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Thread Electroscope
Origin and Date unknown
The thread was demonstrating electrica, attraction by static electricity. Suspended threads soon became part of every experimenter's apparatus, and remain useful today as a simple and sensitive indicator of static electricity. When your hair stands on end in the presence of electricity, it is behaving as a thread would. Thread electroscopes are very sensitive to breezes. Often, experimenters would put lightweight pith balls at the ends of the strings. They'd weight the strings down to cut their sensitivity to air currents, but the pith balls were almost as sensitive to electricity as the string alone. |
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In 1704, Francis Hauksbee was studying an "attractive
force or wind" upon objects held near a revolving glass cylinder.
He hung woolen threads nearby. When he simply spun the cylinder, the
threads moved in the eddies of air stirred by its motion. When a hand
touched the cylinder as it spun (electrifying it by friction) the threads
stiffened into radial rays accompanied by light and by crackling sounds.