In an oscillating $LC$ circuit the maximum charge on the capacitor is $Q$. The charge on the capacitor when the energy is stored equally between the electric and magnetic fields is

A point charge $q$ is placed at a distance $\frac{a}{2}$ directly above the centre of a  square of side $a$ . The electric flux through the square is

When a proton is accelerated through $1\,V,$ then its kinetic energy will be........$eV$

Three plates of common surface area $A$ are connected as shown. The effective capacitance will be

A finite ladder is constructed by connecting several sections of $2\,\mu F$ , $4\,\mu F$ capacitor combinations as shown in the figure. It is terminated by a capacitor of capacitance $C$. What value should be chosen for $C$ such that the equivalent capacitance of the ladder between the points $A$ and $B$ becomes independent of the number of sections in between.......$\mu F$

Two charged spherical conductors of radii $R_1$ and $R_2$ are connected by a wire. The ratio of surface charge densities of the spheres $\sigma _1/\sigma _2$ will be