If the point P has
position vector r relative to some origin, we can write:
Potential energy of q at r in an external field
= qV(r)
(2 27)
where V(r) is the external potential at the point r Thus, if an electron with charge q = e = 1 6×10–19 C is accelerated by
a potential difference of DV = 1 volt, it would gain energy of qDV = 1