answer the questions below (a) and (b)

1.A magnet is an object that produces a magnetic field. This field can attract materials, especially metals containing iron. The strength of a magnet that attracts iron is called magnetism. This attraction is caused by electric charges. (a) State two situations in which a charged particle will experience no magnetic force when placed in a magnetic field. i 2 ) {b)A charged particle moves in a circular path when travelling perpendicular to a uniform magnetic field. By considering the force acting on the charged particle. show that the radius of the path is proportional to the particle's momentum