Two identical capacitors 1 and 2 connected in series to a battery as shown in figure. Capacitor 2 contains a dielectric slab of dielectric constant K as shown. If Q1 is the charge on each capacitor before removing the slab and Q2 is the charge on each capacitor after
moving the slab, then the correct relation between Q1 and Q2
is.
Since the two capacitors are in series both have equal charges. Let Q1 be the charge on the system.Then charge on the system is
Q1=(C×KCC+KC)V1=(KK+1)CV1
∴V1=Q1(K+1)KC ....(1)
On removing the dielectric slab the charge on the system is
Q2=C×CC+CV2=CV22
∴V2=2Q2C....(2)
The battery being the same V1=V2 from
Eqs. (1) and (2) we get Q1Q2=2K(K+1)