Courses: P4, P14, P16
AKA The least dramatic demo ever. A capacitor with an oil dielectric (any oil will do, we often use WD40) and a glass overflow tube which is partially full of fluid. When a voltage is applied to the plates, dielectric is pulled into the capacitor and the fluid level in the tube goes down. Slightly.
Setup: Add oil until it rises about 2/3 of the way up the glass tube. Spread the spacers out to keep the cylinders evenly aligned. The voltage needed is typically around 1800 V. You can increase the voltage until it starts arcing and then back off a bit. (The arcing won't damage anything, though it will spit some oil out.) It's probably a good idea to store it empty, so the oil doesn't end up gumming up parts that would be difficult to clean.
