Electric pressure didn't make a lot of sense to most people at the end of last class period. It's not the easiest concept, and it isn't exactly analogous to fluid pressure. We looked at our results from some complicated circuits, and we kinda could explain it using pressure, but we didn't feel comfortable with it.
We went to lab to watch what happens when capacitors are charged and discharged. It was confusing at first, but then we explained it in terms of electric pressure and it started to make sense. We first modeled electric pressure with colors, using the charging and discharging diagrams from the CASTLE curriculum. But colors seemed limiting. We all knew it.
We immediately used a voltmeter to get numeric values for electric pressure. It was my favorite move of the day. We discarded the color model quickly. I like the color model of electric pressure, but I've found that when a class uses it for too long, it gets confusing. Coming up with a better model quickly made so much more sense.