One plate of a capacitor is fixed and the other plate is connected to a spring, other end of which is attached to a right wall Fig. The plate area of the capacitor is $A$ and the separation between the plates is $d$. When the switch $S$ is closed, the distance between the plates is $d$. When the switch $S$ is closed, the distance between the plates reduces to a steady value $0.8 d$. Find the force constant $k$ of the spring.

A parallel plate capacitor has three different dielectric materials as shown in Fig. Find the equivalent capacitance across the two plates, $P_1$ and $P_2$.

In Fig, we see a system of capacitors joined to a cell of emf $12$ Volts. Find the charge on the capacitor $C_1$ when

Both the two keys $K_1$ and $K_2$ are closed.

In Fig. , we see many capacitors joined to a cell of emf $12$ volts. Find the charge on the capacitor $C_1$ 

when only ${\mathrm{K}}_1$ is closed.

In the given circuit, Fig. a charge of $+80\mu \mathrm{C}$  is given to the upper plate of $4\mu \mathrm{F}$  condenser. Find the charge on the upper plate of the $3 \mathrm{\mu F}$ capacitor.

Find the potential differences between the two points $A$ and $B$ in the circuit shown in figure and the total charge in the circuit.

Find the voltage between the two points $A$ and $B$ in the circuit shown in Fig.

$\left(b\right)$ 

Find the capacitance of the condenser, shown in Fig. $4.94$. The plate area is $A$, distance between the plates is $d$. The three dielectric slabs have equal thickness.