An audio engineer is testing a prototype moving-coil loudspeaker (illustrated below).
a.[1]
State the type of electrical signal (current) that must be passed through the voice coil to produce a continuous acoustic wave.
b.[4]
Explain how this electrical signal causes the diaphragm (cone) to vibrate and generate sound.
c.
[2]
The engineer designs an experiment to investigate how the electromagnetic force on the voice coil depends on:
- the magnetic flux density of the permanent magnet
- the active length of the coil wire situated within the magnetic field.
The engineer collects the following data:
| Magnetic flux density (T) | Length of coil wire in field (m) | Measured force (N) |
|---|---|---|
| 0.20 | 0.4 | 0.08 |
| 0.40 | 0.8 | 0.32 |
| 0.60 | 1.2 | 0.72 |
Explain why these data cannot be used to determine how the length of the coil wire alone affects the force on the coil.