A charge particle moving through a magnetic field experiences a magnetic force. What is the angle between the magnetic field and the force on the particle?

The magnetic force on a moving charged particle is given by:

F = qv*B

F is the magnetic force vector, q is the charge, v is the velocity vector, and B is the magnetic field vector. Note that we are taking the cross product of qv and B, not multiplying scalar quantities.

The cross product of two vectors gives a third vector which is perpendicular to the original two vectors. The very nature of taking a cross product means that F will always be perpendicular to B, i. e. the angle between F and B will always be 90°.