Final answer:
A charged particle is subject to the maximum deflecting force in a magnetic field when it moves perpendicular to the field lines, as this orientation maximizes the magnetic force on the particle.
Step-by-step explanation:
A charged particle experiences the maximum deflecting force in a magnetic field when it moves perpendicular to the field lines. This is due to the fact that the magnetic force is a result of the cross product of the velocity of the particle and the magnetic field strength, which is given by the equation F = qvB sin(θ), where F is the magnetic force, q is the charge, v is the velocity, B is the magnetic field strength, and θ is the angle between the velocity and the magnetic field. When this angle θ is 90 degrees, sin(θ) equals 1, resulting in the maximum possible force on the charged particle.