AQA GCSE Physics — Magnetic Compass simulation
This interactive simulation covers the AQA GCSE Physics topic of magnetic fields and compass behaviour (Magnetism and Electromagnetism, Paper 2). It focuses on how a compass needle — itself a small bar magnet — aligns with the resultant magnetic field at its location, whether that field comes from Earth alone or from the combined effect of Earth and a nearby bar magnet.
Tab 1 – Earth’s Field shows a single draggable compass sitting in Earth’s uniform magnetic field. Animated field lines flow upward toward geographic North, and the compass N (red) needle settles and points in that direction. A key fact box on screen states that geographic North is Earth’s magnetic South pole — which is why the compass N end is drawn toward it by attraction between unlike poles. Students can drag the compass anywhere on the canvas and observe that the needle always returns to the same orientation, demonstrating that Earth’s field is uniform at this scale. Pressing ＋ Add magnet drops a bar magnet onto the canvas. The field lines immediately warp as the two fields combine, and the compass needle responds to the resultant field at its position — deflecting strongly when close to the magnet and recovering toward North when moved far away. A ⇄ Flip button reverses the magnet’s polarity, causing the compass to swing in the opposite direction.
Tab 2 – Near a Magnet shows a draggable bar magnet surrounded by a responsive grid of compasses. Every compass in the grid independently calculates and smoothly rotates to align with the combined field — dipole plus Earth — at its exact position. Close to the magnet the needles follow the curved field lines; far from it they drift back toward geographic North as Earth’s field progressively reasserts. A ⇄ Flip button reverses polarity and the entire grid responds live. Students can also tap anywhere on the empty canvas to place a free-standing, larger compass at that point — it aligns with the local field and can itself be dragged to any position, with a small ✕ button to remove it. This allows targeted investigation of field direction at specific points around the magnet.
Both tabs share the full ClassAdapt SEND accessibility suite: Irlen colour overlays, colour vision deficiency filters, dyslexia-friendly spacing, high contrast mode, text scaling, pause, and reduce motion.
Suggested class activity — Compass and Field Lines Investigation
Works well as a structured enquiry during the magnetism unit, bridging the gap between the abstract concept of a magnetic field and its physical representation.
Setup: Display the simulation on a class screen or share the link for individual/paired use on devices. Students will need a mini-whiteboard or observation sheet.
Part A — Earth’s Field (Tab 1), 5 minutes
- Students drag the compass to different positions on the canvas and record which direction the N needle points each time.
- Ask: “Does the direction of the needle change as you move it? What does this tell you about Earth’s field?” Expected answer: it always points the same way — Earth’s field is uniform at this scale.
- Read the key fact box together: “Geographic North is Earth’s magnetic South pole.” Students write in their own words why the compass N end is attracted to geographic North. (Opposite poles attract.)
Part B — Adding the magnet (Tab 1), 5 minutes
- Click ＋ Add magnet. Students drag the compass close to the magnet’s N pole and sketch the needle direction, then move it to the S pole and sketch again. Ask: “Which pole does the compass N needle point toward when near the N pole? Why?” (Away from it — like poles repel.)
- Click ⇄ Flip. Students observe the needle response and explain what changed and why.
Part C — Field pattern around a magnet (Tab 2), 8 minutes
- Students tap to place five free compasses at positions around the magnet: directly in front of each pole, above and below the centre, and in one corner far away. They sketch the needle directions on their sheet and then draw the field line the needles are tracing.
- Ask: “What do you notice about the compasses near the poles compared to the ones at the sides? What about the compass in the far corner?” (Near poles: strong deflection; far corner: pointing toward geographic North — Earth’s field dominates.)
- Drag the magnet to a new position. Students observe how all compasses respond simultaneously. Ask: “Why do all the compasses change at once when you move the magnet?” (The field exists throughout space and changes everywhere instantly when the source moves.)
Part D — Extend and explain, 5 minutes
- Students flip the polarity and predict — before looking — which way each placed compass will swing. They check their prediction by clicking Flip.
- Written task: “A student places a compass 2 cm from the N pole of a bar magnet and another 20 cm away. Describe and explain the difference in what each compass shows.” This maps directly onto AQA 3–4 mark describe-and-explain questions.
AQA specification links: 7.1 — magnetic poles and fields; 7.2 — magnetic field lines; 7.3 — the Earth’s magnetic field; use of a compass to show the direction of a magnetic field.