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A zinc plate is attached to an electroscope (projected onto the screen) and charged with rubber and fur (negative charge). A small UV lamp is held near the plate and the electroscope steadily discharges. If, however, the zinc plate is charged positively with lucite and silk, the effect vanishes.

Setup Instructions

1. Place the zinc plate (freshly sanded or filed) on top of the electroscope.

2. Charge the rod by rubbing it with fur; this produces negative charge on the rod.

3. Touch the rod to the plate or electroscope top to charge the electroscope and plate.

4. Shine the lamp at the plate. This should release electrons from the plate, and thus decrease the deflection of the electroscope needle.

Note: Sand Off Zinc Plate (BE SURE TO EXPOSE FRESH ZINC with the file)

Parts List

Zinc Plate and File in J. Modern Physics, 1B

Electroscope, Rod, and Fur in G. E & M, 1C

UV Lamp in J. Modern Physics, 1B

Relevant Simulation

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Other Information

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Real-Life Examples

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More Advanced Reading

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