(i) A charged particle travels undeviated through a magnetic field \(\vec B\), if its velocity \(\vec v\) is parallel or antiparallel to \(\vec B\). In this case, the magnetic force on the charge is zero.
(ii) A charged particle travels in a circular path within a magnetic field \(\vec B\), if its velocity \(\vec v\) is perpendicular to \(\vec B\).
(iii) A charged particle travels in a helical path through a magnetic field \(\vec B\), if its velocity \(\vec v\) is inclined at an angle θ to \(\vec B\), 0 < θ < 90°. In this case, the component of \(\vec v\) parallel to \(\vec B\) is unaffected by the magnetic field. The radius and pitch of the helix are determined respectively by the perpendicular and parallel components of \(\vec v\).
