We know that in nuclear reactions , mass is converted into energy which appears as Binding Energy. Now, when we consider electrons coming close to the nucleus during nuclear/atomic phenomenon, can we consider that the energy present in the electric and Nuclear fields is converted into mass?? Can this be generalised to all forces and energy fields..i.e. If a body moves in a certain force field associated with a vector field, does energy change to mass??? When do such changes take place? Why/Why not?