$A$ charge of $10 \,\mu C$ is placed at the origin of an $x-y$ coordinate system. The potential difference between two points $(0, a)$ and $(a, 0)$ in volts will be

Two charges $+q$ and $-q$,each $1 \mu C$,are arranged as shown in the figure. If $x=2 \text{ cm}$ and $y=3 \text{ cm}$,then the potential difference $(V_A - V_B)$ is:

Two concentric hollow spheres of radii $r$ and $R$ $(R > r)$ have the same surface charge density $\sigma$. The total charge $Q$ is distributed between them. The electric potential at the common center is:

Two points $P$ and $Q$ are maintained at the potentials of $10 \ V$ and $-4 \ V$,respectively. The work done in moving $100$ electrons from $P$ to $Q$ is

If the electric potential of the inner sphere is $10\, V$ and that of the outer shell is $50\, V$,then the potential at the common centre is :- (in $, V$)

Two small equal point charges of magnitude $q$ are suspended from a common point on the ceiling by insulating massless strings of equal lengths. They come to equilibrium with each string making an angle $\theta$ from the vertical. If the mass of each charge is $m$,then the electrostatic potential at the centre of the line joining them will be $\left( \frac{1}{4\pi \epsilon_0} = k \right).$