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10. Snap
Purpose To demonstrate how static charges produce sound.
Materials large paper clip
piece of wool: a scarf, coat, or sweater made of 100% wool will work clear plastic sheet
scissors
modeling clay
Procedure
Cut a plastic strip about 1 in. x 8 in. (2.5 cm x 20 cm).
Use the clay to stand the paper clip upright on a table.
Wrap the wool around the plastic strip and quickly pull
the plastic through the cloth. Do this quickly at least
three times.
Immediately hold the plastic near the top of the paper clip.
Results A snapping sound can be heard.
Why? Electrons are rubbed off the wool and onto the plastic. Electrons tend to move from an area where they are concentrated to an area of less concentration. Thus, the electrons move across the span of air between the plastic and the metal clip. The movement of the electrons through the air produces sound waves, resulting in the snapping sound heard.
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