A student investigates building model transformers in the laboratory. Look at the diagram of the transformer set-up: 
The student builds four different transformers, each with different primary and secondary coils. Using an input voltage of 18 V18\text{ V}18 V, the student measures the output voltage. Look at the results in the table:
| Attempt | Number of turns in primary coil | Number of turns in secondary coil | Output voltage (V\text{V}V) |
|---|---|---|---|
| 1 | 150 | 300 | 34.5 |
| 2 | 300 | 150 | 9.0 |
| 3 | 250 | 500 | 34.5 |
| 4 | 500 | 250 | 9.0 |
Explain how a transformer works and analyze whether this data supports the expected output voltages.
The student also completes a project on how dynamic loudspeakers work. Look at their explanation below. The student uses two incorrect words in their work:
"An alternating current is passed through the coil of wire. This current creates a permanent magnetic field around the coil, which interacts with the field of the permanent magnet. This interaction creates a force, causing the coil and the diaphragm to move back and forth. This movement produces sound waves. A loudspeaker is similar to a generator."
Identify one of the incorrect words and write a correct sentence to replace the mistake.
Name a device which uses this effect in reverse.