Purpose:Demonstrate the existence of electric fields and to identify the polarity of the charge on a sphere.
Description:A neon lamp is mounted on a long plastic pole with one side of the lamp grounded. The neon lamp lights when held in the vicinity of the Van de Graaff dome, even without direct contact, indicating the existence of an electric field. The side of the neon bulb which lights is the negative side, so the direction of the electric field can be determined by noting which side of the neon bulb is lighted, if you know how the internal connections of the neon bulb are made. The magnitude of the glow on the neon bulb is proportional to the strength of the field.