This apparatus enables electric field patterns to be shown in much the same way that magnetic fields are demonstrated with iron filings, either by direct viewing or on an overhead projector.

The apparatus comprises a clear plastic dish (90mm x 12mm) and base (140mm x 125mm), which carries a pair of 4mm socket terminals / electrode holders. Alongside each terminal is a thumb screw 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 diameter respectively.

• Requires an EHT 5kV Power Supply (B8R02653), Liquid Paraffin (B8R06467) and Semolina (available from supermarkets).

The dish is placed on the base between the terminals and filled to a depth of 6 to 8 mm with liquid paraffin (not included). A small amount of semolina (also not included) is sprinkled evenly on the surface of the liquid. The electrodes are fitted into the cross-holes of the terminals and are clamped in the desired position. When the terminals are connected to the power supply field patterns are formed in the semolina, and different patterns can be shown by exchanging the pairs of electrodes. Patterns will continue to form even after the semolina has sunk to the bottom of the dish, giving a long viewing time and little disturbance when changing electrodes.