As a physics teacher I became frustrated that there was no way to actually see an electric field; therefore, I challenged myself to create a video1 on the 10 best methods by which to demonstrate electric fields to students. Perhaps the best of these was inspired by an old article about using potassium permanganate crystals to make the electric field visible in water.2 In this article, the author, Michael Bernstein, says that “admittedly the patterns are not as well defined as we would like.” I have solved Bernstein’s problem by using coffee filters instead of water, similar to how chromatography is done. In my experience these patterns are very dramatic and highly illustrative of E-fields. Once you understand how to produce these patterns there is no limit to what you can create.
Safety warning! This demonstration involves high voltages and salt water, and KMnO4 is a toxic...