When a charged particle moves in a magnetic field, the force acting on it is determined by the angle between its velocity and the magnetic field. At 90 degrees, the force is maximized and is calculated using the formula F = qvB, where F is the magnetic force, q is the charge, v is the velocity, and B is the magnetic field strength. At 0 degrees, the force becomes zero since the particle moves parallel to the field lines, resulting in no magnetic force acting on it. The angle between the velocity and the magnetic field is crucial in determining the magnitude of the force experienced by the particle. Understanding these principles is essential for applications in electromagnetism and particle physics.