$A$ hollow metal sphere of radius $15 \,cm$ is charged such that the potential on its surface is $20 \,V$. Then, the potential at the centre of the sphere is (in $V$)

$A$ cube of side $b$ has a charge $q$ at each of its vertices. Determine the potential and electric field due to this charge array at the centre of the cube.

$A$ particle of mass $m$ and charge $q$ is accelerated through a potential difference of $V$ volt. Its energy will be:

If the potential of the inner shell of radius $r$ is $10\,V$ and that of the outer shell of radius $2r$ is $5\,V$, then the potential at the centre will be....$V$

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:

As shown in the figure,on bringing a charge $Q$ from point $A$ to $B$ and from $B$ to $C$,the work done is $2 \, J$ and $-3 \, J$ respectively. The work done to bring the charge from $C$ to $A$ is (in $, J$)