Speaker Becomes a Microphone
Speaker can generate a tiny electrical signal.
Teaching & key ideas
What you do: Speak/tap near speaker wired as input.
What students see: Speaker can generate a tiny electrical signal.
Why it works: Moving voice coil in a magnetic field induces voltage—the reverse of speaker operation.
Question to ask: How can the same device change electricity to sound and sound to electricity?
Lesson flow
Predict → demonstrate → observe → briefly explain → ask: How can the same device change electricity to sound and sound to electricity?