There are four concentric shells $A, B, C $ and $D $ of radii $ a, 2a, 3a$ and $4a$ respectively. Shells $B$ and $D$ are given charges $+q$ and $-q$ respectively. Shell $C$ is now earthed. The potential difference $V_A - V_C $ is :
$\frac{{Kq}}{{2a}}$
$\frac{{Kq}}{{3a}}$
$\frac{{Kq}}{{4a}}$
$\frac{{Kq}}{{6a}}$
Two equal positive point charges are kept at points $A$ and $B$ . The electric potential, while moving from $A$ to $B$ along straight line
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
Four charges $ + Q,\, - Q,\, + Q,\, - Q$ are placed at the corners of a square taken in order. At the centre of the square
Charges of $ + \frac{{10}}{3} \times {10^{ - 9}}C$ are placed at each of the four corners of a square of side $8\,cm$. The potential at the intersection of the diagonals is
Calculate potential on the axis of a disc of radius $R$ due to a charge $Q$ uniformly distributed on its surface.