test. Bring a known pole near each end of the bar: if it is repelled anywhere it is a magnet. If it is only ever attracted, it is unmagnetised magnetic material.
Soft iron and steel, swapped
Candidates reverse the two, or pick the wrong one for the job. Soft iron is easily magnetised and easily demagnetised, so the electromagnet switches off cleanly when the current stops -- that is why it is the core. Steel keeps its magnetism, so it makes good permanent magnets but a poor core. Copper is non-magnetic and cannot be a magnetic core at all.
Flagged Jun 2023 P11 Q38, P12 Q36; Nov 2023 P11 Q38
Metal does not mean magnetic
The only common magnetic materials are iron, steel, cobalt and nickel (and alloys containing them). Copper, aluminium, brass, zinc, tin, gold, silver and every non-metal (plastic, wood, glass) are not attracted by a magnet and cannot be magnetised. In "which would a magnet attract?" questions, pick only the iron/steel/cobalt/nickel items.
Magnetised is not the same as magnetic
A magnetised object is a magnet: it has poles and can repel. A magnetic material is merely one that can be magnetised. An unmagnetised iron nail is a magnetic material but not a magnet, so it can only be attracted, never repel. Answering that a steel bar "is magnetic" therefore does not settle whether that bar is magnetised.
(Extended) Field arrows point N to S
Examiners repeatedly report that the direction of field lines is wrong. Outside the magnet the arrows point away from the N pole and into the S pole, because the field direction is defined as the direction of the force on a N pole placed at that point. Arrows drawn S to N, or left off altogether, lose the direction mark even when the shape of the pattern is right.
Flagged Jun 2023 P11 Q38, P12 Q36; Nov 2023 P11 Q38
Iron filings show shape, not direction
Iron filings sprinkled around a magnet reveal the shape of the field pattern only -- they carry no arrows and cannot show which way the field points. Finding the direction needs a plotting compass, whose needle N pole lines up along the field. An answer that uses filings alone and then asserts a direction does not earn the direction mark.
(Extended) "Area around a magnet" is too vague
The mark-scheme definition is a region in which a magnetic pole experiences a force -- both "magnetic pole" and "force" are needed. Loose answers such as "the area around a magnet" or "where the magnetism is" gain nothing. The same precision applies to direction: say the force acts on a N pole, not just "on a magnet".
Field-line diagram checklist
Label the poles N and S. Put an arrowhead on every line, N to S outside the magnet. Draw the lines closer together near the poles. Lines must never cross or touch, and must leave the N pole and return to the S pole rather than stopping in mid-air.
Use the technical words, not "push"
This leaf is entirely qualitative -- no calculations, so every mark rests on precision. Write attraction and repulsion, not "push" or "stick"; magnetised and unmagnetised; induced magnetism. Then match the number of separate points you make to the mark tariff.
Match the command word
State = a one-line fact ("like poles repel"; "the core is soft iron"). Describe = say what happens or what you would do -- the forces between two magnets, the field pattern, an experiment. Explain = give a reason. Define = use the mark-scheme wording exactly.
Cambridge 0654 spec reference: Section P4 "Electricity and magnetism", sub-topic P4.1 (Core + Extended). This leaf covers magnetic poles and the forces between them (attraction/repulsion), magnetised vs unmagnetised materials, magnetic vs non-magnetic materials, temporary (soft iron) vs permanent (steel) magnets, how a permanent magnet differs from an electromagnet, and (Extended) the magnetic field, its direction, and induced magnetism.
Scope note: this topic is entirely qualitative -- there are no equations. The field around a current-carrying wire/solenoid, the motor effect and electromagnetic induction belong to other leaves and are not covered here.
There are no formulas in this topic -- it is assessed by description, definition and diagrams. The key rules and facts to memorise are:
| Rule / fact | Statement |
|---|---|
| Force between poles | Like poles repel; unlike poles attract |
| Magnet + magnetic material | A magnet attracts an unmagnetised magnetic material |
| Definite test for a magnet | Repulsion only (attraction is not proof) |
| Magnetic materials | iron, steel, cobalt, nickel (and alloys) |
| Non-magnetic materials | copper, aluminium, brass, zinc, most non-metals |
| Temporary magnet (soft iron) | Easily magnetised, easily loses magnetism -- electromagnet core |
| Permanent magnet (steel) | Harder to magnetise, keeps its magnetism |
| Magnetic field (Extended) | A region in which a magnetic pole experiences a force |
| Field direction (Extended) | Direction of the force on a N pole; N to S outside the magnet |
(Core) Name the two poles of a magnet and state the force rule between poles.
(Core) Two bar magnets are placed end to end on a bench.
Describe the force between them when (a) two N poles face each other, and (b) a N pole faces a S pole. Use the words attraction and repulsion. (2 marks)
