The effect of trapped charge on series capacitors

If capacitors are initially charged before placing them in series, charge becomes trapped on the electrically isolated internal plates. The effect of this "trapped charge" on the final charge and voltage distributions in series capacitor networks provides instructors with a new class of engaging capacitor problems not currently addressed in introductory physics textbooks. We present formulae for the final charges on two series capacitors connected to a battery in terms of initial charge values. Various special cases are also considered. Results are verified experimentally using dc voltage and RC time constant measurements. Practical considerations for experimental design are discussed.