You get the same answer with K=1. But different when K ne 1. You are taking two snapshots from two different methods. But there is external energy involved in inserting a dielectric -- not accounted for in your analysis. It's not a closed system comparison. You should ask this on the physics site, though. Here we treat things in bulk, as you are. But there they are more nuanced. Note also that there field lines that also go between the plates outside of the dielectric. It's not all between the plates in simple lines. There is the rest of the story in the lines going through the air/vacuum.
↧
