A simple scientific instrument that detects the presence of electrical charge by observing the movement of thin metal leaves or threads.
From electro- + -scope (viewing instrument, from Greek skopein 'to look'). Invented in the 18th century and widely used in early electrical experiments.
The electroscope was so important to early physics that it was basically the first voltmeter—scientists could actually SEE electricity's presence by watching little gold leaves repel each other, making the invisible visible.
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