  The semiclassical limit of a nonlinear focusing Schr\"odinger equation in
presence of nonconstant electric and magnetic potentials V,A is studied by
taking as initial datum the ground state solution of an associated autonomous
elliptic equation. The concentration curve of the solutions is a
parameterization of the solutions of a Newton ODE involving the electric force
as well as the magnetic force via the Lorenz law of electrodynamics.
