Moving coil Loudspeaker Simulation
The simulation is a real-time interactive 3D model of a moving-coil loudspeaker, built to the AQA GCSE Physics specification. Students view a physically accurate cross-section rendered with metallic PBR materials — chrome back plate and pole piece, ceramic magnet body, copper voice coil with visible winding rings, a paper cone, rubber surround, corrugated spider, and a six-strut steel basket frame.
The physics runs live at every frame. An AC oscillator drives the voice coil, whose current direction flips each half-cycle. Amber tangential arrows on the coil reverse direction with the current. Red radial arrows show the permanent magnetic field in the gap. A green or red force arrow on the cone axis shows the motor-effect force (F = BIL) switching outward and inward in sync — outward producing compression waves (bright cyan rings), inward producing rarefaction waves (dim blue rings). The AC waveform strip in the bottom-left always shows the live signal. Students can drag the speaker to any angle with mouse or touch to inspect the coil in the gap, the surround, or the magnet assembly from any direction.
The 🏷 labels toggle adds the five-step GCSE causal chain across the top and the IBF force badge on the right. Frequency (20–500 Hz) and amplitude sliders change the cone motion, wave density, and the audible tone simultaneously — students hear the pitch rise as they drag the slider, directly connecting the wave equation to perception. The SEND accessibility panel adds Irlen overlays, reading ruler, dyslexia font, high contrast, reduce motion, extra-slow mode, and mute.
Suggested Class Activity
“Build the Explanation” — Paired Prediction and Explanation Task Suitable for: GCSE Physics Year 10/11, 20–30 minutes
Setup (2 min) Display the simulation on the board with labels off. Students work in pairs, each pair with a mini whiteboard or a printed blank diagram of a loudspeaker cross-section.
Stage 1 — Observe and predict (5 min) Run the simulation at 80 Hz, amplitude 50%. Ask pairs to watch the cone and write down:
- What is the cone doing?
- What do you think is causing it to move in both directions?
Stage 2 — Turn on labels, test the prediction (5 min) Toggle 🏷 labels on. Students compare the step-chip sequence to their prediction. Discussion prompt: “Which step did most pairs get right? Which did they miss?”
Stage 3 — Drag and explain (8 min) Each pair takes the simulation (on a tablet or shared screen) and drags the speaker to find the magnetic gap. Task: sketch the gap from the side and draw the I, B, and F vectors onto their whiteboard using the colour code from the badge (amber = I, red = B, green = F). Ask: “What happens to F when the current reverses?”
Stage 4 — Frequency challenge (5 min) Raise the frequency slider to 400 Hz. Ask: “What changes in the sound? What changes in the motion? What stays the same?” Target answers: pitch increases, cone oscillates faster, sound wave rings appear more frequently — but the mechanism (F = BIL) is identical.
Stage 5 — Written explanation (5 min) Students write a four-sentence GCSE-style explanation using the five key terms shown in the step chips: alternating current, magnetic field, motor effect, vibration, compression/rarefaction. Peer-mark using the step chip sequence as a mark scheme.
Adaptation notes
- For lower-confidence students: leave labels on throughout and use the step chips as a writing frame
- For higher ability: challenge them to explain why a direct current (DC) would not work as an audio signal — link to the force arrow never reversing
- For SEND learners: use reduced motion mode and extra slow to observe one complete cycle at a time; the reading ruler supports annotation tasks