Speaker Becomes a Microphone

1. Speaker Becomes a Microphone Materials: Small speaker; amplifier/meter or second speaker What you do: Speak/tap near speaker wired as input. What students see: Speaker can generate a tiny electrical signal. Question: How can the same device change electricity to sound and sound to electricity? 2. Ferrofluid Spikes Materials: Sealed ferrofluid display; strong magnet What you do: Move magnet near sealed ferrofluid. What students see: Liquid grows sharp black spikes. Question: How can a liquid make pointy shapes? 3. TV Remote Seen by a Camera Materials: IR TV remote; phone/tablet camera What you do: Point remote at camera and press buttons. What students see: Camera often shows blinking light invisible to eyes. Question: How can the camera see light we can't?

Predict → observe three demonstrations → compare what changed → choose independent activity station → cleanup/share. Guiding questions: Question: How can the same device change electricity to sound and sound to electricity? Question: How can a liquid make pointy shapes? Question: How can the camera see light we can't?