In question , the capacitor is connected to a battery with terminal voltage V This connection is maintained while the dielectric slab is held in place by the application of a force F. The required force is plates of one of the capacitors so as to fill the gap, the battery remaining connected. The charge on each capacitor will be
Before the introduction of dielectric, the charge on each capacitor will be the same because they are connected in series.
Initial charge on each capacitor q0 = C0V0 When dielectric is introduced, C1 = C0 and C2 = K C0
Charge on each capacitor