Electric Potential - Lightning Plate with Van de Graaff Generator

The lightning plate:

The larch:


(knowing the difference could save your life)

The lightning plate sparks when charged. The charge builds up , increasing the voltage across each of the gaps until the voltage difference exceeds the breakdown voltage, causing a spark. This is one of our more romantic demonstrations, so be sure to dim the lights appropriately to set the mood (and, you know, make it actually visible).