Do free electrons travel to a region of higher potential or lower potential?

Which of the following is a dimension of volt?

Find the electric potential at the origin due to the given distribution of charges.

Particles $A$ and $B$ have charges $+q$ and $+4q$ respectively. Both have the same mass $m$. If they are released from rest and accelerated through the same potential difference $V$,the ratio of their velocities $v_A/v_B$ is:

$A$ neutral spherical copper particle has a radius of $10 \,nm$ $(1 \,nm = 10^{-9} \,m)$. It gets charged by applying the voltage,slowly adding one electron at a time. Then,the graph of the total charge on the particle versus the applied voltage would look like:

Two particles with charges $+q$ and $-q$ are separated by a distance of $2d$. What is the electric potential at the midpoint of the line joining them?