"Friction speaker" experiment

Attach a piece of stainless steel tape on one edge of a cardboard plate and connect a wire to it. Cover the stainless steel tape with a thin and strong paper and wet it with a diluted surfactant (Kao Bath-magiclean is used in the video). Prepare another mirror-surface stainless steel plate and attach a wire to it too. Connect the wires to the speaker output of an audio set. Slide the cardboard on the stainless steel plate keeping the paper pushed against the plate. The cardboard will vibrate and emit sounds.

The friction coefficient between the paper and the stainless steel mirror surface is modulated by the applied audio voltage. The speed of the cardboard is modulated as the friction changes, generating sound waves.

Instead of paper and surfactant, an ion-exchange filter paper and pure water can be used as well. The relationship between the voltage polarity and the friction is opposite between anion-exchange type and cation-exchange type.

Category:

Science & Technology

Tags:

• science
• diy