Speaker = Generator

For people who are unfamiliar with how electric stuff works, it may come as a surprise than driving a speaker can generate electricity! Here I made 10 LEDs light up by dropping a light weight ball on the speaker. Why 10? That's all the LEDs I have! I'm sure that it light up more than 10 (in parallel).
And did you know that every speaker (that uses a copper wire coil and a magnet) can be used as a microphone. It sounds like crap, but it works.

Видео Speaker = Generator канала Giesbert Nijhuis