Interaction of a Point Charge and a Magnet: Comments on 'Hidden Mechanical Momentum Due to Hidden Nonelectromagnetic Forces'

摘要

The interaction of a point charge and a magnetic moment (and by extension apoint charge and a solenoid) is explored within well-defined point-chargemagnetic-moment models where full calculations are possible. It is shownexplicitly how the "hidden mechanical momentum" is introduced by the "hidden"external forces of constraint, requiring a prescribed response (through order1/c^2) of the system to electromagnetic forces. These external forces often gounmentioned in the textbook and research literature. The dependence of "hiddenmechanical momentum" upon detailed external (nonelectromagnetic) forces mayundermine the idea's usefulness in describing nature. Some statements ofdubious validity in the textbook literature are noted.