I have used a petri dish of sunflower oil with semolina floating in it to see the field lines for an electric field. It's similar to doing the iron filings experiment for magnetic fields. I made the metal contacts from a coat hanger and connected it up to 3000 Volts. I projected the result onto the board and you can see the semolina lining up between the contacts. The parallel lines show a uniform field, which will have a constant field strength throughout.
