1. The problem statement, all variables and given/known data Two identical flat capacitors with no dielectric material inside are connected in series to a voltage source. The electric field intensity inside the capacitors is E. If the space inside one of the capacitors is filled with a dielectric material of ε=9 how strongly did the field intensity change if: a) the circuit was connected to the voltage source when the capacitor was filled with a dielectric b) the circuit had been disconnected from the voltage source before the capacitor was filled with the dielectric 2. Relevant equations Electric field intensity becomes reduced by: E = Eexternal / ε C = ε0εS/d 3. The attempt at a solution The capacitance increases by a factor of 9 Therefore the charge on the capacitor must increase by a factor of 9 therefore the charge on the other series capacitor increased by a factor of 9 Therefore the electric field inside the filled capacitor must increase by a factor of 9 Even if the above is correct what difference does having the source connected or disconnected do? I'm assuming it must be related to the fact that the two are in series therefore the charge on each must be the same.