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PIRA Code(s)
Set up time
5 minutes
Physics and Science Concepts
Electrostatics, Surface Charge Density
Use the Van der Graaf or Wimshurst generator to charge the ovoid. Touch a proof plane to the pointed end of the ovoid and another to the spherical end. Place the proof planes on the electroscope plate. The deflection will be greater from the proof plane that touched the pointed end.
Electroscope can be obtained from demonstration number 5A22.22.

A tear-drop shaped conductor demonstrates that c harges tend to accumulate at sharply curved points. In order to maintain uniform electric potential over a whole conductor, the surface charge density must be greater at sharply curved points.