Electrostatic field of a long uniformly charged wire varies with distance $(r)$ according to relation

Two condensers $C_1$ and $C_2$ in a circuit are joined as shown in figure. The  potential of point $A$ is $V_1$ and that of $B$ is $V_2$. The potential of point $D$ will be

In the given circuit if point $C$ is connected to the earth and a potential of $+2000\,V$ is given to the point $A$ , the potential of $B$ is.....$V$

In an adjoining figure three capacitors $C_1,\,C_2$ and $C_3$ are joined to a battery. The correct condition will be (Symbols have their usual meanings)

Two charged spheres of radii $R_1$ and $R_2$ having equal surface charge density. The ratio of their potential is

A parallel plate capacitor with air between the plates has a capacitance of $9\, pF$. The separation between its plates is $'d'$. The space between the plates is now filled with two dielectrics. One of the dielectrics has dielectric constant $K_1=3$ and thickness $\frac{d}{3}$ while the other one has dielectric constant $K_2 = 6$ and thickness $\frac{2d}{3}$ . Capacitance of the capacitor is now.........$pF$