What mechanical device uses electricity to make sound?

What mechanical device uses electricity to make sound?

• A. Amplifier
• B. Transformer
• C. Oscillator
• D. Speaker

Answer: (C)

The key idea is that sound is produced when a device directly converts electrical energy into mechanical motion that moves air. The speaker does exactly that: it has a diaphragm connected to a coil in a magnetic field, and when current flows, the coil moves the diaphragm back and forth, creating sound waves in the air. An oscillator, on the other hand, is an electronic circuit that generates repeating electrical signals; it doesn’t produce sound by itself unless it drives a transducer like a speaker. An amplifier merely boosts an electrical signal, and a transformer changes voltage or current. So the device that uses electricity to make sound directly is the speaker.

The key idea is that sound is produced when a device directly converts electrical energy into mechanical motion that moves air. The speaker does exactly that: it has a diaphragm connected to a coil in a magnetic field, and when current flows, the coil moves the diaphragm back and forth, creating sound waves in the air. An oscillator, on the other hand, is an electronic circuit that generates repeating electrical signals; it doesn’t produce sound by itself unless it drives a transducer like a speaker. An amplifier merely boosts an electrical signal, and a transformer changes voltage or current. So the device that uses electricity to make sound directly is the speaker.