Explain whether an alpha particle will experience any force in a magnetic field if :
(i) it is placed in the field at rest.
(ii) it moves in the magntic field parallel to field lines.
(iii) it moves in the magnetic field perpendicular to field lines.

Explanation

(i) No, because, a charged particle at rest does not interact with magnetic field.
(ii) No, because, the force is zero if current and field are in the same direction.
(iii) Yes, because, the force is maximum when current and magnetic field are maximum .