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

What is the change in kinetic energy of an $\alpha$-particle when it moves from a point at $70\ V$ to a point at $50\ V$?

If identical charges $(-q)$ are placed at each corner of a cube of side '$b$',what will be the $E.P.E$ (Electrostatic Potential Energy) of a charge $(+q)$ placed at the center of the cube?

Two rings of radius $R$ are placed coaxially at a distance $R$ apart. They carry charges $Q_1$ and $Q_2$ respectively. How much work is required to move a charge $q$ from the center of one ring to the center of the other?

Two charges $3 \times 10^{-8} \; C$ and $-2 \times 10^{-8} \; C$ are located $15 \; cm$ apart. At what point on the line joining the two charges is the electric potential zero? Take the potential at infinity to be zero.

Consider a fixed uniformly charged insulating sphere with radius $R$ and total charge $+Q$. $A$ point charge $-q$ $(q \ll Q)$ with mass $m$ is released from rest at a distance of $3R$ from the centre of the charged sphere. When the point charge reaches the surface of the sphere, its speed is:
($\epsilon_0$ is the permittivity of vacuum, neglect gravitational forces).