SEC G3 Combined Science Physics component K326/K327
CP15: Magnetism and Electromagnetism
Connect magnet properties, induced magnetism, current-produced fields, and the motor effect.
Reviewed for the 2027 cohort on 19 July 2026. The official syllabus remains authoritative for assessable wording and paper details.
Core notes
Magnetism questions connect field direction and pattern to material behaviour, current-produced fields, and forces on conductors.
Magnets and induced magnetism
A magnet has north and south poles, attracts suitable magnetic materials, and exerts attraction between unlike poles and repulsion between like poles. When freely suspended away from other magnets, it settles approximately along the north-south direction.
A nearby strong magnet or current-carrying solenoid can magnetise a material by induction. Iron is useful where magnetism should be temporary, while steel is used where magnetism should persist.
Field direction and patterns
The north-seeking end of a small compass points along the magnetic field. Draw arrows from north to south outside a bar magnet, with denser lines where the field is stronger. Between unlike poles of two magnets, lines join across the gap; between like poles, they bend apart and do not join.
A straight current produces circular field lines, while a solenoid produces a bar-magnet-like pattern. Use the right-hand grip rule to relate current direction to field direction. Increasing current strengthens the field and reversing current reverses its direction.
Force on current and coil turning
Place a current-carrying conductor between magnet poles and observe its motion when the circuit is completed. Reverse the current while keeping the field fixed, then reverse the field while keeping the current fixed: either reversal reverses the force. Fleming's left-hand rule relates mutually perpendicular field, current, and force directions.
Opposite forces on the two sides of a current-carrying coil form a turning effect in a magnetic field. The detailed structure of an electric motor is not required.
Assessed representations
Magnetic field patterns to recognise and draw
Field between like poles
Formulae and relationships
This chapter is assessed mainly through models, field patterns and explanations. Build the causal chain before adding any calculation.
Worked examples
Example 1: A wire's current is reversed while the magnetic field is unchanged. What happens to the force?
- Current, field, and force are mutually related directions.
- Only the current direction changes.
- Fleming's left-hand rule therefore gives the opposite force direction.
Answer: The force reverses direction.
Chapter checkpoint
Use these three moves to organise the topic before attempting a mixed or practical question.
- Represent magnetic fields and distinguish permanent from induced magnetism.
- Connect current direction to the magnetic field around a wire or coil.
- Use field direction, conventional current, and force direction correctly in motor-effect questions.
Official outcome coverage
K326 CP15: 9 mapped outcomes, references CP15(a), CP15(b), CP15(c), CP15(d), CP15(e), CP15(f), CP15(g), CP15(h), CP15(i). Check the official K326 syllabus.
K327 CP15: 9 mapped outcomes, references CP15(a), CP15(b), CP15(c), CP15(d), CP15(e), CP15(f), CP15(g), CP15(h), CP15(i). Check the official K327 syllabus.
The outcome wording is not reproduced here. The relevant official syllabus remains authoritative for exact assessable scope.
Practical and data connection
Map a magnetic field with a plotting compass or investigate a current-produced field or force. Change one factor such as current magnitude or direction, keep geometry and heating controlled, record field or motion evidence, and use it to infer direction rather than treating drawn field lines as objects.
Exam traps and retrieval check
Avoid these traps
- Drawing field arrows from south to north outside a magnet.
- Reversing current but leaving the circular field direction unchanged.
- Describing a force without naming which conductor experiences it.
Check from memory
Which compass end shows field direction?
The north-seeking end.
What happens when solenoid current reverses?
Its field direction reverses.
Why does a coil turn?
Forces on opposite sides form a turning effect.
Official Combined Science scope
This shared Combined Physics owner serves both K326 and K327. Magnet properties, induced magnetism, field patterns, current-produced fields, motor force, and coil turning effects.