electricity and magnetism(3)

(a) Since a helium nucleus carries positive charge, its direction of motion is the same as the direction of current to which it contributes. In order for the nucleus to move in a circular path, the magnetic force acting on it shall be directed towards the centre.

Applying Fleming's Left-Hand Rule, the helium nucleus is moving anti-clockwise.

(b) (i) Each individual part will follow the same circular path with the same radius as before the nucleus is split.

It is because the charge and mass of each part are exactly half of those of the original nucleus. Hence, the magnetic force, which depends on the charge, is halved, and because the mass is also halved, the motion of the split nucleus remains the same as before.

(ii) The uncharged part will go in a straight line, becaus there is now no magnetic force acting on it.

The other part, that carries the same charge as the original nucleus but with mass halved, will continue to go on a circular path with a new radius equal to half of that of the original circle.

The reason is because the magnetic force remains the same, but the mass is reduced by half. Hence, the centripetal force acting on the new split part will pull it to circulate in a smaller radius than before.