In the case of motion
of a charge in a magnetic field, the magnetic force is perpendicular to the
velocity of the particle So no work is done and no change in the magnitude
of the velocity is produced (though the direction of momentum may be
changed) [Notice that this is unlike the force due to an electric field, qE,
which can have a component parallel (or antiparallel) to motion and thus
can transfer energy in addition to momentum ]
We shall consider motion of a charged particle in a uniform magnetic
field