PURPOSE: To illustrate the electric field for various geometries.
DESCRIPTION: Samples are mounted in a holder on an overhead projector and charged using the Wimshurst machine. The particles in the solution become polarized and align along the electric field lines. Sample geometries include oppositely charged points, and point surrounded by a circle.
By convention, electric field lines are depicted as moving towards negative charge and originating from and moving outward from positive charge For oppositely charged points of equal magnitude with some radius between them, the electric field lines should align in a manner such that the electric field lines move from the positive charge towards the negative charge, each charge exerting equal push or pull resulting in symmetry. For equally charged points with some radius between them, there should be no electric field lines between the two charges showing no electric field. Depending on whether the charges are both positive or negative, the lines will either originate from or converge away, respectively.
EQUIPMENT: The shallow dish, grass seed, Wimshurst machine and the conductors are stored in the electricity and magnetism cabinets. The dielectric oil is stored on the top shelf of the supplies stored shelf near the entrance door. The projector is stored in the vault.
SETUP TIME: 1 hour
REFERENCES: Oleg Jefimenko, Demonstration of Electric Fields of Current-Carrying Conductors, AJP 30, 19-21 (1962).
Tomoyoshi Kittaka, Lines of Force of an Electric Field By Electromigratio of Ions, TPT 8, 143-144, (1970).
F. S. Chute and F. E. Vermeulen, A Visual Demonstration of Two-Dimensional Electrostatic Fields, AJP 42, 1075-1077 (1974).
Alan Wolf, Stephen J. Van Hook, and Eric R. Weeks, Electric field line diagrams don't work, AJP 64, 714-724 (1996).
Instructions for B-1254 Electostatic Field Experiment Apparatus, Model EF-5N, Arbor Scientific, Ann Harbor, MI.
Updated by RR on 6/14/2007