An a-particle enters a uniform magnetic field at right angles to it as shown in figure. Stating the relevant principle, explain in which direction will this a-particle move?
According to Fleming’s Left Hand Rule, the force acting on a current carrying conductor placed perpendicular to a magnetic field is perpendicular to the direction of current (i.e., flow of positive charges) and the magnetic field. Here, direction of a-particle (i.e., positive charge) is the direction of current. Hence, according to Fleming’s Left Hand Rule, the direction of force acting on a-particle is perpendicular to both the direction of motion of a-particle and the direction of magnetic field. Hence, a-particle will move perpendicular to the plane of the paper and in downward direction.