Since current is flowing from A to B, V(A) > V(B)
and the potential difference across  AB is V = V(A) – V(B) > 0 In a time interval Dt, an amount of charge DQ = I Dt travels from A to
B The potential energy of the charge at A, by definition, was Q V(A) and
similarly at B, it is Q V(B) Thus, change in its potential energy DUpot is
DUpot = Final potential energy – Initial potential energy
         = DQ[(V (B) – V (A)] = –DQ V
         = –I VDt < 0
(3