Place liquid paraffin in the 90mm petri dish and sprinkle semolina or fine grass seed (not supplied) on the surface. 
A simple model for demonstrating electric fields between various electrode configurations. 
Apply a high voltage via the 4mm terminals and the field pattern is generated. 
The clear acrylic base allows the pattern to be projected via an overhead projector. (150 x 150 x 60). 
Note: This apparatus requires a safe, low-current limited 0-5kV EHT supply. Investigate electric fields