Understanding a Charged Device: Polarization and Grounding

[runningirl]

Homework Statement

A demonstration device consists of two parallel metal plates separated by an insulating support. The device is placed on top of a negatively charged van de Graaff generator. In between the plates are several Stryofoam balls covered with metallic paint.

a) Describe what happens to the balls, at first when the bottom plate becomes charged by conduction with the van de Graaff.
b) Describe the steps that happen after that.
c) Explain what would happen if you touch a grounding wire to the top of this device.

Homework Equations

The Attempt at a Solution

a) Would the balls stick to the top because of polarization?
b) I'm not too sure about this part. Wouldn't they just stay there?
c) Would the balls stick to the sides because now the top and bottom are both charged negatively?

 

[gneill]

a) Would the balls stick to the top because of polarization?
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The balls are conductive. At soon as they touch the top plate, what should happen to any charge imbalance? Then what?