How much kinetic energy will be gained by an $\alpha$-particle in going from a point at $70\,V$ to another point at $50\,V$?

What is the electric potential at the center $O$ of a circle of radius $0.4 \ m$ with the charges arranged as shown in the figure?

$A$ charge of $10\, e.s.u.$ is placed at a distance of $2\, cm$ from a charge of $40\, e.s.u.$ and $4\, cm$ from another charge of $20\, e.s.u.$ The potential energy of the charge $10\, e.s.u.$ is (in $ergs$)

$A$ charge of $10 \, \text{esu}$ is placed at a distance of $2 \, \text{cm}$ from a charge of $40 \, \text{esu}$ and at a distance of $4 \, \text{cm}$ from another charge of $-20 \, \text{esu}$. The potential energy of the $10 \, \text{esu}$ charge in ergs is:

Four electric charges $+q, +q, -q$ and $-q$ are placed at the corners of a square of side $2L$ (see figure). The electric potential at point $A$,midway between the two charges $+q$ and $+q$,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 $x=a+r$ (if $a << r$) is: ($\varepsilon_0$ is the permittivity of free space)