Explain why a compass needle points towards the geographic north pole of the Earth.

AQA A-Level Physics (7408) — 3.7.1 Fields · Explain · 5 marks · View as Markdown

Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).

A student places a compass on a desk far away from any magnets or electrical equipment. The compass needle settles so that one end points towards the geographic north pole of the Earth.

Model answer (5 marks)

The Earth generates a magnetic field.
The compass needle is a small magnet and therefore experiences a magnetic force in this field.
The needle is free to rotate about its pivot.
The magnetic force aligns the needle with the magnetic field lines, i.e. along the field direction.
The geographic north pole is the Earth’s magnetic south pole, so the needle’s north‑seeking pole is attracted to it.

Examiner tips

Use the word ‘magnetic field’ early, then explain the needle’s response.
Show the chain: field → force on magnet → rotation → alignment.
Mention the geographic‑magnetic pole relationship to justify the direction.

Common mistakes

Saying the needle points to the geographic north because of gravity or temperature. Confusing geographic north with magnetic north without explaining the pole relationship.

Mark scheme (5 marks)

The Earth has/produces a magnetic field
A magnetic field exerts a force on a magnetic material / the compass needle is a magnet and experiences a force in a magnetic field
The compass needle is free to rotate / pivot
The needle aligns with the magnetic field lines / along the direction of the magnetic field
The geographic north pole corresponds to a magnetic south pole (of the Earth's internal field), so the north-seeking pole of the needle is attracted towards it

Key terms in this question

compass needle · geographic north pole