What is the name of the effect used by the moving-coil loudspeaker to produce sound waves? Explain how a moving-coil loudspeaker produces a sound wave - AQA - GCSE Physics - Question 8 - 2021 - Paper 1

A moving-coil loudspeaker produces a sound wave through the following process:

1. Current Flow: When an alternating current passes through the coil of wire, it creates a magnetic field around the coil.

2. Interaction with Magnet: This magnetic field interacts with the permanent magnet in the loudspeaker.

3. Force Creation: The interaction between these magnetic fields produces a resultant force that causes the coil, and consequently the cone attached to it, to move.

4. Sound Wave Generation: As the direction of the current reverses, the direction of the resultant force also reverses, causing the cone to move back and forth. This motion creates compressions and rarefactions in the surrounding air, thus producing a sound wave.

The results cannot be used to make a valid conclusion because the student changed two variables at the same time: the number of turns on the coil and the frequency of the supply. This means it is not possible to isolate the effect of each variable on the loudness of sound, leading to inconclusive results.