Magnetic Fields & Their Patterns
Magnetic Fields & Their Patterns
- Every magnetic field is made by moving charge — a current, or the electrons circulating inside a magnet. The exam starts with a definition and a drawing, both marked to a checklist.
What a magnetic field is
- A is a region where a force acts on a current-carrying conductor, a moving charge, or a magnetic material — the region idea is one mark, naming a valid victim is the other (9702/41/M/J/23 Q6(a)).
- Field lines run from north poles to south poles outside a magnet; closer lines mean a stronger field. A solenoid (a coil) produces a bar-magnet pattern, made much stronger by an iron core; grip it with the right hand, fingers following the current, and the thumb points to its north end.
- The straight-wire pattern is a three-mark drawing with one mark per feature: concentric circles (draw at least two), spacing that grows with distance (needs at least four circles to show), and arrows — clockwise for current into the page (9702/41/M/J/23 Q6(b)) (9702/41/O/N/24 Q7(b)). Direction from the right-hand rule: thumb along the current, fingers curl with the field.
The Earth is a giant solenoid (2025 twist)
A 2025 question modelled the Earth's core as a solenoid. Two catches: the field is strongest (and perpendicular to the surface) at the poles, weakest (and parallel to the surface) near the equator — and the pole at the geographic north end is a magnetic south pole, since it attracts the north end of every compass (9702/42/M/J/25 Q2(b)).