(If we use the page I posted as a reference)Ok. I understand. But I don't understand the steps to transform or substitutions to make to arrive to eV starting from 1/2 m vv.
The work W done on the electron is W = qV, where q is charge and V is voltage.
Since the charge in this case is the electron charge, e, we put this into the equation and get W = eV.
The kinetic energy KE that the electron gains is KE = (mv2)/2.
The kinetic energy gained equals the work done, so KE = W, which means (mv2)/2 = eV.