At the centre of a half ring of radius $R=10 \ cm$ and linear charge density $\lambda = 4 \ nC \ m^{-1}$,the potential is $x \pi \ V$. The value of $x$ is . . . . .

$64$ identical drops each charged up to a potential of $10 \, mV$ are combined to form a bigger drop. The potential of the bigger drop will be $.......... \, mV$.

$A$ uniformly charged half-ring of radius $R$ has a linear charge density $\sigma$. The electric potential at the centre of the half-ring is ($\epsilon_0$ = permittivity of free space).

For a hollow spherical shell,how does the potential $(V)$ change with respect to the distance $(r)$ from the centre?

Define electron volt and convert it into Joule unit.

$A$ charge of total amount $Q$ is distributed over two concentric hollow spheres of radii $r$ and $R$ $(R > r)$ such that the surface charge densities on the two spheres are equal. The electric potential at the common centre is