The apparatus enables electric field patterns to be shown in much the same way that magnetic fields are demonstrated with iron fillings, either by direct viewing or on an overhead projector. The apparatus comprises a clear plastic dish 90 x 12mm diameter x depth, and base 140 x 125mm. Alongside each terminal is a thumbscrew system which permits fine height adjustment of the electrodes. Six electrodes are supplied, two 'point source' two 'line source' and two circular rings of 35 and 70mm dia. For use with 0-5kV EHT power supply.