Pith Balls
Purpose
Two pith balls on threads demonstrate that like charges repel and opposite charges attract. Charge the balls with glass (positive) and Teflon (negative) rods to show both cases. Use shadow projection or a document camera for visibility in large halls.
Figure 1:
The pith ball apparatus with height-adjustable mounting allows for optimal viewing during demonstrations. The glass and Teflon rods with fur and silk are used to transfer charge to the balls.
Figure 2:
Shadow projection technique dramatically improves visibility of pith ball separation for large lecture halls, making the electrostatic repulsion clearly visible to all students.