physicsTopic 7 · Magnetism and ElectromagnetismPaper 2Grades 8–9
Which regenerative-braking motor should an electric bus use?
Starting scenario
Motor A gives 1800 N force at 220 A. Motor B gives 1650 N at 170 A and returns 28% of braking energy to the battery, compared with 18% for A. B’s coils reach 92 °C on long hills; A reaches 74 °C. Magnetic field strength falls when the air gap increases.
You will work through 8 staged questions that build up the science you need. Then you will answer one big-picture question from memory, with no checklist to help you — and only afterwards will the full connection map be revealed.