A hemispherical bowl of mass $m$ is uniformly charged with charge density $'\sigma '$ . Electric potential due to charge distribution at a point $'A'$ is (which lies at centre of radius as shown).

A spherical conductor of radius $2\,m$ is charged to a potential of $120\,V.$ It is now placed inside another hollow spherical conductor of radius $6\,m.$ Calculate the potential to which the bigger sphere would be raised......$V$

Two point charges $4\,\mu C$ and $ - 1\,\mu C$ are kept at a distance of $3\ m$ from each other. What is the electric potential at the point where the electric field is zero?......$V$

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

The electric potential at the centre of two concentric half rings of radii $R_1$ and $R_2$, having same linear charge density $\lambda$ is

In a region, if electric field is defined as $\vec E = \left( {\hat i + 2\hat j + \hat k} \right)\,V/m$ , then the potential difference between two points $A (0, 0, 0)$ and $B (2, 3, 4)$ in that region, is ......$V$