2 2  Magnetic Field,  Lorentz  Force
Let us suppose that there is  a point charge q (moving
with a velocity v and, located at r at a given time t) in
presence of both the electric field E (r) and the magnetic
field B (r) The force on an electric charge q due to both
of them can be written as
F   = q [ E (r) +  v × B (r)] º Felectric +Fmagnetic
(4 3)
This force was given first  by H