  A general law for electromagnetic induction phenomena is derived from Lorentz
force and Maxwell equation connecting electric field and time variation of
magnetic field. The derivation provides with a unified mathematical treatment
the statement according to which electromagnetic induction is the product of
two independent phenomena: time variation of magnetic field and effects of
magnetic field on moving charges. The general law deals easily-without ad hoc
assumptions-with typical cases usually considered as exceptions to the flux
rule and contains the flux rule as a particular case.
