Which is the important quantity used to describe any force field?

$90 \ J$ of work is done to move an electric charge of magnitude $3 \ C$ from a place $A$,where potential is $-10 \ V$,to another place $B$,where potential is $V_1 \ V$. The value of $V_1$ is: (in $V$)

In the following diagram,the work done in moving a point charge from point $P$ to points $A$,$B$,and $C$ is $W_A$,$W_B$,and $W_C$ respectively. Then:

Three point charges $+Q$,$+2Q$,and $q$ are placed at the vertices of an equilateral triangle. The value of charge $q$ in terms of $Q$,so that the electrical potential energy of the system is zero,is given by:

$A$ point charge $q$ of mass $m$ is placed at the center of a ring of radius $R$ carrying a charge $Q$. When it is slightly displaced,the point charge accelerates to infinity along the $x$-axis. The ultimate speed of the point charge is .......

Along the $x$-axis,three charges $\frac{q}{2}, -q$ and $\frac{q}{2}$ are placed at $x=0, x=a$ and $x=2a$ respectively. The resultant electric potential at a point $P$ located at a distance $r$ from the charge $-q$ $(r > a)$ is ($\varepsilon_0$ is the permittivity of free space):