$A$ hollow metal sphere of radius $10 \ cm$ is charged such that the potential on its surface becomes $80 \ V$. The potential at the centre of the sphere is . . . . . . . (in $V$)

$A$ hollow metal sphere of radius $5\, cm$ is charged so that the potential on its surface is $10\, V$. The potential at the centre of the sphere is.....$V$

Figures $(a)$ and $(b)$ show the field lines of a positive and negative point charge respectively.
$(a)$ Give the signs of the potential difference $V_{P}-V_{Q}$ and $V_{B}-V_{A}$.
$(b)$ Give the sign of the potential energy difference of a small negative charge between the points $Q$ and $P$,and $A$ and $B$.
$(c)$ Give the sign of the work done by the field in moving a small positive charge from $Q$ to $P$.
$(d)$ Give the sign of the work done by the external agency in moving a small negative charge from $B$ to $A$.
$(e)$ Does the kinetic energy of a small negative charge increase or decrease in going from $B$ to $A$?

$64$ drops of mercury,each charged to a potential of $10\,V$,are combined to form one bigger drop. The potential of this bigger drop will be.......$V$ (Assume all the drops to be spherical).

Charges of $2 \mu C$ and $-3 \mu C$ are placed at two points $A$ and $B$ separated by a distance of $1 \ m$. The distance of the point from $A$ where the net potential is zero is: (in $m$)

Which physical quantities are represented by $X$ and $Y$ in the given graph? ($Y$ represents the first quantity.)