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Discharging Zinc Plate
# 7A10.10


Description: A polished zinc plate sits atop an electroscope. A negative charge is placed on the electroscope. The UV light is then shown on the plate to discharge the electroscope.

Instructions: Charge the electroscope with a negative rod (fur or waxed paper on PVC works well for a negative charge--charge by contact, not induction). Turn on the ultraviolet light. Remove the protective glass plate to expose the zinc plate to the UV rays. Replace the glass plate.

Hazards: DO NOT TURN THE UV LIGHT TOWARD THE STUDENTS.

Parts: Mercury lamp, electroscope, rods, fur, plastic

Purchased/Built: purchased

Setup Time: 15 min

Quant. in Demo Room: 1

Demo References
The Video Encyclopedia of Physics Demonstrations Disc 24-19 Zinc plate on an electroscope, charged negative, glass UV barrier.
Hilton A-4b Discharge a zinc plate on an electroscope.
Sutton A-89 UV light shines on a zinc plate on an electroscope. More.
Meiners 38-2.1 A clean zinc plate mounted on a charged electroscope discharges an electroscope when the light source is not covered with glass.
Freier and Anderson Ok-3 Discharge a zinc plate on an electroscope with UV light.

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