In a moving-coil loudspeaker a coil is attached to a paper cone and sits in the field of a permanent magnet. How does an alternating current in the coil produce sound?
The current warms the coil, so the air next to the cone expands and contracts
The current magnetises the cone, which is then attracted and repelled by the magnet
The changing field of the coil makes the permanent magnet vibrate against the cone
The force on the coil changes direction, so the cone vibrates and moves the air
39 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.