OK, I understand the circuit. But how does the buzzer make a sound?
That’s easy. Here’s what happens :
1. The current flows through the buzzer circuit.
2. The current makes the electro-magnet switch on.
3. The electro-magnet pulls the metal strip away from the thin wire.
4. This causes the current to switch off again.
5. When the current switches off, the electro-magnet switches off.
6. This allows the metal strip to spring back towards the thin wire.
7. The metal strip moves quickly up and down. This makes the loud buzzing noise.
Thank, Mario. I get it now.