Elecrtic Forces

Charge Shuttle


Q1: Sketch how the charged can attracts the pith ball in the first place. 

The neutral pith ball polarizes in the presence of the charged can.  The positive charges being repelled to the right side of the ball, the left, negatively charged side of the ball is attracted to the positively charged can.

Q2: Sketch what happens when the charge can and the pith ball contact one and other. 

In contact with the charged can, the pith ball is charged positively by contact.

Q3: Why the ball begins to oscillate between the two cans.  Recall conventional current as well as the displacement of negative charges.
Both can A and the ball being positive, the pith ball is repelled to the right.  When it contacts can B, the relatively negative can takes-up the ball's excess positive charge.  Now repelled by can B, the ball swings back to can A picking up more positive charges when the two come into contact.  The ball oscillates in this fashion, shuttling charges from can A to can B while being alternately repelled be each can.

Advanced Question: Will the oscillating stop?  Explain why the pith ball will or will not stop.

The pith ball will stop oscillating.  At the point when both can A and can B have an equal amount of positive charge the alternating repulsion that pushed the pith ball back and forth between the cans will cease.  The result will be for the pith ball to come to rest in between the cans once again.

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