BCIT Physics Department

Demonstration Manual

Electricity and Magnetism

DEM07 - Electric Field Demonstration, Seed in Oil


- To show an analogy of the electric field or the electric lines of force surrounding conductors of selected geometry.



Theplatform with the bottom half of a Petrie Dish is placed on the O.H. Projector, and connected to the electrodes of the Wimshurst Machine. About 1 cm depth of oil is added, and the desired conductor shapes are plugged in and immersed in the oil. Grass seed is sprinkled lightly and evenly on the oil. The O.H. Projector is focussed on the layer of seeds.

The Wimshurst Machine is then cranked one or two times (only), setting up a potential gradient between the conductors. The seeds become charged and align along the electric lines of force.