Two capacitors (lets call them C1 and C2) in series are connected to a voltage source and charged. While still connected to the source one of them is filled with a dielectric (lets say C2 is filled). I know the charge on C2 will change by a factor of K because the source keeps the potential differences of each capacitor constant. But does the charge of the unfilled capacitor (C1) change? This is more of a conceptual question. EDIT: I got it. The charge on the unfilled capacitor remains the same. I would delete the thread but i can't figure out how to do that.