Permanent vs induced magnets
Permanent magnet: retains its magnetism with no external field; made of a hard magnetic material (e.g. steel). Induced magnet: a magnetic material that becomes magnetised only when placed in an external field and loses most of its magnetism when the field is removed; made of a soft material (e.g. iron). For an induced magnet you must state "temporary" / "loses magnetism when the field is removed" to score both marks.
Hard vs soft magnetic materials
Hard materials (steel, alnico) are difficult to demagnetise and keep their magnetism — used for permanent magnets. Soft materials (iron, nickel, cobalt) are easily magnetised and demagnetised — used for induced magnets and electromagnet cores. "Hard/soft" means ease of demagnetising, NOT mechanical hardness. The only common magnetic materials are iron, steel, nickel, cobalt; copper, aluminium and plastic are non-magnetic.
Magnetic field lines
Field lines run from N to S outside the magnet and continue S to N inside, forming closed loops with no start or end. They never cross (one direction per point), and the closer together they are, the stronger the field — strongest at the poles. A plotting compass maps them: its north-seeking end points along the field, from N to S outside the magnet.
Drawn from real examiner reports.
Field lines are closed loops
Describing field lines as "starting at N and ending at S" is only half true — that is the external field. Inside the magnet they continue from S back to N, so the lines form closed loops with no start or end. The mark-scheme phrase is "closed loops"; "start/end at a pole" implies open lines and loses the pattern mark.
June 2024 Paper 2P — the examiner noted that many candidates did not appreciate the continuous nature of magnetic field lines through the core material, losing marks on the field pattern produced.
Magnetic ≠ electrostatic force
A magnet attracts only iron, steel, nickel and cobalt. Electrostatic force is different: a charged rod attracts paper, dust or foil by electrostatic induction — that is NOT magnetism, and the rod is not a magnet. Do not describe a charged object attracting light objects as a magnetic force.
June 2023 Paper 2PR Q3(b)(ii) — weaker candidates confused electrostatics with magnetism when describing how to test whether an object is charged.
Electromagnet core is soft iron
An electromagnet needs a soft iron core (induced magnetism that switches off with the current), not a permanent or bar magnet. Calling the core "a bar magnet" or "a permanent magnet" scores zero on that marking point — a permanent core could not be switched off.
June 2024 Paper 2P Q6(a) — candidates who described the electromagnet core as "a bar magnet" or "a permanent magnet" scored zero for the final marking point.
Define magnets with two elements
"A magnet that always works" is too vague. A permanent magnet = (1) retains its magnetism (2) without an external field. An induced magnet = (1) becomes magnetised in an external field (2) loses most magnetism when the field is removed. Both elements are needed, with the right material — steel (hard) or iron (soft).
Hard/soft is not mechanical hardness
"Hard" and "soft" describe how difficult a material is to demagnetise, not how physically hard it is. Iron is magnetically soft (easily demagnetised) even though it is a strong metal; steel is magnetically hard (keeps its magnetism). Don't judge by mechanical toughness.
Only 4 materials are magnetic
Only iron, steel, nickel and cobalt are attracted to a magnet. Copper and aluminium are excellent electrical conductors but are non-magnetic — don't confuse conductivity with magnetism. Wood, plastic and glass are non-magnetic too.
Add arrows to every field line
Field-pattern sketches earn a shape mark (pattern, spacing, no crossing) and a separate direction mark (arrows N to S outside). Drawing the right shape but omitting arrows loses the direction mark. Show lines as closed loops through the magnet and label the poles.
Like vs unlike poles pattern
Between unlike poles (N–S), lines curve smoothly and densely through the gap. Between like poles (N–N or S–S), lines bow apart with a neutral point (zero field) midway. Sketching the wrong one — e.g. bowing outward for unlike poles — loses the pattern mark.
Name "induced magnet" and the near pole
For "why is the iron attracted", say: the material becomes an induced magnet, the near end forms the opposite pole, and unlike poles attract. Naming the induced magnet AND the near-end pole scores both marks; "it is magnetic" alone does not.
Distinguish magnets by repulsion
To tell a permanent magnet from an unmagnetised magnetic bar, use repulsion: an unmagnetised bar is always attracted, never repelled, because it becomes an induced magnet. Only two magnets repel — so repulsion at any orientation proves both are magnets.
| Term | Mark-scheme definition |
|---|---|
| Permanent magnet | Retains its magnetism without an external magnetic field; made from a hard magnetic material (e.g. steel) |
| Induced magnet | Becomes magnetised when placed in an external magnetic field; loses most magnetism when the field is removed; made from a soft magnetic material (e.g. iron) |
| Magnetic field | A region in which a magnetic pole or magnetic material experiences a force |
| Magnetic field line | A line showing the direction of the magnetic force; field lines are closed loops running N→S outside the magnet |
Define a permanent magnet.
