Columbia University Physics Lecture Demonstrations


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5A10.2 Electrophorus

[Setup Time: 5 Min.] [Current Condition: Good]

Info

A metal disk can be repeatedly charged and discharged by setting it on a charged, insulated base. The effect can be shown by charging an electroscope.

Setup Instructions

1. Take the metal disk with the handle off of the base and rub the top surface of the base with the wool or fur.

2. Put the metal disk back on the base, and touch the top of the metal disk. A spark will jump from your finger to the disk, charging it up.

3. Now, holding the handle of the disk remove it from the base and discharge it to the electroscope by bringing the rim of the disk close to the top of the scope. The disk is now discharged, and the process can be repeated.

4. Note: The disk can hold even more charge if, while touching it to charge it up, you are also touching the metal foil on the base with your other hand. The electrophorus can be used in other demonstrations where you need to produce a lot of static charge, such as charging up the large capacitor.

Parts List

NOTE: rub the surface with the wool/fur, and NOT the metal base.

Electrophorus Disk, Wool and Base in G. E&M, 1C

Electroscope in G. E&M, 1C

Light Point Source in L. Misc

Relevant Simulation

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Other Information

Rods and Fur or Silk with Electroscope

Real-Life Examples

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More Advanced Reading

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