Speaker Becomes a Microphone

Speaker can generate a tiny electrical signal. Ask students to predict what will happen. Speak/tap near speaker wired as input. Key idea: Moving voice coil in a magnetic field induces voltage—the reverse of speaker operation. Ask: How can the same device change electricity to sound and sound to electricity? Safety and cleanup: Keep amplification low; no loud feedback. https://www.google.com/search?q=%22Speaker+Becomes+a+Microphone%22+science+demonstration+experiment