(a) into the page (b) no deflection
Work Step by Step
We can write an expression for the force on the particle: $F = q~(v\times B)$ To apply the right hand rule, we point the thumb in the direction of the positive charge and the index finger in the direction of the magnetic field. (a) By the right hand rule, the initial force on the particle is directed into the page. (b) Since the direction of the particle and the direction of the magnetic field are parallel, then the force on the particle is zero. The particle is not deflected in this case.