A small electric motor drives a model railway carriage. Its coil is between permanent magnets. A fault prevents the split-ring commutator from reversing the current after each half-turn.
What happens to the coil?
It keeps turning in the same direction, because the current in the coil has not changed
It rotates backwards continuously, because the turning effect reverses after each half-turn
It stops at the half-turn position, because the forces on the coil disappear there
It rocks to and fro before settling, because the turning effect acts in the opposite direction after half a turn
90 exam-style questions on AQA GCSE Physics 7.2 The motor effect, covering 7.2.1 Electromagnetism, 7.2.2 Fleming's left-hand rule (HT only), 7.2.3 Electric motors (HT only), and 7.2.4 Loudspeakers (HT only). Each one has a worked solution and a mark scheme showing where the marks go.