At distances of $5 \ cm$ and $10 \ cm$ outwards from the surface of a uniformly charged solid sphere,the potentials are $100 \ V$ and $75 \ V$ respectively. Then:

The figure shows a diagonal symmetric arrangement of capacitors and a battery. Identify the correct statements.

$A$ parallel plate capacitor is charged and then disconnected from the source of steady $E.M.F.$ The plates are then drawn apart farther. Again it is connected to the same source. Then:

$A$ parallel plate capacitor of plate area $A$ and plate separation $d$ is charged to a potential $V$ and then the battery is disconnected. $A$ slab of dielectric constant $k$ is then inserted between the plates of the capacitor so as to fill the space between the plates. If $Q$,$E$,and $W$ denote respectively the magnitude of charge on each plate,the electric field between the plates (after the slab is inserted),and the work done on the system in the process of inserting the slab,then state the incorrect relation from the following:

Consider two identical metallic spheres of radius $R$ each having charge $Q$ and mass $m$. Their centers have an initial separation of $4 R$. Both the spheres are given an initial speed of $u$ towards each other. The minimum value of $u$, so that they can just touch each other is: (Take $k=\frac{1}{4 \pi \epsilon_0}$ and assume $k Q^2 > G m^2$ where $G$ is the Gravitational constant)

Five capacitors of $10\,\mu F$ capacity each are connected to a $d.c.$ potential of $100\;V$ as shown in the figure. The equivalent capacitance between the points $A$ and $B$ will be equal to..........$\mu F$.